marshal.c

/**********************************************************************

  marshal.c -

  $Author$
  created at: Thu Apr 27 16:30:01 JST 1995

  Copyright (C) 1993-2007 Yukihiro Matsumoto

**********************************************************************/

#include "ruby/internal/config.h"

#include <math.h>
#ifdef HAVE_FLOAT_H
#include <float.h>
#endif
#ifdef HAVE_IEEEFP_H
#include <ieeefp.h>
#endif

#include "encindex.h"
#include "id_table.h"
#include "internal.h"
#include "internal/array.h"
#include "internal/bignum.h"
#include "internal/class.h"
#include "internal/encoding.h"
#include "internal/error.h"
#include "internal/hash.h"
#include "internal/numeric.h"
#include "internal/object.h"
#include "internal/struct.h"
#include "internal/symbol.h"
#include "internal/util.h"
#include "internal/vm.h"
#include "ruby/io.h"
#include "ruby/ruby.h"
#include "ruby/st.h"
#include "ruby/util.h"
#include "builtin.h"
#include "shape.h"

#define BITSPERSHORT (2*CHAR_BIT)
#define SHORTMASK ((1<<BITSPERSHORT)-1)
#define SHORTDN(x) RSHIFT((x),BITSPERSHORT)

#if SIZEOF_SHORT == SIZEOF_BDIGIT
#define SHORTLEN(x) (x)
#else
static size_t
shortlen(size_t len, BDIGIT *ds)
{
    BDIGIT num;
    int offset = 0;

    num = ds[len-1];
    while (num) {
        num = SHORTDN(num);
        offset++;
    }
    return (len - 1)*SIZEOF_BDIGIT/2 + offset;
}
#define SHORTLEN(x) shortlen((x),d)
#endif

#define MARSHAL_MAJOR   4
#define MARSHAL_MINOR   8

#define TYPE_NIL	'0'
#define TYPE_TRUE	'T'
#define TYPE_FALSE	'F'
#define TYPE_FIXNUM	'i'

#define TYPE_EXTENDED	'e'
#define TYPE_UCLASS	'C'
#define TYPE_OBJECT	'o'
#define TYPE_DATA       'd'
#define TYPE_USERDEF	'u'
#define TYPE_USRMARSHAL	'U'
#define TYPE_FLOAT	'f'
#define TYPE_BIGNUM	'l'
#define TYPE_STRING	'"'
#define TYPE_REGEXP	'/'
#define TYPE_ARRAY	'['
#define TYPE_HASH	'{'
#define TYPE_HASH_DEF	'}'
#define TYPE_STRUCT	'S'
#define TYPE_MODULE_OLD	'M'
#define TYPE_CLASS	'c'
#define TYPE_MODULE	'm'

#define TYPE_SYMBOL	':'
#define TYPE_SYMLINK	';'

#define TYPE_IVAR	'I'
#define TYPE_LINK	'@'

static ID s_dump, s_load, s_mdump, s_mload;
static ID s_dump_data, s_load_data, s_alloc, s_call;
static ID s_getbyte, s_read, s_write, s_binmode;
static ID s_encoding_short, s_ruby2_keywords_flag;

#define name_s_dump	"_dump"
#define name_s_load	"_load"
#define name_s_mdump	"marshal_dump"
#define name_s_mload	"marshal_load"
#define name_s_dump_data "_dump_data"
#define name_s_load_data "_load_data"
#define name_s_alloc	"_alloc"
#define name_s_call	"call"
#define name_s_getbyte	"getbyte"
#define name_s_read	"read"
#define name_s_write	"write"
#define name_s_binmode	"binmode"
#define name_s_encoding_short "E"
#define name_s_ruby2_keywords_flag "K"

typedef struct {
    VALUE newclass;
    VALUE oldclass;
    VALUE (*dumper)(VALUE);
    VALUE (*loader)(VALUE, VALUE);
} marshal_compat_t;

static st_table *compat_allocator_tbl;
static VALUE compat_allocator_tbl_wrapper;
static VALUE rb_marshal_dump_limited(VALUE obj, VALUE port, int limit);
static VALUE rb_marshal_load_with_proc(VALUE port, VALUE proc, bool freeze);

static int
mark_marshal_compat_i(st_data_t key, st_data_t value, st_data_t _)
{
    marshal_compat_t *p = (marshal_compat_t *)value;
    rb_gc_mark(p->newclass);
    rb_gc_mark(p->oldclass);
    return ST_CONTINUE;
}

static void
mark_marshal_compat_t(void *tbl)
{
    if (!tbl) return;
    st_foreach(tbl, mark_marshal_compat_i, 0);
}

static st_table *compat_allocator_table(void);

void
rb_marshal_define_compat(VALUE newclass, VALUE oldclass, VALUE (*dumper)(VALUE), VALUE (*loader)(VALUE, VALUE))
{
    marshal_compat_t *compat;
    rb_alloc_func_t allocator = rb_get_alloc_func(newclass);

    if (!allocator) {
        rb_raise(rb_eTypeError, "no allocator");
    }

    compat = ALLOC(marshal_compat_t);
    compat->newclass = Qnil;
    compat->oldclass = Qnil;
    compat->newclass = newclass;
    compat->oldclass = oldclass;
    compat->dumper = dumper;
    compat->loader = loader;

    st_insert(compat_allocator_table(), (st_data_t)allocator, (st_data_t)compat);
}

struct dump_arg {
    VALUE str, dest;
    st_table *symbols;
    st_table *data;
    st_table *compat_tbl;
    st_table *encodings;
    unsigned long num_entries;
};

struct dump_call_arg {
    VALUE obj;
    struct dump_arg *arg;
    int limit;
};

static VALUE
check_dump_arg(VALUE ret, struct dump_arg *arg, const char *name)
{
    if (!arg->symbols) {
        rb_raise(rb_eRuntimeError, "Marshal.dump reentered at %s",
                 name);
    }
    return ret;
}

static VALUE
check_userdump_arg(VALUE obj, ID sym, int argc, const VALUE *argv,
                   struct dump_arg *arg, const char *name)
{
    VALUE ret = rb_funcallv(obj, sym, argc, argv);
    VALUE klass = CLASS_OF(obj);
    if (CLASS_OF(ret) == klass) {
        rb_raise(rb_eRuntimeError, "%"PRIsVALUE"#%s returned same class instance",
                 klass, name);
    }
    return check_dump_arg(ret, arg, name);
}

#define dump_funcall(arg, obj, sym, argc, argv) \
    check_userdump_arg(obj, sym, argc, argv, arg, name_##sym)
#define dump_check_funcall(arg, obj, sym, argc, argv) \
    check_dump_arg(rb_check_funcall(obj, sym, argc, argv), arg, name_##sym)

static void clear_dump_arg(struct dump_arg *arg);

static void
mark_dump_arg(void *ptr)
{
    struct dump_arg *p = ptr;
    if (!p->symbols)
        return;
    rb_mark_set(p->symbols);
    rb_mark_set(p->data);
    rb_mark_hash(p->compat_tbl);
    rb_gc_mark(p->str);
}

static void
free_dump_arg(void *ptr)
{
    clear_dump_arg(ptr);
    xfree(ptr);
}

static size_t
memsize_dump_arg(const void *ptr)
{
    return sizeof(struct dump_arg);
}

static const rb_data_type_t dump_arg_data = {
    "dump_arg",
    {mark_dump_arg, free_dump_arg, memsize_dump_arg,},
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

static VALUE
must_not_be_anonymous(const char *type, VALUE path)
{
    char *n = RSTRING_PTR(path);

    if (!rb_enc_asciicompat(rb_enc_get(path))) {
        /* cannot occur? */
        rb_raise(rb_eTypeError, "can't dump non-ascii %s name % "PRIsVALUE,
                 type, path);
    }
    if (n[0] == '#') {
        rb_raise(rb_eTypeError, "can't dump anonymous %s % "PRIsVALUE,
                 type, path);
    }
    return path;
}

static VALUE
class2path(VALUE klass)
{
    VALUE path = rb_class_path(klass);

    must_not_be_anonymous((RB_TYPE_P(klass, T_CLASS) ? "class" : "module"), path);
    if (rb_path_to_class(path) != rb_class_real(klass)) {
        rb_raise(rb_eTypeError, "% "PRIsVALUE" can't be referred to", path);
    }
    return path;
}

int ruby_marshal_write_long(long x, char *buf);
static void w_long(long, struct dump_arg*);
static int w_encoding(VALUE encname, struct dump_call_arg *arg);
static VALUE encoding_name(VALUE obj, struct dump_arg *arg);

static void
w_nbyte(const char *s, long n, struct dump_arg *arg)
{
    VALUE buf = arg->str;
    rb_str_buf_cat(buf, s, n);
    if (arg->dest && RSTRING_LEN(buf) >= BUFSIZ) {
        rb_io_write(arg->dest, buf);
        rb_str_resize(buf, 0);
    }
}

static void
w_byte(char c, struct dump_arg *arg)
{
    w_nbyte(&c, 1, arg);
}

static void
w_bytes(const char *s, long n, struct dump_arg *arg)
{
    w_long(n, arg);
    w_nbyte(s, n, arg);
}

#define w_cstr(s, arg) w_bytes((s), strlen(s), (arg))

static void
w_short(int x, struct dump_arg *arg)
{
    w_byte((char)((x >> 0) & 0xff), arg);
    w_byte((char)((x >> 8) & 0xff), arg);
}

static void
w_long(long x, struct dump_arg *arg)
{
    char buf[sizeof(long)+1];
    int i = ruby_marshal_write_long(x, buf);
    if (i < 0) {
        rb_raise(rb_eTypeError, "long too big to dump");
    }
    w_nbyte(buf, i, arg);
}

int
ruby_marshal_write_long(long x, char *buf)
{
    int i;

#if SIZEOF_LONG > 4
    if (!(RSHIFT(x, 31) == 0 || RSHIFT(x, 31) == -1)) {
        /* big long does not fit in 4 bytes */
        return -1;
    }
#endif

    if (x == 0) {
        buf[0] = 0;
        return 1;
    }
    if (0 < x && x < 123) {
        buf[0] = (char)(x + 5);
        return 1;
    }
    if (-124 < x && x < 0) {
        buf[0] = (char)((x - 5)&0xff);
        return 1;
    }
    for (i=1;i<(int)sizeof(long)+1;i++) {
        buf[i] = (char)(x & 0xff);
        x = RSHIFT(x,8);
        if (x == 0) {
            buf[0] = i;
            break;
        }
        if (x == -1) {
            buf[0] = -i;
            break;
        }
    }
    return i+1;
}

#ifdef DBL_MANT_DIG
#define DECIMAL_MANT (53-16)	/* from IEEE754 double precision */

#if DBL_MANT_DIG > 32
#define MANT_BITS 32
#elif DBL_MANT_DIG > 24
#define MANT_BITS 24
#elif DBL_MANT_DIG > 16
#define MANT_BITS 16
#else
#define MANT_BITS 8
#endif

static double
load_mantissa(double d, const char *buf, long len)
{
    if (!len) return d;
    if (--len > 0 && !*buf++) {	/* binary mantissa mark */
        int e, s = d < 0, dig = 0;
        unsigned long m;

        modf(ldexp(frexp(fabs(d), &e), DECIMAL_MANT), &d);
        do {
            m = 0;
            switch (len) {
              default: m = *buf++ & 0xff; /* fall through */
#if MANT_BITS > 24
              case 3: m = (m << 8) | (*buf++ & 0xff); /* fall through */
#endif
#if MANT_BITS > 16
              case 2: m = (m << 8) | (*buf++ & 0xff); /* fall through */
#endif
#if MANT_BITS > 8
              case 1: m = (m << 8) | (*buf++ & 0xff);
#endif
            }
            dig -= len < MANT_BITS / 8 ? 8 * (unsigned)len : MANT_BITS;
            d += ldexp((double)m, dig);
        } while ((len -= MANT_BITS / 8) > 0);
        d = ldexp(d, e - DECIMAL_MANT);
        if (s) d = -d;
    }
    return d;
}
#else
#define load_mantissa(d, buf, len) (d)
#endif

#ifdef DBL_DIG
#define FLOAT_DIG (DBL_DIG+2)
#else
#define FLOAT_DIG 17
#endif

static void
w_float(double d, struct dump_arg *arg)
{
    char buf[FLOAT_DIG + (DECIMAL_MANT + 7) / 8 + 10];

    if (isinf(d)) {
        if (d < 0) w_cstr("-inf", arg);
        else       w_cstr("inf", arg);
    }
    else if (isnan(d)) {
        w_cstr("nan", arg);
    }
    else if (d == 0.0) {
        if (signbit(d)) w_cstr("-0", arg);
        else            w_cstr("0", arg);
    }
    else {
        int decpt, sign, digs, len = 0;
        char *e, *p = ruby_dtoa(d, 0, 0, &decpt, &sign, &e);
        if (sign) buf[len++] = '-';
        digs = (int)(e - p);
        if (decpt < -3 || decpt > digs) {
            buf[len++] = p[0];
            if (--digs > 0) buf[len++] = '.';
            memcpy(buf + len, p + 1, digs);
            len += digs;
            len += snprintf(buf + len, sizeof(buf) - len, "e%d", decpt - 1);
        }
        else if (decpt > 0) {
            memcpy(buf + len, p, decpt);
            len += decpt;
            if ((digs -= decpt) > 0) {
                buf[len++] = '.';
                memcpy(buf + len, p + decpt, digs);
                len += digs;
            }
        }
        else {
            buf[len++] = '0';
            buf[len++] = '.';
            if (decpt) {
                memset(buf + len, '0', -decpt);
                len -= decpt;
            }
            memcpy(buf + len, p, digs);
            len += digs;
        }
        xfree(p);
        w_bytes(buf, len, arg);
    }
}

static void
w_symbol(VALUE sym, struct dump_arg *arg)
{
    st_data_t num;
    VALUE encname;

    if (st_lookup(arg->symbols, sym, &num)) {
        w_byte(TYPE_SYMLINK, arg);
        w_long((long)num, arg);
    }
    else {
        const VALUE orig_sym = sym;
        sym = rb_sym2str(sym);
        if (!sym) {
            rb_raise(rb_eTypeError, "can't dump anonymous ID %"PRIdVALUE, sym);
        }
        encname = encoding_name(sym, arg);
        if (NIL_P(encname) ||
            is_ascii_string(sym)) {
            encname = Qnil;
        }
        else {
            w_byte(TYPE_IVAR, arg);
        }
        w_byte(TYPE_SYMBOL, arg);
        w_bytes(RSTRING_PTR(sym), RSTRING_LEN(sym), arg);
        st_add_direct(arg->symbols, orig_sym, arg->symbols->num_entries);
        if (!NIL_P(encname)) {
            struct dump_call_arg c_arg;
            c_arg.limit = 1;
            c_arg.arg = arg;
            w_long(1L, arg);
            w_encoding(encname, &c_arg);
        }
    }
}

static void
w_unique(VALUE s, struct dump_arg *arg)
{
    must_not_be_anonymous("class", s);
    w_symbol(rb_str_intern(s), arg);
}

static void w_object(VALUE,struct dump_arg*,int);

static int
hash_each(VALUE key, VALUE value, VALUE v)
{
    struct dump_call_arg *arg = (void *)v;
    w_object(key, arg->arg, arg->limit);
    w_object(value, arg->arg, arg->limit);
    return ST_CONTINUE;
}

#define SINGLETON_DUMP_UNABLE_P(klass) \
    (rb_id_table_size(RCLASS_M_TBL(klass)) > 0 || \
     rb_ivar_count(klass) > 0)

static void
w_extended(VALUE klass, struct dump_arg *arg, int check)
{
    if (check && FL_TEST(klass, FL_SINGLETON)) {
        VALUE origin = RCLASS_ORIGIN(klass);
        if (SINGLETON_DUMP_UNABLE_P(klass) ||
            (origin != klass && SINGLETON_DUMP_UNABLE_P(origin))) {
            rb_raise(rb_eTypeError, "singleton can't be dumped");
        }
        klass = RCLASS_SUPER(klass);
    }
    while (BUILTIN_TYPE(klass) == T_ICLASS) {
        if (!FL_TEST(klass, RICLASS_IS_ORIGIN) ||
                BUILTIN_TYPE(RBASIC(klass)->klass) != T_MODULE) {
            VALUE path = rb_class_name(RBASIC(klass)->klass);
            w_byte(TYPE_EXTENDED, arg);
            w_unique(path, arg);
        }
        klass = RCLASS_SUPER(klass);
    }
}

static void
w_class(char type, VALUE obj, struct dump_arg *arg, int check)
{
    VALUE path;
    st_data_t real_obj;
    VALUE klass;

    if (arg->compat_tbl &&
                st_lookup(arg->compat_tbl, (st_data_t)obj, &real_obj)) {
        obj = (VALUE)real_obj;
    }
    klass = CLASS_OF(obj);
    w_extended(klass, arg, check);
    w_byte(type, arg);
    path = class2path(rb_class_real(klass));
    w_unique(path, arg);
}

static void
w_uclass(VALUE obj, VALUE super, struct dump_arg *arg)
{
    VALUE klass = CLASS_OF(obj);

    w_extended(klass, arg, TRUE);
    klass = rb_class_real(klass);
    if (klass != super) {
        w_byte(TYPE_UCLASS, arg);
        w_unique(class2path(klass), arg);
    }
}

static bool
rb_hash_ruby2_keywords_p(VALUE obj)
{
    return (RHASH(obj)->basic.flags & RHASH_PASS_AS_KEYWORDS) != 0;
}

static void
rb_hash_ruby2_keywords(VALUE obj)
{
    RHASH(obj)->basic.flags |= RHASH_PASS_AS_KEYWORDS;
}

static inline bool
to_be_skipped_id(const ID id)
{
    if (id == s_encoding_short) return true;
    if (id == s_ruby2_keywords_flag) return true;
    if (id == rb_id_encoding()) return true;
    return !rb_id2str(id);
}

struct w_ivar_arg {
    struct dump_call_arg *dump;
    st_data_t num_ivar;
};

static int
w_obj_each(st_data_t key, st_data_t val, st_data_t a)
{
    ID id = (ID)key;
    VALUE value = (VALUE)val;
    struct w_ivar_arg *ivarg = (struct w_ivar_arg *)a;
    struct dump_call_arg *arg = ivarg->dump;

    if (to_be_skipped_id(id)) {
        if (id == s_encoding_short) {
            rb_warn("instance variable `"name_s_encoding_short"' on class %"PRIsVALUE" is not dumped",
                    CLASS_OF(arg->obj));
        }
        if (id == s_ruby2_keywords_flag) {
            rb_warn("instance variable `"name_s_ruby2_keywords_flag"' on class %"PRIsVALUE" is not dumped",
                    CLASS_OF(arg->obj));
        }
        return ST_CONTINUE;
    }
    --ivarg->num_ivar;
    w_symbol(ID2SYM(id), arg->arg);
    w_object(value, arg->arg, arg->limit);
    return ST_CONTINUE;
}

static int
obj_count_ivars(st_data_t key, st_data_t val, st_data_t a)
{
    ID id = (ID)key;
    if (!to_be_skipped_id(id) && UNLIKELY(!++*(st_index_t *)a)) {
        rb_raise(rb_eRuntimeError, "too many instance variables");
    }
    return ST_CONTINUE;
}

static VALUE
encoding_name(VALUE obj, struct dump_arg *arg)
{
    if (rb_enc_capable(obj)) {
        int encidx = rb_enc_get_index(obj);
        rb_encoding *enc = 0;
        st_data_t name;

        if (encidx <= 0 || !(enc = rb_enc_from_index(encidx))) {
            return Qnil;
        }

        /* special treatment for US-ASCII and UTF-8 */
        if (encidx == rb_usascii_encindex()) {
            return Qfalse;
        }
        else if (encidx == rb_utf8_encindex()) {
            return Qtrue;
        }

        if (arg->encodings ?
            !st_lookup(arg->encodings, (st_data_t)rb_enc_name(enc), &name) :
            (arg->encodings = st_init_strcasetable(), 1)) {
            name = (st_data_t)rb_str_new_cstr(rb_enc_name(enc));
            st_insert(arg->encodings, (st_data_t)rb_enc_name(enc), name);
        }
        return (VALUE)name;
    }
    else {
        return Qnil;
    }
}

static int
w_encoding(VALUE encname, struct dump_call_arg *arg)
{
    int limit = arg->limit;
    if (limit >= 0) ++limit;
    switch (encname) {
      case Qfalse:
      case Qtrue:
        w_symbol(ID2SYM(s_encoding_short), arg->arg);
        w_object(encname, arg->arg, limit);
        return 1;
      case Qnil:
        return 0;
    }
    w_symbol(ID2SYM(rb_id_encoding()), arg->arg);
    w_object(encname, arg->arg, limit);
    return 1;
}

static st_index_t
has_ivars(VALUE obj, VALUE encname, VALUE *ivobj)
{
    st_index_t num = !NIL_P(encname);

    if (SPECIAL_CONST_P(obj)) goto generic;
    switch (BUILTIN_TYPE(obj)) {
      case T_OBJECT:
      case T_CLASS:
      case T_MODULE:
        break; /* counted elsewhere */
      case T_HASH:
        if (rb_hash_ruby2_keywords_p(obj)) ++num;
        /* fall through */
      default:
      generic:
        rb_ivar_foreach(obj, obj_count_ivars, (st_data_t)&num);
        if (num) *ivobj = obj;
    }

    return num;
}

static void
w_ivar_each(VALUE obj, st_index_t num, struct dump_call_arg *arg)
{
    shape_id_t shape_id = rb_shape_get_shape_id(arg->obj);
    struct w_ivar_arg ivarg = {arg, num};
    if (!num) return;
    rb_ivar_foreach(obj, w_obj_each, (st_data_t)&ivarg);

    if (shape_id != rb_shape_get_shape_id(arg->obj)) {
        rb_shape_t * expected_shape = rb_shape_get_shape_by_id(shape_id);
        rb_shape_t * actual_shape = rb_shape_get_shape(arg->obj);

        // If the shape tree got _shorter_ then we probably removed an IV
        // If the shape tree got longer, then we probably added an IV.
        // The exception message might not be accurate when someone adds and
        // removes the same number of IVs, but they will still get an exception
        if (rb_shape_depth(expected_shape) > rb_shape_depth(actual_shape)) {
            rb_raise(rb_eRuntimeError, "instance variable removed from %"PRIsVALUE" instance",
                    CLASS_OF(arg->obj));
        }
        else {
            rb_raise(rb_eRuntimeError, "instance variable added to %"PRIsVALUE" instance",
                    CLASS_OF(arg->obj));
        }
    }
}

static void
w_ivar(st_index_t num, VALUE ivobj, VALUE encname, struct dump_call_arg *arg)
{
    w_long(num, arg->arg);
    num -= w_encoding(encname, arg);
    if (RB_TYPE_P(ivobj, T_HASH) && rb_hash_ruby2_keywords_p(ivobj)) {
        int limit = arg->limit;
        if (limit >= 0) ++limit;
        w_symbol(ID2SYM(s_ruby2_keywords_flag), arg->arg);
        w_object(Qtrue, arg->arg, limit);
        num--;
    }
    if (!UNDEF_P(ivobj) && num) {
        w_ivar_each(ivobj, num, arg);
    }
}

static void
w_objivar(VALUE obj, struct dump_call_arg *arg)
{
    st_data_t num = 0;

    rb_ivar_foreach(obj, obj_count_ivars, (st_data_t)&num);
    w_long(num, arg->arg);
    w_ivar_each(obj, num, arg);
}

#if SIZEOF_LONG > 4
// Optimized dump for fixnum larger than 31-bits
static void
w_bigfixnum(VALUE obj, struct dump_arg *arg)
{
    RUBY_ASSERT(FIXNUM_P(obj));

    w_byte(TYPE_BIGNUM, arg);

#if SIZEOF_LONG == SIZEOF_VALUE
    long num, slen_num;
    num = FIX2LONG(obj);
#else
    long long num, slen_num;
    num = NUM2LL(obj);
#endif

    char sign = num < 0 ? '-' : '+';
    w_byte(sign, arg);

    // Guaranteed not to overflow, as FIXNUM is 1-bit less than long
    if (num < 0) num = -num;

    // calculate the size in shorts
    int slen = 0;
    {
        slen_num = num;
        while (slen_num) {
            slen++;
            slen_num = SHORTDN(slen_num);
        }
    }

    RUBY_ASSERT(slen > 0 && slen <= SIZEOF_LONG / 2);

    w_long((long)slen, arg);

    for (int i = 0; i < slen; i++) {
        w_short(num & SHORTMASK, arg);
        num = SHORTDN(num);
    }

    // We aren't adding this object to the link table, but we need to increment
    // the index.
    arg->num_entries++;

    RUBY_ASSERT(num == 0);
}
#endif

static void
w_remember(VALUE obj, struct dump_arg *arg)
{
    st_add_direct(arg->data, obj, arg->num_entries++);
}

static void
w_object(VALUE obj, struct dump_arg *arg, int limit)
{
    struct dump_call_arg c_arg;
    VALUE ivobj = Qundef;
    st_data_t num;
    st_index_t hasiv = 0;
    VALUE encname = Qnil;

    if (limit == 0) {
        rb_raise(rb_eArgError, "exceed depth limit");
    }

    if (NIL_P(obj)) {
        w_byte(TYPE_NIL, arg);
    }
    else if (obj == Qtrue) {
        w_byte(TYPE_TRUE, arg);
    }
    else if (obj == Qfalse) {
        w_byte(TYPE_FALSE, arg);
    }
    else if (FIXNUM_P(obj)) {
#if SIZEOF_LONG <= 4
        w_byte(TYPE_FIXNUM, arg);
        w_long(FIX2INT(obj), arg);
#else
        if (RSHIFT((long)obj, 31) == 0 || RSHIFT((long)obj, 31) == -1) {
            w_byte(TYPE_FIXNUM, arg);
            w_long(FIX2LONG(obj), arg);
        }
        else {
            w_bigfixnum(obj, arg);
        }
#endif
    }
    else if (SYMBOL_P(obj)) {
        w_symbol(obj, arg);
    }
    else {
        if (st_lookup(arg->data, obj, &num)) {
            w_byte(TYPE_LINK, arg);
            w_long((long)num, arg);
            return;
        }

        if (limit > 0) limit--;
        c_arg.limit = limit;
        c_arg.arg = arg;
        c_arg.obj = obj;

        if (FLONUM_P(obj)) {
            w_remember(obj, arg);
            w_byte(TYPE_FLOAT, arg);
            w_float(RFLOAT_VALUE(obj), arg);
            return;
        }

        VALUE v;

        if (!RBASIC_CLASS(obj)) {
            rb_raise(rb_eTypeError, "can't dump internal %s",
                     rb_builtin_type_name(BUILTIN_TYPE(obj)));
        }

        if (rb_obj_respond_to(obj, s_mdump, TRUE)) {
            w_remember(obj, arg);

            v = dump_funcall(arg, obj, s_mdump, 0, 0);
            w_class(TYPE_USRMARSHAL, obj, arg, FALSE);
            w_object(v, arg, limit);
            return;
        }
        if (rb_obj_respond_to(obj, s_dump, TRUE)) {
            VALUE ivobj2 = Qundef;
            st_index_t hasiv2;
            VALUE encname2;

            v = INT2NUM(limit);
            v = dump_funcall(arg, obj, s_dump, 1, &v);
            if (!RB_TYPE_P(v, T_STRING)) {
                rb_raise(rb_eTypeError, "_dump() must return string");
            }
            hasiv = has_ivars(obj, (encname = encoding_name(obj, arg)), &ivobj);
            hasiv2 = has_ivars(v, (encname2 = encoding_name(v, arg)), &ivobj2);
            if (hasiv2) {
                hasiv = hasiv2;
                ivobj = ivobj2;
                encname = encname2;
            }
            if (hasiv) w_byte(TYPE_IVAR, arg);
            w_class(TYPE_USERDEF, obj, arg, FALSE);
            w_bytes(RSTRING_PTR(v), RSTRING_LEN(v), arg);
            if (hasiv) {
                w_ivar(hasiv, ivobj, encname, &c_arg);
            }
            w_remember(obj, arg);
            return;
        }

        w_remember(obj, arg);

        hasiv = has_ivars(obj, (encname = encoding_name(obj, arg)), &ivobj);
        {
            st_data_t compat_data;
            rb_alloc_func_t allocator = rb_get_alloc_func(RBASIC(obj)->klass);
            if (st_lookup(compat_allocator_tbl,
                          (st_data_t)allocator,
                          &compat_data)) {
                marshal_compat_t *compat = (marshal_compat_t*)compat_data;
                VALUE real_obj = obj;
                obj = compat->dumper(real_obj);
                if (!arg->compat_tbl) {
                    arg->compat_tbl = rb_init_identtable();
                }
                st_insert(arg->compat_tbl, (st_data_t)obj, (st_data_t)real_obj);
                if (obj != real_obj && UNDEF_P(ivobj)) hasiv = 0;
            }
        }
        if (hasiv) w_byte(TYPE_IVAR, arg);

        switch (BUILTIN_TYPE(obj)) {
          case T_CLASS:
            if (FL_TEST(obj, FL_SINGLETON)) {
                rb_raise(rb_eTypeError, "singleton class can't be dumped");
            }
            w_byte(TYPE_CLASS, arg);
            {
                VALUE path = class2path(obj);
                w_bytes(RSTRING_PTR(path), RSTRING_LEN(path), arg);
                RB_GC_GUARD(path);
            }
            break;

          case T_MODULE:
            w_byte(TYPE_MODULE, arg);
            {
                VALUE path = class2path(obj);
                w_bytes(RSTRING_PTR(path), RSTRING_LEN(path), arg);
                RB_GC_GUARD(path);
            }
            break;

          case T_FLOAT:
            w_byte(TYPE_FLOAT, arg);
            w_float(RFLOAT_VALUE(obj), arg);
            break;

          case T_BIGNUM:
            w_byte(TYPE_BIGNUM, arg);
            {
                char sign = BIGNUM_SIGN(obj) ? '+' : '-';
                size_t len = BIGNUM_LEN(obj);
                size_t slen;
                size_t j;
                BDIGIT *d = BIGNUM_DIGITS(obj);

                slen = SHORTLEN(len);
                if (LONG_MAX < slen) {
                    rb_raise(rb_eTypeError, "too big Bignum can't be dumped");
                }

                w_byte(sign, arg);
                w_long((long)slen, arg);
                for (j = 0; j < len; j++) {
#if SIZEOF_BDIGIT > SIZEOF_SHORT
                    BDIGIT num = *d;
                    int i;

                    for (i=0; i<SIZEOF_BDIGIT; i+=SIZEOF_SHORT) {
                        w_short(num & SHORTMASK, arg);
                        num = SHORTDN(num);
                        if (j == len - 1 && num == 0) break;
                    }
#else
                    w_short(*d, arg);
#endif
                    d++;
                }
            }
            break;

          case T_STRING:
            w_uclass(obj, rb_cString, arg);
            w_byte(TYPE_STRING, arg);
            w_bytes(RSTRING_PTR(obj), RSTRING_LEN(obj), arg);
            break;

          case T_REGEXP:
            w_uclass(obj, rb_cRegexp, arg);
            w_byte(TYPE_REGEXP, arg);
            {
                int opts = rb_reg_options(obj);
                w_bytes(RREGEXP_SRC_PTR(obj), RREGEXP_SRC_LEN(obj), arg);
                w_byte((char)opts, arg);
            }
            break;

          case T_ARRAY:
            w_uclass(obj, rb_cArray, arg);
            w_byte(TYPE_ARRAY, arg);
            {
                long i, len = RARRAY_LEN(obj);

                w_long(len, arg);
                for (i=0; i<RARRAY_LEN(obj); i++) {
                    w_object(RARRAY_AREF(obj, i), arg, limit);
                    if (len != RARRAY_LEN(obj)) {
                        rb_raise(rb_eRuntimeError, "array modified during dump");
                    }
                }
            }
            break;

          case T_HASH:
            w_uclass(obj, rb_cHash, arg);
            if (rb_hash_compare_by_id_p(obj)) {
                w_byte(TYPE_UCLASS, arg);
                w_symbol(rb_sym_intern_ascii_cstr("Hash"), arg);
            }
            if (NIL_P(RHASH_IFNONE(obj))) {
                w_byte(TYPE_HASH, arg);
            }
            else if (FL_TEST(obj, RHASH_PROC_DEFAULT)) {
                rb_raise(rb_eTypeError, "can't dump hash with default proc");
            }
            else {
                w_byte(TYPE_HASH_DEF, arg);
            }
            w_long(rb_hash_size_num(obj), arg);
            rb_hash_foreach(obj, hash_each, (st_data_t)&c_arg);
            if (!NIL_P(RHASH_IFNONE(obj))) {
                w_object(RHASH_IFNONE(obj), arg, limit);
            }
            break;

          case T_STRUCT:
            w_class(TYPE_STRUCT, obj, arg, TRUE);
            {
                long len = RSTRUCT_LEN(obj);
                VALUE mem;
                long i;

                w_long(len, arg);
                mem = rb_struct_members(obj);
                for (i=0; i<len; i++) {
                    w_symbol(RARRAY_AREF(mem, i), arg);
                    w_object(RSTRUCT_GET(obj, i), arg, limit);
                }
            }
            break;

          case T_OBJECT:
            w_class(TYPE_OBJECT, obj, arg, TRUE);
            w_objivar(obj, &c_arg);
            break;

          case T_DATA:
            {
                VALUE v;

                if (!rb_obj_respond_to(obj, s_dump_data, TRUE)) {
                    rb_raise(rb_eTypeError,
                             "no _dump_data is defined for class %"PRIsVALUE,
                             rb_obj_class(obj));
                }
                v = dump_funcall(arg, obj, s_dump_data, 0, 0);
                w_class(TYPE_DATA, obj, arg, TRUE);
                w_object(v, arg, limit);
            }
            break;

          default:
            rb_raise(rb_eTypeError, "can't dump %"PRIsVALUE,
                     rb_obj_class(obj));
            break;
        }
        RB_GC_GUARD(obj);
    }
    if (hasiv) {
        w_ivar(hasiv, ivobj, encname, &c_arg);
    }
}

static void
clear_dump_arg(struct dump_arg *arg)
{
    if (!arg->symbols) return;
    st_free_table(arg->symbols);
    arg->symbols = 0;
    st_free_table(arg->data);
    arg->data = 0;
    arg->num_entries = 0;
    if (arg->compat_tbl) {
        st_free_table(arg->compat_tbl);
        arg->compat_tbl = 0;
    }
    if (arg->encodings) {
        st_free_table(arg->encodings);
        arg->encodings = 0;
    }
}

NORETURN(static inline void io_needed(void));
static inline void
io_needed(void)
{
    rb_raise(rb_eTypeError, "instance of IO needed");
}

/*
 * call-seq:
 *      dump( obj [, anIO] , limit=-1 ) -> anIO
 *
 * Serializes obj and all descendant objects. If anIO is
 * specified, the serialized data will be written to it, otherwise the
 * data will be returned as a String. If limit is specified, the
 * traversal of subobjects will be limited to that depth. If limit is
 * negative, no checking of depth will be performed.
 *
 *     class Klass
 *       def initialize(str)
 *         @str = str
 *       end
 *       def say_hello
 *         @str
 *       end
 *     end
 *
 * (produces no output)
 *
 *     o = Klass.new("hello\n")
 *     data = Marshal.dump(o)
 *     obj = Marshal.load(data)
 *     obj.say_hello  #=> "hello\n"
 *
 * Marshal can't dump following objects:
 * * anonymous Class/Module.
 * * objects which are related to system (ex: Dir, File::Stat, IO, File, Socket
 *   and so on)
 * * an instance of MatchData, Data, Method, UnboundMethod, Proc, Thread,
 *   ThreadGroup, Continuation
 * * objects which define singleton methods
 */
static VALUE
marshal_dump(int argc, VALUE *argv, VALUE _)
{
    VALUE obj, port, a1, a2;
    int limit = -1;

    port = Qnil;
    rb_scan_args(argc, argv, "12", &obj, &a1, &a2);
    if (argc == 3) {
        if (!NIL_P(a2)) limit = NUM2INT(a2);
        if (NIL_P(a1)) io_needed();
        port = a1;
    }
    else if (argc == 2) {
        if (FIXNUM_P(a1)) limit = FIX2INT(a1);
        else if (NIL_P(a1)) io_needed();
        else port = a1;
    }
    return rb_marshal_dump_limited(obj, port, limit);
}

VALUE
rb_marshal_dump_limited(VALUE obj, VALUE port, int limit)
{
    struct dump_arg *arg;
    VALUE wrapper; /* used to avoid memory leak in case of exception */

    wrapper = TypedData_Make_Struct(0, struct dump_arg, &dump_arg_data, arg);
    arg->dest = 0;
    arg->symbols = st_init_numtable();
    arg->data    = rb_init_identtable();
    arg->num_entries = 0;
    arg->compat_tbl = 0;
    arg->encodings = 0;
    arg->str = rb_str_buf_new(0);
    if (!NIL_P(port)) {
        if (!rb_respond_to(port, s_write)) {
            io_needed();
        }
        arg->dest = port;
        dump_check_funcall(arg, port, s_binmode, 0, 0);
    }
    else {
        port = arg->str;
    }

    w_byte(MARSHAL_MAJOR, arg);
    w_byte(MARSHAL_MINOR, arg);

    w_object(obj, arg, limit);
    if (arg->dest) {
        rb_io_write(arg->dest, arg->str);
        rb_str_resize(arg->str, 0);
    }
    clear_dump_arg(arg);
    RB_GC_GUARD(wrapper);

    return port;
}

struct load_arg {
    VALUE src;
    char *buf;
    long buflen;
    long readable;
    long offset;
    st_table *symbols;
    st_table *data;
    st_table *partial_objects;
    VALUE proc;
    st_table *compat_tbl;
    bool freeze;
};

static VALUE
check_load_arg(VALUE ret, struct load_arg *arg, const char *name)
{
    if (!arg->symbols) {
        rb_raise(rb_eRuntimeError, "Marshal.load reentered at %s",
                 name);
    }
    return ret;
}
#define load_funcall(arg, obj, sym, argc, argv) \
    check_load_arg(rb_funcallv(obj, sym, argc, argv), arg, name_##sym)

static void clear_load_arg(struct load_arg *arg);

static void
mark_load_arg(void *ptr)
{
    struct load_arg *p = ptr;
    if (!p->symbols)
        return;
    rb_mark_tbl(p->symbols);
    rb_mark_tbl(p->data);
    rb_mark_tbl(p->partial_objects);
    rb_mark_hash(p->compat_tbl);
}

static void
free_load_arg(void *ptr)
{
    clear_load_arg(ptr);
    xfree(ptr);
}

static size_t
memsize_load_arg(const void *ptr)
{
    return sizeof(struct load_arg);
}

static const rb_data_type_t load_arg_data = {
    "load_arg",
    {mark_load_arg, free_load_arg, memsize_load_arg,},
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

#define r_entry(v, arg) r_entry0((v), (arg)->data->num_entries, (arg))
static VALUE r_object(struct load_arg *arg);
static VALUE r_symbol(struct load_arg *arg);

NORETURN(static void too_short(void));
static void
too_short(void)
{
    rb_raise(rb_eArgError, "marshal data too short");
}

static st_index_t
r_prepare(struct load_arg *arg)
{
    st_index_t idx = arg->data->num_entries;

    st_insert(arg->data, (st_data_t)idx, (st_data_t)Qundef);
    return idx;
}

static unsigned char
r_byte1_buffered(struct load_arg *arg)
{
    if (arg->buflen == 0) {
        long readable = arg->readable < BUFSIZ ? arg->readable : BUFSIZ;
        VALUE str, n = LONG2NUM(readable);

        str = load_funcall(arg, arg->src, s_read, 1, &n);
        if (NIL_P(str)) too_short();
        StringValue(str);
        memcpy(arg->buf, RSTRING_PTR(str), RSTRING_LEN(str));
        arg->offset = 0;
        arg->buflen = RSTRING_LEN(str);
    }
    arg->buflen--;
    return arg->buf[arg->offset++];
}

static int
r_byte(struct load_arg *arg)
{
    int c;

    if (RB_TYPE_P(arg->src, T_STRING)) {
        if (RSTRING_LEN(arg->src) > arg->offset) {
            c = (unsigned char)RSTRING_PTR(arg->src)[arg->offset++];
        }
        else {
            too_short();
        }
    }
    else {
        if (arg->readable >0 || arg->buflen > 0) {
            c = r_byte1_buffered(arg);
        }
        else {
            VALUE v = load_funcall(arg, arg->src, s_getbyte, 0, 0);
            if (NIL_P(v)) rb_eof_error();
            c = (unsigned char)NUM2CHR(v);
        }
    }
    return c;
}

NORETURN(static void long_toobig(int size));

static void
long_toobig(int size)
{
    rb_raise(rb_eTypeError, "long too big for this architecture (size "
             STRINGIZE(SIZEOF_LONG)", given %d)", size);
}

static long
r_long(struct load_arg *arg)
{
    register long x;
    int c = (signed char)r_byte(arg);
    long i;

    if (c == 0) return 0;
    if (c > 0) {
        if (4 < c && c < 128) {
            return c - 5;
        }
        if (c > (int)sizeof(long)) long_toobig(c);
        x = 0;
        for (i=0;i<c;i++) {
            x |= (long)r_byte(arg) << (8*i);
        }
    }
    else {
        if (-129 < c && c < -4) {
            return c + 5;
        }
        c = -c;
        if (c > (int)sizeof(long)) long_toobig(c);
        x = -1;
        for (i=0;i<c;i++) {
            x &= ~((long)0xff << (8*i));
            x |= (long)r_byte(arg) << (8*i);
        }
    }
    return x;
}

long
ruby_marshal_read_long(const char **buf, long len)
{
    long x;
    struct RString src;
    struct load_arg arg;
    memset(&arg, 0, sizeof(arg));
    arg.src = rb_setup_fake_str(&src, *buf, len, 0);
    x = r_long(&arg);
    *buf += arg.offset;
    return x;
}

static VALUE
r_bytes1(long len, struct load_arg *arg)
{
    VALUE str, n = LONG2NUM(len);

    str = load_funcall(arg, arg->src, s_read, 1, &n);
    if (NIL_P(str)) too_short();
    StringValue(str);
    if (RSTRING_LEN(str) != len) too_short();

    return str;
}

static VALUE
r_bytes1_buffered(long len, struct load_arg *arg)
{
    VALUE str;

    if (len <= arg->buflen) {
        str = rb_str_new(arg->buf+arg->offset, len);
        arg->offset += len;
        arg->buflen -= len;
    }
    else {
        long buflen = arg->buflen;
        long readable = arg->readable + 1;
        long tmp_len, read_len, need_len = len - buflen;
        VALUE tmp, n;

        readable = readable < BUFSIZ ? readable : BUFSIZ;
        read_len = need_len > readable ? need_len : readable;
        n = LONG2NUM(read_len);
        tmp = load_funcall(arg, arg->src, s_read, 1, &n);
        if (NIL_P(tmp)) too_short();
        StringValue(tmp);

        tmp_len = RSTRING_LEN(tmp);

        if (tmp_len < need_len) too_short();

        str = rb_str_new(arg->buf+arg->offset, buflen);
        rb_str_cat(str, RSTRING_PTR(tmp), need_len);

        if (tmp_len > need_len) {
            buflen = tmp_len - need_len;
            memcpy(arg->buf, RSTRING_PTR(tmp)+need_len, buflen);
            arg->buflen = buflen;
        }
        else {
            arg->buflen = 0;
        }
        arg->offset = 0;
    }

    return str;
}

#define r_bytes(arg) r_bytes0(r_long(arg), (arg))

static VALUE
r_bytes0(long len, struct load_arg *arg)
{
    VALUE str;

    if (len == 0) return rb_str_new(0, 0);
    if (RB_TYPE_P(arg->src, T_STRING)) {
        if (RSTRING_LEN(arg->src) - arg->offset >= len) {
            str = rb_str_new(RSTRING_PTR(arg->src)+arg->offset, len);
            arg->offset += len;
        }
        else {
            too_short();
        }
    }
    else {
        if (arg->readable > 0 || arg->buflen > 0) {
            str = r_bytes1_buffered(len, arg);
        }
        else {
            str = r_bytes1(len, arg);
        }
    }
    return str;
}

static inline int
name_equal(const char *name, size_t nlen, const char *p, long l)
{
    if ((size_t)l != nlen || *p != *name) return 0;
    return nlen == 1 || memcmp(p+1, name+1, nlen-1) == 0;
}

static int
sym2encidx(VALUE sym, VALUE val)
{
    static const char name_encoding[8] = "encoding";
    const char *p;
    long l;
    if (rb_enc_get_index(sym) != ENCINDEX_US_ASCII) return -1;
    RSTRING_GETMEM(sym, p, l);
    if (l <= 0) return -1;
    if (name_equal(name_encoding, sizeof(name_encoding), p, l)) {
        int idx = rb_enc_find_index(StringValueCStr(val));
        return idx;
    }
    if (name_equal(name_s_encoding_short, rb_strlen_lit(name_s_encoding_short), p, l)) {
        if (val == Qfalse) return rb_usascii_encindex();
        else if (val == Qtrue) return rb_utf8_encindex();
        /* bogus ignore */
    }
    return -1;
}

static int
symname_equal(VALUE sym, const char *name, size_t nlen)
{
    const char *p;
    long l;
    if (rb_enc_get_index(sym) != ENCINDEX_US_ASCII) return 0;
    RSTRING_GETMEM(sym, p, l);
    return name_equal(name, nlen, p, l);
}

#define BUILD_ASSERT_POSITIVE(n) \
    /* make 0 negative to workaround the "zero size array" GCC extension, */ \
    ((sizeof(char [2*(ssize_t)(n)-1])+1)/2) /* assuming no overflow */
#define symname_equal_lit(sym, sym_name) \
    symname_equal(sym, sym_name, BUILD_ASSERT_POSITIVE(rb_strlen_lit(sym_name)))

static VALUE
r_symlink(struct load_arg *arg)
{
    st_data_t sym;
    long num = r_long(arg);

    if (!st_lookup(arg->symbols, num, &sym)) {
        rb_raise(rb_eArgError, "bad symbol");
    }
    return (VALUE)sym;
}

static VALUE
r_symreal(struct load_arg *arg, int ivar)
{
    VALUE s = r_bytes(arg);
    VALUE sym;
    int idx = -1;
    st_index_t n = arg->symbols->num_entries;

    if (rb_enc_str_asciionly_p(s)) rb_enc_associate_index(s, ENCINDEX_US_ASCII);
    st_insert(arg->symbols, (st_data_t)n, (st_data_t)s);
    if (ivar) {
        long num = r_long(arg);
        while (num-- > 0) {
            sym = r_symbol(arg);
            idx = sym2encidx(sym, r_object(arg));
        }
    }
    if (idx > 0) {
        rb_enc_associate_index(s, idx);
        if (is_broken_string(s)) {
            rb_raise(rb_eArgError, "invalid byte sequence in %s: %+"PRIsVALUE,
                     rb_enc_name(rb_enc_from_index(idx)), s);
        }
    }

    return s;
}

static VALUE
r_symbol(struct load_arg *arg)
{
    int type, ivar = 0;

  again:
    switch ((type = r_byte(arg))) {
      default:
        rb_raise(rb_eArgError, "dump format error for symbol(0x%x)", type);
      case TYPE_IVAR:
        ivar = 1;
        goto again;
      case TYPE_SYMBOL:
        return r_symreal(arg, ivar);
      case TYPE_SYMLINK:
        if (ivar) {
            rb_raise(rb_eArgError, "dump format error (symlink with encoding)");
        }
        return r_symlink(arg);
    }
}

static VALUE
r_unique(struct load_arg *arg)
{
    return r_symbol(arg);
}

static VALUE
r_string(struct load_arg *arg)
{
    return r_bytes(arg);
}

static VALUE
r_entry0(VALUE v, st_index_t num, struct load_arg *arg)
{
    st_data_t real_obj = (st_data_t)v;
    if (arg->compat_tbl) {
        /* real_obj is kept if not found */
        st_lookup(arg->compat_tbl, v, &real_obj);
    }
    st_insert(arg->data, num, real_obj);
    st_insert(arg->partial_objects, (st_data_t)real_obj, Qtrue);
    return v;
}

static VALUE
r_fixup_compat(VALUE v, struct load_arg *arg)
{
    st_data_t data;
    st_data_t key = (st_data_t)v;
    if (arg->compat_tbl && st_delete(arg->compat_tbl, &key, &data)) {
        VALUE real_obj = (VALUE)data;
        rb_alloc_func_t allocator = rb_get_alloc_func(CLASS_OF(real_obj));
        if (st_lookup(compat_allocator_tbl, (st_data_t)allocator, &data)) {
            marshal_compat_t *compat = (marshal_compat_t*)data;
            compat->loader(real_obj, v);
        }
        v = real_obj;
    }
    return v;
}

static VALUE
r_post_proc(VALUE v, struct load_arg *arg)
{
    if (arg->proc) {
        v = load_funcall(arg, arg->proc, s_call, 1, &v);
    }
    return v;
}

static VALUE
r_leave(VALUE v, struct load_arg *arg, bool partial)
{
    v = r_fixup_compat(v, arg);
    if (!partial) {
        st_data_t data;
        st_data_t key = (st_data_t)v;
        st_delete(arg->partial_objects, &key, &data);
        if (arg->freeze) {
            if (RB_TYPE_P(v, T_MODULE) || RB_TYPE_P(v, T_CLASS)) {
                // noop
            }
            else if (RB_TYPE_P(v, T_STRING)) {
                v = rb_str_to_interned_str(v);
            }
            else {
                OBJ_FREEZE(v);
            }
        }
        v = r_post_proc(v, arg);
    }
    return v;
}

static int
copy_ivar_i(st_data_t key, st_data_t val, st_data_t arg)
{
    VALUE obj = (VALUE)arg, value = (VALUE)val;
    ID vid = (ID)key;

    if (!rb_ivar_defined(obj, vid))
        rb_ivar_set(obj, vid, value);
    return ST_CONTINUE;
}

static VALUE
r_copy_ivar(VALUE v, VALUE data)
{
    rb_ivar_foreach(data, copy_ivar_i, (st_data_t)v);
    return v;
}

static void
r_ivar(VALUE obj, int *has_encoding, struct load_arg *arg)
{
    long len;

    len = r_long(arg);
    if (len > 0) {
        do {
            VALUE sym = r_symbol(arg);
            VALUE val = r_object(arg);
            int idx = sym2encidx(sym, val);
            if (idx >= 0) {
                if (rb_enc_capable(obj)) {
                    rb_enc_associate_index(obj, idx);
                }
                else {
                    rb_raise(rb_eArgError, "%"PRIsVALUE" is not enc_capable", obj);
                }
                if (has_encoding) *has_encoding = TRUE;
            }
            else if (symname_equal_lit(sym, name_s_ruby2_keywords_flag)) {
                if (RB_TYPE_P(obj, T_HASH)) {
                    rb_hash_ruby2_keywords(obj);
                }
                else {
                    rb_raise(rb_eArgError, "ruby2_keywords flag is given but %"PRIsVALUE" is not a Hash", obj);
                }
            }
            else {
                rb_ivar_set(obj, rb_intern_str(sym), val);
            }
        } while (--len > 0);
    }
}

static VALUE
path2class(VALUE path)
{
    VALUE v = rb_path_to_class(path);

    if (!RB_TYPE_P(v, T_CLASS)) {
        rb_raise(rb_eArgError, "%"PRIsVALUE" does not refer to class", path);
    }
    return v;
}

#define path2module(path) must_be_module(rb_path_to_class(path), path)

static VALUE
must_be_module(VALUE v, VALUE path)
{
    if (!RB_TYPE_P(v, T_MODULE)) {
        rb_raise(rb_eArgError, "%"PRIsVALUE" does not refer to module", path);
    }
    return v;
}

static VALUE
obj_alloc_by_klass(VALUE klass, struct load_arg *arg, VALUE *oldclass)
{
    st_data_t data;
    rb_alloc_func_t allocator;

    allocator = rb_get_alloc_func(klass);
    if (st_lookup(compat_allocator_tbl, (st_data_t)allocator, &data)) {
        marshal_compat_t *compat = (marshal_compat_t*)data;
        VALUE real_obj = rb_obj_alloc(klass);
        VALUE obj = rb_obj_alloc(compat->oldclass);
        if (oldclass) *oldclass = compat->oldclass;

        if (!arg->compat_tbl) {
            arg->compat_tbl = rb_init_identtable();
        }
        st_insert(arg->compat_tbl, (st_data_t)obj, (st_data_t)real_obj);
        return obj;
    }

    return rb_obj_alloc(klass);
}

static VALUE
obj_alloc_by_path(VALUE path, struct load_arg *arg)
{
    return obj_alloc_by_klass(path2class(path), arg, 0);
}

static VALUE
append_extmod(VALUE obj, VALUE extmod)
{
    long i = RARRAY_LEN(extmod);
    while (i > 0) {
        VALUE m = RARRAY_AREF(extmod, --i);
        rb_extend_object(obj, m);
    }
    return obj;
}

#define prohibit_ivar(type, str) do { \
        if (!ivp || !*ivp) break; \
        rb_raise(rb_eTypeError, \
                 "can't override instance variable of "type" `%"PRIsVALUE"'", \
                 (str)); \
    } while (0)

static VALUE r_object_for(struct load_arg *arg, bool partial, int *ivp, VALUE extmod, int type);

static VALUE
r_object0(struct load_arg *arg, bool partial, int *ivp, VALUE extmod)
{
    int type = r_byte(arg);
    return r_object_for(arg, partial, ivp, extmod, type);
}

static int
r_move_ivar(st_data_t k, st_data_t v, st_data_t d)
{
    ID key = (ID)k;
    VALUE value = (VALUE)v;
    VALUE dest = (VALUE)d;

    if (rb_is_instance_id(key)) {
        rb_ivar_set(dest, key, value);
        return ST_DELETE;
    }
    return ST_CONTINUE;
}

static VALUE
r_object_for(struct load_arg *arg, bool partial, int *ivp, VALUE extmod, int type)
{
    VALUE (*hash_new_with_size)(st_index_t) = rb_hash_new_with_size;
    VALUE v = Qnil;
    long id;
    st_data_t link;

    switch (type) {
      case TYPE_LINK:
        id = r_long(arg);
        if (!st_lookup(arg->data, (st_data_t)id, &link)) {
            rb_raise(rb_eArgError, "dump format error (unlinked)");
        }
        v = (VALUE)link;
        if (!st_lookup(arg->partial_objects, (st_data_t)v, &link)) {
            v = r_post_proc(v, arg);
        }
        break;

      case TYPE_IVAR:
        {
            int ivar = TRUE;
            v = r_object0(arg, true, &ivar, extmod);
            if (ivar) r_ivar(v, NULL, arg);
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_EXTENDED:
        {
            VALUE path = r_unique(arg);
            VALUE m = rb_path_to_class(path);
            if (NIL_P(extmod)) extmod = rb_ary_hidden_new(0);

            if (RB_TYPE_P(m, T_CLASS)) { /* prepended */
                VALUE c;

                v = r_object0(arg, true, 0, Qnil);
                c = CLASS_OF(v);
                if (c != m || FL_TEST(c, FL_SINGLETON)) {
                    rb_raise(rb_eArgError,
                             "prepended class %"PRIsVALUE" differs from class %"PRIsVALUE,
                             path, rb_class_name(c));
                }
                c = rb_singleton_class(v);
                while (RARRAY_LEN(extmod) > 0) {
                    m = rb_ary_pop(extmod);
                    rb_prepend_module(c, m);
                }
            }
            else {
                must_be_module(m, path);
                rb_ary_push(extmod, m);

                v = r_object0(arg, true, 0, extmod);
                while (RARRAY_LEN(extmod) > 0) {
                    m = rb_ary_pop(extmod);
                    rb_extend_object(v, m);
                }
            }
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_UCLASS:
        {
            VALUE c = path2class(r_unique(arg));

            if (FL_TEST(c, FL_SINGLETON)) {
                rb_raise(rb_eTypeError, "singleton can't be loaded");
            }
            type = r_byte(arg);
            if ((c == rb_cHash) &&
                /* Hack for compare_by_identify */
                (type == TYPE_HASH || type == TYPE_HASH_DEF)) {
                hash_new_with_size = rb_ident_hash_new_with_size;
                goto type_hash;
            }
            v = r_object_for(arg, partial, 0, extmod, type);
            if (rb_special_const_p(v) || RB_TYPE_P(v, T_OBJECT) || RB_TYPE_P(v, T_CLASS)) {
                goto format_error;
            }
            if (RB_TYPE_P(v, T_MODULE) || !RTEST(rb_class_inherited_p(c, RBASIC(v)->klass))) {
                VALUE tmp = rb_obj_alloc(c);

                if (TYPE(v) != TYPE(tmp)) goto format_error;
            }
            RBASIC_SET_CLASS(v, c);
        }
        break;

      format_error:
        rb_raise(rb_eArgError, "dump format error (user class)");

      case TYPE_NIL:
        v = Qnil;
        v = r_leave(v, arg, false);
        break;

      case TYPE_TRUE:
        v = Qtrue;
        v = r_leave(v, arg, false);
        break;

      case TYPE_FALSE:
        v = Qfalse;
        v = r_leave(v, arg, false);
        break;

      case TYPE_FIXNUM:
        {
            long i = r_long(arg);
            v = LONG2FIX(i);
        }
        v = r_leave(v, arg, false);
        break;

      case TYPE_FLOAT:
        {
            double d;
            VALUE str = r_bytes(arg);
            const char *ptr = RSTRING_PTR(str);

            if (strcmp(ptr, "nan") == 0) {
                d = nan("");
            }
            else if (strcmp(ptr, "inf") == 0) {
                d = HUGE_VAL;
            }
            else if (strcmp(ptr, "-inf") == 0) {
                d = -HUGE_VAL;
            }
            else {
                char *e;
                d = strtod(ptr, &e);
                d = load_mantissa(d, e, RSTRING_LEN(str) - (e - ptr));
            }
            v = DBL2NUM(d);
            v = r_entry(v, arg);
            v = r_leave(v, arg, false);
        }
        break;

      case TYPE_BIGNUM:
        {
            long len;
            VALUE data;
            int sign;

            sign = r_byte(arg);
            len = r_long(arg);

            if (SIZEOF_VALUE >= 8 && len <= 4) {
                // Representable within uintptr, likely FIXNUM
                VALUE num = 0;
                for (int i = 0; i < len; i++) {
                    num |= (VALUE)r_byte(arg) << (i * 16);
                    num |= (VALUE)r_byte(arg) << (i * 16 + 8);
                }
#if SIZEOF_VALUE == SIZEOF_LONG
                v = ULONG2NUM(num);
#else
                v = ULL2NUM(num);
#endif
                if (sign == '-') {
                    v = rb_int_uminus(v);
                }
            }
            else {
                data = r_bytes0(len * 2, arg);
                v = rb_integer_unpack(RSTRING_PTR(data), len, 2, 0,
                    INTEGER_PACK_LITTLE_ENDIAN | (sign == '-' ? INTEGER_PACK_NEGATIVE : 0));
                rb_str_resize(data, 0L);
            }
            v = r_entry(v, arg);
            v = r_leave(v, arg, false);
        }
        break;

      case TYPE_STRING:
        v = r_entry(r_string(arg), arg);
        v = r_leave(v, arg, partial);
        break;

      case TYPE_REGEXP:
        {
            VALUE str = r_bytes(arg);
            int options = r_byte(arg);
            int has_encoding = FALSE;
            st_index_t idx = r_prepare(arg);

            if (ivp) {
                r_ivar(str, &has_encoding, arg);
                *ivp = FALSE;
            }
            if (!has_encoding) {
                /* 1.8 compatibility; remove escapes undefined in 1.8 */
                char *ptr = RSTRING_PTR(str), *dst = ptr, *src = ptr;
                long len = RSTRING_LEN(str);
                long bs = 0;
                for (; len-- > 0; *dst++ = *src++) {
                    switch (*src) {
                      case '\\': bs++; break;
                      case 'g': case 'h': case 'i': case 'j': case 'k': case 'l':
                      case 'm': case 'o': case 'p': case 'q': case 'u': case 'y':
                      case 'E': case 'F': case 'H': case 'I': case 'J': case 'K':
                      case 'L': case 'N': case 'O': case 'P': case 'Q': case 'R':
                      case 'S': case 'T': case 'U': case 'V': case 'X': case 'Y':
                        if (bs & 1) --dst;
                        /* fall through */
                      default: bs = 0; break;
                    }
                }
                rb_str_set_len(str, dst - ptr);
            }
            VALUE regexp = rb_reg_new_str(str, options);
            rb_ivar_foreach(str, r_move_ivar, regexp);

            v = r_entry0(regexp, idx, arg);
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_ARRAY:
        {
            long len = r_long(arg);

            v = rb_ary_new2(len);
            v = r_entry(v, arg);
            arg->readable += len - 1;
            while (len--) {
                rb_ary_push(v, r_object(arg));
                arg->readable--;
            }
            v = r_leave(v, arg, partial);
            arg->readable++;
        }
        break;

      case TYPE_HASH:
      case TYPE_HASH_DEF:
      type_hash:
        {
            long len = r_long(arg);

            v = hash_new_with_size(len);
            v = r_entry(v, arg);
            arg->readable += (len - 1) * 2;
            while (len--) {
                VALUE key = r_object(arg);
                VALUE value = r_object(arg);
                rb_hash_aset(v, key, value);
                arg->readable -= 2;
            }
            arg->readable += 2;
            if (type == TYPE_HASH_DEF) {
                RHASH_SET_IFNONE(v, r_object(arg));
            }
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_STRUCT:
        {
            VALUE mem, values;
            long i;
            VALUE slot;
            st_index_t idx = r_prepare(arg);
            VALUE klass = path2class(r_unique(arg));
            long len = r_long(arg);

            v = rb_obj_alloc(klass);
            if (!RB_TYPE_P(v, T_STRUCT)) {
                rb_raise(rb_eTypeError, "class %"PRIsVALUE" not a struct", rb_class_name(klass));
            }
            mem = rb_struct_s_members(klass);
            if (RARRAY_LEN(mem) != len) {
                rb_raise(rb_eTypeError, "struct %"PRIsVALUE" not compatible (struct size differs)",
                         rb_class_name(klass));
            }

            arg->readable += (len - 1) * 2;
            v = r_entry0(v, idx, arg);
            values = rb_ary_new2(len);
            {
                VALUE keywords = Qfalse;
                if (RTEST(rb_struct_s_keyword_init(klass))) {
                    keywords = rb_hash_new();
                    rb_ary_push(values, keywords);
                }

                for (i=0; i<len; i++) {
                    VALUE n = rb_sym2str(RARRAY_AREF(mem, i));
                    slot = r_symbol(arg);

                    if (!rb_str_equal(n, slot)) {
                        rb_raise(rb_eTypeError, "struct %"PRIsVALUE" not compatible (:%"PRIsVALUE" for :%"PRIsVALUE")",
                                 rb_class_name(klass),
                                 slot, n);
                    }
                    if (keywords) {
                        rb_hash_aset(keywords, RARRAY_AREF(mem, i), r_object(arg));
                    }
                    else {
                        rb_ary_push(values, r_object(arg));
                    }
                    arg->readable -= 2;
                }
            }
            rb_struct_initialize(v, values);
            v = r_leave(v, arg, partial);
            arg->readable += 2;
        }
        break;

      case TYPE_USERDEF:
        {
            VALUE name = r_unique(arg);
            VALUE klass = path2class(name);
            VALUE data;
            st_data_t d;

            if (!rb_obj_respond_to(klass, s_load, TRUE)) {
                rb_raise(rb_eTypeError, "class %"PRIsVALUE" needs to have method `_load'",
                         name);
            }
            data = r_string(arg);
            if (ivp) {
                r_ivar(data, NULL, arg);
                *ivp = FALSE;
            }
            v = load_funcall(arg, klass, s_load, 1, &data);
            v = r_entry(v, arg);
            if (st_lookup(compat_allocator_tbl, (st_data_t)rb_get_alloc_func(klass), &d)) {
                marshal_compat_t *compat = (marshal_compat_t*)d;
                v = compat->loader(klass, v);
            }
            if (!partial) v = r_post_proc(v, arg);
        }
        break;

      case TYPE_USRMARSHAL:
        {
            VALUE name = r_unique(arg);
            VALUE klass = path2class(name);
            VALUE oldclass = 0;
            VALUE data;

            v = obj_alloc_by_klass(klass, arg, &oldclass);
            if (!NIL_P(extmod)) {
                /* for the case marshal_load is overridden */
                append_extmod(v, extmod);
            }
            if (!rb_obj_respond_to(v, s_mload, TRUE)) {
                rb_raise(rb_eTypeError, "instance of %"PRIsVALUE" needs to have method `marshal_load'",
                         name);
            }
            v = r_entry(v, arg);
            data = r_object(arg);
            load_funcall(arg, v, s_mload, 1, &data);
            v = r_fixup_compat(v, arg);
            v = r_copy_ivar(v, data);
            v = r_post_proc(v, arg);
            if (!NIL_P(extmod)) {
                if (oldclass) append_extmod(v, extmod);
                rb_ary_clear(extmod);
            }
        }
        break;

      case TYPE_OBJECT:
        {
            st_index_t idx = r_prepare(arg);
            v = obj_alloc_by_path(r_unique(arg), arg);
            if (!RB_TYPE_P(v, T_OBJECT)) {
                rb_raise(rb_eArgError, "dump format error");
            }
            v = r_entry0(v, idx, arg);
            r_ivar(v, NULL, arg);
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_DATA:
        {
            VALUE name = r_unique(arg);
            VALUE klass = path2class(name);
            VALUE oldclass = 0;
            VALUE r;

            v = obj_alloc_by_klass(klass, arg, &oldclass);
            if (!RB_TYPE_P(v, T_DATA)) {
                rb_raise(rb_eArgError, "dump format error");
            }
            v = r_entry(v, arg);
            if (!rb_obj_respond_to(v, s_load_data, TRUE)) {
                rb_raise(rb_eTypeError,
                         "class %"PRIsVALUE" needs to have instance method `_load_data'",
                         name);
            }
            r = r_object0(arg, partial, 0, extmod);
            load_funcall(arg, v, s_load_data, 1, &r);
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_MODULE_OLD:
        {
            VALUE str = r_bytes(arg);

            v = rb_path_to_class(str);
            prohibit_ivar("class/module", str);
            v = r_entry(v, arg);
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_CLASS:
        {
            VALUE str = r_bytes(arg);

            v = path2class(str);
            prohibit_ivar("class", str);
            v = r_entry(v, arg);
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_MODULE:
        {
            VALUE str = r_bytes(arg);

            v = path2module(str);
            prohibit_ivar("module", str);
            v = r_entry(v, arg);
            v = r_leave(v, arg, partial);
        }
        break;

      case TYPE_SYMBOL:
        if (ivp) {
            v = r_symreal(arg, *ivp);
            *ivp = FALSE;
        }
        else {
            v = r_symreal(arg, 0);
        }
        v = rb_str_intern(v);
        v = r_leave(v, arg, partial);
        break;

      case TYPE_SYMLINK:
        v = rb_str_intern(r_symlink(arg));
        break;

      default:
        rb_raise(rb_eArgError, "dump format error(0x%x)", type);
        break;
    }

    if (UNDEF_P(v)) {
        rb_raise(rb_eArgError, "dump format error (bad link)");
    }

    return v;
}

static VALUE
r_object(struct load_arg *arg)
{
    return r_object0(arg, false, 0, Qnil);
}

static void
clear_load_arg(struct load_arg *arg)
{
    if (arg->buf) {
        xfree(arg->buf);
        arg->buf = 0;
    }
    arg->buflen = 0;
    arg->offset = 0;
    arg->readable = 0;
    if (!arg->symbols) return;
    st_free_table(arg->symbols);
    arg->symbols = 0;
    st_free_table(arg->data);
    arg->data = 0;
    st_free_table(arg->partial_objects);
    arg->partial_objects = 0;
    if (arg->compat_tbl) {
        st_free_table(arg->compat_tbl);
        arg->compat_tbl = 0;
    }
}

VALUE
rb_marshal_load_with_proc(VALUE port, VALUE proc, bool freeze)
{
    int major, minor;
    VALUE v;
    VALUE wrapper; /* used to avoid memory leak in case of exception */
    struct load_arg *arg;

    v = rb_check_string_type(port);
    if (!NIL_P(v)) {
        port = v;
    }
    else if (rb_respond_to(port, s_getbyte) && rb_respond_to(port, s_read)) {
        rb_check_funcall(port, s_binmode, 0, 0);
    }
    else {
        io_needed();
    }
    wrapper = TypedData_Make_Struct(0, struct load_arg, &load_arg_data, arg);
    arg->src = port;
    arg->offset = 0;
    arg->symbols = st_init_numtable();
    arg->data    = rb_init_identtable();
    arg->partial_objects = rb_init_identtable();
    arg->compat_tbl = 0;
    arg->proc = 0;
    arg->readable = 0;
    arg->freeze = freeze;

    if (NIL_P(v))
        arg->buf = xmalloc(BUFSIZ);
    else
        arg->buf = 0;

    major = r_byte(arg);
    minor = r_byte(arg);
    if (major != MARSHAL_MAJOR || minor > MARSHAL_MINOR) {
        clear_load_arg(arg);
        rb_raise(rb_eTypeError, "incompatible marshal file format (can't be read)\n\
\tformat version %d.%d required; %d.%d given",
                 MARSHAL_MAJOR, MARSHAL_MINOR, major, minor);
    }
    if (RTEST(ruby_verbose) && minor != MARSHAL_MINOR) {
        rb_warn("incompatible marshal file format (can be read)\n\
\tformat version %d.%d required; %d.%d given",
                MARSHAL_MAJOR, MARSHAL_MINOR, major, minor);
    }

    if (!NIL_P(proc)) arg->proc = proc;
    v = r_object(arg);
    clear_load_arg(arg);
    RB_GC_GUARD(wrapper);

    return v;
}

static VALUE
marshal_load(rb_execution_context_t *ec, VALUE mod, VALUE source, VALUE proc, VALUE freeze)
{
    return rb_marshal_load_with_proc(source, proc, RTEST(freeze));
}

#include "marshal.rbinc"

/*
 * The marshaling library converts collections of Ruby objects into a
 * byte stream, allowing them to be stored outside the currently
 * active script. This data may subsequently be read and the original
 * objects reconstituted.
 *
 * Marshaled data has major and minor version numbers stored along
 * with the object information. In normal use, marshaling can only
 * load data written with the same major version number and an equal
 * or lower minor version number. If Ruby's ``verbose'' flag is set
 * (normally using -d, -v, -w, or --verbose) the major and minor
 * numbers must match exactly. Marshal versioning is independent of
 * Ruby's version numbers. You can extract the version by reading the
 * first two bytes of marshaled data.
 *
 *     str = Marshal.dump("thing")
 *     RUBY_VERSION   #=> "1.9.0"
 *     str[0].ord     #=> 4
 *     str[1].ord     #=> 8
 *
 * Some objects cannot be dumped: if the objects to be dumped include
 * bindings, procedure or method objects, instances of class IO, or
 * singleton objects, a TypeError will be raised.
 *
 * If your class has special serialization needs (for example, if you
 * want to serialize in some specific format), or if it contains
 * objects that would otherwise not be serializable, you can implement
 * your own serialization strategy.
 *
 * There are two methods of doing this, your object can define either
 * marshal_dump and marshal_load or _dump and _load.  marshal_dump will take
 * precedence over _dump if both are defined.  marshal_dump may result in
 * smaller Marshal strings.
 *
 * == Security considerations
 *
 * By design, Marshal.load can deserialize almost any class loaded into the
 * Ruby process. In many cases this can lead to remote code execution if the
 * Marshal data is loaded from an untrusted source.
 *
 * As a result, Marshal.load is not suitable as a general purpose serialization
 * format and you should never unmarshal user supplied input or other untrusted
 * data.
 *
 * If you need to deserialize untrusted data, use JSON or another serialization
 * format that is only able to load simple, 'primitive' types such as String,
 * Array, Hash, etc. Never allow user input to specify arbitrary types to
 * deserialize into.
 *
 * == marshal_dump and marshal_load
 *
 * When dumping an object the method marshal_dump will be called.
 * marshal_dump must return a result containing the information necessary for
 * marshal_load to reconstitute the object.  The result can be any object.
 *
 * When loading an object dumped using marshal_dump the object is first
 * allocated then marshal_load is called with the result from marshal_dump.
 * marshal_load must recreate the object from the information in the result.
 *
 * Example:
 *
 *   class MyObj
 *     def initialize name, version, data
 *       @name    = name
 *       @version = version
 *       @data    = data
 *     end
 *
 *     def marshal_dump
 *       [@name, @version]
 *     end
 *
 *     def marshal_load array
 *       @name, @version = array
 *     end
 *   end
 *
 * == _dump and _load
 *
 * Use _dump and _load when you need to allocate the object you're restoring
 * yourself.
 *
 * When dumping an object the instance method _dump is called with an Integer
 * which indicates the maximum depth of objects to dump (a value of -1 implies
 * that you should disable depth checking).  _dump must return a String
 * containing the information necessary to reconstitute the object.
 *
 * The class method _load should take a String and use it to return an object
 * of the same class.
 *
 * Example:
 *
 *   class MyObj
 *     def initialize name, version, data
 *       @name    = name
 *       @version = version
 *       @data    = data
 *     end
 *
 *     def _dump level
 *       [@name, @version].join ':'
 *     end
 *
 *     def self._load args
 *       new(*args.split(':'))
 *     end
 *   end
 *
 * Since Marshal.dump outputs a string you can have _dump return a Marshal
 * string which is Marshal.loaded in _load for complex objects.
 */
void
Init_marshal(void)
{
    VALUE rb_mMarshal = rb_define_module("Marshal");
#define set_id(sym) sym = rb_intern_const(name_##sym)
    set_id(s_dump);
    set_id(s_load);
    set_id(s_mdump);
    set_id(s_mload);
    set_id(s_dump_data);
    set_id(s_load_data);
    set_id(s_alloc);
    set_id(s_call);
    set_id(s_getbyte);
    set_id(s_read);
    set_id(s_write);
    set_id(s_binmode);
    set_id(s_encoding_short);
    set_id(s_ruby2_keywords_flag);

    rb_define_module_function(rb_mMarshal, "dump", marshal_dump, -1);

    /* major version */
    rb_define_const(rb_mMarshal, "MAJOR_VERSION", INT2FIX(MARSHAL_MAJOR));
    /* minor version */
    rb_define_const(rb_mMarshal, "MINOR_VERSION", INT2FIX(MARSHAL_MINOR));
}

static st_table *
compat_allocator_table(void)
{
    if (compat_allocator_tbl) return compat_allocator_tbl;
    compat_allocator_tbl = st_init_numtable();
#undef RUBY_UNTYPED_DATA_WARNING
#define RUBY_UNTYPED_DATA_WARNING 0
    compat_allocator_tbl_wrapper =
        Data_Wrap_Struct(0, mark_marshal_compat_t, 0, compat_allocator_tbl);
    rb_gc_register_mark_object(compat_allocator_tbl_wrapper);
    return compat_allocator_tbl;
}

VALUE
rb_marshal_dump(VALUE obj, VALUE port)
{
    return rb_marshal_dump_limited(obj, port, -1);
}

VALUE
rb_marshal_load(VALUE port)
{
    return rb_marshal_load_with_proc(port, Qnil, false);
}