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101 lines
2.8 KiB
101 lines
2.8 KiB
/**
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* node-compress-commons
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*
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* Copyright (c) 2014 Chris Talkington, contributors.
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* Licensed under the MIT license.
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* https://github.com/archiverjs/node-compress-commons/blob/master/LICENSE-MIT
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*/
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var zipUtil = require('./util');
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var DATA_DESCRIPTOR_FLAG = 1 << 3;
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var ENCRYPTION_FLAG = 1 << 0;
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var NUMBER_OF_SHANNON_FANO_TREES_FLAG = 1 << 2;
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var SLIDING_DICTIONARY_SIZE_FLAG = 1 << 1;
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var STRONG_ENCRYPTION_FLAG = 1 << 6;
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var UFT8_NAMES_FLAG = 1 << 11;
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var GeneralPurposeBit = module.exports = function() {
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if (!(this instanceof GeneralPurposeBit)) {
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return new GeneralPurposeBit();
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}
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this.descriptor = false;
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this.encryption = false;
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this.utf8 = false;
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this.numberOfShannonFanoTrees = 0;
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this.strongEncryption = false;
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this.slidingDictionarySize = 0;
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return this;
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};
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GeneralPurposeBit.prototype.encode = function() {
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return zipUtil.getShortBytes(
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(this.descriptor ? DATA_DESCRIPTOR_FLAG : 0) |
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(this.utf8 ? UFT8_NAMES_FLAG : 0) |
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(this.encryption ? ENCRYPTION_FLAG : 0) |
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(this.strongEncryption ? STRONG_ENCRYPTION_FLAG : 0)
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);
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};
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GeneralPurposeBit.prototype.parse = function(buf, offset) {
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var flag = zipUtil.getShortBytesValue(buf, offset);
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var gbp = new GeneralPurposeBit();
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gbp.useDataDescriptor((flag & DATA_DESCRIPTOR_FLAG) !== 0);
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gbp.useUTF8ForNames((flag & UFT8_NAMES_FLAG) !== 0);
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gbp.useStrongEncryption((flag & STRONG_ENCRYPTION_FLAG) !== 0);
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gbp.useEncryption((flag & ENCRYPTION_FLAG) !== 0);
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gbp.setSlidingDictionarySize((flag & SLIDING_DICTIONARY_SIZE_FLAG) !== 0 ? 8192 : 4096);
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gbp.setNumberOfShannonFanoTrees((flag & NUMBER_OF_SHANNON_FANO_TREES_FLAG) !== 0 ? 3 : 2);
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return gbp;
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};
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GeneralPurposeBit.prototype.setNumberOfShannonFanoTrees = function(n) {
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this.numberOfShannonFanoTrees = n;
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};
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GeneralPurposeBit.prototype.getNumberOfShannonFanoTrees = function() {
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return this.numberOfShannonFanoTrees;
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};
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GeneralPurposeBit.prototype.setSlidingDictionarySize = function(n) {
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this.slidingDictionarySize = n;
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};
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GeneralPurposeBit.prototype.getSlidingDictionarySize = function() {
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return this.slidingDictionarySize;
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};
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GeneralPurposeBit.prototype.useDataDescriptor = function(b) {
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this.descriptor = b;
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};
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GeneralPurposeBit.prototype.usesDataDescriptor = function() {
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return this.descriptor;
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};
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GeneralPurposeBit.prototype.useEncryption = function(b) {
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this.encryption = b;
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};
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GeneralPurposeBit.prototype.usesEncryption = function() {
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return this.encryption;
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};
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GeneralPurposeBit.prototype.useStrongEncryption = function(b) {
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this.strongEncryption = b;
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};
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GeneralPurposeBit.prototype.usesStrongEncryption = function() {
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return this.strongEncryption;
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};
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GeneralPurposeBit.prototype.useUTF8ForNames = function(b) {
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this.utf8 = b;
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};
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GeneralPurposeBit.prototype.usesUTF8ForNames = function() {
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return this.utf8;
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}; |