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Add comment for lept_encode_utf8 in tutorial04. #225

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33 changes: 23 additions & 10 deletions tutorial04_answer/leptjson.c
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Original file line number Diff line number Diff line change
Expand Up @@ -104,24 +104,37 @@ static const char* lept_parse_hex4(const char* p, unsigned* u) {
return p;
}

/**
* Code point <-> UTF-8 conversion
* --------------------------------------------------------------------------------
* First code point | Last code point | Byte 1 | Byte 2 | Byte 3 | Byte 4 |
* U+0000 | U+007F| 0xxxxxxx |
* U+0080 | U+07FF| 110xxxxx | 10xxxxxx |
* U+0800 | U+FFFF| 1110xxxx | 10xxxxxx | 10xxxxxx |
* U+10000 | U+10FFFF| 11110xxx | 10xxxxxx | 10xxxxxx | 10xxxxxx |
* --------------------------------------------------------------------------------
* * Reference: https://en.wikipedia.org/wiki/UTF-8
* @param c lept_context
* @param u unsigned int
*/
static void lept_encode_utf8(lept_context* c, unsigned u) {
if (u <= 0x7F)
PUTC(c, u & 0xFF);
PUTC(c, u & 0xFF); /* set Byte 1 */
else if (u <= 0x7FF) {
PUTC(c, 0xC0 | ((u >> 6) & 0xFF));
PUTC(c, 0x80 | ( u & 0x3F));
PUTC(c, 0xC0 | ((u >> 6) & 0xFF)); /* set Byte 1 */
PUTC(c, 0x80 | ( u & 0x3F)); /* set Byte 2 */
}
else if (u <= 0xFFFF) {
PUTC(c, 0xE0 | ((u >> 12) & 0xFF));
PUTC(c, 0x80 | ((u >> 6) & 0x3F));
PUTC(c, 0x80 | ( u & 0x3F));
PUTC(c, 0xE0 | ((u >> 12) & 0xFF)); /* set Byte 1 */
PUTC(c, 0x80 | ((u >> 6) & 0x3F)); /* set Byte 2 */
PUTC(c, 0x80 | ( u & 0x3F)); /* set Byte 3 */
}
else {
assert(u <= 0x10FFFF);
PUTC(c, 0xF0 | ((u >> 18) & 0xFF));
PUTC(c, 0x80 | ((u >> 12) & 0x3F));
PUTC(c, 0x80 | ((u >> 6) & 0x3F));
PUTC(c, 0x80 | ( u & 0x3F));
PUTC(c, 0xF0 | ((u >> 18) & 0xFF)); /* set Byte 1 */
PUTC(c, 0x80 | ((u >> 12) & 0x3F)); /* set Byte 2 */
PUTC(c, 0x80 | ((u >> 6) & 0x3F)); /* set Byte 3 */
PUTC(c, 0x80 | ( u & 0x3F)); /* set Byte 4 */
}
}

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