pdfjs-dist/lib/core/run_length_stream.js

/**
 * @licstart The following is the entire license notice for the
 * JavaScript code in this page
 *
 * Copyright 2022 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.
 *
 * @licend The above is the entire license notice for the
 * JavaScript code in this page
 */
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.RunLengthStream = void 0;

var _decode_stream = require("./decode_stream.js");

class RunLengthStream extends _decode_stream.DecodeStream {
  constructor(str, maybeLength) {
    super(maybeLength);
    this.str = str;
    this.dict = str.dict;
  }

  readBlock() {
    const repeatHeader = this.str.getBytes(2);

    if (!repeatHeader || repeatHeader.length < 2 || repeatHeader[0] === 128) {
      this.eof = true;
      return;
    }

    let buffer;
    let bufferLength = this.bufferLength;
    let n = repeatHeader[0];

    if (n < 128) {
      buffer = this.ensureBuffer(bufferLength + n + 1);
      buffer[bufferLength++] = repeatHeader[1];

      if (n > 0) {
        const source = this.str.getBytes(n);
        buffer.set(source, bufferLength);
        bufferLength += n;
      }
    } else {
      n = 257 - n;
      const b = repeatHeader[1];
      buffer = this.ensureBuffer(bufferLength + n + 1);

      for (let i = 0; i < n; i++) {
        buffer[bufferLength++] = b;
      }
    }

    this.bufferLength = bufferLength;
  }

}

exports.RunLengthStream = RunLengthStream;