164 lines
2.7 KiB
JavaScript
164 lines
2.7 KiB
JavaScript
/*!
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* hashlist.js - memory optimal hash list
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* Copyright (c) 2017, Christopher Jeffrey (MIT License).
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* https://github.com/bcoin-org/bcoin
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*/
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'use strict';
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const assert = require('bsert');
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/*
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* Constants
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*/
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const DUMMY = Buffer.allocUnsafe(0);
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/**
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* HashList
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*/
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class HashList {
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/**
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* @param {Number} size
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*/
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constructor(size) {
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assert((size >>> 0) === size);
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assert((size & 1) === 0);
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this.size = size;
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this.data = DUMMY;
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this.pos = 0;
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}
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get length() {
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return (this.pos / this.size) >>> 0;
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}
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set length(len) {
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this.pos = (len >>> 0) * this.size;
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if (this.pos > this.data.length)
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this.pos = this.data.length;
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}
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[Symbol.iterator]() {
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return this.values();
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}
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keys() {
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return this.values();
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}
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*values() {
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for (let i = 0; i < this.pos; i += this.size)
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yield this.data.slice(i, i + this.size);
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}
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/**
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* @returns {HashList}
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*/
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clone() {
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// @ts-ignore
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const list = new this.constructor();
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list.data = copy(this.data);
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list.pos = this.pos;
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return list;
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}
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push(hash) {
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assert(Buffer.isBuffer(hash) && hash.length === this.size);
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if (this.data.length === 0)
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this.data = Buffer.allocUnsafe(256 * this.size);
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if (this.pos === this.data.length)
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this.data = realloc(this.data, this.pos * 2);
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assert(this.pos + this.size <= this.data.length);
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this.pos += hash.copy(this.data, this.pos);
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return this;
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}
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pop() {
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if (this.pos === 0)
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return null;
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this.pos -= this.size;
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return this.data.slice(this.pos, this.pos + this.size);
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}
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clear() {
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this.pos = 0;
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return this;
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}
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encode() {
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return this.data.slice(0, this.pos);
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}
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decode(data) {
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assert(Buffer.isBuffer(data));
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assert((data.length % this.size) === 0);
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this.data = data;
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this.pos = data.length;
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return this;
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}
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static decode(data, size) {
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return new HashList(size).decode(data);
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}
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*valuesSafe() {
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for (let i = 0; i < this.pos; i += this.size)
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yield copy(this.data.slice(i, i + this.size));
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}
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popSafe() {
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const hash = this.pop();
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if (!hash)
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return null;
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return copy(hash);
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}
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encodeSafe() {
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return copy(this.encode());
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}
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decodeSafe(data) {
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return this.decode(copy(data));
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}
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static decodeSafe(data, size) {
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return new HashList(size).decodeSafe(data);
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}
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}
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/*
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* Helpers
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*/
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function realloc(data, size) {
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assert(Buffer.isBuffer(data));
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assert((size >>> 0) === size);
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assert(size >= data.length);
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const buf = Buffer.allocUnsafe(size);
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data.copy(buf, 0);
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return buf;
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}
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function copy(buf) {
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return realloc(buf, buf.length);
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}
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/*
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* Expose
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*/
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module.exports = HashList;
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