47 lines
1.2 KiB
C
47 lines
1.2 KiB
C
/*
|
|
* This code was written by Rich Felker in 2010; no copyright is claimed.
|
|
* This code is in the public domain. Attribution is appreciated but
|
|
* unnecessary.
|
|
*/
|
|
|
|
#include <stdlib.h>
|
|
#include <inttypes.h>
|
|
#include <wchar.h>
|
|
#include <errno.h>
|
|
|
|
#include "internal.h"
|
|
|
|
/* Decodes UTF-8 byte-by-byte. The c argument must be initialized to 0
|
|
* to begin decoding; when finished it will contain the Unicode scalar
|
|
* value decoded. Return value is 1 if finished, 0 if in-progress, and
|
|
* -1 if an invalid sequence was encountered. After an invalid sequence,
|
|
* the state (in c) automatically resets to 0 if a continuation byte was
|
|
* expected to facilitate a calling idiom of immediately retrying a
|
|
* failed decode call after processing the invalid sequence. If the
|
|
* second try fails, the byte is invalid as a starter as well.
|
|
*
|
|
* A trivial usage idiom is:
|
|
* while (src<end && (n=decode(dst, *src))>=0) 1[dst+=n]=0, src++;
|
|
*/
|
|
|
|
int decode(unsigned *c, unsigned b)
|
|
{
|
|
if (!*c) {
|
|
if (b < 0x80) {
|
|
*c = b;
|
|
return 1;
|
|
} else if (b-SA >= SB-SA) {
|
|
*c = FAILSTATE;
|
|
return -1;
|
|
}
|
|
*c = bittab[b-SA];
|
|
return 0;
|
|
}
|
|
|
|
if (OOB(*c,b)) {
|
|
*c = 0;
|
|
return -1;
|
|
}
|
|
*c = *c<<6 | b-0x80;
|
|
return !(*c&(1U<<31));
|
|
}
|