Refactor JS view, working JS code for Bloom filters
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Phyks
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.gitignore
vendored
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.gitignore
vendored
@ -1,3 +1,4 @@
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*/__pycache__
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*/search_index*
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*/pages_index.json
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*.pyc
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@ -14,5 +14,6 @@
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</form>
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<div id="results"></div>
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<script type="text/javascript" src="js/bloom.js"></script>
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<script type="text/javascript" src="js/app.js"></script>
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</body>
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</html>
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229
js/bloom.js
229
js/bloom.js
@ -1,104 +1,153 @@
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var loading = false;
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var usable = false;
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var search_index = false;
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/*
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* BloomFilters as implemented by https://github.com/jasondavies/bloomfilter.js
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*
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* Original license kept
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*
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* Modified by Phyks to be constructed using the (capacity, error_rate) syntax rather
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* than the explicit (number of bits, number of hash functions) syntax.
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*/
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// Check endianness to serve right file
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function checkEndian(){
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var a = new ArrayBuffer(4);
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var b = new Uint8Array(a);
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var c = new Uint32Array(a);
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b[0] = 0xa1;
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b[1] = 0xb2;
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b[2] = 0xc3;
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b[3] = 0xd4;
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if(c[0] == 0xd4c3b2a1) return "little";
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if(c[0] == 0xa1b2c3d4) return "big";
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else return 0;
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}
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(function(exports) {
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exports.BloomFilter = BloomFilter;
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exports.fnv_1a = fnv_1a;
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exports.fnv_1a_b = fnv_1a_b;
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var typedArrays = typeof ArrayBuffer !== "undefined";
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document.getElementById('search_form').addEventListener('submit', function(e) {
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e.preventDefault();
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});
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document.getElementById('search').addEventListener('click', function() {
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if(this.value == "Search for articles...") {
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this.value = "";
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}
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if(search_index === false) {
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loading = true;
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document.getElementById("loading").innerHTML = "Loading index file...";
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var oReq = new XMLHttpRequest();
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oReq.open("GET", "data/search_index_"+checkEndian(), true);
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oReq.responseType = "arraybuffer";
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oReq.onload = function (oEvent) {
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var arrayBuffer = oReq.response; // Note: not oReq.responseText
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if (arrayBuffer) {
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var tmp = new Uint8Array(arrayBuffer);
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var nb_filters = tmp[0]*256+tmp[1];
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search_index = new Array(nb_filters);
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// For each of the bitarrays, parse it
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var offset = 2;
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for (var i = 0; i < nb_filters; i++) {
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// Size of the filter
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var length = tmp[offset]*256+tmp[offset+1]; // length is a number of bytes
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var length_offset = Math.ceil(length/8);
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search_index[i] = new Uint8Array(length_offset);
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// Parse filter
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for (var j = 2; j < 2 + length_offset; j++) {
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search_index[i][j] = tmp[offset + j];
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}
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offset += 2 + length_offset;
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}
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console.log(search_index);
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document.getElementById("loading").innerHTML = "";
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loading = false;
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usable = true;
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// Creates a new bloom filter given its minimal capacity and an error_rate.
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// Calculation taken from https://en.wikipedia.org/wiki/Bloom_filter.
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// If *capacity* is an array-like object, with a length
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// property, then the bloom filter is loaded with data from the array, where
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// each element is a 32-bit integer.
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// *error_rate* is an estimation of the required error_rate.
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function BloomFilter(capacity, error_rate) {
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// *m* is the number of bits. Note that *m* is rounded up to
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// the nearest multiple of 32. *k* specifies the number of hashing functions.
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var a, i = -1;
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// Number of slices, k
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var k = Math.ceil(- Math.log(error_rate) / Math.log(2));
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// Total number of bits, m
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// Size of the UInt32 table, n
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var m, n;
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if (typeof capacity !== "number") {
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a = capacity;
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// Total number of bits, m
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m = a.length * 32;
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// Size of the UInt32 table, n
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n = a.length;
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}
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else {
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document.getElementById("loading").innerHTML = "Error while loading search index.";
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// Total number of bits, m
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m = Math.ceil(capacity * Math.abs(Math.log(error_rate)) / (k * Math.pow(Math.log(2), 2))) * k;
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// Size of the UInt32 table, n
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n = Math.ceil(m / 32);
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// Round total number of bits to closest multiple of 32
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m = n * 32;
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}
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this.m = m;
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this.k = k;
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if (typedArrays) {
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var kbytes = 1 << Math.ceil(Math.log(Math.ceil(Math.log(m) / Math.LN2 / 8)) / Math.LN2),
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array = kbytes === 1 ? Uint8Array : kbytes === 2 ? Uint16Array : Uint32Array,
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kbuffer = new ArrayBuffer(kbytes * k),
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buckets = this.buckets = new Int32Array(n);
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if (a) while (++i < n) buckets[i] = a[i];
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this._locations = new array(kbuffer);
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} else {
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var buckets = this.buckets = [];
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if (a) while (++i < n) buckets[i] = a[i];
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else while (++i < n) buckets[i] = 0;
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this._locations = [];
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}
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}
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// See http://willwhim.wordpress.com/2011/09/03/producing-n-hash-functions-by-hashing-only-once/
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BloomFilter.prototype.locations = function(v) {
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var k = this.k,
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m = this.m,
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r = this._locations,
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a = fnv_1a(v),
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b = fnv_1a_b(a),
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i = -1,
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x = a % m;
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while (++i < k) {
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r[i] = x < 0 ? (x + m) : x;
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x = (x + b) % m;
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}
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return r;
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};
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oReq.send(null);
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var oReq2 = new XMLHttpRequest();
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oReq2.open("GET", "data/pages_index.json", true);
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oReq2.onreadystatechange = function() {
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if (this.readyState == 4) {
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if (this.status == 200) {
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pages_index = window.JSON ? JSON.parse(this.responseText) : eval("("+this.responseText+")");
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}
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else {
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document.getElementById("loading").innerHTML = "Error while loading pages index : HTTP error " + this.status + " " + this.statusText;
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BloomFilter.prototype.add = function(v) {
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var l = this.locations(v + ""),
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i = -1,
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k = this.k,
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buckets = this.buckets;
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while (++i < k) buckets[Math.floor(l[i] / 32)] |= 1 << (l[i] % 32);
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};
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BloomFilter.prototype.test = function(v) {
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var l = this.locations(v + ""),
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i = -1,
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k = this.k,
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b,
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buckets = this.buckets;
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while (++i < k) {
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b = l[i];
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if ((buckets[Math.floor(b / 32)] & (1 << (b % 32))) === 0) {
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return false;
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}
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}
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return true;
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};
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// Estimated cardinality.
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BloomFilter.prototype.size = function() {
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var buckets = this.buckets,
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bits = 0;
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for (var i = 0, n = buckets.length; i < n; ++i) bits += popcnt(buckets[i]);
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return -this.m * Math.log(1 - bits / this.m) / this.k;
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};
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// http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
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function popcnt(v) {
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v -= (v >> 1) & 0x55555555;
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v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
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return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
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}
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oReq2.send();
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// Fowler/Noll/Vo hashing.
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function fnv_1a(v) {
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var n = v.length,
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a = 2166136261,
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c,
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d,
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i = -1;
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while (++i < n) {
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c = v.charCodeAt(i);
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if (d = c & 0xff000000) {
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a ^= d >> 24;
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a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
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}
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});
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/*function callback_change() {
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if(!usable) {
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return;
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if (d = c & 0xff0000) {
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a ^= d >> 16;
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a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
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}
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var search = document.getElementById("search").value;
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document.getElementById("results").innerHTML = "<h2>Results :</h2>";
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//* for(var key in index) {
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if(index[key].test(search)) {
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document.getElementById("results").innerHTML += "<p>"+key+"</p>";
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if (d = c & 0xff00) {
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a ^= d >> 8;
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a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
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}
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}* //
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if(!document.querySelectorAll("#results p").length) {
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document.getElementById("results").innerHTML += "<p>No results...</p>";
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a ^= c & 0xff;
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a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
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}
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// From http://home.comcast.net/~bretm/hash/6.html
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a += a << 13;
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a ^= a >> 7;
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a += a << 3;
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a ^= a >> 17;
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a += a << 5;
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return a & 0xffffffff;
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}
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document.getElementById("search").addEventListener('input', callback_change);*/
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// One additional iteration of FNV, given a hash.
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function fnv_1a_b(a) {
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a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
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a += a << 13;
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a ^= a >> 7;
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a += a << 3;
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a ^= a >> 17;
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a += a << 5;
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return a & 0xffffffff;
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}
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})(typeof exports !== "undefined" ? exports : this);
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36
js/test.js
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36
js/test.js
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/* These are some basic unit-tests for the bloom.js module */
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var bloom = new BloomFilter(4, 0.1);
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console.log(bloom);
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// Add some elements to the filter.
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bloom.add("foo");
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bloom.add("bar");
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// Test if an item is in our filter.
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// Returns true if an item is probably in the set,
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// or false if an item is definitely not in the set.
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console.assert(bloom.test("foo") === true);
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console.assert(bloom.test("bar") === true);
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console.assert(bloom.test("blah") === false);
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console.assert(bloom.test("blahahvhzfeh") === false);
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console.assert(bloom.test("blahahvhzfehgfgahafgfa") === false);
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// Serialisation. Note that bloom.buckets may be a typed array,
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// so we convert to a normal array first.
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var array = [].slice.call(bloom.buckets),
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json = JSON.stringify(array);
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console.log(array);
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// Deserialisation. Note that the any array-like object is supported, but
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// this will be used directly, so you may wish to use a typed array for
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// performance.
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var bloom = new BloomFilter(array, 0.1);
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console.log(bloom);
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console.assert(bloom.test("foo") === true);
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console.assert(bloom.test("bar") === true);
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console.assert(bloom.test("blah") === false);
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console.assert(bloom.test("blahahvhzfeh") === false);
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console.assert(bloom.test("blahahvhzfehgfgahafgfa") === false);
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