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/*
* MacRuby Strings.
*
* This file is covered by the Ruby license. See COPYING for more details.
*
* Copyright (C) 2007-2011, Apple Inc. All rights reserved.
* Copyright (C) 1993-2007 Yukihiro Matsumoto
* Copyright (C) 2000 Network Applied Communication Laboratory, Inc.
* Copyright (C) 2000 Information-technology Promotion Agency, Japan
*/

#include <stdio.h>
#include <stdarg.h>
#include <wctype.h>
#include <unistd.h>

#include "macruby_internal.h"
#include "ruby/encoding.h"
#include "encoding.h"
#include "re.h"
#include "objc.h"
#include "id.h"
#include "ruby/node.h"
#include "vm.h"
#include "class.h"
#include "encoding_ucnv.h"

#include <unicode/unum.h>
#include <unicode/utrans.h>
#include <unicode/uchar.h>

#define SET_CLASS(dst, src) \
do{ \
if (RSTR(dst) != NULL && RSTR(src) != NULL) { \
RBASIC(dst)->klass = RBASIC(src)->klass; \
} \
} while(0)

VALUE rb_cRubyString;

VALUE rb_fs;

static SEL selMATCH;

// rb_str_t primitives.

static void
str_update_flags_utf16(rb_str_t *self)
{
    assert(IS_UTF16_ENC(self->encoding));

    bool ascii_only = true;
    bool valid_encoding = true;
    // if the length is an odd number, it can't be valid UTF-16
    if (ODD_NUMBER(self->length_in_bytes)) {
valid_encoding = false;
    }

    UChar *uchars = (UChar *)self->bytes;
    long uchars_count = BYTES_TO_UCHARS(self->length_in_bytes);
    bool native_byte_order = IS_NATIVE_UTF16_ENC(self->encoding);
    UChar32 lead = 0;
    for (int i = 0; i < uchars_count; ++i) {
UChar32 c;
if (native_byte_order) {
c = uchars[i];
}
else {
uint8_t *bytes = (uint8_t *)&uchars[i];
c = (uint16_t)bytes[0] << 8 | (uint16_t)bytes[1];
}
if (U16_IS_SURROGATE(c)) { // surrogate
if (U16_IS_SURROGATE_LEAD(c)) { // lead surrogate
// a lead surrogate should not be
// after an other lead surrogate
if (lead != 0) {
valid_encoding = false;
}
lead = c;
}
else { // trail surrogate
// a trail surrogate must follow a lead surrogate
if (lead == 0) {
valid_encoding = false;
}
else {
c = U16_GET_SUPPLEMENTARY(lead, c);
if (!U_IS_UNICODE_CHAR(c)) {
valid_encoding = false;
}
}
lead = 0;
}
}
else { // not a surrogate
// a non-surrogate character should not be after a lead surrogate
// and it should be a valid Unicode character
// Warning: Ruby 1.9 does not do the IS_UNICODE_CHAR check
// (for 1.9, 0xffff is valid though it's not a Unicode character)
if ((lead != 0) || !U_IS_UNICODE_CHAR(c)) {
valid_encoding = false;
}

if (c > 127) {
ascii_only = false;
}
}
    }
    // the last character should not be a lead surrogate
    if (lead != 0) {
valid_encoding = false;
    }

    if (valid_encoding) {
str_set_valid_encoding(self, true);
str_set_ascii_only(self, ascii_only);
    }
    else {
str_set_valid_encoding(self, false);
str_set_ascii_only(self, false);
    }
}

void
str_update_flags(rb_str_t *self)
{
    if (self->length_in_bytes == 0) {
str_set_valid_encoding(self, true);
str_set_ascii_only(self, true);
    }
    else if (IS_BINARY_ENC(self->encoding)) {
str_set_valid_encoding(self, true);
bool ascii_only = true;
for (long i = 0; i < self->length_in_bytes; ++i) {
if ((uint8_t)self->bytes[i] > 127) {
ascii_only = false;
break;
}
}
str_set_ascii_only(self, ascii_only);
    }
    else if (IS_UTF8_ENC(self->encoding)) {
bool ascii_only = true;
bool valid_encoding = true;

for (int i = 0; i < self->length_in_bytes; ) {
UChar32 c;
U8_NEXT(self->bytes, i, self->length_in_bytes, c);
if (c == U_SENTINEL) {
valid_encoding = false;
ascii_only = false;
break;
}
else if (c > 127) {
ascii_only = false;
}
}

str_set_valid_encoding(self, valid_encoding);
str_set_ascii_only(self, ascii_only);
    }
    else if (IS_UTF16_ENC(self->encoding)) {
str_update_flags_utf16(self);
    }
    else {
str_ucnv_update_flags(self);
    }
}

static rb_encoding_t *
str_compatible_encoding(rb_str_t *str1, rb_str_t *str2)
{
    if (str1->encoding == str2->encoding) {
return str1->encoding;
    }
    if (str2->length_in_bytes == 0) {
return str1->encoding;
    }
    if (str1->length_in_bytes == 0) {
return str2->encoding;
    }
    if (!str1->encoding->ascii_compatible
|| !str2->encoding->ascii_compatible) {
return NULL;
    }
    if (str_is_ruby_ascii_only(str2)) {
return str1->encoding;
    }
    if (str_is_ruby_ascii_only(str1)) {
return str2->encoding;
    }
    return NULL;
}

static rb_encoding_t *
str_must_have_compatible_encoding(rb_str_t *str1, rb_str_t *str2)
{
    rb_encoding_t *new_encoding = str_compatible_encoding(str1, str2);
    if (new_encoding == NULL) {
rb_raise(rb_eEncCompatError,
"incompatible character encodings: %s and %s",
str1->encoding->public_name, str2->encoding->public_name);
    }
    return new_encoding;
}

static void
str_modifiable(VALUE str)
{
    if (OBJ_FROZEN(str)) {
rb_error_frozen("string");
    }
    if (!OBJ_UNTRUSTED(str) && rb_safe_level() >= 4) {
rb_raise(rb_eSecurityError, "Insecure: can't modify string");
    }
}

static rb_str_t *
str_alloc(VALUE klass)
{
    assert(rb_klass_is_rstr(klass));
    assert(klass != 0);

    NEWOBJ(str, rb_str_t);
    str->basic.flags = 0;
    str->basic.klass = klass;
    str->encoding = rb_encodings[ENCODING_UTF8];
    str->capacity_in_bytes = 0;
    str->length_in_bytes = 0;
    str->bytes = NULL;
    str_reset_flags(str);

    return str;
}

static VALUE
str_new_empty(VALUE str)
{
    VALUE v = rb_str_new5(str, 0, 0);
    OBJ_INFECT(v, str);
    return v;
}

static VALUE
str_new_like(VALUE obj)
{
    return (VALUE)str_alloc(rb_obj_class(obj));
}

static void str_resize_bytes(rb_str_t *self, long new_capacity);
static void str_concat_bytes(rb_str_t *self, const char *bytes, long len);

static void
str_replace_with_bytes(rb_str_t *self, const char *bytes, long len,
rb_encoding_t *enc)
{
    assert(len >= 0);
    assert(enc != NULL);

    str_reset_flags(self);
    self->encoding = enc;
    if (len > 0) {
str_resize_bytes(self, len);
if (bytes != NULL) {
memcpy(self->bytes, bytes, len);
self->length_in_bytes = len;
}
else {
self->length_in_bytes = 0;
}
    }
    else {
self->length_in_bytes = 0;
    }
}

void
str_replace_with_string(rb_str_t *self, rb_str_t *source)
{
    if (self == source) {
return;
    }
    str_replace_with_bytes(self, source->bytes, source->length_in_bytes,
source->encoding);
    if (!source->flags) {
str_update_flags(source);
    }
    self->flags = source->flags;
}

static void
str_append_uchar32(rb_str_t *self, UChar32 c)
{
    str_reset_flags(self);
    if ((c <= 127) && self->encoding->ascii_compatible) {
str_resize_bytes(self, self->length_in_bytes + 1);
self->bytes[self->length_in_bytes] = c;
self->length_in_bytes++;
    }
    else if (IS_UTF8_ENC(self->encoding)) {
long len = U8_LENGTH(c);
if (len > 0) {
str_resize_bytes(self, self->length_in_bytes + len);
U8_APPEND_UNSAFE(self->bytes, self->length_in_bytes, c);
// U8_APPEND_UNSAFE increments length_in_bytes
// by the number of bytes appended
}
    }
    else if (IS_NATIVE_UTF32_ENC(self->encoding)) {
str_concat_bytes(self, (char *)&c, 4);
    }
    else if (IS_NATIVE_UTF16_ENC(self->encoding) && U_IS_BMP(c)) {
UChar uchar = c;
str_concat_bytes(self, (char *)&uchar, 2);
    }
    else {
rb_str_t *str = RSTR(rb_enc_str_new((char *)&c, 4,
rb_encodings[ENCODING_UTF32_NATIVE]));
str = str_simple_transcode(str, self->encoding);
str_concat_bytes(self, str->bytes, str->length_in_bytes);
    }
}

static void str_concat_uchars(rb_str_t *self, const UChar *chars, long len);
static void
str_replace_with_uchars(rb_str_t *self, const UChar *chars, long len)
{
    assert(len >= 0);

    str_reset_flags(self);
    self->length_in_bytes = 0;
    self->encoding = rb_encodings[ENCODING_UTF8];
    if (len > 0) {
if (chars == NULL) {
str_resize_bytes(self, len);
}
else if (self->bytes == (char *)chars) {
self->length_in_bytes = UCHARS_TO_BYTES(len);
}
else {
str_concat_uchars(self, chars, len);
}
    }
}

static void
str_replace_with_cfstring(rb_str_t *self, CFStringRef source)
{
    const long len = CFStringGetLength(source);
    UniChar *chars = NULL;
    if (len > 0) {
chars = (UniChar *)malloc(sizeof(UniChar) * len);
assert(chars != NULL);
CFStringGetCharacters(source, CFRangeMake(0, len), chars);
    }
    str_replace_with_uchars(self, chars, len);
    if (chars != NULL) {
free(chars);
    }
}

static void
str_replace(rb_str_t *self, VALUE arg)
{
    switch (TYPE(arg)) {
case T_STRING:
if (IS_RSTR(arg)) {
str_replace_with_string(self, RSTR(arg));
}
else {
str_replace_with_cfstring(self, (CFStringRef)arg);
}
break;
default:
str_replace(self, rb_str_to_str(arg));
break;
    }
}

static rb_str_t *
str_dup(rb_str_t *source)
{
    rb_str_t *destination = str_alloc(rb_cRubyString);
    str_replace_with_string(destination, source);
    if (source->flags & STRING_ASCII_ONLY_SET) {
str_set_ascii_only(destination, str_is_ascii_only(source));
    }
    return destination;
}

rb_str_t *
str_new_from_cfstring(CFStringRef source)
{
    rb_str_t *destination = str_alloc(rb_cRubyString);
    str_replace_with_cfstring(destination, source);
    return destination;
}

static long
str_length_with_cache(rb_str_t *self, character_boundaries_cache_t *cache)
{
    // fast paths
    if (self->length_in_bytes == 0) {
return 0;
    }
    else if (self->encoding->single_byte_encoding
|| (self->encoding->ascii_compatible && str_is_ascii_only(self))) {
return self->length_in_bytes;
    }
    else if (IS_UTF16_ENC(self->encoding)) {
return div_round_up(self->length_in_bytes, 2);
    }

    if (cache != NULL
&& cache->cached_length >= 0) {
return cache->cached_length;
    }

    // slow paths
    long length = 0;
    if (IS_UTF8_ENC(self->encoding)) {
int i = 0;
while (i < self->length_in_bytes) {
UChar32 c;
int old_i = i;
U8_NEXT(self->bytes, i, self->length_in_bytes, c);
if (c == U_SENTINEL) {
length += i - old_i;
}
else if (U_IS_BMP(c)) {
length++;
}
else {
length += 2;
}
}
    }
    else {
length = str_ucnv_length(self, true);
    }

    if (cache != NULL) {
cache->cached_length = length;
    }
    return length;
}

static long
str_length(rb_str_t *self)
{
    return str_length_with_cache(self, NULL);
}

NORETURN(static void
str_invalid_byte_sequence(rb_str_t *str))
{
    rb_raise(rb_eArgError, "invalid byte sequence in %s", str->encoding->public_name);
}

// Note that each_uchar32 iterates on Unicode characters
// With a character not in the BMP the callback will only be called once!
// start_offset_in_bytes MUST be at a character boundary
static void
str_each_uchar32_starting_from(rb_str_t *self,
long start_offset_in_bytes,
each_uchar32_callback_t callback)
{
    if (IS_BINARY_ENC(self->encoding) || IS_ASCII_ENC(self->encoding)) {
bool stop = false;
for (long i = start_offset_in_bytes; i < self->length_in_bytes; ++i) {
UChar32 c = (uint8_t)self->bytes[i];
if (!IS_BINARY_ENC(self->encoding) && c > 127) {
c = U_SENTINEL;
}
callback(c, i, 1, &stop);
if (stop) {
return;
}
}
    }
    else if (IS_UTF8_ENC(self->encoding)) {
bool stop = false;
for (int i = start_offset_in_bytes; i < self->length_in_bytes; ) {
UChar32 c;
int old_i = i;
U8_NEXT(self->bytes, i, self->length_in_bytes, c);
int char_length = i - old_i;
if (c == U_SENTINEL) {
for (long j = 0; j < char_length; ++j) {
callback(c, old_i+j, 1, &stop);
if (stop) {
return;
}
}
}
else {
callback(c, old_i, char_length, &stop);
if (stop) {
return;
}
}
};
    }
    else if (IS_NATIVE_UTF16_ENC(self->encoding)) {
assert(!ODD_NUMBER(start_offset_in_bytes));
bool stop = false;
long length = BYTES_TO_UCHARS(self->length_in_bytes);
UChar *uchars = (UChar *)self->bytes;
for (long i = 0; i < length;) {
UChar32 c;
long old_i = i;
U16_NEXT(uchars, i, length, c);
callback(c, UCHARS_TO_BYTES(old_i),
UCHARS_TO_BYTES(i-old_i), &stop);
if (stop) {
return;
}
// in case the length changed
// (it should not happen but never know)
length = BYTES_TO_UCHARS(self->length_in_bytes);
};
    }
    else {
str_ucnv_each_uchar32_starting_from(self,
start_offset_in_bytes, callback);
    }
}

static void
str_each_uchar32(rb_str_t *self, each_uchar32_callback_t callback)
{
    str_each_uchar32_starting_from(self, 0, callback);
}

static UChar
str_get_uchar(rb_str_t *self, long pos)
{
    assert(pos >= 0 && pos < str_length(self));

    UChar c = self->bytes[pos];
    if ((c <= 127) && str_is_ruby_ascii_only(self)) {
return c;
    }

    if (IS_NATIVE_UTF16_ENC(self->encoding)) {
return c;
    }

    __block UChar return_value = 0;
    __block long i = 0;
    str_each_uchar32(self, ^(UChar32 c, long start_index, long char_len, bool *stop) {
if (c == U_SENTINEL || U_IS_BMP(c)) {
if (i == pos) {
return_value = c;
*stop = true;
}
else {
++i;
}
}
else {
if (i == pos) {
return_value = U16_LEAD(c);
*stop = true;
}
else if (i+1 == pos) {
return_value = U16_TRAIL(c);
*stop = true;
}
else {
i += 2;
}
}
    });

    return return_value;
}

static long
str_bytesize(rb_str_t *self)
{
    return self->length_in_bytes;
}

static rb_str_t *
str_new_similar_empty_string(rb_str_t *self)
{
    rb_str_t *str = str_alloc(rb_obj_class((VALUE)self));
    str->encoding = self->encoding;
    return str;
}

static rb_str_t *
str_new_copy_of_part(rb_str_t *self, long offset_in_bytes,
long length_in_bytes)
{
    assert(length_in_bytes > 0);
    rb_str_t *str = str_alloc(rb_obj_class((VALUE)self));
    str->encoding = self->encoding;
    str->capacity_in_bytes = str->length_in_bytes = length_in_bytes;
    GC_WB(&str->bytes, xmalloc(length_in_bytes));
    memcpy(str->bytes, &self->bytes[offset_in_bytes],
length_in_bytes);
    if ((self->flags & STRING_ASCII_ONLY_SET) && (self->flags & STRING_ASCII_ONLY)) {
// if the source string is ASCII only,
// then a part of that string is also ASCII only
str_set_ascii_only(str, true);
    }
    return str;
}

// you cannot cut a surrogate in an encoding that is not UTF-16
// (it's in theory possible to store the surrogate in
// UTF-8 or UTF-32 but that would be incorrect Unicode)
NORETURN(static void
str_cannot_cut_surrogate(void))
{
    rb_raise(rb_eIndexError, "You can't cut a surrogate in two in an encoding that is not UTF-16");
}

static character_boundaries_t
str_get_character_boundaries(rb_str_t *self, long index,
character_boundaries_cache_t *cache)
{
    character_boundaries_t boundaries = {-1, -1};

    // fast paths
    if (self->encoding->single_byte_encoding
|| (self->encoding->ascii_compatible && str_is_ascii_only(self))) {
if (index < 0) {
index += self->length_in_bytes;
if (index < 0) {
return boundaries;
}
}
boundaries.start_offset_in_bytes = index;
boundaries.end_offset_in_bytes = boundaries.start_offset_in_bytes + 1;

return boundaries; // getting the offset is fast so no use caching it
    }
    else if (IS_UTF16_ENC(self->encoding)) {
if (index < 0) {
index += div_round_up(self->length_in_bytes, 2);
if (index < 0) {
return boundaries;
}
}
boundaries.start_offset_in_bytes = UCHARS_TO_BYTES(index);
boundaries.end_offset_in_bytes = boundaries.start_offset_in_bytes + 2;

return boundaries; // getting the offset is fast so no use caching it
    }

    // slow path
    if (index < 0) {
index += str_length_with_cache(self, cache);
if (index < 0) {
return boundaries;
}
    }

    bool can_use_cache = (cache != NULL
&& cache->cached_boundaries_index >= 0);
    if (can_use_cache && cache->cached_boundaries_index == index) {
return cache->cached_boundaries;
    }

    if (IS_UTF8_ENC(self->encoding)) {
long pos = 0;
int index_in_bytes = 0;
if (can_use_cache && cache->cached_boundaries_index < index) {
// if we are in the middle of a non-BMP character,
// end_offset_in_bytes or start_offset_in_bytes might be -1
if (cache->cached_boundaries.end_offset_in_bytes == -1) {
index_in_bytes = cache->cached_boundaries.start_offset_in_bytes;
pos = cache->cached_boundaries_index;
}
else {
index_in_bytes = cache->cached_boundaries.end_offset_in_bytes;
pos = cache->cached_boundaries_index + 1;
}
}
while (index_in_bytes < self->length_in_bytes) {
UChar32 c;
int old_index_in_bytes = index_in_bytes;
long new_pos = pos;
U8_NEXT(self->bytes, index_in_bytes, self->length_in_bytes, c);
if (c == U_SENTINEL) {
new_pos += index_in_bytes - old_index_in_bytes;
if (new_pos > index) {
boundaries.start_offset_in_bytes =
old_index_in_bytes + (index - pos);
boundaries.end_offset_in_bytes =
boundaries.start_offset_in_bytes + 1;
break;
}
}
else if (U_IS_BMP(c)) {
new_pos++;
if (new_pos > index) {
boundaries.start_offset_in_bytes = old_index_in_bytes;
boundaries.end_offset_in_bytes = index_in_bytes;
break;
}
}
else {
new_pos += 2;
if (new_pos > index) {
if (index == pos) {
boundaries.start_offset_in_bytes = old_index_in_bytes;
}
else {
assert(index == pos + 1);
boundaries.end_offset_in_bytes = index_in_bytes;
}
break;
}
}
pos = new_pos;
}
    }
    else {
boundaries = str_ucnv_get_character_boundaries(self, index, true);
    }

    if (cache != NULL) {
cache->cached_boundaries_index = index;
cache->cached_boundaries = boundaries;
    }

    return boundaries;
}

static rb_str_t *
str_get_characters(rb_str_t *self, long first, long last,
character_boundaries_cache_t *cache)
{
    if (self->length_in_bytes == 0) {
if (first == 0) {
return str_new_similar_empty_string(self);
}
else {
return NULL;
}
    }

    character_boundaries_cache_t local_cache;
    if (cache == NULL) {
reset_character_boundaries_cache(&local_cache);
cache = &local_cache;
    }

    character_boundaries_t first_boundaries =
str_get_character_boundaries(self, first, cache);
    character_boundaries_t last_boundaries =
str_get_character_boundaries(self, last, cache);

    if ((first_boundaries.start_offset_in_bytes == -1) ||
(last_boundaries.end_offset_in_bytes == -1)) {
// you cannot cut a surrogate in an encoding that is not UTF-16
str_cannot_cut_surrogate();
    }

    if (first_boundaries.start_offset_in_bytes == self->length_in_bytes) {
return str_new_similar_empty_string(self);
    }
    else if (first_boundaries.start_offset_in_bytes > self->length_in_bytes) {
return NULL;
    }
    if (last_boundaries.end_offset_in_bytes >= self->length_in_bytes) {
last_boundaries.end_offset_in_bytes = self->length_in_bytes;
    }

    return str_new_copy_of_part(self, first_boundaries.start_offset_in_bytes,
last_boundaries.end_offset_in_bytes
- first_boundaries.start_offset_in_bytes);
}

static void
str_resize_bytes(rb_str_t *self, long new_capacity)
{
    if (new_capacity < 0) {
rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    if (self->capacity_in_bytes < new_capacity) {
size_t capacity = new_capacity * 1.2;
if (capacity > 0){
new_capacity = capacity;
}
if (self->bytes == NULL) {
GC_WB(&self->bytes, xmalloc(new_capacity));
}
else {
char *bytes = xrealloc(self->bytes, new_capacity);
if (bytes != self->bytes) {
GC_WB(&self->bytes, bytes);
}
}
self->capacity_in_bytes = new_capacity;
    }
}

static void
str_ensure_null_terminator(rb_str_t *self)
{
    if (self->length_in_bytes > 0
&& (self->capacity_in_bytes == self->length_in_bytes
|| self->bytes[self->length_in_bytes] != '\0')) {
str_resize_bytes(self, self->length_in_bytes + 1);
self->bytes[self->length_in_bytes] = '\0';
    }
}

static void
str_splice(rb_str_t *self, long pos, long len, rb_str_t *str)
{
    // self[pos..pos+len] = str
    assert(pos >= 0 && len >= 0);

    if (str != NULL) {
str_must_have_compatible_encoding(self, str);
    }

    character_boundaries_t beg, end;
    if (pos + len == 0) {
// Positioning before the string.
const long offset = 0;
beg.start_offset_in_bytes = beg.end_offset_in_bytes = offset;
end.start_offset_in_bytes = end.end_offset_in_bytes = offset;
    }
    else if (len == 0 && str_length(self) == pos) {
// Positioning after the string.
const long offset = self->length_in_bytes;
beg.start_offset_in_bytes = beg.end_offset_in_bytes = offset;
end.start_offset_in_bytes = end.end_offset_in_bytes = offset;
    }
    else {
character_boundaries_cache_t local_cache;
reset_character_boundaries_cache(&local_cache);

// Positioning in the string.
beg = str_get_character_boundaries(self, pos, &local_cache);
end = str_get_character_boundaries(self, pos + len - 1, &local_cache);

if ((beg.start_offset_in_bytes == -1) ||
(end.end_offset_in_bytes == -1)) {
// you cannot cut a surrogate in an encoding that is not UTF-16
str_cannot_cut_surrogate();
}
    }

    const long bytes_to_splice = end.end_offset_in_bytes
- beg.start_offset_in_bytes;

    long bytes_to_add = 0;
    if (str != NULL) {
if (str->length_in_bytes > 0 && self->flags != str->flags) {
str_reset_flags(self);
}
if (str->length_in_bytes > bytes_to_splice) {
str_resize_bytes(self, self->length_in_bytes
+ (str->length_in_bytes - bytes_to_splice));
}
bytes_to_add = str->length_in_bytes;
    }

    if (beg.start_offset_in_bytes == end.end_offset_in_bytes
&& end.end_offset_in_bytes == self->length_in_bytes) {
     if (bytes_to_add > 0) {
// We are splicing at the very end.
memcpy(self->bytes + self->length_in_bytes, str->bytes,
bytes_to_add);
}
    }
    else {
// We are splicing in the middle.
memmove(self->bytes + beg.start_offset_in_bytes + bytes_to_add,
self->bytes + end.end_offset_in_bytes,
self->length_in_bytes - end.end_offset_in_bytes);
if (bytes_to_add > 0) {
memcpy(self->bytes + beg.start_offset_in_bytes,
str->bytes, bytes_to_add);
}
    }

    self->length_in_bytes = self->length_in_bytes - bytes_to_splice
+ bytes_to_add;
}

static void
str_delete(rb_str_t *self, long pos, long len)
{
    if (str_is_ruby_ascii_only(self) &&
self->length_in_bytes <= pos + len) {
self->length_in_bytes = pos;
return;
    }
    str_splice(self, pos, len, NULL);
}

static void
str_insert(rb_str_t *self, long pos, rb_str_t *str)
{
    str_splice(self, pos, 0, str);
}

static void
str_concat_bytes(rb_str_t *self, const char *bytes, long len)
{
    assert(bytes != NULL && len >= 0);

    const long new_length_in_bytes = self->length_in_bytes + len;

    str_resize_bytes(self, new_length_in_bytes);
    memcpy(self->bytes + self->length_in_bytes, bytes, len);
    self->length_in_bytes = new_length_in_bytes;
}

static void
str_concat_uchars(rb_str_t *self, const UChar *chars, long len)
{
    if (len == 0) {
return;
    }
    str_reset_flags(self);
    if (IS_UTF8_ENC(self->encoding)) {
long new_length_in_bytes = self->length_in_bytes;
for (long i = 0; i < len; ) {
UChar32 c;
U16_NEXT(chars, i, len, c);
new_length_in_bytes += U8_LENGTH(c);
}
str_resize_bytes(self, new_length_in_bytes);
for (long pos_in_src = 0, pos_in_dst = self->length_in_bytes;
pos_in_src < len; ) {
UChar32 c;
UBool is_error;
U16_NEXT(chars, pos_in_src, len, c);
U8_APPEND((uint8_t *)self->bytes, pos_in_dst,
new_length_in_bytes, c, is_error);
}
self->length_in_bytes = new_length_in_bytes;
    }
    else if (IS_NATIVE_UTF16_ENC(self->encoding)) {
str_concat_bytes(self, (char *)chars, UCHARS_TO_BYTES(len));
    }
    else if (IS_BINARY_ENC(self->encoding) || IS_ASCII_ENC(self->encoding)) {
const long new_length_in_bytes = RSTR(self)->length_in_bytes + len;

str_resize_bytes(self, new_length_in_bytes);
char *ptr = (RSTR(self)->bytes + RSTR(self)->length_in_bytes);
for (int i = 0; i < len; ++i) {
ptr[i] = chars[i];
}
self->length_in_bytes = new_length_in_bytes;
    }
    else {
rb_str_t *str = RSTR(rb_enc_str_new((char *)chars,
UCHARS_TO_BYTES(len),
rb_encodings[ENCODING_UTF16_NATIVE]));
str = str_simple_transcode(str, self->encoding);
str_concat_bytes(self, str->bytes, str->length_in_bytes);
    }
}

static void
str_concat_string(rb_str_t *self, rb_str_t *str)
{
    if (str->length_in_bytes == 0) {
return;
    }

    rb_encoding_t *enc = str_must_have_compatible_encoding(self, str);
    if (!str->flags) {
str_update_flags(str);
    }
    if (self->flags != str->flags) {
str_reset_flags(self);
    }
    self->encoding = enc;
    str_concat_bytes(self, str->bytes, str->length_in_bytes);
}

static void
str_concat_string_part(rb_str_t *self, rb_str_t *str, long start, long len,
character_boundaries_cache_t *cache_for_str)
{
    assert(len >= 0 && start >= 0);
    if (len == 0) {
return;
    }

    rb_encoding_t *enc = str_must_have_compatible_encoding(self, str);
    str_reset_flags(self);
    self->encoding = enc;

    character_boundaries_t first_boundaries =
str_get_character_boundaries(str, start, cache_for_str);
    character_boundaries_t last_boundaries;
    if (len == 1) {
last_boundaries = first_boundaries;
    }
    else {
last_boundaries = str_get_character_boundaries(str, start+len-1,
cache_for_str);
    }

    if ((first_boundaries.start_offset_in_bytes == -1) ||
(last_boundaries.end_offset_in_bytes == -1)) {
// you cannot cut a surrogate in an encoding that is not UTF-16
str_cannot_cut_surrogate();
    }

    str_concat_bytes(self, &str->bytes[first_boundaries.start_offset_in_bytes],
last_boundaries.end_offset_in_bytes -
first_boundaries.start_offset_in_bytes);
}

static int
str_compare(rb_str_t *self, rb_str_t *str)
{
    if (self == str) {
return 0;
    }

    if (self->length_in_bytes == 0 && str->length_in_bytes == 0) {
// both strings are empty
return 0;
    }

    if (str_compatible_encoding(self, str) == NULL) {
// incompatible encodings
return -1;
    }

    const long min_len = self->length_in_bytes < str->length_in_bytes
? self->length_in_bytes : str->length_in_bytes;

    const int res = memcmp(self->bytes, str->bytes, min_len);

    if (res == 0) {
if (self->length_in_bytes == str->length_in_bytes) {
return 0;
}
return self->length_in_bytes > str->length_in_bytes
? 1 : -1;
    }
    return res > 0 ? 1 : -1;
}

int
rstr_compare(rb_str_t *str1, rb_str_t *str2)
{
    return str_compare(str1, str2);
}

static int
str_case_compare(rb_str_t *self, rb_str_t *str)
{
    if (self == str) {
return 0;
    }

    if (self->length_in_bytes == 0 && str->length_in_bytes == 0) {
// both strings are empty
return 0;
    }

    if (str_compatible_encoding(self, str) == NULL) {
// incompatible encodings
return -1;
    }

    const long min_length = self->length_in_bytes < str->length_in_bytes
? self->length_in_bytes : str->length_in_bytes;

    for (long i = 0; i < min_length; i++) {
char c1 = self->bytes[i];
char c2 = str->bytes[i];
if (c1 != c2) {
c1 = isascii(c1) ? toupper(c1) : c1;
c2 = isascii(c2) ? toupper(c2) : c2;
if (c1 != c2) {
return c1 < c2 ? -1 : 1;
}
}
    }

    if (self->length_in_bytes == str->length_in_bytes) {
return 0;
    }
    return self->length_in_bytes > str->length_in_bytes ? 1 : -1;
}

static long
str_offset_in_bytes_to_index(rb_str_t *self, long offset_in_bytes)
{
    if ((offset_in_bytes >= self->length_in_bytes) || (offset_in_bytes < 0)) {
return -1;
    }
    if (offset_in_bytes == 0) {
return 0;
    }

    if (self->encoding->single_byte_encoding
|| (self->encoding->ascii_compatible && str_is_ascii_only(self))) {
return offset_in_bytes;
    }
    else if (IS_UTF16_ENC(self->encoding)) {
if (!ODD_NUMBER(offset_in_bytes)) {
// if we are in the middle of a character, there's no valid index
return -1;
}
return BYTES_TO_UCHARS(offset_in_bytes);
    }
    else {
return str_ucnv_offset_in_bytes_to_index(self, offset_in_bytes, true);
    }
}

static long
str_index_for_string_with_cache(rb_str_t *self, rb_str_t *searched,
long start_index, long end_index, bool backward_search,
character_boundaries_cache_t *cache)
{
    str_must_have_compatible_encoding(self, searched);

    if (searched->length_in_bytes == 0 && self->length_in_bytes == 0) {
return start_index;
    }
    if (searched->length_in_bytes > self->length_in_bytes) {
return -1;
    }

    long start_offset_in_bytes;
    if (start_index == 0) {
start_offset_in_bytes = 0;
    }
    else {
character_boundaries_t boundaries = str_get_character_boundaries(self,
start_index, cache);
if (boundaries.start_offset_in_bytes == -1) {
if (boundaries.end_offset_in_bytes == -1) {
return -1;
}
else {
// you cannot cut a surrogate in an encoding that is not UTF-16
str_cannot_cut_surrogate();
}
}
start_offset_in_bytes = boundaries.start_offset_in_bytes;
    }

    if (self == searched) {
if (start_offset_in_bytes == 0) {
return 0;
}
else {
return -1;
}
    }

    if (start_offset_in_bytes >= self->length_in_bytes) {
return -1;
    }

    long last_offset_in_bytes;
    if (end_index < 0
|| end_index == str_length_with_cache(self, cache)) {
last_offset_in_bytes = self->length_in_bytes;
    }
    else {
character_boundaries_t boundaries = str_get_character_boundaries(self,
end_index, cache);
if (boundaries.start_offset_in_bytes == -1) {
if (boundaries.end_offset_in_bytes == -1) {
return -1;
}
else {
// you cannot cut a surrogate in an encoding that is not UTF-16
str_cannot_cut_surrogate();
}
}
last_offset_in_bytes = boundaries.start_offset_in_bytes;
    }
    long min_end_offset = self->length_in_bytes - searched->length_in_bytes;
    if (last_offset_in_bytes > min_end_offset) {
last_offset_in_bytes = min_end_offset;
    }

    if (!backward_search) {
if (searched->length_in_bytes == 0) {
assert(start_index >= 0);
return start_index;
}
__block long returned_index = -1;
__block long current_index = start_index;
str_each_uchar32_starting_from(self, start_offset_in_bytes,
^(UChar32 c, long character_start_offset, long char_len, bool *stop) {
if (character_start_offset > last_offset_in_bytes) {
// not enough characters left: we could not find the string
*stop = true;
return;
}
if (memcmp(self->bytes + character_start_offset,
searched->bytes, searched->length_in_bytes) == 0) {
returned_index = current_index;
*stop = true;
return;
}
if (U_IS_BMP(c)) {
++current_index;
}
else {
current_index += 2;
}
});
return returned_index;
    }

    // backward search
    if (searched->length_in_bytes == 0) {
if (end_index < 0) {
return str_length_with_cache(self, cache);
}
else {
return end_index;
}
    }

    for (;;) {
long offset_found = -1;
for (long offset = last_offset_in_bytes;
offset >= start_offset_in_bytes;
--offset) {
if (memcmp(self->bytes + offset, searched->bytes,
searched->length_in_bytes) == 0) {
offset_found = offset;
break;
}
}
if (offset_found < 0) {
// not found
return -1;
}

long index = str_offset_in_bytes_to_index(RSTR(self), offset_found);
if (index != -1) {
// the offset was valid, at the start of a character
return index;
}

last_offset_in_bytes = offset_found - 1;
    }
}

static long
str_index_for_string(rb_str_t *self, rb_str_t *searched, long start_index,
long end_index, bool backward_search)
{
    character_boundaries_cache_t local_cache;
    reset_character_boundaries_cache(&local_cache);
    return str_index_for_string_with_cache(self, searched, start_index,
end_index, backward_search, &local_cache);
}

static bool
str_include_string(rb_str_t *self, rb_str_t *searched)
{
    return str_index_for_string_with_cache(self, searched,
0, -1, false, NULL) != -1;
}

rb_str_t *
str_need_string(VALUE str)
{
    switch (TYPE(str)) {
case T_SYMBOL:
str = rb_sym_to_s(str);
break;

case T_STRING:
break;

default:
str = rb_str_to_str(str);
break;
    }
    return IS_RSTR(str)
? (rb_str_t *)str : str_new_from_cfstring((CFStringRef)str);
}

static void
str_extract_uchars_range(rb_str_t *self, long range_start_offset_in_uchars,
long range_length_in_uchars, UChar *buffer)
{
    if (range_length_in_uchars <= 0) {
return;
    }
    if (self->encoding->ascii_compatible && str_is_ascii_only(self)) {
char *source_bytes = &self->bytes[range_start_offset_in_uchars];
for (long i = 0; i < range_length_in_uchars; ++i) {
buffer[i] = source_bytes[i];
}
    }
    else if (IS_UTF8_ENC(self->encoding)) {
long pos_in_src = 0;
long pos_in_dst = 0;
for (int i = 0; i < self->length_in_bytes; ) {
UChar32 c;
int old_i = i;
U8_NEXT(self->bytes, i, self->length_in_bytes, c);
if (c == U_SENTINEL) {
int diff = i - old_i;
if (pos_in_src + diff > range_start_offset_in_uchars) {
int start = range_start_offset_in_uchars - pos_in_src;
if (start < 0) {
start = 0;
}
for (int j = start; j < diff && pos_in_dst < range_length_in_uchars; ++j) {
buffer[pos_in_dst++] = self->bytes[old_i+j];
}
}
pos_in_src += diff;
}
else if (U_IS_BMP(c)) {
if (pos_in_src >= range_start_offset_in_uchars) {
buffer[pos_in_dst++] = c;
}
++pos_in_src;
}
else {
if (pos_in_src >= range_start_offset_in_uchars) {
buffer[pos_in_dst++] = U16_LEAD(c);
if (pos_in_dst < range_length_in_uchars) {
buffer[pos_in_dst++] = U16_TRAIL(c);
}
}
else if (pos_in_src + 1 >= range_length_in_uchars) {
buffer[pos_in_dst++] = U16_TRAIL(c);
}
pos_in_src += 2;
}
if (pos_in_dst >= range_length_in_uchars) {
break;
}
}
    }
    else if (IS_NATIVE_UTF16_ENC(self->encoding)) {
memcpy(buffer,
&self->bytes[UCHARS_TO_BYTES(range_start_offset_in_uchars)],
UCHARS_TO_BYTES(range_length_in_uchars));
    }
    else {
__block long pos_in_src = 0;
__block long pos_in_dst = 0;
str_each_uchar32(self, ^(UChar32 c, long start_index, long char_len, bool *stop) {
if (pos_in_src >= range_start_offset_in_uchars) {
if (c == U_SENTINEL) {
if (char_len == 1) {
buffer[pos_in_dst++] = self->bytes[start_index];
}
else {
UChar accumulator = 0;
if (self->encoding->little_endian) {
for (long i = char_len-1; i >= 0; --i) {
accumulator = accumulator << 8
| self->bytes[start_index+i];
}
}
else {
for (long i = 0; i < char_len; ++i) {
accumulator = accumulator << 8
| self->bytes[start_index+i];
}
}
buffer[pos_in_dst++] = accumulator;
}
}
else if (U_IS_BMP(c)) {
buffer[pos_in_dst++] = c;
}
else {
buffer[pos_in_dst++] = U16_LEAD(c);
if (pos_in_dst < range_length_in_uchars) {
buffer[pos_in_dst++] = U16_TRAIL(c);
}
}
}
if ((c == U_SENTINEL) || U_IS_BMP(c)) {
pos_in_src++;
}
else {
if (pos_in_src + 1 == range_start_offset_in_uchars) {
buffer[pos_in_dst++] = U16_TRAIL(c);
}
pos_in_src += 2;
}
if (pos_in_dst >= range_length_in_uchars) {
*stop = true;
}
});
assert(pos_in_dst == range_length_in_uchars);
    }
}

void
rb_str_get_uchars_always(VALUE str, rb_str_uchars_buf_t *buf)
{
    long len = 0;

    buf->chars = NULL;

    if (IS_RSTR(str)) {
rb_str_t *rstr = RSTR(str);
if (rstr->length_in_bytes > 0) {
len = str_length(rstr);
if (IS_NATIVE_UTF16_ENC(rstr->encoding)) {
buf->chars = (UChar *)rstr->bytes;
}
else {
if (len > STR_UCHARS_STATIC_BUFSIZE) {
buf->chars = (UChar *)xmalloc(sizeof(UChar) * len);
assert(buf->chars != NULL);
}
else {
buf->chars = buf->static_buf;
}
str_extract_uchars_range(rstr, 0, len, buf->chars);
}
}
    }
    else {
len = CFStringGetLength((CFStringRef)str);
if (len > 0) {
if (len > STR_UCHARS_STATIC_BUFSIZE) {
buf->chars = (UChar *)xmalloc(sizeof(UChar) * len);
assert(buf->chars != NULL);
}
else {
buf->chars = buf->static_buf;
}
CFStringGetCharacters((CFStringRef)str, CFRangeMake(0, len),
buf->chars);
}
    }

    buf->len = len;
}

UChar *
rb_str_xcopy_uchars(VALUE str, long *len_p)
{
    UChar *chars = NULL;
    long len = 0;

    if (IS_RSTR(str)) {
rb_str_t *rstr = RSTR(str);
len = str_length(rstr);
if (len > 0) {
chars = (UChar *)xmalloc(sizeof(UChar) * len);
str_extract_uchars_range(rstr, 0, len, chars);
}
    }
    else {
len = CFStringGetLength((CFStringRef)str);
if (len > 0) {
chars = (UChar *)xmalloc(sizeof(UChar) * len);
CFStringGetCharacters((CFStringRef)str, CFRangeMake(0, len),
chars);
}
    }

    if (len_p != NULL) {
*len_p = len;
    }
    return chars;
}

static VALUE
rstr_substr_with_cache(VALUE str, long beg, long len,
character_boundaries_cache_t *cache)
{
    if (len < 0) {
return Qnil;
    }

    const long n = str_length_with_cache(RSTR(str), cache);
    if (beg < 0) {
beg += n;
    }
    if (beg > n || beg < 0) {
return Qnil;
    }
    if (len == 0 || beg == n) {
return str_new_empty(str);
    }
    if (beg + len > n) {
len = n - beg;
    }

    rb_str_t *substr = str_get_characters(RSTR(str), beg, beg + len - 1, cache);
    OBJ_INFECT(substr, str);
    return substr == NULL ? Qnil : (VALUE)substr;
}

static VALUE
rstr_substr(VALUE str, long beg, long len)
{
    return rstr_substr_with_cache(str, beg, len, NULL);
}

static void
rstr_splice(VALUE self, long beg, long len, VALUE str)
{
    rb_str_t *strstr = str_need_string(str);

    if (len < 0) {
rb_raise(rb_eIndexError, "negative length %ld", len);
    }

    const long slen = str_length(RSTR(self));
    if (slen < beg) {
out_of_range:
rb_raise(rb_eIndexError, "index %ld out of string", beg);
    }
    if (beg < 0) {
if (-beg > slen) {
goto out_of_range;
}
beg += slen;
    }
    if (slen < len || slen < beg + len) {
len = slen - beg;
    }

    rstr_modify(self);

    str_splice(RSTR(self), beg, len, strstr);

    OBJ_INFECT(self, strstr);
}

static void
rstr_append(VALUE str, VALUE substr)
{
    str_concat_string(RSTR(str), str_need_string(substr));
    OBJ_INFECT(str, substr);
}

static void inline
str_concat_ascii_cstr(rb_str_t *self, char *cstr)
{
    str_reset_flags(self);
    long len = strlen(cstr);
    if (self->encoding->ascii_compatible) {
str_concat_bytes(self, cstr, len);
    }
    else {
rb_str_t *str = RSTR(rb_enc_str_new(cstr, len, rb_encodings[ENCODING_ASCII]));
str = str_simple_transcode(str, self->encoding);
str_concat_bytes(self, str->bytes, str->length_in_bytes);
    }
}

rb_str_t *
str_transcode(rb_str_t *self, rb_encoding_t *src_encoding, rb_encoding_t *dst_encoding,
int behavior_for_invalid, int behavior_for_undefined, rb_str_t *replacement_str)
{
    if ((behavior_for_invalid == TRANSCODE_BEHAVIOR_REPLACE_WITH_STRING)
|| (behavior_for_undefined == TRANSCODE_BEHAVIOR_REPLACE_WITH_STRING)) {
assert(replacement_str != NULL);
assert(replacement_str->encoding != NULL);
assert((replacement_str->length_in_bytes == 0) || (replacement_str->encoding == dst_encoding));
    }

    rb_str_t *dst_str = str_alloc(rb_cRubyString);
    dst_str->encoding = dst_encoding;

    if ((self->length_in_bytes == 0) &&
(behavior_for_undefined != TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_ATTR)) {
return dst_str;
    }

    rb_encoding_t *src_encoding_used;
    rb_encoding_t *dst_encoding_used;
    if (IS_BINARY_ENC(dst_encoding)) {
dst_encoding_used = rb_encodings[ENCODING_ASCII];
    }
    else {
dst_encoding_used = dst_encoding;
    }
    if (IS_BINARY_ENC(src_encoding)) {
src_encoding_used = rb_encodings[ENCODING_ASCII];
    }
    else {
src_encoding_used = src_encoding;
    }

    if (behavior_for_undefined == TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_ATTR) {
str_concat_ascii_cstr(dst_str, "\"");
    }

    long pos_in_src = 0;
    for (;;) {
UChar *utf16;
long utf16_length;
// we need to transcode even if the source encoding is native UTF-16
// because it could contain invalid bytes
str_ucnv_transcode_to_utf16(src_encoding_used,
self, &pos_in_src, &utf16, &utf16_length);

if (utf16_length > 0) {
if ((behavior_for_undefined == TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_TEXT)
|| (behavior_for_undefined == TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_ATTR)) {
long new_utf16_length = 0;
for (long i = 0; i < utf16_length; ++i) {
switch (utf16[i]) {
case '&':
new_utf16_length += 5;
break;
case '<':
case '>':
new_utf16_length += 4;
break;
case '"':
if (behavior_for_undefined == TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_ATTR) {
new_utf16_length += 6;
}
else {
++new_utf16_length;
}
break;
default:
++new_utf16_length;
}
}
if (new_utf16_length != utf16_length) {
UChar *new_utf16 = xmalloc(UCHARS_TO_BYTES(new_utf16_length));
long new_utf16_pos = 0;
for (long i = 0; i < utf16_length; ++i) {
switch (utf16[i]) {
case '&':
new_utf16[new_utf16_pos++] = '&';
new_utf16[new_utf16_pos++] = 'a';
new_utf16[new_utf16_pos++] = 'm';
new_utf16[new_utf16_pos++] = 'p';
new_utf16[new_utf16_pos++] = ';';
break;
case '<':
new_utf16[new_utf16_pos++] = '&';
new_utf16[new_utf16_pos++] = 'l';
new_utf16[new_utf16_pos++] = 't';
new_utf16[new_utf16_pos++] = ';';
break;
case '>':
new_utf16[new_utf16_pos++] = '&';
new_utf16[new_utf16_pos++] = 'g';
new_utf16[new_utf16_pos++] = 't';
new_utf16[new_utf16_pos++] = ';';
break;
case '"':
if (behavior_for_undefined == TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_ATTR) {
new_utf16[new_utf16_pos++] = '&';
new_utf16[new_utf16_pos++] = 'q';
new_utf16[new_utf16_pos++] = 'u';
new_utf16[new_utf16_pos++] = 'o';
new_utf16[new_utf16_pos++] = 't';
new_utf16[new_utf16_pos++] = ';';
}
else {
new_utf16[new_utf16_pos++] = utf16[i];
}
break;
default:
new_utf16[new_utf16_pos++] = utf16[i];
}
}
utf16_length = new_utf16_length;
utf16 = new_utf16;
}
}

long utf16_pos = 0;
for (;;) {
long bytes_length;
char *bytes;
str_ucnv_transcode_from_utf16(dst_encoding_used,
utf16, utf16_length, &utf16_pos, &bytes, &bytes_length);
if (bytes_length > 0) {
str_concat_bytes(dst_str, bytes, bytes_length);
}
if (utf16_pos < utf16_length) {
// undefined char
UChar32 c;
U16_NEXT(utf16, utf16_pos, utf16_length, c);
switch (behavior_for_undefined) {
case TRANSCODE_BEHAVIOR_RAISE_EXCEPTION:
rb_raise(rb_eUndefinedConversionError, "U+%04X from %s to %s", c, src_encoding->public_name, dst_encoding->public_name);
break;
case TRANSCODE_BEHAVIOR_REPLACE_WITH_STRING:
if (replacement_str->length_in_bytes > 0) {
str_concat_bytes(dst_str, replacement_str->bytes, replacement_str->length_in_bytes);
}
break;
case TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_TEXT:
case TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_ATTR:
{
char xml[10];
snprintf(xml, 10, "&#x%X;", c);
str_concat_ascii_cstr(dst_str, xml);
}
break;
default:
abort();
}
}
if (utf16_pos == utf16_length) {
break;
}
}
}

if (pos_in_src < self->length_in_bytes) {
// invalid bytes
long invalid_bytes_length = src_encoding->min_char_size;
if (invalid_bytes_length + pos_in_src > self->length_in_bytes) {
invalid_bytes_length = self->length_in_bytes - pos_in_src;
}
switch (behavior_for_invalid) {
case TRANSCODE_BEHAVIOR_RAISE_EXCEPTION:
{
char *bytes_list = xmalloc(invalid_bytes_length * 4);
char *bytes_list_pos = bytes_list;
for (long i = 0; i < invalid_bytes_length; ++i) {
sprintf(bytes_list_pos, "\\x%02X", (unsigned char)self->bytes[pos_in_src+i]);
bytes_list_pos += 4;
}
rb_raise(rb_eInvalidByteSequenceError, "\"%s\" on %s", bytes_list, src_encoding->public_name);
}
break;
case TRANSCODE_BEHAVIOR_REPLACE_WITH_STRING:
if (replacement_str->length_in_bytes > 0) {
str_concat_bytes(dst_str, replacement_str->bytes, replacement_str->length_in_bytes);
}
break;
default:
abort();
}
pos_in_src += invalid_bytes_length;
}

if (pos_in_src == self->length_in_bytes) {
break;
}
    }

    if (behavior_for_undefined == TRANSCODE_BEHAVIOR_REPLACE_WITH_XML_ATTR) {
str_concat_ascii_cstr(dst_str, "\"");
    }

    return dst_str;
}


//----------------------------------------------
// Functions called by MacRuby

VALUE
mr_enc_s_is_compatible(VALUE klass, SEL sel, VALUE str1, VALUE str2)
{
    rb_encoding_t *encoding = str_compatible_encoding(str_need_string(str1),
str_need_string(str2));
    if (encoding == NULL) {
return Qnil;
    }
    return (VALUE)encoding;
}

static VALUE
rstr_alloc(VALUE klass, SEL sel)
{
    return (VALUE)str_alloc(klass);
}

/*
* call-seq:
* String.try_convert(obj) -> string or nil
*
* Try to convert <i>obj</i> into a String, using to_str method.
* Returns converted regexp or nil if <i>obj</i> cannot be converted
* for any reason.
*
* String.try_convert("str") # => str
* String.try_convert(/re/) # => nil
*/

static VALUE
rstr_try_convert(VALUE self, SEL sel, VALUE other)
{
    return rb_check_string_type(other);
}

/*
* call-seq:
* str.replace(other_str) => str
*
* Replaces the contents and taintedness of <i>str</i> with the corresponding
* values in <i>other_str</i>.
*
* s = "hello" #=> "hello"
* s.replace "world" #=> "world"
*/

static VALUE
rstr_replace(VALUE self, SEL sel, VALUE arg)
{
    rstr_modify(self);
    if (self != arg) {
str_replace(RSTR(self), arg);
OBJ_INFECT(self, arg);
    }
    return self;
}

/*
* call-seq:
* String.new(str="") => new_str
*
* Returns a new string object containing a copy of <i>str</i>.
*/

static VALUE
rstr_initialize(VALUE self, SEL sel, int argc, VALUE *argv)
{
    VALUE orig;
    if (argc > 0 && rb_scan_args(argc, argv, "01", &orig) == 1) {
rstr_replace(self, 0, orig);
    }
    return self;
}

static VALUE
rstr_dup(VALUE str, SEL sel)
{
    VALUE klass = CLASS_OF(str);
    while (RCLASS_SINGLETON(klass)) {
klass = RCLASS_SUPER(klass);
    }
    assert(rb_klass_is_rstr(klass));

    VALUE dup = rstr_alloc(klass, 0);
    rb_obj_invoke_initialize_copy(dup, str);

    OBJ_INFECT(dup, str);
    return dup;
}

/*
* call-seq:
* string.clear -> string
*
* Makes string empty.
*
* a = "abcde"
* a.clear #=> ""
*/

static VALUE
rstr_clear(VALUE self, SEL sel)
{
    rstr_modify(self);
    RSTR(self)->length_in_bytes = 0;
    return self;
}

/*
* call-seq:
* str.length => integer
* str.size => integer
*
* Returns the character length of <i>str</i>.
*/

static VALUE
rstr_length(VALUE self, SEL sel)
{
    return INT2NUM(str_length(RSTR(self)));
}

/*
* call-seq:
* str.empty? => true or false
*
* Returns <code>true</code> if <i>str</i> has a length of zero.
*
* "hello".empty? #=> false
* "".empty? #=> true
*/

static VALUE
rstr_empty(VALUE self, SEL sel)
{
    return RSTR(self)->length_in_bytes == 0 ? Qtrue : Qfalse;
}

/*
* call-seq:
* str.bytesize => integer
*
* Returns the length of <i>str</i> in bytes.
*/

static VALUE
rstr_bytesize(VALUE self, SEL sel)
{
    return INT2NUM(str_bytesize(RSTR(self)));
}

static VALUE
rstr_encoding(VALUE self, SEL sel)
{
    return (VALUE)RSTR(self)->encoding;
}

/*
* call-seq:
* str.getbyte(index) => 0 .. 255
*
* returns the <i>index</i>th byte as an integer.
*/

static VALUE
rstr_getbyte(VALUE self, SEL sel, VALUE index)
{
    unsigned char c = 0;
    long idx = NUM2LONG(index);

    if (idx < 0) {
idx += RSTR(self)->length_in_bytes;
if (idx < 0) {
return Qnil;
}
    }
    if (idx >= RSTR(self)->length_in_bytes) {
return Qnil;
    }
    c = RSTR(self)->bytes[idx];

    return INT2FIX(c);
}

/*
* call-seq:
* str.setbyte(index, int) => int
*
* modifies the <i>index</i>th byte as <i>int</i>.
*/

static VALUE
rstr_setbyte(VALUE self, SEL sel, VALUE idx, VALUE value)
{
    rstr_modify(self);

    long index = NUM2LONG(idx);
    int byte = NUM2INT(value);
    if ((index < -RSTR(self)->length_in_bytes)
|| (index >= RSTR(self)->length_in_bytes)) {
rb_raise(rb_eIndexError, "index %ld out of string", index);
    }
    if (index < 0) {
index += RSTR(self)->length_in_bytes;
    }
    str_reset_flags(RSTR(self));
    RSTR(self)->bytes[index] = byte;
    return value;
}

/*
* call-seq:
* str.to_data => NSData
*
* returns an NSData object wrapping the receiver's internal storage.
*
*/

static VALUE
rstr_to_data(VALUE self, SEL sel)
{
    CFDataRef data = CFDataCreate(NULL, (const UInt8 *)RSTR(self)->bytes,
RSTR(self)->length_in_bytes);
    CFMakeCollectable(data);
    return (VALUE)data;
}

/*
* call-seq:
* str.pointer => Pointer
*
* returns a Pointer object wrapping the receiver's internal storage (be
* very careful, changing the pointer will change the original string's
* content!).
*/

static VALUE
rstr_pointer(VALUE self, SEL sel)
{
    return rb_pointer_new("C", RSTR(self)->bytes,
RSTR(self)->length_in_bytes);
}

/*
* call-seq:
* str.force_encoding(encoding) => str
*
* Changes the encoding to +encoding+ and returns self.
*/

void
rb_str_force_encoding(VALUE str, rb_encoding_t *enc)
{
    assert(IS_RSTR(str));
    if (enc != RSTR(str)->encoding) {
RSTR(str)->encoding = enc;
str_reset_flags(RSTR(str));
    }
}

static VALUE
rstr_force_encoding(VALUE self, SEL sel, VALUE encoding)
{
    rstr_modify(self);
    rb_str_force_encoding(self, rb_to_encoding(encoding));
    return self;
}

/*
* call-seq:
* str.valid_encoding? => true or false
*
* Returns true for a string which encoded correctly.
*
* "\xc2\xa1".force_encoding("UTF-8").valid_encoding? => true
* "\xc2".force_encoding("UTF-8").valid_encoding? => false
* "\x80".force_encoding("UTF-8").valid_encoding? => false
*/

static VALUE
rstr_is_valid_encoding(VALUE self, SEL sel)
{
    return str_is_valid_encoding(RSTR(self)) ? Qtrue : Qfalse;
}

/*
* call-seq:
* str.ascii_only? => true or false
*
* Returns true for a string which has only ASCII characters.
*
* "abc".force_encoding("UTF-8").ascii_only? => true
* "abc\u{6666}".force_encoding("UTF-8").ascii_only? => false
*/

static VALUE
rstr_is_ascii_only(VALUE self, SEL sel)
{
    return str_is_ruby_ascii_only(RSTR(self)) ? Qtrue : Qfalse;
}


/*
* call-seq:
* str[fixnum] => new_str or nil
* str[fixnum, fixnum] => new_str or nil
* str[range] => new_str or nil
* str[regexp] => new_str or nil
* str[regexp, fixnum] => new_str or nil
* str[other_str] => new_str or nil
* str.slice(fixnum) => new_str or nil
* str.slice(fixnum, fixnum) => new_str or nil
* str.slice(range) => new_str or nil
* str.slice(regexp) => new_str or nil
* str.slice(regexp, fixnum) => new_str or nil
* str.slice(other_str) => new_str or nil
*
* Element Reference---If passed a single <code>Fixnum</code>, returns a
* substring of one character at that position. If passed two <code>Fixnum</code>
* objects, returns a substring starting at the offset given by the first, and
* a length given by the second. If given a range, a substring containing
* characters at offsets given by the range is returned. In all three cases, if
* an offset is negative, it is counted from the end of <i>str</i>. Returns
* <code>nil</code> if the initial offset falls outside the string, the length
* is negative, or the beginning of the range is greater than the end.
*
* If a <code>Regexp</code> is supplied, the matching portion of <i>str</i> is
* returned. If a numeric parameter follows the regular expression, that
* component of the <code>MatchData</code> is returned instead. If a
* <code>String</code> is given, that string is returned if it occurs in
* <i>str</i>. In both cases, <code>nil</code> is returned if there is no
* match.
*
* a = "hello there"
* a[1] #=> "e"
* a[1,3] #=> "ell"
* a[1..3] #=> "ell"
* a[-3,2] #=> "er"
* a[-4..-2] #=> "her"
* a[12..-1] #=> nil
* a[-2..-4] #=> ""
* a[/[aeiou](.)\1/] #=> "ell"
* a[/[aeiou](.)\1/, 0] #=> "ell"
* a[/[aeiou](.)\1/, 1] #=> "l"
* a[/[aeiou](.)\1/, 2] #=> nil
* a["lo"] #=> "lo"
* a["bye"] #=> nil
*/

static VALUE
rb_str_subpat(VALUE str, VALUE re, int nth)
{
    if (rb_reg_search(re, str, 0, false) >= 0) {
return rb_reg_nth_match(nth, rb_backref_get());
    }
    return Qnil;
}

VALUE
rstr_aref(VALUE str, SEL sel, int argc, VALUE *argv)
{
    VALUE result = Qnil;
    bool tainted = OBJ_TAINTED(str);

    if (argc == 2) {
if (TYPE(argv[0]) == T_REGEXP) {
result = rb_str_subpat(str, argv[0], NUM2INT(argv[1]));
}
else {
result = rstr_substr(str, NUM2LONG(argv[0]), NUM2LONG(argv[1]));
}
goto bail;
    }

    if (argc != 1) {
rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }

    VALUE indx = argv[0];
    switch (TYPE(indx)) {
case T_FIXNUM:
result = rstr_substr(str, FIX2LONG(indx), 1);
if (NIL_P(result) || rb_str_chars_len(result) == 0) {
return Qnil;
}
break;

case T_REGEXP:
result = rb_str_subpat(str, indx, 0);
break;

case T_STRING:
{
tainted = false;
if (IS_RSTR(indx)) {
rb_str_t *searched = RSTR(indx);
if (str_include_string(RSTR(str), searched)) {
result = (VALUE)str_dup(searched);
SET_CLASS(result, searched);
goto bail;
}
}
else {
rb_str_t *searched =
str_new_from_cfstring((CFStringRef)indx);
if (str_include_string(RSTR(str), searched)) {
// no need to duplicate the string as we just
// created it
result = (VALUE)searched;
goto bail;
}
}
return Qnil;
}

default:
{
long beg = 0, len = 0;
switch (rb_range_beg_len(indx, &beg, &len,
str_length(RSTR(str)), 0)) {
case Qfalse:
break;
case Qnil:
return Qnil;
default:
result = rstr_substr(str, beg, len);
goto bail;
}
result = rstr_substr(str, NUM2LONG(indx), 1);
if (NIL_P(result) || rb_str_chars_len(result) == 0) {
return Qnil;
}
break;
}
    }

bail:
    if (!tainted) {
for (int i = 0; i < argc; i++) {
if (OBJ_TAINTED(argv[i])) {
tainted = true;
break;
}
}
    }
    if (tainted) {
OBJ_TAINT(result);
    }
    return result;
}

/*
* call-seq:
* str[fixnum] = new_str
* str[fixnum, fixnum] = new_str
* str[range] = aString
* str[regexp] = new_str
* str[regexp, fixnum] = new_str
* str[other_str] = new_str
*
* Element Assignment---Replaces some or all of the content of <i>str</i>. The
* portion of the string affected is determined using the same criteria as
* <code>String#[]</code>. If the replacement string is not the same length as
* the text it is replacing, the string will be adjusted accordingly. If the
* regular expression or string is used as the index doesn't match a position
* in the string, <code>IndexError</code> is raised. If the regular expression
* form is used, the optional second <code>Fixnum</code> allows you to specify
* which portion of the match to replace (effectively using the
* <code>MatchData</code> indexing rules. The forms that take a
* <code>Fixnum</code> will raise an <code>IndexError</code> if the value is
* out of range; the <code>Range</code> form will raise a
* <code>RangeError</code>, and the <code>Regexp</code> and <code>String</code>
* forms will silently ignore the assignment.
*/

static void
rb_str_subpat_set(VALUE str, VALUE re, int nth, VALUE val)
{
    if (rb_reg_search(re, str, 0, false) < 0) {
rb_raise(rb_eIndexError, "regexp not matched");
    }
    VALUE match = rb_backref_get();

    int count = 0;
    rb_match_result_t *results = rb_reg_match_results(match, &count);
    assert(count > 0);

    if (nth >= count) {
out_of_range:
rb_raise(rb_eIndexError, "index %d out of regexp", nth);
    }
    if (nth < 0) {
if (-nth >= count) {
goto out_of_range;
}
nth += count;
    }

    const long start = results[nth].beg;
    if (start == -1) {
rb_raise(rb_eIndexError, "regexp group %d not matched", nth);
    }
    const long end = results[nth].end;
    const long len = end - start;
    rstr_splice(str, start, len, val);
}

static VALUE
rstr_aset(VALUE str, SEL sel, int argc, VALUE *argv)
{
    if (argc == 3) {
if (TYPE(argv[0]) == T_REGEXP) {
rb_str_subpat_set(str, argv[0], NUM2INT(argv[1]), argv[2]);
}
else {
rstr_splice(str, NUM2LONG(argv[0]), NUM2LONG(argv[1]),
argv[2]);
}
return argv[2];
    }

    if (argc != 2) {
rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }

    VALUE indx = argv[0];
    VALUE val = argv[1];
    long pos = 0;

    switch (TYPE(indx)) {
case T_FIXNUM:
pos = FIX2LONG(indx);
num_index:
rstr_splice(str, pos, 1, val);
return val;

case T_REGEXP:
rb_str_subpat_set(str, indx, 0, val);
return val;

case T_STRING:
pos = str_index_for_string(RSTR(str), str_need_string(indx),
0, -1, false);
if (pos < 0) {
rb_raise(rb_eIndexError, "string not matched");
}
rstr_splice(str, pos, rb_str_chars_len(indx), val);
return val;

default:
/* check if indx is Range */
{
long beg, len;
if (rb_range_beg_len(indx, &beg, &len,
str_length(RSTR(str)), 2)) {
rstr_splice(str, beg, len, val);
return val;
}
}
pos = NUM2LONG(indx);
goto num_index;
    }
}

/*
* call-seq:
* str.slice!(fixnum) => fixnum or nil
* str.slice!(fixnum, fixnum) => new_str or nil
* str.slice!(range) => new_str or nil
* str.slice!(regexp) => new_str or nil
* str.slice!(other_str) => new_str or nil
*
* Deletes the specified portion from <i>str</i>, and returns the portion
* deleted.
*
* string = "this is a string"
* string.slice!(2) #=> "i"
* string.slice!(3..6) #=> " is "
* string.slice!(/s.*t/) #=> "sa st"
* string.slice!("r") #=> "r"
* string #=> "thing"
*/

static VALUE
rstr_slice_bang(VALUE str, SEL sel, int argc, VALUE *argv)
{
    if (argc < 1 || 2 < argc) {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }

    rstr_modify(str);

    int i;
    VALUE buf[3];
    for (i=0; i < argc; i++) {
        buf[i] = argv[i];
    }
    buf[i] = rb_str_new(NULL, 0);

    VALUE result = rstr_aref(str, 0, argc, buf);
    if (!NIL_P(result)) {
        rstr_aset(str, 0, argc + 1, buf);
    }
    return result;
}

/*
* call-seq:
* str.insert(index, other_str) => str
*
* Inserts <i>other_str</i> before the character at the given
* <i>index</i>, modifying <i>str</i>. Negative indices count from the
* end of the string, and insert <em>after</em> the given character.
* The intent is insert <i>aString</i> so that it starts at the given
* <i>index</i>.
*
* "abcd".insert(0, 'X') #=> "Xabcd"
* "abcd".insert(3, 'X') #=> "abcXd"
* "abcd".insert(4, 'X') #=> "abcdX"
* "abcd".insert(-3, 'X') #=> "abXcd"
* "abcd".insert(-1, 'X') #=> "abcdX"
*/

static VALUE
rstr_insert(VALUE str, SEL sel, VALUE idx, VALUE substr)
{
    long pos = NUM2LONG(idx);
    if (pos == -1) {
rstr_append(str, substr);
    }
    else {
if (pos < 0) {
pos++;
}
rstr_splice(str, pos, 0, substr);
    }
    return str;
}

/*
* call-seq:
* str.index(substring [, offset]) => fixnum or nil
* str.index(fixnum [, offset]) => fixnum or nil
* str.index(regexp [, offset]) => fixnum or nil
*
* Returns the index of the first occurrence of the given <i>substring</i>,
* character (<i>fixnum</i>), or pattern (<i>regexp</i>) in <i>str</i>. Returns
* <code>nil</code> if not found. If the second parameter is present, it
* specifies the position in the string to begin the search.
*
* "hello".index('e') #=> 1
* "hello".index('lo') #=> 3
* "hello".index('a') #=> nil
* "hello".index(?e) #=> 1
* "hello".index(101) #=> 1
* "hello".index(/[aeiou]/, -3) #=> 4
*/

static VALUE
rstr_index(VALUE self, SEL sel, int argc, VALUE *argv)
{
    const long len = str_length(RSTR(self));
    VALUE sub, initpos;
    long pos;

    if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
pos = NUM2LONG(initpos);
if (pos < 0) {
pos += len;
}
if (pos < 0) {
if (TYPE(sub) == T_REGEXP) {
rb_backref_set(Qnil);
}
return Qnil;
}
    }
    else {
pos = 0;
    }

    switch (TYPE(sub)) {
case T_REGEXP:
if (pos > len) {
return Qnil;
}
pos = rb_reg_search(sub, self, pos, false);
break;

default:
StringValue(sub);
// fall through
case T_STRING:
if (pos == len && rb_str_chars_len(sub) == 0) {
// Do nothing... RubySpec compliance...
}
else {
pos = str_index_for_string(RSTR(self), str_need_string(sub),
pos, -1, false);
}
break;
    }

    return pos >= 0 ? LONG2NUM(pos) : Qnil;
}

/*
* call-seq:
* str.rindex(substring [, fixnum]) => fixnum or nil
* str.rindex(fixnum [, fixnum]) => fixnum or nil
* str.rindex(regexp [, fixnum]) => fixnum or nil
*
* Returns the index of the last occurrence of the given <i>substring</i>,
* character (<i>fixnum</i>), or pattern (<i>regexp</i>) in <i>str</i>. Returns
* <code>nil</code> if not found. If the second parameter is present, it
* specifies the position in the string to end the search---characters beyond
* this point will not be considered.
*
* "hello".rindex('e') #=> 1
* "hello".rindex('l') #=> 3
* "hello".rindex('a') #=> nil
* "hello".rindex(?e) #=> 1
* "hello".rindex(101) #=> 1
* "hello".rindex(/[aeiou]/, -2) #=> 1
*/

static VALUE
rstr_rindex(VALUE self, SEL sel, int argc, VALUE *argv)
{
    const long len = str_length(RSTR(self));
    VALUE sub, initpos;
    long pos;

    if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
pos = NUM2LONG(initpos);
if (pos < 0) {
pos += len;
if (pos < 0) {
if (TYPE(sub) == T_REGEXP) {
rb_backref_set(Qnil);
}
return Qnil;
}
}
if (pos >= len) {
pos = len;
}
    }
    else {
pos = len;
    }

    switch (TYPE(sub)) {
case T_REGEXP:
pos = rb_reg_search(sub, self, pos, true);
break;

default:
StringValue(sub);
// fall through
case T_STRING:
if (rb_str_chars_len(sub) > 0) {
pos = str_index_for_string(RSTR(self), str_need_string(sub),
0, pos, true);
}
break;
    }

    return pos >= 0 ? LONG2NUM(pos) : Qnil;
}

/*
* call-seq:
* str + other_str => new_str
*
* Concatenation---Returns a new <code>String</code> containing
* <i>other_str</i> concatenated to <i>str</i>.
*
* "Hello from " + self.to_s #=> "Hello from main"
*/

static VALUE
rstr_plus(VALUE self, SEL sel, VALUE other)
{
    StringValue(other);

    rb_str_t *newstr = str_dup(RSTR(self));
    rb_str_t *otherstr = str_need_string(other);
    str_concat_string(newstr, otherstr);
    if (OBJ_TAINTED(self) || OBJ_TAINTED(other)) {
OBJ_TAINT(newstr);
    }
    return (VALUE)newstr;
}

/*
* call-seq:
* str * integer => new_str
*
* Copy---Returns a new <code>String</code> containing <i>integer</i> copies of
* the receiver.
*
* "Ho! " * 3 #=> "Ho! Ho! Ho! "
*/

static VALUE
rstr_times(VALUE self, SEL sel, VALUE times)
{
    const long n = NUM2LONG(times);
    if (n < 0) {
rb_raise(rb_eArgError, "negative argument");
    }
    if (n > 0 && LONG_MAX/n < RSTR(self)->length_in_bytes) {
rb_raise(rb_eArgError, "argument too big");
    }

    VALUE new = str_new_like(self);
    str_resize_bytes(RSTR(new), n * RSTR(self)->length_in_bytes);
    if (n) {
str_concat_string(RSTR(new), RSTR(self));
long i;
for (i = 1; i <= n/2; i *= 2) {
str_concat_string(RSTR(new), RSTR(new));
}
memcpy(RSTR(new)->bytes + RSTR(new)->length_in_bytes,
RSTR(new)->bytes,
(n - i) * RSTR(self)->length_in_bytes);
RSTR(new)->length_in_bytes = n * RSTR(self)->length_in_bytes;
    }
    OBJ_INFECT(new, self);
    return new;
}

/*
* call-seq:
* str % arg => new_str
*
* Format---Uses <i>str</i> as a format specification, and returns the result
* of applying it to <i>arg</i>. If the format specification contains more than
* one substitution, then <i>arg</i> must be an <code>Array</code> containing
* the values to be substituted. See <code>Kernel::sprintf</code> for details
* of the format string.
*
* "%05d" % 123 #=> "00123"
* "%-5s: %08x" % [ "ID", self.object_id ] #=> "ID : 200e14d6"
*/

static VALUE
rstr_format(VALUE str, SEL sel, VALUE arg)
{
    VALUE tmp = rb_check_array_type(arg);

    if (!NIL_P(tmp)) {
return rb_str_format(RARRAY_LEN(tmp), RARRAY_PTR(tmp), str);
    }
    return rb_str_format(1, &arg, str);
}

/*
* call-seq:
* str << fixnum => str
* str.concat(fixnum) => str
* str << obj => str
* str.concat(obj) => str
*
* Append---Concatenates the given object to <i>str</i>. If the object is a
* <code>Fixnum</code>, it is considered as a codepoint, and is converted
* to a character before concatenation.
*
* a = "hello "
* a << "world" #=> "hello world"
* a.concat(33) #=> "hello world!"
*/

VALUE
rstr_concat(VALUE self, SEL sel, VALUE other)
{
    rstr_modify(self);

    long codepoint = 0;
    switch (TYPE(other)) {
case T_FIXNUM:
codepoint = FIX2LONG(other);
break;

case T_BIGNUM:
codepoint = rb_big2ulong(other);
break;

default:
rstr_append(self, other);
return self;
    }

    if (IS_UTF8_ENC(RSTR(self)->encoding)) {
const int bytelen = U8_LENGTH(codepoint);
if (bytelen <= 0) {
goto out_of_range;
}
uint8_t *buf = (uint8_t *)malloc(bytelen);
assert(buf != NULL);
int offset = 0;
UBool error = false;
U8_APPEND(buf, offset, bytelen, codepoint, error);
if (error) {
free(buf);
goto out_of_range;
}
str_reset_flags(RSTR(self));
str_concat_bytes(RSTR(self), (const char *)buf, bytelen);
free(buf);
    }
    else {
rb_raise(rb_eArgError,
"receiver encoding `%s' not supported for codepoint insertion",
RSTRING_PTR(rb_inspect((VALUE)RSTR(self)->encoding)));
    }

    return self;

out_of_range:
    rb_raise(rb_eArgError, "codepoint %ld out of range", codepoint);
}

/*
* call-seq:
* str == obj => true or false
*
* Equality---If <i>obj</i> is not a <code>String</code>, returns
* <code>false</code>. Otherwise, returns <code>true</code> if <i>str</i>
* <code><=></code> <i>obj</i> returns zero.
*/

static VALUE
rstr_equal(VALUE self, SEL sel, VALUE other)
{
    if (self == other) {
return Qtrue;
    }
    if (TYPE(other) != T_STRING) {
if (!rb_respond_to(other, rb_intern("to_str"))) {
return Qfalse;
}
return rb_equal(other, self);
    }
    return str_compare(RSTR(self), str_need_string(other)) == 0
? Qtrue : Qfalse;
}

/*
* call-seq:
* str <=> other_str => -1, 0, +1
*
* Comparison---Returns -1 if <i>other_str</i> is less than, 0 if
* <i>other_str</i> is equal to, and +1 if <i>other_str</i> is greater than
* <i>str</i>. If the strings are of different lengths, and the strings are
* equal when compared up to the shortest length, then the longer string is
* considered greater than the shorter one. In older versions of Ruby, setting
* <code>$=</code> allowed case-insensitive comparisons; this is now deprecated
* in favor of using <code>String#casecmp</code>.
*
* <code><=></code> is the basis for the methods <code><</code>,
* <code><=</code>, <code>></code>, <code>>=</code>, and <code>between?</code>,
* included from module <code>Comparable</code>. The method
* <code>String#==</code> does not use <code>Comparable#==</code>.
*
* "abcdef" <=> "abcde" #=> 1
* "abcdef" <=> "abcdef" #=> 0
* "abcdef" <=> "abcdefg" #=> -1
* "abcdef" <=> "ABCDEF" #=> 1
*/

static VALUE
rstr_cmp(VALUE self, SEL sel, VALUE other)
{
    long result;

    if (TYPE(other) != T_STRING) {
if (!rb_respond_to(other, rb_intern("to_str"))) {
return Qnil;
}
else if (!rb_vm_respond_to(other, selCmp, false)) {
return Qnil;
}
else {
VALUE tmp = rb_vm_call(other, selCmp, 1, &self);
if (NIL_P(tmp)) {
return Qnil;
}
if (!FIXNUM_P(tmp)) {
return rb_vm_call(LONG2FIX(0), selMINUS, 1, &tmp);
}
result = -FIX2LONG(tmp);
}
    }
    else {
result = str_compare(RSTR(self), str_need_string(other));
    }
    return LONG2NUM(result);
}

/*
* call-seq:
* str.casecmp(other_str) => -1, 0, +1 or nil
*
* Case-insensitive version of <code>String#<=></code>.
*
* "abcdef".casecmp("abcde") #=> 1
* "aBcDeF".casecmp("abcdef") #=> 0
* "abcdef".casecmp("abcdefg") #=> -1
* "abcdef".casecmp("ABCDEF") #=> 0
*/

static VALUE
rstr_casecmp(VALUE str, SEL sel, VALUE other)
{
    return INT2FIX(str_case_compare(RSTR(str), str_need_string(other)));
}

/*
* call-seq:
* str.eql?(other) => true or false
*
* Two strings are equal if they have the same length and content.
*/

static VALUE
rstr_eql(VALUE self, SEL sel, VALUE other)
{
    if (self == other) {
return Qtrue;
    }
    if (TYPE(other) != T_STRING) {
return Qfalse;
    }
    return str_compare(RSTR(self), str_need_string(other)) == 0
? Qtrue : Qfalse;
}

/*
* call-seq:
* str.include? other_str => true or false
* str.include? fixnum => true or false
*
* Returns <code>true</code> if <i>str</i> contains the given string or
* character.
*
* "hello".include? "lo" #=> true
* "hello".include? "ol" #=> false
* "hello".include? ?h #=> true
*/

static VALUE
rstr_includes(VALUE self, SEL sel, VALUE searched)
{
    return str_include_string(RSTR(self), str_need_string(searched))
? Qtrue : Qfalse;
}

/*
* call-seq:
* str.start_with?([prefix]+) => true or false
*
* Returns true if <i>str</i> starts with the prefix given.
*/

static VALUE
rstr_start_with(VALUE str, SEL sel, int argc, VALUE *argv)
{
    for (int i = 0; i < argc; i++) {
VALUE tmp = rb_check_string_type(argv[i]);
if (NIL_P(tmp)) {
continue;
}
const long pos = str_index_for_string(RSTR(str), str_need_string(tmp),
0, rb_str_chars_len(tmp), false);
if (pos == 0) {
return Qtrue;
}
    }
    return Qfalse;
}

/*
* call-seq:
* str.end_with?([suffix]+) => true or false
*
* Returns true if <i>str</i> ends with the suffix given.
*/

static VALUE
rstr_end_with(VALUE str, SEL sel, int argc, VALUE *argv)
{
    const long len = rb_str_chars_len(str);
    for (int i = 0; i < argc; i++) {
VALUE tmp = rb_check_string_type(argv[i]);
if (NIL_P(tmp)) {
continue;
}
const long sublen = rb_str_chars_len(tmp);
if (sublen > len) {
continue;
}
const long pos = str_index_for_string(RSTR(str), str_need_string(tmp),
len - sublen, len, false);
if (pos == len - sublen) {
return Qtrue;
}
    }
    return Qfalse;
}

/*
* call-seq:
* str.to_s => str
* str.to_str => str
*
* Returns the receiver.
*/

static VALUE
rstr_to_s(VALUE self, SEL sel)
{
    if (CLASS_OF(self) != rb_cRubyString) {
VALUE dup = (VALUE)str_dup(RSTR(self));
OBJ_INFECT(dup, self);
return dup;
    }
    return self;
}

/*
* call-seq:
* str.intern => symbol
* str.to_sym => symbol
*
* Returns the <code>Symbol</code> corresponding to <i>str</i>, creating the
* symbol if it did not previously exist. See <code>Symbol#id2name</code>.
*
* "Koala".intern #=> :Koala
* s = 'cat'.to_sym #=> :cat
* s == :cat #=> true
* s = '@cat'.to_sym #=> :@cat
* s == :@cat #=> true
*
* This can also be used to create symbols that cannot be represented using the
* <code>:xxx</code> notation.
*
* 'cat and dog'.to_sym #=> :"cat and dog"
*/

static VALUE
rstr_intern(VALUE self, SEL sel)
{
    if (OBJ_TAINTED(self) && rb_safe_level() >= 1) {
rb_raise(rb_eSecurityError, "Insecure: can't intern tainted string");
    }
    return rb_str_intern_fast(self);
}

VALUE
rb_str_intern(VALUE self)
{
    return rstr_intern(self, 0);
}
/*
* call-seq:
* str.inspect => string
*
* Returns a printable version of _str_, surrounded by quote marks,
* with special characters escaped.
*
* str = "hello"
* str[3] = "\b"
* str.inspect #=> "\"hel\\bo\""
*/

static void
inspect_append(VALUE result, UChar32 c, bool escape)
{
    if (escape) {
str_append_uchar32(RSTR(result), '\\');
    }
    str_append_uchar32(RSTR(result), c);
}

static VALUE
str_inspect(rb_str_t *str, bool dump)
{
    VALUE result;
    if (str->length_in_bytes == 0) {
result = rb_str_new2("\"\"");
OBJ_INFECT(result, str);
return result;
    }

    const long result_init_len = str->length_in_bytes * 3 / 2;
    result = rb_unicode_str_new(NULL, result_init_len);

    inspect_append(result, '"', false);
    __block UChar32 prev = 0;
    str_each_uchar32(str, ^(UChar32 c, long start_index, long char_len, bool *stop) {
// 1.9 considers U+00AD (soft-hyphen) printable whereas ICU does not
bool print = u_isprint(c) || (c == 0xAD);
if (IS_BINARY_ENC(str->encoding) && c > 127) {
print = false;
}
if (dump && prev == '#') {
inspect_append(result, prev, (c == '$' || c == '@' || c == '{'));
}
if (print) {
if (c == '"' || c == '\\') {
inspect_append(result, c, true);
}
else if (c != '#' || !dump) {
inspect_append(result, c, false);
}
}
else if (c == '\n') {
inspect_append(result, 'n', true);
}
else if (c == '\r') {
inspect_append(result, 'r', true);
}
else if (c == '\t') {
inspect_append(result, 't', true);
}
else if (c == '\f') {
inspect_append(result, 'f', true);
}
else if (c == '\013') {
inspect_append(result, 'v', true);
}
else if (c == '\010') {
inspect_append(result, 'b', true);
}
else if (c == '\007') {
inspect_append(result, 'a', true);
}
else if (c == 033) {
inspect_append(result, 'e', true);
}
else {
char buf[10];
for (long i = 0; i < char_len; ++i) {
uint8_t byte = (uint8_t)str->bytes[start_index+i];
snprintf(buf, sizeof buf, "\\x%02X", byte);
char *p = buf;
while (*p != '\0') {
inspect_append(result, *p, false);
p++;
}
}
}
prev = c;
    });
    if (dump && prev == '#') {
inspect_append(result, prev, false);
    }
    inspect_append(result, '"', false);

    OBJ_INFECT(result, str);
    return result;
}

static VALUE
rstr_inspect(VALUE self, SEL sel)
{
    return str_inspect(RSTR(self), false);
}

/*
* call-seq:
* str.dump => new_str
*
* Produces a version of <i>str</i> with all nonprinting characters replaced by
* <code>\nnn</code> notation and all special characters escaped.
*/

static VALUE
rstr_dump(VALUE self, SEL sel)
{
    VALUE res = str_inspect(RSTR(self), true);
    *(VALUE *)res = *(VALUE *)self;
    return res;
}

/*
* call-seq:
* str.match(pattern) => matchdata or nil
*
* Converts <i>pattern</i> to a <code>Regexp</code> (if it isn't already one),
* then invokes its <code>match</code> method on <i>str</i>. If the second
* parameter is present, it specifies the position in the string to begin the
* search.
*
* 'hello'.match('(.)\1') #=> #<MatchData "ll" 1:"l">
* 'hello'.match('(.)\1')[0] #=> "ll"
* 'hello'.match(/(.)\1/)[0] #=> "ll"
* 'hello'.match('xx') #=> nil
*
* If a block is given, invoke the block with MatchData if match succeed, so
* that you can write
*
* str.match(pat) {|m| ...}
*
* instead of
*
* if m = str.match(pat)
* ...
* end
*
* The return value is a value from block execution in this case.
*/

static VALUE
get_pat(VALUE pat, bool quote)
{
    switch (TYPE(pat)) {
case T_REGEXP:
return pat;

case T_STRING:
break;

default:
{
VALUE val = rb_check_string_type(pat);
if (NIL_P(val)) {
Check_Type(pat, T_REGEXP);
}
pat = val;
}
    }

    if (quote) {
pat = rb_reg_quote(pat);
    }
    return rb_reg_regcomp(pat);
}

static VALUE
rstr_match2(VALUE self, SEL sel, int argc, VALUE *argv)
{
    if (argc < 1) {
rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }
    VALUE re = get_pat(argv[0], false);
    argv[0] = self;
    VALUE result = rb_vm_call(re, selMATCH, argc, argv);
    if (!NIL_P(result) && rb_block_given_p()) {
return rb_yield(result);
    }
    return result;
}

/*
* call-seq:
* str =~ obj => fixnum or nil
*
* Match---If <i>obj</i> is a <code>Regexp</code>, use it as a pattern to match
* against <i>str</i>,and returns the position the match starts, or
* <code>nil</code> if there is no match. Otherwise, invokes
* <i>obj.=~</i>, passing <i>str</i> as an argument. The default
* <code>=~</code> in <code>Object</code> returns <code>false</code>.
*
* "cat o' 9 tails" =~ /\d/ #=> 7
* "cat o' 9 tails" =~ 9 #=> nil
*/

static VALUE
rstr_match(VALUE self, SEL sel, VALUE other)
{
    switch (TYPE(other)) {
case T_STRING:
rb_raise(rb_eTypeError, "type mismatch: String given");

case T_REGEXP:
return regexp_match(other, 0, self);

default:
return rb_vm_call(other, selEqTilde, 1, &self);
    }
}

/*
* call-seq:
* str.scan(pattern) => array
* str.scan(pattern) {|match, ...| block } => str
*
* Both forms iterate through <i>str</i>, matching the pattern (which may be a
* <code>Regexp</code> or a <code>String</code>). For each match, a result is
* generated and either added to the result array or passed to the block. If
* the pattern contains no groups, each individual result consists of the
* matched string, <code>$&</code>. If the pattern contains groups, each
* individual result is itself an array containing one entry per group.
*
* a = "cruel world"
* a.scan(/\w+/) #=> ["cruel", "world"]
* a.scan(/.../) #=> ["cru", "el ", "wor"]
* a.scan(/(...)/) #=> [["cru"], ["el "], ["wor"]]
* a.scan(/(..)(..)/) #=> [["cr", "ue"], ["l ", "wo"]]
*
* And the block form:
*
* a.scan(/\w+/) {|w| print "<<#{w}>> " }
* print "\n"
* a.scan(/(.)(.)/) {|x,y| print y, x }
* print "\n"
*
* <em>produces:</em>
*
* <<cruel>> <<world>>
* rceu lowlr
*/

static VALUE
rstr_scan(VALUE self, SEL sel, VALUE pat)
{
    const bool block_given = rb_block_given_p();

    const bool untrusted = OBJ_UNTRUSTED(self) || OBJ_UNTRUSTED(pat);
    const bool tainted = OBJ_TAINTED(self) || OBJ_TAINTED(pat);
    pat = get_pat(pat, true);

    character_boundaries_cache_t local_cache;
    reset_character_boundaries_cache(&local_cache);

    VALUE ary = 0;
    if (!block_given) {
ary = rb_ary_new();
    }

    VALUE matcher = rb_reg_matcher_new(pat, self);

    VALUE match = Qnil;
    long start = 0;
    while (rb_reg_matcher_search(pat, matcher, start, false) >= 0) {
match = rb_backref_get();

int count = 0;
rb_match_result_t *results = rb_reg_match_results(match, &count);
assert(count > 0);

if (results[0].beg == results[0].end) {
start = results[0].end + 1;
}
else {
start = results[0].end;
}

VALUE scan_result;
if (count == 1) {
scan_result = rb_reg_nth_match_with_cache(0, match, &local_cache);
if (tainted) {
OBJ_TAINT(scan_result);
}
if (untrusted) {
OBJ_UNTRUST(scan_result);
}
}
else {
scan_result = rb_ary_new2(count);
for (int i = 1; i < count; i++) {
VALUE substr = rb_reg_nth_match_with_cache(i, match,
&local_cache);
if (tainted) {
OBJ_TAINT(substr);
}
if (untrusted) {
OBJ_UNTRUST(substr);
}
rb_ary_push(scan_result, substr);
}
}

if (block_given) {
rb_match_busy(match);
rb_yield(scan_result);
rb_backref_set(match);
RETURN_IF_BROKEN();
}
else {
rb_ary_push(ary, scan_result);
}
    }

    rb_backref_set(match);

    rb_reg_matcher_destroy(matcher);

    return block_given ? self : ary;
}

/*
* call-seq:
* str.split(pattern=$;, [limit]) => anArray
*
* Divides <i>str</i> into substrings based on a delimiter, returning an array
* of these substrings.
*
* If <i>pattern</i> is a <code>String</code>, then its contents are used as
* the delimiter when splitting <i>str</i>. If <i>pattern</i> is a single
* space, <i>str</i> is split on whitespace, with leading whitespace and runs
* of contiguous whitespace characters ignored.
*
* If <i>pattern</i> is a <code>Regexp</code>, <i>str</i> is divided where the
* pattern matches. Whenever the pattern matches a zero-length string,
* <i>str</i> is split into individual characters. If <i>pattern</i> contains
* groups, the respective matches will be returned in the array as well.
*
* If <i>pattern</i> is omitted, the value of <code>$;</code> is used. If
* <code>$;</code> is <code>nil</code> (which is the default), <i>str</i> is
* split on whitespace as if ` ' were specified.
*
* If the <i>limit</i> parameter is omitted, trailing null fields are
* suppressed. If <i>limit</i> is a positive number, at most that number of
* fields will be returned (if <i>limit</i> is <code>1</code>, the entire
* string is returned as the only entry in an array). If negative, there is no
* limit to the number of fields returned, and trailing null fields are not
* suppressed.
*
* " now's the time".split #=> ["now's", "the", "time"]
* " now's the time".split(' ') #=> ["now's", "the", "time"]
* " now's the time".split(/ /) #=> ["", "now's", "", "the", "time"]
* "1, 2.34,56, 7".split(%r{,\s*}) #=> ["1", "2.34", "56", "7"]
* "hello".split(//) #=> ["h", "e", "l", "l", "o"]
* "hello".split(//, 3) #=> ["h", "e", "llo"]
* "hi mom".split(%r{\s*}) #=> ["h", "i", "m", "o", "m"]
*
* "mellow yellow".split("ello") #=> ["m", "w y", "w"]
* "1,2,,3,4,,".split(',') #=> ["1", "2", "", "3", "4"]
* "1,2,,3,4,,".split(',', 4) #=> ["1", "2", "", "3,4,,"]
* "1,2,,3,4,,".split(',', -4) #=> ["1", "2", "", "3", "4", "", ""]
*/

static VALUE str_strip(VALUE str, int direction);
#define IS_SPLIT_AWK_SPACE(c) (c == ' ' || c == '\t' || c == '\n' || c == '\v')

static VALUE
rstr_split(VALUE str, SEL sel, int argc, VALUE *argv)
{
    character_boundaries_cache_t local_cache;
    reset_character_boundaries_cache(&local_cache);
    const long len = str_length_with_cache(RSTR(str), &local_cache);
    int lim = 0;

    VALUE spat, limit;
    if (rb_scan_args(argc, argv, "02", &spat, &limit) == 2) {
lim = NUM2INT(limit);
if (lim <= 0) {
limit = Qnil;
}
else if (lim == 1) {
if (len == 0) {
return rb_ary_new2(0);
}
return rb_ary_new4(1, &str);
}
    }

    VALUE result = rb_ary_new();
    if (len == 0) {
return result;
    }

    bool awk_split = false, spat_string = false;
    long spat_len = 0;
    if (NIL_P(spat)) {
if (!NIL_P(rb_fs)) {
spat = rb_fs;
goto fs_set;
}
awk_split = true;
    }
    else {
fs_set:
if (TYPE(spat) == T_STRING) {
spat_string = true;
spat_len = rb_str_chars_len(spat);
if (spat_len == 1 && rb_str_get_uchar(spat, 0) == ' ') {
awk_split = true;
}
}
else {
spat = get_pat(spat, true);
}
    }

    const int lim_orig = lim;
    long beg = 0;
    if (awk_split) {
RB_STR_GET_UCHARS(str, chars, chars_len);

for (long i = 0; i < chars_len; i++) {
UChar c = chars[i];
if (IS_SPLIT_AWK_SPACE(c)) {
if ((i + 1 < chars_len) && IS_SPLIT_AWK_SPACE(chars[i+1])) {
continue;
}
VALUE substr = rstr_substr_with_cache(str, beg, i - beg,
&local_cache);
str_strip(substr, 0);
if (rb_str_chars_len(substr) > 0) {
rb_ary_push(result, substr);
lim--;
}
beg = i + 1;

if (limit != Qnil && lim <= 1) {
break;
}
}
}
    }
    else if (spat_string) {
if (spat_len == 0) {
__block int block_lim = lim;
__block long block_beg = 0;
str_each_uchar32(RSTR(str), ^(UChar32 c, long start_index, long char_len, bool *stop) {
VALUE substr = (VALUE)str_new_copy_of_part(RSTR(str), start_index, char_len);
rb_ary_push(result, substr);
if (U_IS_BMP(c)) {
++block_beg;
}
else {
block_beg += 2;
}
if (limit != Qnil && --block_lim <= 1) {
*stop = true;
}
});
lim = block_lim;
beg = block_beg;
}
else {
rb_str_t *spat_str = str_need_string(spat);
const long spat_len = str_length(spat_str);
do {
const long pos = str_index_for_string_with_cache(RSTR(str),
spat_str, beg, -1, false, &local_cache);
if (pos == -1) {
break;
}
rb_ary_push(result, rstr_substr_with_cache(str, beg, pos - beg,
&local_cache));
beg = pos + spat_len;
}
while (limit == Qnil || --lim > 1);
}
    }
    else {
long start = beg;
bool last_null = false;
VALUE matcher = rb_reg_matcher_new(spat, str);
again:
do {
const long pos = rb_reg_matcher_search(spat, matcher, start, false);
if (pos < 0) {
break;
}
VALUE match = rb_backref_get();

int count = 0;
rb_match_result_t *results = rb_reg_match_results(match, &count);
assert(count > 0);

if (start == pos && results[0].beg == results[0].end) {
if (last_null) {
VALUE substr;
if (beg + 1 <= len) {
substr = rstr_substr_with_cache(str, beg, 1,
&local_cache);
}
else {
substr = str_new_empty(str);
}
rb_ary_push(result, substr);
beg = start;
}
else {
start++;
last_null = true;
goto again;
}
}
else {
VALUE substr = rstr_substr_with_cache(str, beg, pos - beg,
&local_cache);
rb_ary_push(result, substr);
beg = start = results[0].end;
}
last_null = false;

for (int i = 1; i < count; i++) {
if (results[i].beg == -1 || results[i].end == -1) {
continue;
}
VALUE substr;
if (results[i].beg == results[i].end) {
substr = str_new_empty(str);
}
else {
substr = rstr_substr_with_cache(str, results[i].beg,
results[i].end - results[i].beg, &local_cache);
}
rb_ary_push(result, substr);
}
}
while (limit == Qnil || --lim > 1);

rb_reg_matcher_destroy(matcher);
    }

    if (len > 0 && (!NIL_P(limit) || len > beg || lim_orig < 0)) {
VALUE tmp;
if (beg >= len) {
tmp = str_new_empty(str);
}
else {
tmp = rb_str_substr(str, beg, len - beg);
}
rb_ary_push(result, tmp);
    }

    if (NIL_P(limit) && lim_orig == 0) {
while (true) {
const long n = RARRAY_LEN(result);
if (n > 0 && rb_str_chars_len(RARRAY_AT(result, n - 1)) == 0) {
rb_ary_pop(result);
}
else {
break;
}
}
    }

    if (OBJ_TAINTED(str)) {
for (int i = 0, count = RARRAY_LEN(result); i < count; i++) {
OBJ_TAINT(RARRAY_AT(result, i));
}
    }

    return result;
}

/*
* call-seq:
* str.to_i(base=10) => integer
*
* Returns the result of interpreting leading characters in <i>str</i> as an
* integer base <i>base</i> (between 2 and 36). Extraneous characters past the
* end of a valid number are ignored. If there is not a valid number at the
* start of <i>str</i>, <code>0</code> is returned. This method never raises an
* exception.
*
* "12345".to_i #=> 12345
* "99 red balloons".to_i #=> 99
* "0a".to_i #=> 0
* "0a".to_i(16) #=> 10
* "hello".to_i #=> 0
* "1100101".to_i(2) #=> 101
* "1100101".to_i(8) #=> 294977
* "1100101".to_i(10) #=> 1100101
* "1100101".to_i(16) #=> 17826049
*/

static VALUE
rstr_to_i(VALUE str, SEL sel, int argc, VALUE *argv)
{
    int base = 10;

    if (argc > 0) {
VALUE b;
rb_scan_args(argc, argv, "01", &b);

base = NUM2INT(b);
if (base < 0) {
rb_raise(rb_eArgError, "invalid radix %d", base);
}
    }

    return rb_str_to_inum(str, base, Qfalse);
}

/*
* call-seq:
* str.hex => integer
*
* Treats leading characters from <i>str</i> as a string of hexadecimal digits
* (with an optional sign and an optional <code>0x</code>) and returns the
* corresponding number. Zero is returned on error.
*
* "0x0a".hex #=> 10
* "-1234".hex #=> -4660
* "0".hex #=> 0
* "wombat".hex #=> 0
*/

static VALUE
rstr_hex(VALUE str, SEL sel)
{
    return rb_str_to_inum(str, 16, Qfalse);
}

/*
* call-seq:
* str.oct => integer
*
* Treats leading characters of <i>str</i> as a string of octal digits (with an
* optional sign) and returns the corresponding number. Returns 0 if the
* conversion fails.
*
* "123".oct #=> 83
* "-377".oct #=> -255
* "bad".oct #=> 0
* "0377bad".oct #=> 255
*/

static VALUE
rstr_oct(VALUE str, SEL sel)
{
    return rb_str_to_inum(str, -8, Qfalse);
}

/*
* call-seq:
* str.ord => integer
*
* Return the <code>Integer</code> ordinal of a one-character string.
*
* "a".ord #=> 97
*/

static VALUE
rstr_ord(VALUE str, SEL sel)
{
    if (RSTR(str)->length_in_bytes == 0) {
rb_raise(rb_eArgError, "empty string");
    }
    UChar c = rb_str_get_uchar(str, 0);
    if (c == (UChar)U_SENTINEL) {
str_invalid_byte_sequence(RSTR(str));
    }
    return INT2NUM(c);
}

/*
* call-seq:
* string.chr -> string
*
* Returns a one-character string at the beginning of the string.
*
* a = "abcde"
* a.chr #=> "a"
*/

static VALUE
rstr_chr(VALUE str, SEL sel)
{
    return rstr_substr(str, 0, 1);
}

/*
* call-seq:
* str.to_f => float
*
* Returns the result of interpreting leading characters in <i>str</i> as a
* floating point number. Extraneous characters past the end of a valid number
* are ignored. If there is not a valid number at the start of <i>str</i>,
* <code>0.0</code> is returned. This method never raises an exception.
*
* "123.45e1".to_f #=> 1234.5
* "45.67 degrees".to_f #=> 45.67
* "thx1138".to_f #=> 0.0
*/

static VALUE
rstr_to_f(VALUE str, SEL sel)
{
    return DOUBLE2NUM(rb_str_to_dbl(str, 0));
}

/*
* call-seq:
* str.chomp!(separator=$/) => str or nil
*
* Modifies <i>str</i> in place as described for <code>String#chomp</code>,
* returning <i>str</i>, or <code>nil</code> if no modifications were made.
*/

static VALUE
rstr_chomp_bang(VALUE str, SEL sel, int argc, VALUE *argv)
{
    VALUE rs;
    if (rb_scan_args(argc, argv, "01", &rs) == 0) {
rs = rb_rs;
    }
    rstr_modify(str);
    if (rs == Qnil) {
return Qnil;
    }
    StringValue(rs);

    const long len = rb_str_chars_len(str);
    if (len == 0) {
return Qnil;
    }

    const long rslen = rb_str_chars_len(rs);
    long to_del = 0;

    if (rs == rb_default_rs
|| (rslen == 1 && rb_str_get_uchar(rs, 0) == '\n')) {
// Remove trailing carriage return.
UChar c = str_get_uchar(RSTR(str), len - 1);
if (c == '\n') {
to_del++;
c = len > 1 ? str_get_uchar(RSTR(str), len - 2) : 0;
}
if (c == '\r' && (rslen > 0 || to_del != 0)) {
to_del++;
}
    }
    else if (rslen == 0) {
// Remove all trailing carriage returns.
for (int i = len - 1; i >= 0; i--) {
UChar c = str_get_uchar(RSTR(str), i);
if (c != '\n') {
break;
}
to_del++;
if (i > 0 && str_get_uchar(RSTR(str), i - 1) == '\r') {
to_del++;
i--;
}
}
    }
    else if (rslen <= len) {
// Remove trailing substring.
if (str_index_for_string(RSTR(str), str_need_string(rs),
len - rslen, -1, false) >= 0) {
to_del += rslen;
}
    }

    if (to_del == 0) {
return Qnil;
    }
    str_delete(RSTR(str), len - to_del, to_del);
    return str;
}

/*
* call-seq:
* str.chomp(separator=$/) => new_str
*
* Returns a new <code>String</code> with the given record separator removed
* from the end of <i>str</i> (if present). If <code>$/</code> has not been
* changed from the default Ruby record separator, then <code>chomp</code> also
* removes carriage return characters (that is it will remove <code>\n</code>,
* <code>\r</code>, and <code>\r\n</code>).
*
* "hello".chomp #=> "hello"
* "hello\n".chomp #=> "hello"
* "hello\r\n".chomp #=> "hello"
* "hello\n\r".chomp #=> "hello\n"
* "hello\r".chomp #=> "hello"
* "hello \n there".chomp #=> "hello \n there"
* "hello".chomp("llo") #=> "he"
*/

static VALUE
rstr_chomp(VALUE str, SEL sel, int argc, VALUE *argv)
{
    str = rb_str_new3(str);
    rstr_chomp_bang(str, 0, argc, argv);
    return str;
}

/*
* call-seq:
* str.chop! => str or nil
*
* Processes <i>str</i> as for <code>String#chop</code>, returning <i>str</i>,
* or <code>nil</code> if <i>str</i> is the empty string. See also
* <code>String#chomp!</code>.
*/

static VALUE
rstr_chop_bang(VALUE str, SEL sel)
{
    rstr_modify(str);

    const long len = str_length(RSTR(str));
    if (len == 0) {
return Qnil;
    }

    long to_del = 1;
    if (len >= 2) {
// if the string ends with \r\n we have to remove both \r and \n
// if the string ends with a character not in the BMP,
// we have to remove the whole character
UChar last_char = rb_str_get_uchar(str, len - 1);
if ((last_char == '\n') || U16_IS_TRAIL(last_char)) {
UChar before_last = rb_str_get_uchar(str, len - 2);
if (((before_last == '\r') && (last_char == '\n'))
|| (U16_IS_LEAD(before_last) && U16_IS_TRAIL(last_char))) {
to_del++;
}
}
    }

    str_delete(RSTR(str), len - to_del, to_del);
    return str;
}

/*
* call-seq:
* str.chop => new_str
*
* Returns a new <code>String</code> with the last character removed. If the
* string ends with <code>\r\n</code>, both characters are removed. Applying
* <code>chop</code> to an empty string returns an empty
* string. <code>String#chomp</code> is often a safer alternative, as it leaves
* the string unchanged if it doesn't end in a record separator.
*
* "string\r\n".chop #=> "string"
* "string\n\r".chop #=> "string\n"
* "string\n".chop #=> "string"
* "string".chop #=> "strin"
* "x".chop.chop #=> ""
*/

static VALUE
rstr_chop(VALUE str, SEL sel)
{
    str = rb_str_new3(str);
    rstr_chop_bang(str, 0);
    return str;
}

/*
* call-seq:
* str.sub!(pattern, replacement) => str or nil
* str.sub!(pattern) {|match| block } => str or nil
*
* Performs the substitutions of <code>String#sub</code> in place,
* returning <i>str</i>, or <code>nil</code> if no substitutions were
* performed.
*/

static VALUE
rb_reg_regsub(VALUE str, VALUE src, VALUE regexp, rb_match_result_t *results,
int results_count, character_boundaries_cache_t *cache_for_src)
{
    VALUE val = 0;

    RB_STR_GET_UCHARS(str, str_chars, str_chars_len);

    long pos = 0;

    // if we already have a cache, we will make a local copy just before
    // using it to be sure not to have to start from scratch later
    // (as for instance with "\\2\\1" would make us do)
    character_boundaries_cache_t local_cache_for_src;
    reset_character_boundaries_cache(&local_cache_for_src);

    for (long i = 0; i < str_chars_len; i++) {
UChar c = str_chars[i];
if (c != '\\') {
continue;
}
if (i + 1 == str_chars_len) {
break;
}

if (val == 0) {
val = rb_unicode_str_new(NULL, 0);
}
str_concat_uchars(RSTR(val), &str_chars[pos], i - pos);

i++;
pos = i + 1;

int no = -1;
c = str_chars[i];
switch (c) {
case '1': case '2': case '3':
case '4': case '5': case '6':
case '7': case '8': case '9':
no = c - '0';
break;

case '0':
case '&':
no = 0;
break;

case '`':
if (cache_for_src != NULL) {
local_cache_for_src = *cache_for_src;
}
str_concat_string_part(RSTR(val), RSTR(src),
0, results[0].beg, cache_for_src);
break;

case '\'':
{
long src_chars_len;
if (cache_for_src == NULL) {
src_chars_len = str_length_with_cache(RSTR(src),
&local_cache_for_src);
}
else {
src_chars_len = str_length_with_cache(RSTR(src),
cache_for_src);
local_cache_for_src = *cache_for_src;
}
str_concat_string_part(RSTR(val), RSTR(src),
results[0].end, src_chars_len - results[0].end,
cache_for_src);
}
break;

case '+':
no = results_count - 1;
while (results[no].beg == -1 && no > 0) {
no--;
}
if (no == 0) {
no = -1;
}
break;

default:
str_append_uchar32(RSTR(val), '\\');
// fall through
case '\\':
str_append_uchar32(RSTR(val), c);
break;
}

if (no >= 0) {
if (no >= results_count) {
continue;
}
if (results[no].beg == -1) {
continue;
}
if (cache_for_src != NULL) {
local_cache_for_src = *cache_for_src;
}
str_concat_string_part(RSTR(val), RSTR(src),
results[no].beg, results[no].end - results[no].beg,
cache_for_src);
}
    }

    if (val != 0 && pos < str_chars_len) {
str_concat_uchars(RSTR(val), &str_chars[pos], str_chars_len - pos);
    }

    if (val == 0) {
return str;
    }
    else {
return val;
    }
}

static VALUE
rstr_sub_bang(VALUE str, SEL sel, int argc, VALUE *argv)
{
    VALUE repl, hash = Qnil;
    bool block_given = false;
    bool tainted = false;
    bool untrusted = false;

    if (argc == 1 && rb_block_given_p()) {
block_given = true;
    }
    else if (argc == 2) {
repl = argv[1];
hash = rb_check_convert_type(argv[1], T_HASH, "Hash", "to_hash");
if (NIL_P(hash)) {
StringValue(repl);
}
if (OBJ_TAINTED(repl)) {
tainted = true;
}
if (OBJ_UNTRUSTED(repl)) {
untrusted = true;
}
    }
    else {
rb_raise(rb_eArgError, "wrong number of arguments (%d for 2)", argc);
    }

    if (!block_given) {
// RubySpec compliance...
rstr_modify(str);
    }

    VALUE pat = get_pat(argv[0], true);
    str_modifiable(str);
    if (rb_reg_search(pat, str, 0, false) >= 0) {
VALUE match = rb_backref_get();
int count = 0;
rb_match_result_t *results = rb_reg_match_results(match, &count);
assert(count > 0);

if (block_given || !NIL_P(hash)) {
            if (block_given) {
rb_match_busy(match);
const unsigned long hash = rb_str_hash(str);
repl = rb_obj_as_string(rb_yield(rb_reg_nth_match(0, match)));
if (rb_str_hash(str) != hash) {
rb_raise(rb_eRuntimeError, "string modified");
}
            }
            else {
                repl = rb_hash_aref(hash, rstr_substr(str, results[0].beg,
results[0].end - results[0].beg));
                repl = rb_obj_as_string(repl);
            }
rstr_frozen_check(str);
if (block_given) {
rb_backref_set(match);
RETURN_IF_BROKEN();
}
}
else {
repl = rb_reg_regsub(repl, str, pat, results, count, NULL);
}

rstr_modify(str);
str_splice(RSTR(str), results[0].beg, results[0].end - results[0].beg,
str_need_string(repl));
if (OBJ_TAINTED(repl)) {
tainted = true;
}
if (OBJ_UNTRUSTED(repl)) {
untrusted = true;
}

if (tainted) {
OBJ_TAINT(str);
}
if (untrusted) {
OBJ_UNTRUST(str);
}
return str;
    }
    return Qnil;
}

/*
* call-seq:
* str.sub(pattern, replacement) => new_str
* str.sub(pattern) {|match| block } => new_str
*
* Returns a copy of <i>str</i> with the <em>first</em> occurrence of
* <i>pattern</i> replaced with either <i>replacement</i> or the value of the
* block. The <i>pattern</i> will typically be a <code>Regexp</code>; if it is
* a <code>String</code> then no regular expression metacharacters will be
* interpreted (that is <code>/\d/</code> will match a digit, but
* <code>'\d'</code> will match a backslash followed by a 'd').
*
* If the method call specifies <i>replacement</i>, special variables such as
* <code>$&</code> will not be useful, as substitution into the string occurs
* before the pattern match starts. However, the sequences <code>\1</code>,
* <code>\2</code>, <code>\k<group_name></code>, etc., may be used.
*
* In the block form, the current match string is passed in as a parameter, and
* variables such as <code>$1</code>, <code>$2</code>, <code>$`</code>,
* <code>$&</code>, and <code>$'</code> will be set appropriately. The value
* returned by the block will be substituted for the match on each call.
*
* The result inherits any tainting in the original string or any supplied
* replacement string.
*
* "hello".sub(/[aeiou]/, '*') #=> "h*llo"
* "hello".sub(/([aeiou])/, '<\1>') #=> "h<e>llo"
* "hello".sub(/./) {|s| s[0].ord.to_s + ' ' } #=> "104 ello"
* "hello".sub(/(?<foo>[aeiou])/, '*\k<foo>*') #=> "h*e*llo"
*/

static VALUE
rstr_sub(VALUE str, SEL sel, int argc, VALUE *argv)
{
    str = rb_str_new3(str);
    rstr_sub_bang(str, 0, argc, argv);
    return str;
}

/*
* call-seq:
* str.gsub!(pattern, replacement) => str or nil
* str.gsub!(pattern) {|match| block } => str or nil
*
* Performs the substitutions of <code>String#gsub</code> in place, returning
* <i>str</i>, or <code>nil</code> if no substitutions were performed.
*/

static VALUE
str_gsub(SEL sel, int argc, VALUE *argv, VALUE str, bool bang)
{
    bool block_given = false;
    bool tainted = false;
    bool untrusted = false;
    VALUE hash = Qnil, repl = Qnil;

    switch (argc) {
case 1:
RETURN_ENUMERATOR(str, argc, argv);
block_given = true;
break;

case 2:
repl = argv[1];
hash = rb_check_convert_type(argv[1], T_HASH, "Hash", "to_hash");
if (NIL_P(hash)) {
StringValue(repl);
}
if (OBJ_TAINTED(repl)) {
tainted = true;
}
if (OBJ_UNTRUSTED(repl)) {
untrusted = true;
}
break;

default:
rb_raise(rb_eArgError, "wrong number of arguments (%d for 2)",
argc);
    }

    VALUE pat = get_pat(argv[0], 1);
    VALUE dest = rb_str_new5(str, NULL, 0);
    long offset = 0, last = 0;
    bool changed = false;
    const long len = str_length(RSTR(str));
    VALUE match = Qnil;

    if (bang) {
// RubySpec compliance...
rstr_modify(str);
    }

    VALUE matcher = rb_reg_matcher_new(pat, str);

    character_boundaries_cache_t local_cache_for_str;
    reset_character_boundaries_cache(&local_cache_for_str);

    while (true) {
        const long pos = rb_reg_matcher_search(pat, matcher, offset, false);
if (pos < 0) {
if (!changed) {
rb_reg_matcher_destroy(matcher);
return bang ? Qnil : rstr_dup(str, 0);
}
if (last < len) {
VALUE substr = rstr_substr_with_cache(str, last, len - last,
&local_cache_for_str);
if (substr != Qnil) {
str_concat_string(RSTR(dest), RSTR(substr));
}
}
break;
}

if (pos - last > 0) {
// this concatenation must be done before calling the block
// or doing the replacement or else the cache can't be used
str_concat_string_part(RSTR(dest), RSTR(str), last, pos - last,
&local_cache_for_str);
}

match = rb_backref_get();
int count = 0;
rb_match_result_t *results = rb_reg_match_results(match, &count);
assert(count > 0);

VALUE val;
if (block_given || !NIL_P(hash)) {
            if (block_given) {
rb_match_busy(match);
VALUE to_yield = rb_reg_nth_match_with_cache(0, match,
&local_cache_for_str);
val = rb_obj_as_string(rb_yield(to_yield));
            }
            else {
                val = rb_hash_aref(hash, rstr_substr_with_cache(str,
results[0].beg,
results[0].end - results[0].beg,
&local_cache_for_str));
                val = rb_obj_as_string(val);
            }
if (bang) {
rstr_frozen_check(str);
}
if (block_given) {
rb_backref_set(match);
RETURN_IF_BROKEN();
}
}
else {
val = rb_reg_regsub(repl, str, pat, results, count,
&local_cache_for_str);
}

str_concat_string(RSTR(dest), str_need_string(val));

if (OBJ_TAINTED(val)) {
tainted = true;
}
if (OBJ_UNTRUSTED(val)) {
untrusted = true;
}
changed = true;

offset = last = results[0].end;
if (results[0].beg == offset) {
offset++;
}
    }

    rb_reg_matcher_destroy(matcher);

    rb_backref_set(match);

    if (bang) {
str_replace(RSTR(str), dest);
    }
    else {
     if (!tainted && OBJ_TAINTED(str)) {
tainted = true;
}
if (!untrusted && OBJ_UNTRUSTED(str)) {
untrusted = true;
}
str = dest;
    }

    if (tainted) {
OBJ_TAINT(str);
    }
    if (untrusted) {
OBJ_UNTRUST(str);
    }
    return str;
}

static VALUE
rstr_gsub_bang(VALUE str, SEL sel, int argc, VALUE *argv)
{
    return str_gsub(sel, argc, argv, str, true);
}

/*
* call-seq:
* str.gsub(pattern, replacement) => new_str
* str.gsub(pattern) {|match| block } => new_str
*
* Returns a copy of <i>str</i> with <em>all</em> occurrences of <i>pattern</i>
* replaced with either <i>replacement</i> or the value of the block. The
* <i>pattern</i> will typically be a <code>Regexp</code>; if it is a
* <code>String</code> then no regular expression metacharacters will be
* interpreted (that is <code>/\d/</code> will match a digit, but
* <code>'\d'</code> will match a backslash followed by a 'd').
*
* If a string is used as the replacement, special variables from the match
* (such as <code>$&</code> and <code>$1</code>) cannot be substituted into it,
* as substitution into the string occurs before the pattern match
* starts. However, the sequences <code>\1</code>, <code>\2</code>,
* <code>\k<group_name></code>, and so on may be used to interpolate
* successive groups in the match.
*
* In the block form, the current match string is passed in as a parameter, and
* variables such as <code>$1</code>, <code>$2</code>, <code>$`</code>,
* <code>$&</code>, and <code>$'</code> will be set appropriately. The value
* returned by the block will be substituted for the match on each call.
*
* The result inherits any tainting in the original string or any supplied
* replacement string.
*
* "hello".gsub(/[aeiou]/, '*') #=> "h*ll*"
* "hello".gsub(/([aeiou])/, '<\1>') #=> "h<e>ll<o>"
* "hello".gsub(/./) {|s| s[0].ord.to_s + ' '} #=> "104 101 108 108 111 "
* "hello".gsub(/(?<foo>[aeiou])/, '{\k<foo>}') #=> "h{e}ll{o}"
*/

static VALUE
rstr_gsub(VALUE str, SEL sel, int argc, VALUE *argv)
{
    return str_gsub(sel, argc, argv, str, false);
}

/*
* call-seq:
* str.downcase! => str or nil
*
* Downcases the contents of <i>str</i>, returning <code>nil</code> if no
* changes were made.
* Note: case replacement is effective only in ASCII region.
*/
typedef char (^change_case_callback_t)(char c, bool first_char);
static bool
rstr_change_case(VALUE str, change_case_callback_t callback)
{
    if (RSTR(str)->encoding->ascii_compatible) {
bool changed = false;
for (long i = 0; i < RSTR(str)->length_in_bytes; ++i) {
char c = RSTR(str)->bytes[i];
if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) {
char new_c = callback(c, i == 0);
if (new_c != c) {
changed = true;
RSTR(str)->bytes[i] = new_c;
}
}
}
return changed;
    }
    else {
assert(IS_UTF32_ENC(RSTR(str)->encoding)
|| IS_UTF16_ENC(RSTR(str)->encoding));

__block bool changed = true;
str_each_uchar32(RSTR(str), ^(UChar32 c, long start_index, long char_len, bool *stop) {
if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) {
char new_c = callback(c, start_index == 0);
if (new_c != c) {
changed = true;
memset(&RSTR(str)->bytes[start_index], 0, char_len);
if (RSTR(str)->encoding->little_endian) {
RSTR(str)->bytes[start_index] = new_c;
}
else {
RSTR(str)->bytes[start_index+char_len-1] = new_c;
}
}
}
});
return changed;
    }
}

static VALUE
rstr_downcase_bang(VALUE str, SEL sel)
{
    rstr_modify(str);

    bool changed = rstr_change_case(str, ^ char (char c, bool first_char) {
if (c >= 'A' && c <= 'Z') {
return 'a' + (c - 'A');
}
return c;
    });

    return changed ? str : Qnil;
}

/*
* call-seq:
* str.downcase => new_str
*
* Returns a copy of <i>str</i> with all uppercase letters replaced with their
* lowercase counterparts. The operation is locale insensitive---only
* characters ``A'' to ``Z'' are affected.
* Note: case replacement is effective only in ASCII region.
*
* "hEllO".downcase #=> "hello"
*/

VALUE
rstr_downcase(VALUE str, SEL sel)
{
    str = rb_str_new3(str);
    rstr_downcase_bang(str, 0);
    return str;
}

/*
* call-seq:
* str.upcase! => str or nil
*
* Upcases the contents of <i>str</i>, returning <code>nil</code> if no changes
* were made.
* Note: case replacement is effective only in ASCII region.
*/

static VALUE
rstr_upcase_bang(VALUE str, SEL sel)
{
    rstr_modify(str);

    bool changed = rstr_change_case(str, ^ char (char c, bool first_char) {
if (c >= 'a' && c <= 'z') {
return 'A' + (c - 'a');
}
return c;
    });

    return changed ? str : Qnil;
}

/*
* call-seq:
* str.upcase => new_str
*
* Returns a copy of <i>str</i> with all lowercase letters replaced with their
* uppercase counterparts. The operation is locale insensitive---only
* characters ``a'' to ``z'' are affected.
* Note: case replacement is effective only in ASCII region.
*
* "hEllO".upcase #=> "HELLO"
*/

VALUE
rstr_upcase(VALUE str, SEL sel)
{
    str = rb_str_new3(str);
    rstr_upcase_bang(str, 0);
    return str;
}

/*
* call-seq:
* str.swapcase! => str or nil
*
* Equivalent to <code>String#swapcase</code>, but modifies the receiver in
* place, returning <i>str</i>, or <code>nil</code> if no changes were made.
* Note: case conversion is effective only in ASCII region.
*/

static VALUE
rstr_swapcase_bang(VALUE str, SEL sel)
{
    rstr_modify(str);

    bool changed = rstr_change_case(str, ^ char (char c, bool first_char) {
if (c >= 'A' && c <= 'Z') {
return 'a' + (c - 'A');
}
        else if (c >= 'a' && c <= 'z') {
return 'A' + (c - 'a');
}
return c;
    });

    return changed ? str : Qnil;
}

/*
* call-seq:
* str.swapcase => new_str
*
* Returns a copy of <i>str</i> with uppercase alphabetic characters converted
* to lowercase and lowercase characters converted to uppercase.
* Note: case conversion is effective only in ASCII region.
*
* "Hello".swapcase #=> "hELLO"
* "cYbEr_PuNk11".swapcase #=> "CyBeR_pUnK11"
*/

VALUE
rstr_swapcase(VALUE str, SEL sel)
{
    str = rb_str_new3(str);
    rstr_swapcase_bang(str, 0);
    return str;
}

/*
* call-seq:
* str.capitalize! => str or nil
*
* Modifies <i>str</i> by converting the first character to uppercase and the
* remainder to lowercase. Returns <code>nil</code> if no changes are made.
* Note: case conversion is effective only in ASCII region.
*
* a = "hello"
* a.capitalize! #=> "Hello"
* a #=> "Hello"
* a.capitalize! #=> nil
*/

static VALUE
rstr_capitalize_bang(VALUE str, SEL sel)
{
    rstr_modify(str);

    bool changed = rstr_change_case(str, ^ char (char c, bool first_char) {
        if (first_char) {
if (c >= 'a' && c <= 'z') {
return 'A' + (c - 'a');
}
}
else if (c >= 'A' && c <= 'Z') {
return 'a' + (c - 'A');
}
return c;
    });

    return changed ? str : Qnil;
}

/*
* call-seq:
* str.capitalize => new_str
*
* Returns a copy of <i>str</i> with the first character converted to uppercase
* and the remainder to lowercase.
* Note: case conversion is effective only in ASCII region.
*
* "hello".capitalize #=> "Hello"
* "HELLO".capitalize #=> "Hello"
* "123ABC".capitalize #=> "123abc"
*/

VALUE
rstr_capitalize(VALUE str, SEL sel)
{
    str = rb_str_new3(str);
    rstr_capitalize_bang(str, 0);
    return str;
}

/*
* call-seq:
* str.ljust(integer, padstr=' ') => new_str
*
* If <i>integer</i> is greater than the length of <i>str</i>, returns a new
* <code>String</code> of length <i>integer</i> with <i>str</i> left justified
* and padded with <i>padstr</i>; otherwise, returns <i>str</i>.
*
* "hello".ljust(4) #=> "hello"
* "hello".ljust(20) #=> "hello "
* "hello".ljust(20, '1234') #=> "hello123412341234123"
*/

static void
rstr_justify_part(rb_str_t *str, rb_str_t *pad, long width, long padwidth,
long index)
{
    do {
if (padwidth > width) {
pad = RSTR(rstr_substr((VALUE)pad, 0, width));
}
str_insert(str, index, pad);
width -= padwidth;
index += padwidth;
    }
    while (width > 0);
}

static VALUE
rstr_justify(int argc, VALUE *argv, VALUE str, char mode)
{
    VALUE w, pad;
    rb_scan_args(argc, argv, "11", &w, &pad);

    if (NIL_P(pad)) {
pad = rb_str_new(" ", 1);
    }
    else {
StringValue(pad);
    }

    rb_str_t *padstr = str_need_string(pad);
    const long padwidth = str_length(RSTR(padstr));
    if (padwidth == 0) {
rb_raise(rb_eArgError, "zero width padding");
    }

    const long len = str_length(RSTR(str));
    long width = NUM2LONG(w);
    str = rb_str_new3(str);
    if (width < 0 || width <= len) {
return str;
    }
    width -= len;

    if (mode == 'c') {
rstr_justify_part(RSTR(str), padstr, ceil(width / 2.0), padwidth, len);
rstr_justify_part(RSTR(str), padstr, floor(width / 2.0), padwidth, 0);
    }
    else if (mode == 'l') {
rstr_justify_part(RSTR(str), padstr, width, padwidth, len);
    }
    else if (mode == 'r') {
rstr_justify_part(RSTR(str), padstr, width, padwidth, 0);
    }
    else {
rb_bug("invalid mode");
    }

    OBJ_INFECT(str, pad);

    return str;
}

static VALUE
rstr_ljust(VALUE str, SEL sel, int argc, VALUE *argv)
{
    return rstr_justify(argc, argv, str, 'l');
}

/*
* call-seq:
* str.rjust(integer, padstr=' ') => new_str
*
* If <i>integer</i> is greater than the length of <i>str</i>, returns a new
* <code>String</code> of length <i>integer</i> with <i>str</i> right justified
* and padded with <i>padstr</i>; otherwise, returns <i>str</i>.
*
* "hello".rjust(4) #=> "hello"
* "hello".rjust(20) #=> " hello"
* "hello".rjust(20, '1234') #=> "12341234123412