jiapengyu
80 lines
2.1 KiB
JavaScript
80 lines
2.1 KiB
JavaScript
import { getShortBytes, getShortBytesValue } from "./util.js";
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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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export default class GeneralPurposeBit {
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constructor() {
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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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encode() {
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return 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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static parse(buf, offset) {
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var flag = 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(
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(flag & SLIDING_DICTIONARY_SIZE_FLAG) !== 0 ? 8192 : 4096,
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);
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gbp.setNumberOfShannonFanoTrees(
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(flag & NUMBER_OF_SHANNON_FANO_TREES_FLAG) !== 0 ? 3 : 2,
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);
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return gbp;
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}
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setNumberOfShannonFanoTrees(n) {
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this.numberOfShannonFanoTrees = n;
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}
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getNumberOfShannonFanoTrees() {
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return this.numberOfShannonFanoTrees;
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}
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setSlidingDictionarySize(n) {
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this.slidingDictionarySize = n;
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}
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getSlidingDictionarySize() {
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return this.slidingDictionarySize;
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}
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useDataDescriptor(b) {
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this.descriptor = b;
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}
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usesDataDescriptor() {
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return this.descriptor;
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}
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useEncryption(b) {
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this.encryption = b;
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}
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usesEncryption() {
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return this.encryption;
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}
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useStrongEncryption(b) {
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this.strongEncryption = b;
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}
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usesStrongEncryption() {
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return this.strongEncryption;
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}
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useUTF8ForNames(b) {
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this.utf8 = b;
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}
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usesUTF8ForNames() {
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return this.utf8;
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}
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}
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