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