7e6de580a7
- some files in zlib.js upstream had missing source code themselves
(closure-compiler.jar) or are not needed here, and have been removed
to save space; see debian/missing-sources/README for details
136 lines
3.1 KiB
JavaScript
136 lines
3.1 KiB
JavaScript
/**
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* @fileoverview Heap Sort 実装. ハフマン符号化で使用する.
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*/
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goog.provide('Zlib.Heap');
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goog.require('USE_TYPEDARRAY');
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goog.scope(function() {
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/**
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* カスタムハフマン符号で使用するヒープ実装
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* @param {number} length ヒープサイズ.
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* @constructor
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*/
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Zlib.Heap = function(length) {
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this.buffer = new (USE_TYPEDARRAY ? Uint16Array : Array)(length * 2);
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this.length = 0;
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};
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/**
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* 親ノードの index 取得
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* @param {number} index 子ノードの index.
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* @return {number} 親ノードの index.
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*
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*/
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Zlib.Heap.prototype.getParent = function(index) {
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return ((index - 2) / 4 | 0) * 2;
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};
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/**
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* 子ノードの index 取得
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* @param {number} index 親ノードの index.
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* @return {number} 子ノードの index.
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*/
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Zlib.Heap.prototype.getChild = function(index) {
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return 2 * index + 2;
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};
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/**
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* Heap に値を追加する
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* @param {number} index キー index.
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* @param {number} value 値.
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* @return {number} 現在のヒープ長.
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*/
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Zlib.Heap.prototype.push = function(index, value) {
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var current, parent,
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heap = this.buffer,
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swap;
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current = this.length;
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heap[this.length++] = value;
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heap[this.length++] = index;
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// ルートノードにたどり着くまで入れ替えを試みる
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while (current > 0) {
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parent = this.getParent(current);
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// 親ノードと比較して親の方が小さければ入れ替える
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if (heap[current] > heap[parent]) {
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swap = heap[current];
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heap[current] = heap[parent];
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heap[parent] = swap;
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swap = heap[current + 1];
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heap[current + 1] = heap[parent + 1];
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heap[parent + 1] = swap;
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current = parent;
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// 入れ替えが必要なくなったらそこで抜ける
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} else {
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break;
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}
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}
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return this.length;
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};
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/**
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* Heapから一番大きい値を返す
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* @return {{index: number, value: number, length: number}} {index: キーindex,
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* value: 値, length: ヒープ長} の Object.
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*/
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Zlib.Heap.prototype.pop = function() {
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var index, value,
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heap = this.buffer, swap,
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current, parent;
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value = heap[0];
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index = heap[1];
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// 後ろから値を取る
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this.length -= 2;
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heap[0] = heap[this.length];
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heap[1] = heap[this.length + 1];
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parent = 0;
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// ルートノードから下がっていく
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while (true) {
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current = this.getChild(parent);
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// 範囲チェック
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if (current >= this.length) {
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break;
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}
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// 隣のノードと比較して、隣の方が値が大きければ隣を現在ノードとして選択
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if (current + 2 < this.length && heap[current + 2] > heap[current]) {
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current += 2;
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}
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// 親ノードと比較して親の方が小さい場合は入れ替える
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if (heap[current] > heap[parent]) {
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swap = heap[parent];
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heap[parent] = heap[current];
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heap[current] = swap;
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swap = heap[parent + 1];
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heap[parent + 1] = heap[current + 1];
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heap[current + 1] = swap;
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} else {
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break;
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}
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parent = current;
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}
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return {index: index, value: value, length: this.length};
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};
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// end of scope
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});
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/* vim:set expandtab ts=2 sw=2 tw=80: */
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