forked from fruxo/turbobadger
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utf8.cpp
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/
utf8.cpp
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#include "utf8/utf8.h"
namespace utf8 {
/** is c the start of a UTF-8 sequence? */
#define isutf(c) (((c)&0xC0)!=0x80)
UCS4 decode(const char *&src, const char *src_end)
{
const char* start = src;
if (src == src_end)
return 0;
unsigned char ch1 = *(src++);
if (ch1 <= 0x7F)
return ch1;
// should not have continuation character here
if ((ch1 & 0xC0) != 0x80 && src < src_end)
{
unsigned char ch2 = *(src++);
// should be continuation
if ((ch2 & 0xC0) != 0x80)
goto invalid;
if ((ch1 & 0xE0) == 0xC0)
{
if ((ch2 & 0xC0) == 0x80)
{
unsigned int rv = ((ch1 & 0x1F) << 6) + (ch2 & 0x3F);
if (rv >= 0x80)
return rv;
}
goto invalid;
}
if (src < src_end)
{
unsigned char ch3 = *(src++);
// should be continuation
if ((ch3 & 0xC0) != 0x80)
goto invalid;
if ((ch1 & 0xF0) == 0xE0)
{
unsigned rv = ((ch1 & 0x0F) << 12)
+ ((ch2 & 0x3F) << 6)
+ (ch3 & 0x3F);
if (rv <= 0x800)
goto invalid;
return rv;
}
if (src < src_end)
{
unsigned char ch4 = *(src++);
if ((ch4 & 0xC0) != 0x80)
goto invalid;
UCS4 rv = ((ch1 & 0x07) << 18)
+ ((ch2 & 0x3F) << 12)
+ ((ch3 & 0x3F) << 6)
+ (ch4 & 0x3F);
if (rv > 0xFFFF)
return rv;
}
}
}
invalid:
src = start;
return 0xFFFF;
}
int encode(UCS4 ch, char *dst)
{
if (ch < 0x80) {
dst[0] = (char) ch;
return 1;
} else if (ch < 0x800) {
dst[0] = (char) (0xC0 + (ch >> 6));
dst[1] = (char) (0x80 + (ch & 0x3F));
return 2;
} else if (ch < 0x10000) {
dst[0] = (char) (0xE0 + (ch >> 12));
dst[1] = (char) (0x80 + ((ch >> 6) & 0x3F));
dst[2] = (char) (0x80 + (ch & 0x3F));
return 3;
} else if (ch <= 0x10FFFF) {
dst[0] = (char) (0xF0 + (ch >> 18));
dst[1] = (char) (0x80 + ((ch >> 12) & 0x3F));
dst[2] = (char) (0x80 + ((ch >> 6) & 0x3F));
dst[3] = (char) (0x80 + (ch & 0x3F));
return 4;
} else {
// output UTF-8 encoding of 0xFFFF
dst[0] = (char)0xEF;
dst[1] = (char)0xBF;
dst[2] = (char)0xBF;
return 3;
}
}
UCS4 decode_next(const char *str, int *i, int i_max)
{
str += *i;
i_max -= *i;
const char *old_str = str;
// Handle wrapping that could happen if the caller use
// something really large for i_max if src is known to
// be null terminated (like TB_ALL_TO_TERMINATION)
const char *str_end = str + i_max;
if (str_end < str)
str_end = (const char *) (-1);
UCS4 ch = decode(str, str_end);
if (ch == 0xFFFF) // Invalid character!
(*i)++;
else
*i += str - old_str;
return ch;
}
void move_inc(const char *str, int *i, int i_max)
{
(void) ((*i < i_max && isutf(str[++(*i)])) ||
(*i < i_max && isutf(str[++(*i)])) ||
(*i < i_max && isutf(str[++(*i)])) ||
(*i < i_max && ++(*i)));
}
void move_dec(const char *str, int *i)
{
(void) ((*i > 0 && isutf(str[--(*i)])) ||
(*i > 0 && isutf(str[--(*i)])) ||
(*i > 0 && isutf(str[--(*i)])) ||
(*i > 0 && --(*i)));
}
int count_characters(const char *str, int i_max)
{
int count = 0;
int i = 0;
while (i < i_max && decode_next(str, &i, i_max))
count++;
return count;
}
}; // namespace utf8