Fixed spped degradation: set arrays sizes & data types

lib/zlib/deflate.js

@@ -171,7 +171,7 @@ function fill_window(s) {
        zlib, so we don't care about this pathological case.)
        */
       n = s.hash_size;
-      p = s.head[n];
+      p = n;
       do {
         m = s.head[--p];
         s.head[p] = m >= wsize ? m - wsize : 0;
@@ -179,7 +179,7 @@ function fill_window(s) {
 
       n = wsize;
       if (FASTEST) {
-        p = s.prev[n];
+        p = n;
         do {
           m = s.head[--p];
           s.head[p] = m >= wsize ? m - wsize : 0;
@@ -499,13 +499,13 @@ function DeflateState() {
    * is directly used as sliding window.
    */
 
-  this.prev = Z_NULL;
+  this.prev = null;
   /* Link to older string with same hash index. To limit the size of this
    * array to 64K, this link is maintained only for the last 32K strings.
    * An index in this array is thus a window index modulo 32K.
    */
 
-  this.head = Z_NULL;
+  this.head = null;
   /* Heads of the hash chains or NIL. */
 
   this.ins_h = 0;
@@ -659,6 +659,12 @@ function deflateInit2(strm, level, method, windowBits, memLevel, strategy) {
   s.strategy = strategy;
   s.method = method;
 
+  // precreate & prefill head/prev arrays to optimize v8 types
+  s.head = new Array(s.hash_size);
+  s.prev = new Array(s.w_size);
+  utils.fill(s.head, 0);
+  utils.fill(s.prev, 0);
+
   return deflateReset(strm);
 }
 

lib/zlib/utils.js

@@ -1,6 +1,6 @@
 'use strict';
 
-exports.assign = function(obj /*from1, from2, from3, ...*/) {
+exports.assign = function (obj /*from1, from2, from3, ...*/) {
   var sources = Array.prototype.slice.call(arguments, 1);
   while (sources.length) {
     var source = sources.shift();
@@ -21,7 +21,7 @@ exports.assign = function(obj /*from1, from2, from3, ...*/) {
 };
 
 
-exports.arraySet = function(dest, src, src_offs, len, dest_offs) {
+exports.arraySet = function (dest, src, src_offs, len, dest_offs) {
 
   // Suppose, that with typed array support destination is
   // always typed - don't check it
@@ -45,7 +45,7 @@ exports.arraySet = function(dest, src, src_offs, len, dest_offs) {
 };
 
 
-exports.arrayCreate = function(length) {
+exports.arrayCreate = function (length) {
 
   if ((typeof Uint8Array !== 'undefined')) {
     return new Uint8Array(length);
@@ -54,3 +54,12 @@ exports.arrayCreate = function(length) {
   // Fallback to ordinary array
   return new Array(length);
 };
+
+
+exports.fill = function (buf, val) {
+  var len = buf.length;
+
+  if (!len) { return;}
+
+  while (--len) { buf[len] = val}
+}