Simplified Adler32() until deopt traces investigated - now fast enougth

lib/zlib/adler32.js

@@ -1,55 +1,28 @@
 'use strict';
 
-function adler32(adler, buf, len, start)
-{
-  var BASE = 65521;      /* largest prime smaller than 65536 */
-  var NMAX =  5552;
+// TODO: investigate why --trace_deopt shows something
+// (though speed doesn't seems to reduce)
+//
+function adler32(adler, buf, len, pos) {
+  var s1 = adler & 0xffff
+    , s2 = (adler >>> 16) & 0xffff
+    , n = 0;
 
-  var i = start;
-  /* split Adler-32 into component sums */
-  var sum2 = (adler >> 16) & 0xffff;
-  adler &= 0xffff;
+  while (len !== 0) {
+    n = len > 5552 ? 5552 : len;
+    len -= n;
 
-  /* in case user likes doing a byte at a time, keep it fast */
-  if (len === 1) {
-    adler += buf[0];
-    if (adler >= BASE) {
-      adler -= BASE;
-    }
-    sum2 += adler;
-    if (sum2 >= BASE) {
-      sum2 -= BASE;
-    }
-    return (adler | (sum2 << 16)) >>> 0;
+    do {
+      s1 += buf[pos++];
+      s2 += s1;
+    } while (--n);
+
+    s1 %= 65521;
+    s2 %= 65521;
   }
 
-  /* in case short lengths are provided, keep it somewhat fast */
-  if (len < 16) {
-    for(i=0;i<len;i++) {
-      adler += buf[i];
-      sum2 += adler;
-    }
-    if (adler >= BASE) {
-      adler -= BASE;
-    }
-    sum2 %= BASE;            /* only added so many BASE's */
-    return (adler | (sum2 << 16)) >>> 0;
-  }
-
-  while (len>0) {
-    var cursor = len > NMAX ? NMAX : len;
-    len -= cursor;
-    for(var j=0;j<cursor;j++) {
-      adler += buf[i++];
-      sum2 += adler;
-    }
-
-    adler %= BASE;
-    sum2 %= BASE;
-  }
-
-  /* return recombined sums */
-  return (adler | (sum2 << 16)) >>> 0;
+  return (s1 | (s2 << 16));
 }
 
+
 module.exports = adler32;