4df82ad31e
Unless you actually need to check that something is both a `Dict` and also of the *correct* type, using `instanceof Dict` directly should be a tiny bit more efficient since it avoids one function call and an unnecessary `undefined` check. This patch uses ESLint to enforce this, since we obviously still want to keep the `isDict` helper function for where it makes sense.
75 lines
2.3 KiB
JavaScript
75 lines
2.3 KiB
JavaScript
/* 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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import { BaseStream } from "./base_stream.js";
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import { DecodeStream } from "./decode_stream.js";
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import { Dict } from "./primitives.js";
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import { Jbig2Image } from "./jbig2.js";
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import { shadow } from "../shared/util.js";
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/**
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* For JBIG2's we use a library to decode these images and
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* the stream behaves like all the other DecodeStreams.
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*/
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class Jbig2Stream extends DecodeStream {
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constructor(stream, maybeLength, params) {
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super(maybeLength);
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this.stream = stream;
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this.dict = stream.dict;
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this.maybeLength = maybeLength;
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this.params = params;
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}
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get bytes() {
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// If `this.maybeLength` is null, we'll get the entire stream.
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return shadow(this, "bytes", this.stream.getBytes(this.maybeLength));
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}
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ensureBuffer(requested) {
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// No-op, since `this.readBlock` will always parse the entire image and
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// directly insert all of its data into `this.buffer`.
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}
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readBlock() {
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if (this.eof) {
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return;
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}
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const jbig2Image = new Jbig2Image();
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const chunks = [];
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if (this.params instanceof Dict) {
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const globalsStream = this.params.get("JBIG2Globals");
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if (globalsStream instanceof BaseStream) {
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const globals = globalsStream.getBytes();
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chunks.push({ data: globals, start: 0, end: globals.length });
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}
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}
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chunks.push({ data: this.bytes, start: 0, end: this.bytes.length });
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const data = jbig2Image.parseChunks(chunks);
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const dataLength = data.length;
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// JBIG2 had black as 1 and white as 0, inverting the colors
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for (let i = 0; i < dataLength; i++) {
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data[i] ^= 0xff;
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}
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this.buffer = data;
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this.bufferLength = dataLength;
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this.eof = true;
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}
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}
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export { Jbig2Stream };
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