pdfjs-dist/lib/core/ascii_hex_stream.js

/**
 * @licstart The following is the entire license notice for the
 * Javascript code in this page
 *
 * Copyright 2021 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.AsciiHexStream = void 0;

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

class AsciiHexStream extends _decode_stream.DecodeStream {
  constructor(str, maybeLength) {
    if (maybeLength) {
      maybeLength = 0.5 * maybeLength;
    }

    super(maybeLength);
    this.str = str;
    this.dict = str.dict;
    this.firstDigit = -1;
  }

  readBlock() {
    const UPSTREAM_BLOCK_SIZE = 8000;
    const bytes = this.str.getBytes(UPSTREAM_BLOCK_SIZE);

    if (!bytes.length) {
      this.eof = true;
      return;
    }

    const maxDecodeLength = bytes.length + 1 >> 1;
    const buffer = this.ensureBuffer(this.bufferLength + maxDecodeLength);
    let bufferLength = this.bufferLength;
    let firstDigit = this.firstDigit;

    for (const ch of bytes) {
      let digit;

      if (ch >= 0x30 && ch <= 0x39) {
        digit = ch & 0x0f;
      } else if (ch >= 0x41 && ch <= 0x46 || ch >= 0x61 && ch <= 0x66) {
        digit = (ch & 0x0f) + 9;
      } else if (ch === 0x3e) {
        this.eof = true;
        break;
      } else {
        continue;
      }

      if (firstDigit < 0) {
        firstDigit = digit;
      } else {
        buffer[bufferLength++] = firstDigit << 4 | digit;
        firstDigit = -1;
      }
    }

    if (firstDigit >= 0 && this.eof) {
      buffer[bufferLength++] = firstDigit << 4;
      firstDigit = -1;
    }

    this.firstDigit = firstDigit;
    this.bufferLength = bufferLength;
  }

}

exports.AsciiHexStream = AsciiHexStream;