From 6c1a321500e08ec2917a2541b80fcc16ec4faa3f Mon Sep 17 00:00:00 2001 From: Jonas Jenwald Date: Tue, 27 Apr 2021 12:55:23 +0200 Subject: [PATCH] Move the `LZWStream` from `src/core/stream.js` and into its own file --- src/core/lzw_stream.js | 156 +++++++++++++++++++++++++++++++++++++++++ src/core/parser.js | 2 +- src/core/stream.js | 138 ------------------------------------ 3 files changed, 157 insertions(+), 139 deletions(-) create mode 100644 src/core/lzw_stream.js diff --git a/src/core/lzw_stream.js b/src/core/lzw_stream.js new file mode 100644 index 000000000..4d3a8cdce --- /dev/null +++ b/src/core/lzw_stream.js @@ -0,0 +1,156 @@ +/* Copyright 2012 Mozilla Foundation + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +/* eslint-disable no-var */ + +import { DecodeStream } from "./stream.js"; + +var LZWStream = (function LZWStreamClosure() { + // eslint-disable-next-line no-shadow + function LZWStream(str, maybeLength, earlyChange) { + this.str = str; + this.dict = str.dict; + this.cachedData = 0; + this.bitsCached = 0; + + var maxLzwDictionarySize = 4096; + var lzwState = { + earlyChange, + codeLength: 9, + nextCode: 258, + dictionaryValues: new Uint8Array(maxLzwDictionarySize), + dictionaryLengths: new Uint16Array(maxLzwDictionarySize), + dictionaryPrevCodes: new Uint16Array(maxLzwDictionarySize), + currentSequence: new Uint8Array(maxLzwDictionarySize), + currentSequenceLength: 0, + }; + for (var i = 0; i < 256; ++i) { + lzwState.dictionaryValues[i] = i; + lzwState.dictionaryLengths[i] = 1; + } + this.lzwState = lzwState; + + DecodeStream.call(this, maybeLength); + } + + LZWStream.prototype = Object.create(DecodeStream.prototype); + + LZWStream.prototype.readBits = function LZWStream_readBits(n) { + var bitsCached = this.bitsCached; + var cachedData = this.cachedData; + while (bitsCached < n) { + var c = this.str.getByte(); + if (c === -1) { + this.eof = true; + return null; + } + cachedData = (cachedData << 8) | c; + bitsCached += 8; + } + this.bitsCached = bitsCached -= n; + this.cachedData = cachedData; + this.lastCode = null; + return (cachedData >>> bitsCached) & ((1 << n) - 1); + }; + + LZWStream.prototype.readBlock = function LZWStream_readBlock() { + var blockSize = 512; + var estimatedDecodedSize = blockSize * 2, + decodedSizeDelta = blockSize; + var i, j, q; + + var lzwState = this.lzwState; + if (!lzwState) { + return; // eof was found + } + + var earlyChange = lzwState.earlyChange; + var nextCode = lzwState.nextCode; + var dictionaryValues = lzwState.dictionaryValues; + var dictionaryLengths = lzwState.dictionaryLengths; + var dictionaryPrevCodes = lzwState.dictionaryPrevCodes; + var codeLength = lzwState.codeLength; + var prevCode = lzwState.prevCode; + var currentSequence = lzwState.currentSequence; + var currentSequenceLength = lzwState.currentSequenceLength; + + var decodedLength = 0; + var currentBufferLength = this.bufferLength; + var buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize); + + for (i = 0; i < blockSize; i++) { + var code = this.readBits(codeLength); + var hasPrev = currentSequenceLength > 0; + if (code < 256) { + currentSequence[0] = code; + currentSequenceLength = 1; + } else if (code >= 258) { + if (code < nextCode) { + currentSequenceLength = dictionaryLengths[code]; + for (j = currentSequenceLength - 1, q = code; j >= 0; j--) { + currentSequence[j] = dictionaryValues[q]; + q = dictionaryPrevCodes[q]; + } + } else { + currentSequence[currentSequenceLength++] = currentSequence[0]; + } + } else if (code === 256) { + codeLength = 9; + nextCode = 258; + currentSequenceLength = 0; + continue; + } else { + this.eof = true; + delete this.lzwState; + break; + } + + if (hasPrev) { + dictionaryPrevCodes[nextCode] = prevCode; + dictionaryLengths[nextCode] = dictionaryLengths[prevCode] + 1; + dictionaryValues[nextCode] = currentSequence[0]; + nextCode++; + codeLength = + (nextCode + earlyChange) & (nextCode + earlyChange - 1) + ? codeLength + : Math.min( + Math.log(nextCode + earlyChange) / 0.6931471805599453 + 1, + 12 + ) | 0; + } + prevCode = code; + + decodedLength += currentSequenceLength; + if (estimatedDecodedSize < decodedLength) { + do { + estimatedDecodedSize += decodedSizeDelta; + } while (estimatedDecodedSize < decodedLength); + buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize); + } + for (j = 0; j < currentSequenceLength; j++) { + buffer[currentBufferLength++] = currentSequence[j]; + } + } + lzwState.nextCode = nextCode; + lzwState.codeLength = codeLength; + lzwState.prevCode = prevCode; + lzwState.currentSequenceLength = currentSequenceLength; + + this.bufferLength = currentBufferLength; + }; + + return LZWStream; +})(); + +export { LZWStream }; diff --git a/src/core/parser.js b/src/core/parser.js index 6692adbda..5c79654b0 100644 --- a/src/core/parser.js +++ b/src/core/parser.js @@ -17,7 +17,6 @@ import { Ascii85Stream, AsciiHexStream, FlateStream, - LZWStream, NullStream, PredictorStream, RunLengthStream, @@ -47,6 +46,7 @@ import { CCITTFaxStream } from "./ccitt_stream.js"; import { Jbig2Stream } from "./jbig2_stream.js"; import { JpegStream } from "./jpeg_stream.js"; import { JpxStream } from "./jpx_stream.js"; +import { LZWStream } from "./lzw_stream.js"; const MAX_LENGTH_TO_CACHE = 1000; const MAX_ADLER32_LENGTH = 5552; diff --git a/src/core/stream.js b/src/core/stream.js index 20717d3dc..258f0205e 100644 --- a/src/core/stream.js +++ b/src/core/stream.js @@ -1196,143 +1196,6 @@ var RunLengthStream = (function RunLengthStreamClosure() { return RunLengthStream; })(); -var LZWStream = (function LZWStreamClosure() { - // eslint-disable-next-line no-shadow - function LZWStream(str, maybeLength, earlyChange) { - this.str = str; - this.dict = str.dict; - this.cachedData = 0; - this.bitsCached = 0; - - var maxLzwDictionarySize = 4096; - var lzwState = { - earlyChange, - codeLength: 9, - nextCode: 258, - dictionaryValues: new Uint8Array(maxLzwDictionarySize), - dictionaryLengths: new Uint16Array(maxLzwDictionarySize), - dictionaryPrevCodes: new Uint16Array(maxLzwDictionarySize), - currentSequence: new Uint8Array(maxLzwDictionarySize), - currentSequenceLength: 0, - }; - for (var i = 0; i < 256; ++i) { - lzwState.dictionaryValues[i] = i; - lzwState.dictionaryLengths[i] = 1; - } - this.lzwState = lzwState; - - DecodeStream.call(this, maybeLength); - } - - LZWStream.prototype = Object.create(DecodeStream.prototype); - - LZWStream.prototype.readBits = function LZWStream_readBits(n) { - var bitsCached = this.bitsCached; - var cachedData = this.cachedData; - while (bitsCached < n) { - var c = this.str.getByte(); - if (c === -1) { - this.eof = true; - return null; - } - cachedData = (cachedData << 8) | c; - bitsCached += 8; - } - this.bitsCached = bitsCached -= n; - this.cachedData = cachedData; - this.lastCode = null; - return (cachedData >>> bitsCached) & ((1 << n) - 1); - }; - - LZWStream.prototype.readBlock = function LZWStream_readBlock() { - var blockSize = 512; - var estimatedDecodedSize = blockSize * 2, - decodedSizeDelta = blockSize; - var i, j, q; - - var lzwState = this.lzwState; - if (!lzwState) { - return; // eof was found - } - - var earlyChange = lzwState.earlyChange; - var nextCode = lzwState.nextCode; - var dictionaryValues = lzwState.dictionaryValues; - var dictionaryLengths = lzwState.dictionaryLengths; - var dictionaryPrevCodes = lzwState.dictionaryPrevCodes; - var codeLength = lzwState.codeLength; - var prevCode = lzwState.prevCode; - var currentSequence = lzwState.currentSequence; - var currentSequenceLength = lzwState.currentSequenceLength; - - var decodedLength = 0; - var currentBufferLength = this.bufferLength; - var buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize); - - for (i = 0; i < blockSize; i++) { - var code = this.readBits(codeLength); - var hasPrev = currentSequenceLength > 0; - if (code < 256) { - currentSequence[0] = code; - currentSequenceLength = 1; - } else if (code >= 258) { - if (code < nextCode) { - currentSequenceLength = dictionaryLengths[code]; - for (j = currentSequenceLength - 1, q = code; j >= 0; j--) { - currentSequence[j] = dictionaryValues[q]; - q = dictionaryPrevCodes[q]; - } - } else { - currentSequence[currentSequenceLength++] = currentSequence[0]; - } - } else if (code === 256) { - codeLength = 9; - nextCode = 258; - currentSequenceLength = 0; - continue; - } else { - this.eof = true; - delete this.lzwState; - break; - } - - if (hasPrev) { - dictionaryPrevCodes[nextCode] = prevCode; - dictionaryLengths[nextCode] = dictionaryLengths[prevCode] + 1; - dictionaryValues[nextCode] = currentSequence[0]; - nextCode++; - codeLength = - (nextCode + earlyChange) & (nextCode + earlyChange - 1) - ? codeLength - : Math.min( - Math.log(nextCode + earlyChange) / 0.6931471805599453 + 1, - 12 - ) | 0; - } - prevCode = code; - - decodedLength += currentSequenceLength; - if (estimatedDecodedSize < decodedLength) { - do { - estimatedDecodedSize += decodedSizeDelta; - } while (estimatedDecodedSize < decodedLength); - buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize); - } - for (j = 0; j < currentSequenceLength; j++) { - buffer[currentBufferLength++] = currentSequence[j]; - } - } - lzwState.nextCode = nextCode; - lzwState.codeLength = codeLength; - lzwState.prevCode = prevCode; - lzwState.currentSequenceLength = currentSequenceLength; - - this.bufferLength = currentBufferLength; - }; - - return LZWStream; -})(); - var NullStream = (function NullStreamClosure() { // eslint-disable-next-line no-shadow function NullStream() { @@ -1350,7 +1213,6 @@ export { DecodeStream, DecryptStream, FlateStream, - LZWStream, NullStream, PredictorStream, RunLengthStream,