phyks/bloomfilter.js
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Improvements to typed arrays.

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This commit is contained in:
Jason Davies 2011-12-07 00:41:09 +00:00
parent bd104575b5
commit 450423ebf6
1 changed files with 16 additions and 10 deletions
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26
bloomfilter.js
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@ -6,19 +6,20 @@
function BloomFilter(m, k) {
this.m = m;
this.k = k;
var buckets,
n = Math.ceil(m / k),
i = -1;
var n = Math.ceil(m / k);
try {
var buffer = new ArrayBuffer(4 * n),
kbuffer = new ArrayBuffer(4 * k);
buckets = this.buckets = new Uint32Array(buffer);
this._locations = new Uint32Array(kbuffer);
kbytes = 1 << Math.ceil(Math.log(Math.ceil(Math.log(m) / Math.LN2 / 8)) / Math.LN2),
array = kbytes === 1 ? Uint8Array : kbytes === 2 ? Uint16Array : Uint32Array,
kbuffer = new ArrayBuffer(kbytes * k);
this.buckets = new Uint32Array(buffer);
this._locations = new array(kbuffer);
} catch (e) {
buckets = this.buckets = [];
var buckets = this.buckets = [],
i = -1;
while (++i < n) buckets[i] = 0;
this._locations = [];
}
while (++i < n) buckets[i] = 0;
}
// See http://willwhim.wordpress.com/2011/09/03/producing-n-hash-functions-by-hashing-only-once/
@ -28,8 +29,12 @@
r = this._locations,
a = fnv_1a(v),
b = fnv_1a_b(a),
i = -1;
while (++i < k) r[i] = (a + b * i) % m;
i = -1,
x;
while (++i < k) {
x = (a + b * i) % m;
r[i] = x < 0 ? x + m : x;
}
return r;
};
@ -67,6 +72,7 @@
c = v.charCodeAt(i);
a ^= (c & 0xff00) >> 8;
a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
// Trickery to work around 32-bit signed integers (we need unsigned).
a &= 0xffffffff;
a ^= c & 0xff;
a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);