@meterio/devkit
Version:
Typescript library to aid DApp development on Meter network
64 lines • 3.96 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.Bloom = void 0;
const blake2b_1 = require("./cry/blake2b");
/**
* 2048 bits Bloom filter
*/
class Bloom {
/** estimate k(number of hash functions) according to item count */
static estimateK(itemCount) {
const k = Math.round((this.BITS_LENGTH / itemCount) * Math.LN2);
return Math.max(Math.min(k, this.MAX_K), 1);
}
/**
* new bloom filter instance
* @param k number of hash functions
* @param bits leave it out to construct an empty one
*/
constructor(k, bits) {
if (bits) {
this.bits = bits;
}
else {
this.bits = Buffer.alloc(Bloom.BITS_LENGTH / 8);
}
this.k = k;
}
/**
* add item
* @param item
*/
add(item) {
this.distribute(item, (index, bit) => {
this.bits[index] |= bit;
return true;
});
}
/**
* test if an item contained. (false positive)
* @param item
*/
test(item) {
return this.distribute(item, (index, bit) => {
return (this.bits[index] & bit) === bit;
});
}
distribute(item, cb) {
const hash = (0, blake2b_1.blake2b256)(item);
for (let i = 0; i < this.k; i += 1) {
const d = (hash[i * 2 + 1] + (hash[i * 2] << 8)) % Bloom.BITS_LENGTH;
const bit = 1 << d % 8;
if (!cb(Math.floor(d / 8), bit)) {
return false;
}
}
return true;
}
}
/** number of hash functions */
Bloom.MAX_K = 16;
/** bit length */
Bloom.BITS_LENGTH = 2048;
exports.Bloom = Bloom;
//# sourceMappingURL=data:application/json;base64,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