in zlib/contrib/puff/puff.c [436:510]
local int codes(struct state *s,
const struct huffman *lencode,
const struct huffman *distcode)
{
int symbol; /* decoded symbol */
int len; /* length for copy */
unsigned dist; /* distance for copy */
static const short lens[29] = { /* Size base for length codes 257..285 */
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258};
static const short lext[29] = { /* Extra bits for length codes 257..285 */
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0};
static const short dists[30] = { /* Offset base for distance codes 0..29 */
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
8193, 12289, 16385, 24577};
static const short dext[30] = { /* Extra bits for distance codes 0..29 */
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
12, 12, 13, 13};
/* decode literals and length/distance pairs */
do {
symbol = decode(s, lencode);
if (symbol < 0)
return symbol; /* invalid symbol */
if (symbol < 256) { /* literal: symbol is the byte */
/* write out the literal */
if (s->out != NIL) {
if (s->outcnt == s->outlen)
return 1;
s->out[s->outcnt] = symbol;
}
s->outcnt++;
}
else if (symbol > 256) { /* length */
/* get and compute length */
symbol -= 257;
if (symbol >= 29)
return -10; /* invalid fixed code */
len = lens[symbol] + bits(s, lext[symbol]);
/* get and check distance */
symbol = decode(s, distcode);
if (symbol < 0)
return symbol; /* invalid symbol */
dist = dists[symbol] + bits(s, dext[symbol]);
#ifndef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
if (dist > s->outcnt)
return -11; /* distance too far back */
#endif
/* copy length bytes from distance bytes back */
if (s->out != NIL) {
if (s->outcnt + len > s->outlen)
return 1;
while (len--) {
s->out[s->outcnt] =
#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
dist > s->outcnt ?
0 :
#endif
s->out[s->outcnt - dist];
s->outcnt++;
}
}
else
s->outcnt += len;
}
} while (symbol != 256); /* end of block symbol */
/* done with a valid fixed or dynamic block */
return 0;
}