diff --git a/lib/zlib/deflate.js b/lib/zlib/deflate.js
index 5ec531a..64fabed 100644
--- a/lib/zlib/deflate.js
+++ b/lib/zlib/deflate.js
@@ -40,12 +40,12 @@ var BS_FINISH_DONE    = 4; /* finish done, accept no more input or output */
 
 var OS_CODE = 0x03; // Unix :) . Don't detect, use this default.
 
-var NIL = 0;
 
 function rank (f) {
   return ((f) << 1) - ((f) > 4 ? 9 : 0);
 }
 
+
 /* =========================================================================
  * Flush as much pending output as possible. All deflate() output goes
  * through this function so some applications may wish to modify it
@@ -73,20 +73,19 @@ function flush_pending(strm) {
   }
 }
 
+
 function flush_block_only (s, last) {
   trees._tr_flush_block(s, (s.block_start >= 0 ? s.block_start : -1), s.strstart - s.block_start, last);
   s.block_start = s.strstart;
   flush_pending(s.strm);
 }
 
-function update_hash (s, h, c) {
-  return (((h) << s.hash_shift) ^ (c)) & s.hash_mask;
-}
 
 function put_byte(s, b) {
   s.pending_buf[s.pending++] = b;
 }
 
+
 /* =========================================================================
  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
  * IN assertion: the stream state is correct and there is enough room in
@@ -99,6 +98,7 @@ function putShortMSB(s, b) {
   s.pending_buf[s.pending++] = b & 0xff;
 }
 
+
 /* ===========================================================================
  * Read a new buffer from the current input stream, update the adler32
  * and total number of bytes read.  All deflate() input goes through
@@ -147,7 +147,7 @@ function longest_match(s, cur_match) {
   var best_len = s.prev_length;              /* best match length so far */
   var nice_match = s.nice_match;             /* stop if match long enough */
   var limit = (s.strstart > (s.w_size - MIN_LOOKAHEAD)) ?
-      s.strstart - (s.w_size - MIN_LOOKAHEAD) : NIL;
+      s.strstart - (s.w_size - MIN_LOOKAHEAD) : 0/*NIL*/;
 
   var _win = s.window; // shortcut
 
@@ -254,13 +254,15 @@ function longest_match(s, cur_match) {
  */
 function fill_window(s) {
   var _w_size = s.w_size;
-  var p = 0, n = 0, m = 0, more, str;
+  var p, n, m, more, str;
 
   //Assert(s->lookahead < MIN_LOOKAHEAD, "already enough lookahead");
 
   do {
     more = s.window_size - s.lookahead - s.strstart;
 
+    // TODO: this check seems to be needed only for
+    // 2-byte int-s (16-bit arch)
     if (more === 0 && s.strstart === 0 && s.lookahead === 0) {
       more = _w_size;
 
@@ -334,12 +336,16 @@ function fill_window(s) {
     if (s.lookahead + s.insert >= MIN_MATCH) {
       str = s.strstart - s.insert;
       s.ins_h = s.window[str];
-      s.ins_h = update_hash(s, s.ins_h, s.window[str + 1]);
+
+      /* 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;
 //#if MIN_MATCH != 3
 //        Call update_hash() MIN_MATCH-3 more times
 //#endif
       while (s.insert) {
-        s.ins_h = update_hash(s, s.ins_h, s.window[str + MIN_MATCH - 1]);
+        /* 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.prev[str & s.w_mask] = s.head[s.ins_h];
         s.head[s.ins_h] = str;
         str++;
@@ -523,7 +529,7 @@ function deflate_fast(s, flush) {
     /* Insert the string window[strstart .. strstart+2] in the
      * dictionary, and set hash_head to the head of the hash chain:
      */
-    hash_head = NIL;
+    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;
@@ -536,7 +542,7 @@ function deflate_fast(s, flush) {
     /* Find the longest match, discarding those <= prev_length.
      * At this point we have always match_length < MIN_MATCH
      */
-    if (hash_head !== NIL && ((s.strstart - hash_head) <= (s.w_size - MIN_LOOKAHEAD))) {
+    if (hash_head !== 0/*NIL*/ && ((s.strstart - hash_head) <= (s.w_size - MIN_LOOKAHEAD))) {
       /* To simplify the code, we prevent matches with the string
        * of window index 0 (in particular we have to avoid a match
        * of the string with itself at the start of the input file).
@@ -654,7 +660,7 @@ function deflate_slow(s, flush) {
     /* Insert the string window[strstart .. strstart+2] in the
      * dictionary, and set hash_head to the head of the hash chain:
      */
-    hash_head = NIL;
+    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;
@@ -670,7 +676,7 @@ function deflate_slow(s, flush) {
     s.prev_match = s.match_start;
     s.match_length = MIN_MATCH-1;
 
-    if (hash_head !== NIL && s.prev_length < s.max_lazy_match &&
+    if (hash_head !== 0/*NIL*/ && s.prev_length < s.max_lazy_match &&
         s.strstart - hash_head <= (s.w_size-MIN_LOOKAHEAD)/*MAX_DIST(s)*/) {
       /* To simplify the code, we prevent matches with the string
        * of window index 0 (in particular we have to avoid a match
@@ -985,7 +991,7 @@ function lm_init(s) {
   s.window_size = 2 * s.w_size;
 
   /*** CLEAR_HASH(s); ***/
-  utils.fill(s.head, NIL);
+  utils.fill(s.head, 0/*NIL*/);
 
   /* Set the default configuration parameters:
    */
@@ -1005,7 +1011,8 @@ function lm_init(s) {
 
 
 var TreeDesc = function() {
-  this.dyn_tree = [];         /* the dynamic tree */
+  // TODO: null or [] ? Check speed
+  this.dyn_tree = null;         /* the dynamic tree */
   this.max_code = 0;          /* largest code with non zero frequency */
   this.stat_desc = null;      /* the corresponding static tree */
 };
@@ -1068,7 +1075,7 @@ function DeflateState() {
 
   this.match_length = 0;      /* length of best match */
   this.prev_match = 0;        /* previous match */
-  this.match_available = 1;   /* set if previous match exists */
+  this.match_available = 0;   /* set if previous match exists */
   this.strstart = 0;          /* start of string to insert */
   this.match_start = 0;       /* start of matching string */
   this.lookahead = 0;         /* number of valid bytes ahead in window */
@@ -1216,6 +1223,12 @@ function deflateResetKeep(strm) {
   strm.total_in = strm.total_out = 0;
   strm.data_type = c.Z_UNKNOWN;
 
+  // TODO: enable
+  /*if (strm == Z_NULL || strm->state == Z_NULL ||
+      strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
+      return Z_STREAM_ERROR;
+  }*/
+
   var s = strm.state;
   s.pending = 0;
   s.pending_out = 0;
@@ -1262,6 +1275,15 @@ function deflateInit2(strm, level, method, windowBits, memLevel, strategy) {
     windowBits -= 16;
   }
 
+
+  // TODO: enable
+  /*if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
+    windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
+    strategy < 0 || strategy > Z_FIXED) {
+    return Z_STREAM_ERROR;
+  }*/
+
+
   if (windowBits === 8) {
     windowBits = 9;
   }
@@ -1281,7 +1303,7 @@ function deflateInit2(strm, level, method, windowBits, memLevel, strategy) {
   s.hash_bits = memLevel + 7;
   s.hash_size = 1 << s.hash_bits;
   s.hash_mask = s.hash_size - 1;
-  s.hash_shift = (s.hash_bits + MIN_MATCH - 1) / MIN_MATCH;
+  s.hash_shift = ~~((s.hash_bits + MIN_MATCH - 1) / MIN_MATCH);
 
   s.window = utils.arrayCreate(s.w_size * 2);
   s.head = utils.array16Create(s.hash_size);
@@ -1294,7 +1316,7 @@ function deflateInit2(strm, level, method, windowBits, memLevel, strategy) {
   s.pending_buf_size = s.lit_bufsize * 4;
   s.pending_buf = utils.arrayCreate(s.pending_buf_size);
 
-  s.d_buf = Math.floor(s.lit_bufsize / 2);
+  s.d_buf = s.lit_bufsize >> 1;
   s.l_buf = (1 + 2) * s.lit_bufsize;
 
   s.level = level;
@@ -1310,21 +1332,26 @@ function deflateInit(strm, level) {
 
 
 function deflate(strm, flush) {
-  var s = strm.state;
+  var old_flush, s;
 
-//  if (strm.next_out == Z_NULL ||
-//    (strm.next_in == Z_NULL && strm.avail_in !== 0) ||
-//    (s.status == FINISH_STATE && flush != c.Z_FINISH)) {
-//    return c.Z_STREAM_ERROR;
-//  }
-  if (strm.avail_out === 0) {
-    return c.Z_BUF_ERROR;
-  }
+  // TODO: enable
+  /*if (strm.next_out == Z_NULL ||
+    (strm.next_in == Z_NULL && strm.avail_in !== 0) ||
+    (s.status == FINISH_STATE && flush != c.Z_FINISH)) {
+    return c.Z_STREAM_ERROR;
+  }*/
 
-  s.strm = strm;
-  /* just in case */
-  var old_flush = s.last_flush;
-  /* value of flush param for previous deflate call */
+  s = strm.state;
+
+  // TODO: enable
+  /*if (strm->next_out == Z_NULL ||
+      (strm->next_in == Z_NULL && strm->avail_in != 0) ||
+      (s->status == FINISH_STATE && flush != Z_FINISH)) {
+      ERR_RETURN(strm, Z_STREAM_ERROR);
+  }*/
+
+  s.strm = strm; /* just in case */
+  old_flush = s.last_flush;
   s.last_flush = flush;
 
   /* Write the header */
@@ -1435,17 +1462,19 @@ function deflate(strm, flush) {
        */
     }
     if (bstate === BS_BLOCK_DONE) {
-      /*if (flush === c.Z_PARTIAL_FLUSH) {
-        //todo:_tr_align(s);
-      } else*/
-      if (flush !== c.Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
+      if (flush === c.Z_PARTIAL_FLUSH) {
+        // TODO: implement
+        trees._tr_align(s);
+      }
+      else if (flush !== c.Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
+
         trees._tr_stored_block(s, 0, 0, 0);
         /* For a full flush, this empty block will be recognized
          * as a special marker by inflate_sync().
          */
         if (flush === c.Z_FULL_FLUSH) {
           /*** CLEAR_HASH(s); ***/             /* forget history */
-          utils.fill(s.head, NIL);
+          utils.fill(s.head, 0/*NIL*/);
 
           if (s.lookahead === 0) {
             s.strstart = 0;
@@ -1456,8 +1485,7 @@ function deflate(strm, flush) {
       }
       flush_pending(strm);
       if (strm.avail_out === 0) {
-        s.last_flush = -1;
-        /* avoid BUF_ERROR at next call, see above */
+        s.last_flush = -1; /* avoid BUF_ERROR at next call, see above */
         return c.Z_OK;
       }
     }
diff --git a/lib/zlib/trees.js b/lib/zlib/trees.js
index e28f140..b8c0cef 100644
--- a/lib/zlib/trees.js
+++ b/lib/zlib/trees.js
@@ -228,7 +228,7 @@ function gen_bitlen(s, desc)
   /* In a first pass, compute the optimal bit lengths (which may
    * overflow in the case of the bit length tree).
    */
-  tree[(s.heap[s.heap_max])*2 + 1]/*.Len*/ = 0; /* root of the heap */
+  tree[s.heap[s.heap_max]*2 + 1]/*.Len*/ = 0; /* root of the heap */
 
   for (h = s.heap_max+1; h < HEAP_SIZE; h++) {
     n = s.heap[h];
@@ -305,7 +305,7 @@ function gen_codes(tree, max_code, bl_count)
 //    int max_code;              /* largest code with non zero frequency */
 //    ushf *bl_count;            /* number of codes at each bit length */
 {
-  var next_code = [/*MAX_BITS+1*/]; /* next code value for each bit length */
+  var next_code = new Array(MAX_BITS+1); /* next code value for each bit length */
   var code = 0;              /* running code value */
   var bits;                  /* bit index */
   var n;                     /* code index */
@@ -436,7 +436,7 @@ function tr_static_init() {
   // TODO: we could pass empty array instead of null in original
   // BUT (!) at first check, that it will not break condition in build_tree()
   // static_bl_desc =new StaticTreeDesc([],          extra_blbits, 0,         BL_CODES, MAX_BL_BITS);
-  static_bl_desc =new StaticTreeDesc(null,          extra_blbits, 0,         BL_CODES, MAX_BL_BITS);
+  static_bl_desc =new StaticTreeDesc(null,         extra_blbits, 0,         BL_CODES, MAX_BL_BITS);
 
   //static_init_done = true;
 }
@@ -462,7 +462,7 @@ function init_block(s) {
 /* ===========================================================================
  * Flush the bit buffer and align the output on a byte boundary
  */
-function bi_windup (s)
+function bi_windup(s)
 {
   if (s.bi_valid > 8) {
     put_short(s, s.bi_buf);
@@ -478,7 +478,7 @@ function bi_windup (s)
  * Copy a stored block, storing first the length and its
  * one's complement if requested.
  */
-function copy_block (s, buf, len, header)
+function copy_block(s, buf, len, header)
 //DeflateState *s;
 //charf    *buf;    /* the input data */
 //unsigned len;     /* its length */
@@ -520,6 +520,7 @@ function pqdownheap(s, tree, k)
 //    ct_data *tree;  /* the tree to restore */
 //    int k;               /* node to move down */
 {
+  // TODO: check if shortcut to `heap` needed
   var v = s.heap[k];
   var j = k << 1;  /* left son of k */
   while (j <= s.heap_len) {
@@ -628,7 +629,7 @@ function build_tree(s, desc)
 
   for (n = 0; n < elems; n++) {
     if (tree[n * 2]/*.Freq*/ !== 0) {
-      s.heap[++(s.heap_len)] = max_code = n;
+      s.heap[++s.heap_len] = max_code = n;
       s.depth[n] = 0;
 
     } else {
@@ -642,7 +643,7 @@ function build_tree(s, desc)
    * two codes of non zero frequency.
    */
   while (s.heap_len < 2) {
-    node = s.heap[++(s.heap_len)] = (max_code < 2 ? ++max_code : 0);
+    node = s.heap[++s.heap_len] = (max_code < 2 ? ++max_code : 0);
     tree[node * 2]/*.Freq*/ = 1;
     s.depth[node] = 0;
     s.opt_len--;
@@ -675,8 +676,8 @@ function build_tree(s, desc)
 
     m = s.heap[1/*SMALLEST*/]; /* m = node of next least frequency */
 
-    s.heap[--(s.heap_max)] = n; /* keep the nodes sorted by frequency */
-    s.heap[--(s.heap_max)] = m;
+    s.heap[--s.heap_max] = n; /* keep the nodes sorted by frequency */
+    s.heap[--s.heap_max] = m;
 
     /* Create a new node father of n and m */
     tree[node * 2]/*.Freq*/ = tree[n * 2]/*.Freq*/ + tree[m * 2]/*.Freq*/;
@@ -689,7 +690,7 @@ function build_tree(s, desc)
 
   } while (s.heap_len >= 2);
 
-  s.heap[--(s.heap_max)] = s.heap[1/*SMALLEST*/];
+  s.heap[--s.heap_max] = s.heap[1/*SMALLEST*/];
 
   /* At this point, the fields freq and dad are set. We can now
    * generate the bit lengths.
@@ -991,7 +992,7 @@ function _tr_stored_block(s, buf, stored_len, last)
 //int last;         /* one if this is the last block for a file */
 {
   send_bits(s, (STORED_BLOCK<<1)+(last ? 1 : 0), 3);    /* send block type */
-  copy_block(s, buf, stored_len, 1); /* with header */
+  copy_block(s, buf, stored_len, true); /* with header */
 }
 
 /* ===========================================================================