diff --git a/lib/zlib/deflate.js b/lib/zlib/deflate.js index 61cdfc8..e2e4b65 100644 --- a/lib/zlib/deflate.js +++ b/lib/zlib/deflate.js @@ -96,6 +96,13 @@ const zero = (buf) => { }; +/* eslint-disable new-cap */ +let HASH_ZLIB = (s, prev, data) => ((prev << s.hash_shift) ^ data) & s.hash_mask; +// This hash causes less collisions, https://github.com/nodeca/pako/issues/135 +// But breaks binary compatibility +//let HASH_FAST = (s, prev, data) => ((prev << 8) + (prev >> 8) + (data << 4)) & s.hash_mask; +let HASH = HASH_ZLIB; + /* ========================================================================= * Flush as much pending output as possible. All deflate() output goes * through this function so some applications may wish to modify it @@ -395,13 +402,13 @@ const fill_window = (s) => { s.ins_h = s.window[str]; /* UPDATE_HASH(s, s->ins_h, s->window[str + 1]); */ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[str + 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[str + 1]); //#if MIN_MATCH != 3 // Call update_hash() MIN_MATCH-3 more times //#endif while (s.insert) { /* UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]); */ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[str + MIN_MATCH - 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[str + MIN_MATCH - 1]); s.prev[str & s.w_mask] = s.head[s.ins_h]; s.head[s.ins_h] = str; @@ -591,7 +598,7 @@ const deflate_fast = (s, flush) => { hash_head = 0/*NIL*/; if (s.lookahead >= MIN_MATCH) { /*** INSERT_STRING(s, s.strstart, hash_head); ***/ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[s.strstart + MIN_MATCH - 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[s.strstart + MIN_MATCH - 1]); hash_head = s.prev[s.strstart & s.w_mask] = s.head[s.ins_h]; s.head[s.ins_h] = s.strstart; /***/ @@ -625,7 +632,7 @@ const deflate_fast = (s, flush) => { do { s.strstart++; /*** INSERT_STRING(s, s.strstart, hash_head); ***/ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[s.strstart + MIN_MATCH - 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[s.strstart + MIN_MATCH - 1]); hash_head = s.prev[s.strstart & s.w_mask] = s.head[s.ins_h]; s.head[s.ins_h] = s.strstart; /***/ @@ -640,7 +647,7 @@ const deflate_fast = (s, flush) => { s.match_length = 0; s.ins_h = s.window[s.strstart]; /* UPDATE_HASH(s, s.ins_h, s.window[s.strstart+1]); */ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[s.strstart + 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[s.strstart + 1]); //#if MIN_MATCH != 3 // Call UPDATE_HASH() MIN_MATCH-3 more times @@ -721,7 +728,7 @@ const deflate_slow = (s, flush) => { hash_head = 0/*NIL*/; if (s.lookahead >= MIN_MATCH) { /*** INSERT_STRING(s, s.strstart, hash_head); ***/ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[s.strstart + MIN_MATCH - 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[s.strstart + MIN_MATCH - 1]); hash_head = s.prev[s.strstart & s.w_mask] = s.head[s.ins_h]; s.head[s.ins_h] = s.strstart; /***/ @@ -773,7 +780,7 @@ const deflate_slow = (s, flush) => { do { if (++s.strstart <= max_insert) { /*** INSERT_STRING(s, s.strstart, hash_head); ***/ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[s.strstart + MIN_MATCH - 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[s.strstart + MIN_MATCH - 1]); hash_head = s.prev[s.strstart & s.w_mask] = s.head[s.ins_h]; s.head[s.ins_h] = s.strstart; /***/ @@ -1798,7 +1805,7 @@ const deflateSetDictionary = (strm, dictionary) => { let n = s.lookahead - (MIN_MATCH - 1); do { /* UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]); */ - s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[str + MIN_MATCH - 1]) & s.hash_mask; + s.ins_h = HASH(s, s.ins_h, s.window[str + MIN_MATCH - 1]); s.prev[str & s.w_mask] = s.head[s.ins_h];