Move the LZWStream from src/core/stream.js and into its own file
This commit is contained in:
Jonas Jenwald
parent
d10da907da
commit
6c1a321500
156
src/core/lzw_stream.js
Normal file
156
src/core/lzw_stream.js
Normal file
@ -0,0 +1,156 @@
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/* Copyright 2012 Mozilla Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* eslint-disable no-var */
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import { DecodeStream } from "./stream.js";
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var LZWStream = (function LZWStreamClosure() {
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// eslint-disable-next-line no-shadow
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function LZWStream(str, maybeLength, earlyChange) {
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this.str = str;
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this.dict = str.dict;
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this.cachedData = 0;
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this.bitsCached = 0;
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var maxLzwDictionarySize = 4096;
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var lzwState = {
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earlyChange,
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codeLength: 9,
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nextCode: 258,
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dictionaryValues: new Uint8Array(maxLzwDictionarySize),
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dictionaryLengths: new Uint16Array(maxLzwDictionarySize),
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dictionaryPrevCodes: new Uint16Array(maxLzwDictionarySize),
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currentSequence: new Uint8Array(maxLzwDictionarySize),
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currentSequenceLength: 0,
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};
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for (var i = 0; i < 256; ++i) {
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lzwState.dictionaryValues[i] = i;
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lzwState.dictionaryLengths[i] = 1;
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}
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this.lzwState = lzwState;
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DecodeStream.call(this, maybeLength);
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}
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LZWStream.prototype = Object.create(DecodeStream.prototype);
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LZWStream.prototype.readBits = function LZWStream_readBits(n) {
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var bitsCached = this.bitsCached;
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var cachedData = this.cachedData;
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while (bitsCached < n) {
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var c = this.str.getByte();
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if (c === -1) {
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this.eof = true;
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return null;
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}
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cachedData = (cachedData << 8) | c;
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bitsCached += 8;
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}
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this.bitsCached = bitsCached -= n;
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this.cachedData = cachedData;
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this.lastCode = null;
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return (cachedData >>> bitsCached) & ((1 << n) - 1);
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};
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LZWStream.prototype.readBlock = function LZWStream_readBlock() {
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var blockSize = 512;
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var estimatedDecodedSize = blockSize * 2,
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decodedSizeDelta = blockSize;
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var i, j, q;
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var lzwState = this.lzwState;
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if (!lzwState) {
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return; // eof was found
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}
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var earlyChange = lzwState.earlyChange;
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var nextCode = lzwState.nextCode;
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var dictionaryValues = lzwState.dictionaryValues;
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var dictionaryLengths = lzwState.dictionaryLengths;
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var dictionaryPrevCodes = lzwState.dictionaryPrevCodes;
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var codeLength = lzwState.codeLength;
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var prevCode = lzwState.prevCode;
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var currentSequence = lzwState.currentSequence;
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var currentSequenceLength = lzwState.currentSequenceLength;
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var decodedLength = 0;
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var currentBufferLength = this.bufferLength;
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var buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize);
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for (i = 0; i < blockSize; i++) {
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var code = this.readBits(codeLength);
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var hasPrev = currentSequenceLength > 0;
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if (code < 256) {
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currentSequence[0] = code;
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currentSequenceLength = 1;
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} else if (code >= 258) {
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if (code < nextCode) {
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currentSequenceLength = dictionaryLengths[code];
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for (j = currentSequenceLength - 1, q = code; j >= 0; j--) {
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currentSequence[j] = dictionaryValues[q];
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q = dictionaryPrevCodes[q];
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}
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} else {
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currentSequence[currentSequenceLength++] = currentSequence[0];
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}
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} else if (code === 256) {
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codeLength = 9;
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nextCode = 258;
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currentSequenceLength = 0;
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continue;
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} else {
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this.eof = true;
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delete this.lzwState;
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break;
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}
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if (hasPrev) {
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dictionaryPrevCodes[nextCode] = prevCode;
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dictionaryLengths[nextCode] = dictionaryLengths[prevCode] + 1;
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dictionaryValues[nextCode] = currentSequence[0];
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nextCode++;
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codeLength =
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(nextCode + earlyChange) & (nextCode + earlyChange - 1)
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? codeLength
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: Math.min(
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Math.log(nextCode + earlyChange) / 0.6931471805599453 + 1,
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12
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) | 0;
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}
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prevCode = code;
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decodedLength += currentSequenceLength;
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if (estimatedDecodedSize < decodedLength) {
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do {
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estimatedDecodedSize += decodedSizeDelta;
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} while (estimatedDecodedSize < decodedLength);
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buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize);
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}
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for (j = 0; j < currentSequenceLength; j++) {
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buffer[currentBufferLength++] = currentSequence[j];
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}
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}
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lzwState.nextCode = nextCode;
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lzwState.codeLength = codeLength;
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lzwState.prevCode = prevCode;
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lzwState.currentSequenceLength = currentSequenceLength;
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this.bufferLength = currentBufferLength;
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};
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return LZWStream;
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})();
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export { LZWStream };
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@ -17,7 +17,6 @@ import {
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Ascii85Stream,
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AsciiHexStream,
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FlateStream,
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LZWStream,
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NullStream,
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PredictorStream,
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RunLengthStream,
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@ -47,6 +46,7 @@ import { CCITTFaxStream } from "./ccitt_stream.js";
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import { Jbig2Stream } from "./jbig2_stream.js";
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import { JpegStream } from "./jpeg_stream.js";
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import { JpxStream } from "./jpx_stream.js";
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import { LZWStream } from "./lzw_stream.js";
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const MAX_LENGTH_TO_CACHE = 1000;
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const MAX_ADLER32_LENGTH = 5552;
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@ -1196,143 +1196,6 @@ var RunLengthStream = (function RunLengthStreamClosure() {
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return RunLengthStream;
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})();
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var LZWStream = (function LZWStreamClosure() {
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// eslint-disable-next-line no-shadow
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function LZWStream(str, maybeLength, earlyChange) {
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this.str = str;
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this.dict = str.dict;
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this.cachedData = 0;
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this.bitsCached = 0;
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var maxLzwDictionarySize = 4096;
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var lzwState = {
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earlyChange,
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codeLength: 9,
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nextCode: 258,
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dictionaryValues: new Uint8Array(maxLzwDictionarySize),
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dictionaryLengths: new Uint16Array(maxLzwDictionarySize),
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dictionaryPrevCodes: new Uint16Array(maxLzwDictionarySize),
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currentSequence: new Uint8Array(maxLzwDictionarySize),
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currentSequenceLength: 0,
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};
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for (var i = 0; i < 256; ++i) {
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lzwState.dictionaryValues[i] = i;
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lzwState.dictionaryLengths[i] = 1;
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}
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this.lzwState = lzwState;
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DecodeStream.call(this, maybeLength);
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}
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LZWStream.prototype = Object.create(DecodeStream.prototype);
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LZWStream.prototype.readBits = function LZWStream_readBits(n) {
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var bitsCached = this.bitsCached;
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var cachedData = this.cachedData;
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while (bitsCached < n) {
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var c = this.str.getByte();
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if (c === -1) {
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this.eof = true;
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return null;
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}
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cachedData = (cachedData << 8) | c;
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bitsCached += 8;
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}
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this.bitsCached = bitsCached -= n;
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this.cachedData = cachedData;
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this.lastCode = null;
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return (cachedData >>> bitsCached) & ((1 << n) - 1);
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};
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LZWStream.prototype.readBlock = function LZWStream_readBlock() {
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var blockSize = 512;
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var estimatedDecodedSize = blockSize * 2,
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decodedSizeDelta = blockSize;
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var i, j, q;
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var lzwState = this.lzwState;
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if (!lzwState) {
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return; // eof was found
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}
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var earlyChange = lzwState.earlyChange;
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var nextCode = lzwState.nextCode;
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var dictionaryValues = lzwState.dictionaryValues;
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var dictionaryLengths = lzwState.dictionaryLengths;
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var dictionaryPrevCodes = lzwState.dictionaryPrevCodes;
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var codeLength = lzwState.codeLength;
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var prevCode = lzwState.prevCode;
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var currentSequence = lzwState.currentSequence;
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var currentSequenceLength = lzwState.currentSequenceLength;
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var decodedLength = 0;
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var currentBufferLength = this.bufferLength;
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var buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize);
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for (i = 0; i < blockSize; i++) {
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var code = this.readBits(codeLength);
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var hasPrev = currentSequenceLength > 0;
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if (code < 256) {
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currentSequence[0] = code;
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currentSequenceLength = 1;
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} else if (code >= 258) {
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if (code < nextCode) {
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currentSequenceLength = dictionaryLengths[code];
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for (j = currentSequenceLength - 1, q = code; j >= 0; j--) {
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currentSequence[j] = dictionaryValues[q];
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q = dictionaryPrevCodes[q];
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}
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} else {
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currentSequence[currentSequenceLength++] = currentSequence[0];
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}
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} else if (code === 256) {
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codeLength = 9;
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nextCode = 258;
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currentSequenceLength = 0;
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continue;
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} else {
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this.eof = true;
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delete this.lzwState;
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break;
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}
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if (hasPrev) {
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dictionaryPrevCodes[nextCode] = prevCode;
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dictionaryLengths[nextCode] = dictionaryLengths[prevCode] + 1;
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dictionaryValues[nextCode] = currentSequence[0];
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nextCode++;
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codeLength =
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(nextCode + earlyChange) & (nextCode + earlyChange - 1)
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? codeLength
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: Math.min(
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Math.log(nextCode + earlyChange) / 0.6931471805599453 + 1,
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12
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) | 0;
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}
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prevCode = code;
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decodedLength += currentSequenceLength;
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if (estimatedDecodedSize < decodedLength) {
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do {
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estimatedDecodedSize += decodedSizeDelta;
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} while (estimatedDecodedSize < decodedLength);
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buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize);
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}
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for (j = 0; j < currentSequenceLength; j++) {
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buffer[currentBufferLength++] = currentSequence[j];
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}
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}
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lzwState.nextCode = nextCode;
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lzwState.codeLength = codeLength;
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lzwState.prevCode = prevCode;
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lzwState.currentSequenceLength = currentSequenceLength;
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this.bufferLength = currentBufferLength;
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};
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return LZWStream;
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})();
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var NullStream = (function NullStreamClosure() {
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// eslint-disable-next-line no-shadow
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function NullStream() {
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@ -1350,7 +1213,6 @@ export {
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DecodeStream,
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DecryptStream,
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FlateStream,
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LZWStream,
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NullStream,
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PredictorStream,
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RunLengthStream,
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