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/*
* 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));
}
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