pdfjs-dist/external/cmapscompress/compress.js

/* Copyright 2014 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.
 */

var fs = require('fs');
var path = require('path');
var parseAdobeCMap = require('./parse.js').parseAdobeCMap;
var optimizeCMap = require('./optimize.js').optimizeCMap;

function compressCmap(srcPath, destPath, verify) {
  var content = fs.readFileSync(srcPath).toString();
  var inputData = parseAdobeCMap(content);
  optimizeCMap(inputData);

  var out = writeByte((inputData.type << 1) | inputData.wmode);
  if (inputData.comment) {
    out += writeByte(0xE0) + writeString(inputData.comment);
  }
  if (inputData.usecmap) {
    out += writeByte(0xE1) + writeString(inputData.usecmap);
  }
  var i = 0;
  while (i < inputData.body.length) {
    var item = inputData.body[i++], subitems = item.items;
    var first = item.items[0];
    var sequence = item.sequence === true;
    var flags = (item.type << 5) | (sequence ? 0x10 : 0);
    var nextStart, nextCode;
    switch (item.type) {
      case 0:
        out += writeByte(flags | getHexSize(first.start)) + writeNumber(subitems.length);
        out += first.start + writeNumber(subHex(first.end, first.start));
        nextStart = incHex(first.end);
        for (var j = 1; j < subitems.length; j++) {
          out += writeNumber(subHex(subitems[j].start, nextStart)) +
            writeNumber(subHex(subitems[j].end, subitems[j].start));
          nextStart = incHex(subitems[j].end);
        }
        break;
      case 1:
        out += writeByte(flags | getHexSize(first.start)) + writeNumber(subitems.length);
        out += first.start + writeNumber(subHex(first.end, first.start)) + writeNumber(first.code);
        nextStart = incHex(first.end);
        for (var j = 1; j < subitems.length; j++) {
          out += writeNumber(subHex(subitems[j].start, nextStart)) +
            writeNumber(subHex(subitems[j].end, subitems[j].start)) +
            writeNumber(subitems[j].code);
          nextStart = incHex(subitems[j].end);
        }
        break;
      case 2:
        out += writeByte(flags | getHexSize(first.char)) + writeNumber(subitems.length);
        out += first.char + writeNumber(first.code);
        nextStart = incHex(first.char);
        nextCode = first.code + 1;
        for (var j = 1; j < subitems.length; j++) {
          out += (sequence ? '' : writeNumber(subHex(subitems[j].char, nextStart))) +
            writeSigned(subitems[j].code - nextCode);
          nextStart = incHex(subitems[j].char);
          nextCode = item.items[j].code + 1;
        }
        break;
      case 3:
        out += writeByte(flags | getHexSize(first.start)) + writeNumber(subitems.length);
        out += first.start + writeNumber(subHex(first.end, first.start)) + writeNumber(first.code);
        nextStart = incHex(first.end);
        for (var j = 1; j < subitems.length; j++) {
          out += (sequence ? '' : writeNumber(subHex(subitems[j].start, nextStart))) +
            writeNumber(subHex(subitems[j].end, subitems[j].start)) +
            writeNumber(subitems[j].code);
          nextStart = incHex(subitems[j].end);
        }
        break;
      case 4:
        out += writeByte(flags | getHexSize(first.code)) + writeNumber(subitems.length);
        out += first.char + first.code;
        nextStart = incHex(first.char);
        nextCode = incHex(first.code);
        for (var j = 1; j < subitems.length; j++) {
          out += (sequence ? '' : writeNumber(subHex(subitems[j].char, nextStart))) +
            writeSigned(subHex(subitems[j].code, nextCode));
          nextStart = incHex(subitems[j].char);
          nextCode = incHex(subitems[j].code);
        }
        break;
      case 5:
        out += writeByte(flags | getHexSize(first.code)) + writeNumber(subitems.length);
        out += first.start + writeNumber(subHex(first.end, first.start)) + first.code;
        nextStart = incHex(first.end);
        for (var j = 1; j < subitems.length; j++) {
          out += (sequence ? '' : writeNumber(subHex(subitems[j].start, nextStart))) +
            writeNumber(subHex(subitems[j].end, subitems[j].start)) +
            subitems[j].code;
          nextStart = incHex(subitems[j].end);
        }
        break;

    }
  }

  fs.writeFileSync(destPath, new Buffer(out, 'hex'));

  if (verify) {
    var result2 = parseCMap(out);
    var isGood = JSON.stringify(inputData) == JSON.stringify(result2);
    if (!isGood) {
      throw new Error('Extracted data does not match the expected result');
    }
  }

  return {
    orig: fs.statSync(srcPath).size,
    packed: out.length >> 1
  };
}

function parseCMap(binaryData) {
  var reader = {
    buffer: binaryData,
    pos: 0,
    end: binaryData.length,
    readByte: function () {
      if (this.pos >= this.end) {
        return -1;
      }
      var d1 = fromHexDigit(this.buffer[this.pos]);
      var d2 = fromHexDigit(this.buffer[this.pos + 1]);
      this.pos += 2;
      return (d1 << 4) | d2;
    },
    readNumber: function () {
      var n = 0;
      var last;
      do {
        var b = this.readByte();
        last = !(b & 0x80);
        n = (n << 7) | (b & 0x7F);
      } while (!last);
      return n;
    },
    readSigned: function () {
      var n = this.readNumber();
      return (n & 1) ? -(n >>> 1) - 1 : n >>> 1;
    },
    readHex: function (size) {
      var lengthInChars = (size + 1) << 1;
      var s = this.buffer.substr(this.pos, lengthInChars);
      this.pos += lengthInChars;
      return s;
    },
    readHexNumber: function (size) {
      var lengthInChars = (size + 1) << 1;
      var stack = [];
      do {
        var b = this.readByte();
        last = !(b & 0x80);
        stack.push(b & 0x7F);
      } while (!last);
      var s = '', buffer = 0, bufferSize = 0;
      while (s.length < lengthInChars) {
        while (bufferSize < 4 && stack.length > 0) {
          buffer = (stack.pop() << bufferSize) | buffer;
          bufferSize += 7;
        }
        s = toHexDigit(buffer & 15) + s;
        buffer >>= 4;
        bufferSize -= 4;
      }
      return s;
    },
    readHexSigned: function (size) {
      var num = this.readHexNumber(size);
      var sign = fromHexDigit(num[num.length - 1]) & 1 ? 15 : 0;
      var c = 0;
      var result = '';
      for (var i = 0; i < num.length; i++) {
        c = (c << 4) | fromHexDigit(num[i]);
        result += toHexDigit(sign ? (c >> 1) ^ sign : (c >> 1));
        c &= 1;
      }
      return result;
    },
    readString: function () {
      var len = this.readNumber();
      var s = '';
      for (var i = 0; i < len; i++) {
        s += String.fromCharCode(this.readNumber());
      }
      return s;
    }
  };

  var header = reader.readByte();
  var result = {
    type: header >> 1,
    wmode: header & 1,
    comment: null,
    usecmap: null,
    body: []
  };

  var b;
  while ((b = reader.readByte()) >= 0) {
    var type = b >> 5;
    if (type === 7) {
      switch (b & 0x1F) {
        case 0:
          result.comment = reader.readString();
          break;
        case 1:
          result.usecmap = reader.readString();
          break;
      }
      continue;
    }
    var sequence = !!(b & 0x10);
    var dataSize = b & 15;
    var subitems = [];
    var item = {
      type: type,
      items: subitems
    };
    if (sequence) {
      item.sequence = true;
    }
    var ucs2DataSize = 1;
    var subitemsCount = reader.readNumber();
    var start, end, code, char;
    switch (type) {
      case 0:
        start = reader.readHex(dataSize);
        end = addHex(reader.readHexNumber(dataSize), start);
        subitems.push({start: start, end: end});
        for (var i = 1; i < subitemsCount; i++) {
          start = addHex(reader.readHexNumber(dataSize), incHex(end));
          end = addHex(reader.readHexNumber(dataSize), start);
          subitems.push({start: start, end: end});
        }
        break;
      case 1:
        start = reader.readHex(dataSize);
        end = addHex(reader.readHexNumber(dataSize), start);
        code = reader.readNumber();
        subitems.push({start: start, end: end, code: code});
        for (var i = 1; i < subitemsCount; i++) {
          start = addHex(reader.readHexNumber(dataSize), incHex(end));
          end = addHex(reader.readHexNumber(dataSize), start);
          code = reader.readNumber();
          subitems.push({start: start, end: end, code: code});
        }
        break;
      case 2:
        char = reader.readHex(dataSize);
        code = reader.readNumber();
        subitems.push({char: char, code: code});
        for (var i = 1; i < subitemsCount; i++) {
          char = sequence ? incHex(char) : addHex(reader.readHexNumber(dataSize), incHex(char));
          code = reader.readSigned() + (code + 1);
          subitems.push({char: char, code: code});
        }
        break;
      case 3:
        start = reader.readHex(dataSize);
        end = addHex(reader.readHexNumber(dataSize), start);
        code = reader.readNumber();
        subitems.push({start: start, end: end, code: code});
        for (var i = 1; i < subitemsCount; i++) {
          start = sequence ? incHex(end) : addHex(reader.readHexNumber(dataSize), incHex(end));
          end = addHex(reader.readHexNumber(dataSize), start);
          code = reader.readNumber();
          subitems.push({start: start, end: end, code: code});
        }
        break;
      case 4:
        char = reader.readHex(ucs2DataSize);
        code = reader.readHex(dataSize);
        subitems.push({char: char, code: code});
        for (var i = 1; i < subitemsCount; i++) {
          char = sequence ? incHex(char) : addHex(reader.readHexNumber(ucs2DataSize), incHex(char));
          code = addHex(reader.readHexSigned(dataSize), incHex(code));
          subitems.push({char: char, code: code});
        }
        break;
      case 5:
        start = reader.readHex(ucs2DataSize);
        end = addHex(reader.readHexNumber(ucs2DataSize), start);
        code = reader.readHex(dataSize);
        subitems.push({start: start, end: end, code: code});
        for (var i = 1; i < subitemsCount; i++) {
          start = sequence ? incHex(end) : addHex(reader.readHexNumber(ucs2DataSize), incHex(end));
          end = addHex(reader.readHexNumber(ucs2DataSize), start);
          code = reader.readHex(dataSize);
          subitems.push({start: start, end: end, code: code});
        }
        break;
      default:
        throw new Error('Unknown type: ' + type)
    }
    result.body.push(item);
  }

  return result;
}

function toHexDigit(n) {
  return n.toString(16);
}
function fromHexDigit(s) {
  return parseInt(s, 16);
}
function getHexSize(s) {
  return (s.length >> 1) - 1;
}
function writeByte(b) {
  return toHexDigit((b >> 4) & 15) + toHexDigit(b & 15);
}
function writeNumber(n) {
  if (typeof n === 'string') {
    var s = '', buffer = 0, bufferSize = 0;
    var i = n.length;
    while (i > 0) {
      --i;
      buffer = (fromHexDigit(n[i]) << bufferSize) | buffer;
      bufferSize += 4;
      if (bufferSize >= 7) {
        s = writeByte((buffer & 0x7f) | (s.length > 0 ? 0x80 : 0)) + s;
        buffer >>>= 7;
        bufferSize -= 7;
      }
    }
    if (buffer > 0) {
      s = writeByte((buffer & 0x7f) | (s.length > 0 ? 0x80 : 0)) + s;
    }
    while (s.indexOf('80') === 0) {
      s = s.substr(2);
    }
    return s;
  } else {
    var s = writeByte(n & 0x7F);
    n >>>= 7;
    while (n > 0) {
      s = writeByte((n & 0x7F) | 0x80) + s;
      n >>>= 7;
    }
    return s;
  }
}
function writeSigned(n) {
  if (typeof n === 'string') {
    var t = '';
    var c = fromHexDigit(n[0]);
    var neg = c >= 8;
    c = neg ? (c ^ 15) : c;
    for (var i = 1; i < n.length; i++) {
      var d = fromHexDigit(n[i]);
      c = (c << 4) | (neg ? (d ^ 15) : d);
      t += toHexDigit(c >> 3);
      c = c & 7;
    }
    t += toHexDigit((c << 1) | (neg ? 1 : 0));
    return writeNumber(t);
  }
  return n < 0 ? writeNumber(-2 * n - 1) : writeNumber(2 * n);
}
function writeString(s) {
  var t = writeNumber(s.length);
  for (var i = 0; i < s.length; i++) {
    t += writeNumber(s.charCodeAt(i));
  }
  return t;
}
function addHex(a, b) {
  var c = 0, s = '';
  for (var i = a.length - 1; i >= 0; i--) {
    c += fromHexDigit(a[i]) + fromHexDigit(b[i]);
    if (c >= 16) {
      s = toHexDigit(c - 16) + s;
      c = 1;
    } else {
      s = toHexDigit(c) + s;
      c = 0;
    }
  }
  return s;
}
function subHex(a, b) {
  var c = 0, s = '';
  for (var i = a.length - 1; i >= 0; i--) {
    c += fromHexDigit(a[i]) - fromHexDigit(b[i]);
    if (c < 0) {
      s = toHexDigit(c + 16) + s;
      c = -1;
    } else {
      s = toHexDigit(c) + s;
      c = 0;
    }
  }
  return s;
}
function incHex(a) {
  var c = 1, s = '';
  for (var i = a.length - 1; i >= 0; i--) {
    c += fromHexDigit(a[i]);
    if (c >= 16) {
      s = toHexDigit(c - 16) + s;
      c = 1;
    } else {
      s = toHexDigit(c) + s;
      c = 0;
    }
  }
  return s;
}

exports.compressCmaps = function (src, dest, verify) {
  var files = fs.readdirSync(src).filter(function (fn) {
    return fn.indexOf('.') < 0; // skipping files with the extension
  });
  files.forEach(function (fn) {
    var srcPath = path.join(src, fn);
    var destPath = path.join(dest, fn + '.bcmap');
    var stats = compressCmap(srcPath, destPath, verify);
    console.log('Compressing ' + fn + ': ' + stats.orig + ' vs ' + stats.packed +
      ' ' + (stats.packed / stats.orig * 100).toFixed(1) + '%');
  });
};