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#include "../../include/mgl/system/utf8.h"
static inline bool utf8_get_codepoint_length(unsigned char b, size_t *codepoint_length) {
if((b & 0x80) == 0) {
*codepoint_length = 1;
return true;
} else if((b & 0xE0) == 0xC0) {
*codepoint_length = 2;
return true;
} else if((b & 0xF0) == 0xE0) {
*codepoint_length = 3;
return true;
} else if((b & 0xF8) == 0xF0) {
*codepoint_length = 4;
return true;
} else {
return false;
}
}
/* TODO: Optimize (remove branching, etc) */
bool mgl_utf8_decode(const unsigned char *str, size_t size, uint32_t *decoded_codepoint, size_t *codepoint_length) {
if(size == 0) {
*decoded_codepoint = 0;
*codepoint_length = 0;
return false;
}
size_t clen;
if(!utf8_get_codepoint_length(str[0], &clen)) {
*decoded_codepoint = str[0];
*codepoint_length = 1;
return false;
}
if(size < clen) {
*decoded_codepoint = str[0];
*codepoint_length = 1;
return false;
}
for(size_t i = 1; i < clen; ++i) {
if((str[i] & 0xC0) != 0x80) {
*decoded_codepoint = str[0];
*codepoint_length = 1;
return false;
}
}
uint32_t codepoint;
switch(clen) {
case 1:
codepoint = (uint32_t)(str[0] & 0x7F);
break;
case 2:
codepoint = ((uint32_t)(str[0] & 0x1F) << 6);
codepoint |= (uint32_t)(str[1] & 0x3F);
break;
case 3:
codepoint = ((uint32_t)(str[0] & 0x0F) << 12);
codepoint |= ((uint32_t)(str[1] & 0x3F) << 6);
codepoint |= (uint32_t)(str[2] & 0x3F);
break;
case 4:
codepoint = ((uint32_t)(str[0] & 0x07) << 18);
codepoint |= ((uint32_t)(str[1] & 0x3F) << 12);
codepoint |= ((uint32_t)(str[2] & 0x3F) << 6);
codepoint |= (uint32_t)(str[3] & 0x3F);
break;
}
*codepoint_length = clen;
*decoded_codepoint = codepoint;
return true;
}
/* TODO: Optimize (remove branching, etc) */
size_t mgl_utf8_get_start_of_codepoint(const unsigned char *str, size_t size, size_t offset) {
if(size == 0)
return 0;
if(offset > size - 1)
offset = size - 1;
/* i <= offset is an overflow (underflow?) check */
for(size_t i = offset; i <= offset; --i) {
if((str[i] & 0xC0) != 0x80)
return i;
}
return 0;
}
/* TODO: Optimize (remove branching, etc) */
size_t mgl_utf8_index_to_offset(const unsigned char *str, size_t size, size_t index) {
size_t codepoint_index = 0;
for(size_t i = 0; i < size;) {
const unsigned char *cp = &str[i];
uint32_t codepoint;
size_t clen;
if(!mgl_utf8_decode(cp, size - i, &codepoint, &clen)) {
codepoint = *cp;
clen = 1;
}
if(codepoint_index >= index)
return i;
i += clen;
++codepoint_index;
}
return size;
}
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