void ZopfliBlockSplit(const ZopfliOptions* options,
const unsigned char* in, size_t instart, size_t inend,
size_t maxblocks, size_t** splitpoints, size_t* npoints) {
size_t pos = 0;
size_t i;
ZopfliBlockState s;
size_t* lz77splitpoints = 0;
size_t nlz77points = 0;
ZopfliLZ77Store store;
ZopfliHash hash;
ZopfliHash* h = &hash;
ZopfliInitLZ77Store(in, &store);
ZopfliInitBlockState(options, instart, inend, 0, &s);
ZopfliAllocHash(ZOPFLI_WINDOW_SIZE, h);
*npoints = 0;
*splitpoints = 0;
/* Unintuitively, Using a simple LZ77 method here instead of ZopfliLZ77Optimal
results in better blocks. */
ZopfliLZ77Greedy(&s, in, instart, inend, &store, h);
ZopfliBlockSplitLZ77(options,
&store, maxblocks,
&lz77splitpoints, &nlz77points);
/* Convert LZ77 positions to positions in the uncompressed input. */
pos = instart;
if (nlz77points > 0) {
for (i = 0; i < store.size; i++) {
size_t length = store.dists[i] == 0 ? 1 : store.litlens[i];
if (lz77splitpoints[*npoints] == i) {
ZOPFLI_APPEND_DATA(pos, splitpoints, npoints);
if (*npoints == nlz77points) break;
}
pos += length;
}
}
assert(*npoints == nlz77points);
free(lz77splitpoints);
ZopfliCleanBlockState(&s);
ZopfliCleanLZ77Store(&store);
ZopfliCleanHash(h);
}
void ZopfliLZ77Greedy(ZopfliBlockState* s, const unsigned char* in,
size_t instart, size_t inend,
ZopfliLZ77Store* store) {
size_t i = 0, j;
unsigned short leng;
unsigned short dist;
int lengvalue;
size_t windowstart = instart > ZOPFLI_WINDOW_SIZE
? instart - ZOPFLI_WINDOW_SIZE : 0;
unsigned short dummysublen[259];
ZopfliHash hash;
ZopfliHash* h = &hash;
#ifdef ZOPFLI_LAZY_MATCHING
/* Lazy matching. */
unsigned prev_length = 0;
unsigned prev_match = 0;
int prevlengvalue;
int match_available = 0;
#endif
if (instart == inend) return;
ZopfliInitHash(ZOPFLI_WINDOW_SIZE, h);
ZopfliWarmupHash(in, windowstart, inend, h);
for (i = windowstart; i < instart; i++) {
ZopfliUpdateHash(in, i, inend, h);
}
for (i = instart; i < inend; i++) {
ZopfliUpdateHash(in, i, inend, h);
ZopfliFindLongestMatch(s, h, in, i, inend, ZOPFLI_MAX_MATCH, dummysublen,
&dist, &leng);
lengvalue = GetLengthValue(leng, dist);
#ifdef ZOPFLI_LAZY_MATCHING
/* Lazy matching. */
prevlengvalue = GetLengthValue(prev_length, prev_match);
if (match_available) {
match_available = 0;
if (lengvalue > prevlengvalue + 1) {
ZopfliStoreLitLenDist(in[i - 1], 0, store);
if (lengvalue >= ZOPFLI_MIN_MATCH && lengvalue < ZOPFLI_MAX_MATCH) {
match_available = 1;
prev_length = leng;
prev_match = dist;
continue;
}
} else {
/* Add previous to output. */
leng = prev_length;
dist = prev_match;
lengvalue = prevlengvalue;
/* Add to output. */
ZopfliVerifyLenDist(in, inend, i - 1, dist, leng);
ZopfliStoreLitLenDist(leng, dist, store);
for (j = 2; j < leng; j++) {
assert(i < inend);
i++;
ZopfliUpdateHash(in, i, inend, h);
}
continue;
}
}
else if (lengvalue >= ZOPFLI_MIN_MATCH && leng < ZOPFLI_MAX_MATCH) {
match_available = 1;
prev_length = leng;
prev_match = dist;
continue;
}
/* End of lazy matching. */
#endif
/* Add to output. */
if (lengvalue >= ZOPFLI_MIN_MATCH) {
ZopfliVerifyLenDist(in, inend, i, dist, leng);
ZopfliStoreLitLenDist(leng, dist, store);
} else {
leng = 1;
ZopfliStoreLitLenDist(in[i], 0, store);
}
for (j = 1; j < leng; j++) {
assert(i < inend);
i++;
ZopfliUpdateHash(in, i, inend, h);
}
}
ZopfliCleanHash(h);
}