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Refactor JS view, working JS code for Bloom filters

This commit is contained in:
Phyks 2014-10-27 22:17:19 +01:00
parent a1fea61f4f
commit 775a8ab930
5 changed files with 183 additions and 96 deletions
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1
.gitignore vendored
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@ -1,3 +1,4 @@
*/__pycache__ */__pycache__
*/search_index* */search_index*
*/pages_index.json */pages_index.json
*.pyc

0
data/index.html
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1
index.html
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@ -14,5 +14,6 @@
</form> </form>
<div id="results"></div> <div id="results"></div>
<script type="text/javascript" src="js/bloom.js"></script> <script type="text/javascript" src="js/bloom.js"></script>
<script type="text/javascript" src="js/app.js"></script>
</body> </body>
</html> </html>

241
js/bloom.js
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@ -1,104 +1,153 @@
var loading = false; /*
var usable = false; * BloomFilters as implemented by https://github.com/jasondavies/bloomfilter.js
var search_index = false; *
* Original license kept
*
* Modified by Phyks to be constructed using the (capacity, error_rate) syntax rather
* than the explicit (number of bits, number of hash functions) syntax.
*/
// Check endianness to serve right file (function(exports) {
function checkEndian(){ exports.BloomFilter = BloomFilter;
var a = new ArrayBuffer(4); exports.fnv_1a = fnv_1a;
var b = new Uint8Array(a); exports.fnv_1a_b = fnv_1a_b;
var c = new Uint32Array(a); var typedArrays = typeof ArrayBuffer !== "undefined";
b[0] = 0xa1;
b[1] = 0xb2;
b[2] = 0xc3;
b[3] = 0xd4;
if(c[0] == 0xd4c3b2a1) return "little";
if(c[0] == 0xa1b2c3d4) return "big";
else return 0;
}
document.getElementById('search_form').addEventListener('submit', function(e) { // Creates a new bloom filter given its minimal capacity and an error_rate.
e.preventDefault(); // Calculation taken from https://en.wikipedia.org/wiki/Bloom_filter.
}); // If *capacity* is an array-like object, with a length
// property, then the bloom filter is loaded with data from the array, where
document.getElementById('search').addEventListener('click', function() { // each element is a 32-bit integer.
if(this.value == "Search for articles...") { // *error_rate* is an estimation of the required error_rate.
this.value = ""; function BloomFilter(capacity, error_rate) {
// *m* is the number of bits. Note that *m* is rounded up to
// the nearest multiple of 32. *k* specifies the number of hashing functions.
var a, i = -1;
// Number of slices, k
var k = Math.ceil(- Math.log(error_rate) / Math.log(2));
// Total number of bits, m
// Size of the UInt32 table, n
var m, n;
if (typeof capacity !== "number") {
a = capacity;
// Total number of bits, m
m = a.length * 32;
// Size of the UInt32 table, n
n = a.length;
}
else {
// Total number of bits, m
m = Math.ceil(capacity * Math.abs(Math.log(error_rate)) / (k * Math.pow(Math.log(2), 2))) * k;
// Size of the UInt32 table, n
n = Math.ceil(m / 32);
// Round total number of bits to closest multiple of 32
m = n * 32;
}
this.m = m;
this.k = k;
if (typedArrays) {
var 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),
buckets = this.buckets = new Int32Array(n);
if (a) while (++i < n) buckets[i] = a[i];
this._locations = new array(kbuffer);
} else {
var buckets = this.buckets = [];
if (a) while (++i < n) buckets[i] = a[i];
else while (++i < n) buckets[i] = 0;
this._locations = [];
}
} }
// See http://willwhim.wordpress.com/2011/09/03/producing-n-hash-functions-by-hashing-only-once/
if(search_index === false) { BloomFilter.prototype.locations = function(v) {
loading = true; var k = this.k,
document.getElementById("loading").innerHTML = "Loading index file..."; m = this.m,
r = this._locations,
var oReq = new XMLHttpRequest(); a = fnv_1a(v),
oReq.open("GET", "data/search_index_"+checkEndian(), true); b = fnv_1a_b(a),
oReq.responseType = "arraybuffer"; i = -1,
x = a % m;
oReq.onload = function (oEvent) { while (++i < k) {
var arrayBuffer = oReq.response; // Note: not oReq.responseText r[i] = x < 0 ? (x + m) : x;
x = (x + b) % m;
if (arrayBuffer) { }
var tmp = new Uint8Array(arrayBuffer); return r;
var nb_filters = tmp[0]*256+tmp[1]; };
BloomFilter.prototype.add = function(v) {
search_index = new Array(nb_filters); var l = this.locations(v + ""),
i = -1,
// For each of the bitarrays, parse it k = this.k,
var offset = 2; buckets = this.buckets;
for (var i = 0; i < nb_filters; i++) { while (++i < k) buckets[Math.floor(l[i] / 32)] |= 1 << (l[i] % 32);
// Size of the filter };
var length = tmp[offset]*256+tmp[offset+1]; // length is a number of bytes BloomFilter.prototype.test = function(v) {
var l = this.locations(v + ""),
var length_offset = Math.ceil(length/8); i = -1,
k = this.k,
search_index[i] = new Uint8Array(length_offset); b,
buckets = this.buckets;
// Parse filter while (++i < k) {
for (var j = 2; j < 2 + length_offset; j++) { b = l[i];
search_index[i][j] = tmp[offset + j]; if ((buckets[Math.floor(b / 32)] & (1 << (b % 32))) === 0) {
} return false;
offset += 2 + length_offset;
}
console.log(search_index);
document.getElementById("loading").innerHTML = "";
loading = false;
usable = true;
}
else {
document.getElementById("loading").innerHTML = "Error while loading search index.";
}
};
oReq.send(null);
var oReq2 = new XMLHttpRequest();
oReq2.open("GET", "data/pages_index.json", true);
oReq2.onreadystatechange = function() {
if (this.readyState == 4) {
if (this.status == 200) {
pages_index = window.JSON ? JSON.parse(this.responseText) : eval("("+this.responseText+")");
}
else {
document.getElementById("loading").innerHTML = "Error while loading pages index : HTTP error " + this.status + " " + this.statusText;
}
} }
} }
oReq2.send(); return true;
};
// Estimated cardinality.
BloomFilter.prototype.size = function() {
var buckets = this.buckets,
bits = 0;
for (var i = 0, n = buckets.length; i < n; ++i) bits += popcnt(buckets[i]);
return -this.m * Math.log(1 - bits / this.m) / this.k;
};
// http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
function popcnt(v) {
v -= (v >> 1) & 0x55555555;
v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
} }
}); // Fowler/Noll/Vo hashing.
function fnv_1a(v) {
/*function callback_change() { var n = v.length,
if(!usable) { a = 2166136261,
return; c,
} d,
var search = document.getElementById("search").value; i = -1;
document.getElementById("results").innerHTML = "<h2>Results :</h2>"; while (++i < n) {
//* for(var key in index) { c = v.charCodeAt(i);
if(index[key].test(search)) { if (d = c & 0xff000000) {
document.getElementById("results").innerHTML += "<p>"+key+"</p>"; a ^= d >> 24;
a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
}
if (d = c & 0xff0000) {
a ^= d >> 16;
a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
}
if (d = c & 0xff00) {
a ^= d >> 8;
a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
}
a ^= c & 0xff;
a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
} }
}* // // From http://home.comcast.net/~bretm/hash/6.html
if(!document.querySelectorAll("#results p").length) { a += a << 13;
document.getElementById("results").innerHTML += "<p>No results...</p>"; a ^= a >> 7;
a += a << 3;
a ^= a >> 17;
a += a << 5;
return a & 0xffffffff;
} }
} // One additional iteration of FNV, given a hash.
function fnv_1a_b(a) {
document.getElementById("search").addEventListener('input', callback_change);*/ a += (a << 1) + (a << 4) + (a << 7) + (a << 8) + (a << 24);
a += a << 13;
a ^= a >> 7;
a += a << 3;
a ^= a >> 17;
a += a << 5;
return a & 0xffffffff;
}
})(typeof exports !== "undefined" ? exports : this);

36
js/test.js Normal file
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/* These are some basic unit-tests for the bloom.js module */
var bloom = new BloomFilter(4, 0.1);
console.log(bloom);
// Add some elements to the filter.
bloom.add("foo");
bloom.add("bar");
// Test if an item is in our filter.
// Returns true if an item is probably in the set,
// or false if an item is definitely not in the set.
console.assert(bloom.test("foo") === true);
console.assert(bloom.test("bar") === true);
console.assert(bloom.test("blah") === false);
console.assert(bloom.test("blahahvhzfeh") === false);
console.assert(bloom.test("blahahvhzfehgfgahafgfa") === false);
// Serialisation. Note that bloom.buckets may be a typed array,
// so we convert to a normal array first.
var array = [].slice.call(bloom.buckets),
json = JSON.stringify(array);
console.log(array);
// Deserialisation. Note that the any array-like object is supported, but
// this will be used directly, so you may wish to use a typed array for
// performance.
var bloom = new BloomFilter(array, 0.1);
console.log(bloom);
console.assert(bloom.test("foo") === true);
console.assert(bloom.test("bar") === true);
console.assert(bloom.test("blah") === false);
console.assert(bloom.test("blahahvhzfeh") === false);
console.assert(bloom.test("blahahvhzfehgfgahafgfa") === false);