From d8800632ea11b652fbb042d01b3f0ae0fe5c566b Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Fri, 20 May 2016 16:03:07 -0700
Subject: [PATCH] optimize new generations with rolling filter.

---
 lib/bcoin/bloom.js | 36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/lib/bcoin/bloom.js b/lib/bcoin/bloom.js
index cd0825d3..fc86c1d5 100644
--- a/lib/bcoin/bloom.js
+++ b/lib/bcoin/bloom.js
@@ -255,6 +255,7 @@ RollingFilter.prototype.reset = function reset() {
 
 RollingFilter.prototype.add = function add(val, enc) {
   var i, j, hash, bits, pos, pos1, pos2, bit, oct;
+  var m1, m2, v1, v2, mhi, mlo;
 
   if (typeof val === 'string')
     val = new Buffer(val, enc);
@@ -266,19 +267,22 @@ RollingFilter.prototype.add = function add(val, enc) {
     if (this.generation === 4)
       this.generation = 1;
 
+    m1 = (this.generation & 1) * 0xffffffff;
+    m2 = (this.generation >>> 1) * 0xffffffff;
+
     for (i = 0; i < this.items; i += 2) {
       pos1 = i * 8;
       pos2 = (i + 1) * 8;
-      for (j = 0; j < 64; j++) {
-        bit = j % 8;
-        oct = (j - bit) / 8;
-        bits = (this.filter[pos1 + oct] >>> bit) & 1;
-        bits |= ((this.filter[pos2 + oct] >>> bit) & 1) << 1;
-        if (bits === this.generation) {
-          this.filter[pos1 + oct] &= ~((this.generation & 1) << bit);
-          this.filter[pos2 + oct] &= ~((this.generation >>> 1) << bit);
-        }
-      }
+      v1 = read(this.filter, pos1);
+      v2 = read(this.filter, pos2);
+      mhi = (v1.hi ^ m1) | (v2.hi ^ m2);
+      mlo = (v1.lo ^ m1) | (v2.lo ^ m2);
+      v1.hi &= mhi;
+      v1.lo &= mlo;
+      v2.hi &= mhi;
+      v2.lo &= mlo;
+      write(this.filter, v1, pos1);
+      write(this.filter, v2, pos2);
     }
   }
 
@@ -459,6 +463,18 @@ function rotl32(w, b) {
   return (w << b) | (w >>> (32 - b));
 }
 
+function read(data, off) {
+  return {
+    hi: data.readUInt32LE(off + 4, true),
+    lo: data.readUInt32LE(off, true)
+  };
+}
+
+function write(data, value, off) {
+  data.writeUInt32LE(value.hi, off + 4, true);
+  data.writeUInt32LE(value.lo, off, true);
+}
+
 /*
  * Expose
  */