pdfjs-dist/src/function.js

/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* globals EOF, error, isArray, isBool, Lexer, TODO */
/* 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.
 */

'use strict';

var PDFFunction = (function PDFFunctionClosure() {
  var CONSTRUCT_SAMPLED = 0;
  var CONSTRUCT_INTERPOLATED = 2;
  var CONSTRUCT_STICHED = 3;
  var CONSTRUCT_POSTSCRIPT = 4;

  return {
    getSampleArray: function PDFFunction_getSampleArray(size, outputSize, bps,
                                                       str) {
      var length = 1;
      for (var i = 0, ii = size.length; i < ii; i++)
        length *= size[i];
      length *= outputSize;

      var array = [];
      var codeSize = 0;
      var codeBuf = 0;
      // 32 is a valid bps so shifting won't work
      var sampleMul = 1.0 / (Math.pow(2.0, bps) - 1);

      var strBytes = str.getBytes((length * bps + 7) / 8);
      var strIdx = 0;
      for (var i = 0; i < length; i++) {
        while (codeSize < bps) {
          codeBuf <<= 8;
          codeBuf |= strBytes[strIdx++];
          codeSize += 8;
        }
        codeSize -= bps;
        array.push((codeBuf >> codeSize) * sampleMul);
        codeBuf &= (1 << codeSize) - 1;
      }
      return array;
    },

    getIR: function PDFFunction_getIR(xref, fn) {
      var dict = fn.dict;
      if (!dict)
        dict = fn;

      var types = [this.constructSampled,
                   null,
                   this.constructInterpolated,
                   this.constructStiched,
                   this.constructPostScript];

      var typeNum = dict.get('FunctionType');
      var typeFn = types[typeNum];
      if (!typeFn)
        error('Unknown type of function');

      return typeFn.call(this, fn, dict, xref);
    },

    fromIR: function PDFFunction_fromIR(IR) {
      var type = IR[0];
      switch (type) {
        case CONSTRUCT_SAMPLED:
          return this.constructSampledFromIR(IR);
        case CONSTRUCT_INTERPOLATED:
          return this.constructInterpolatedFromIR(IR);
        case CONSTRUCT_STICHED:
          return this.constructStichedFromIR(IR);
        //case CONSTRUCT_POSTSCRIPT:
        default:
          return this.constructPostScriptFromIR(IR);
      }
    },

    parse: function PDFFunction_parse(xref, fn) {
      var IR = this.getIR(xref, fn);
      return this.fromIR(IR);
    },

    constructSampled: function PDFFunction_constructSampled(str, dict) {
      function toMultiArray(arr) {
        var inputLength = arr.length;
        var outputLength = arr.length / 2;
        var out = [];
        var index = 0;
        for (var i = 0; i < inputLength; i += 2) {
          out[index] = [arr[i], arr[i + 1]];
          ++index;
        }
        return out;
      }
      var domain = dict.get('Domain');
      var range = dict.get('Range');

      if (!domain || !range)
        error('No domain or range');

      var inputSize = domain.length / 2;
      var outputSize = range.length / 2;

      domain = toMultiArray(domain);
      range = toMultiArray(range);

      var size = dict.get('Size');
      var bps = dict.get('BitsPerSample');
      var order = dict.get('Order') || 1;
      if (order !== 1) {
        // No description how cubic spline interpolation works in PDF32000:2008
        // As in poppler, ignoring order, linear interpolation may work as good
        TODO('No support for cubic spline interpolation: ' + order);
      }

      var encode = dict.get('Encode');
      if (!encode) {
        encode = [];
        for (var i = 0; i < inputSize; ++i) {
          encode.push(0);
          encode.push(size[i] - 1);
        }
      }
      encode = toMultiArray(encode);

      var decode = dict.get('Decode');
      if (!decode)
        decode = range;
      else
        decode = toMultiArray(decode);

      var samples = this.getSampleArray(size, outputSize, bps, str);

      return [
        CONSTRUCT_SAMPLED, inputSize, domain, encode, decode, samples, size,
        outputSize, Math.pow(2, bps) - 1, range
      ];
    },

    constructSampledFromIR: function PDFFunction_constructSampledFromIR(IR) {
      // See chapter 3, page 109 of the PDF reference
      function interpolate(x, xmin, xmax, ymin, ymax) {
        return ymin + ((x - xmin) * ((ymax - ymin) / (xmax - xmin)));
      }

      return function constructSampledFromIRResult(args) {
        // See chapter 3, page 110 of the PDF reference.
        var m = IR[1];
        var domain = IR[2];
        var encode = IR[3];
        var decode = IR[4];
        var samples = IR[5];
        var size = IR[6];
        var n = IR[7];
        var mask = IR[8];
        var range = IR[9];

        if (m != args.length)
          error('Incorrect number of arguments: ' + m + ' != ' +
                args.length);

        var x = args;

        // Building the cube vertices: its part and sample index
        // http://rjwagner49.com/Mathematics/Interpolation.pdf
        var cubeVertices = 1 << m;
        var cubeN = new Float64Array(cubeVertices);
        var cubeVertex = new Uint32Array(cubeVertices);
        for (var j = 0; j < cubeVertices; j++)
          cubeN[j] = 1;

        var k = n, pos = 1;
        // Map x_i to y_j for 0 <= i < m using the sampled function.
        for (var i = 0; i < m; ++i) {
          // x_i' = min(max(x_i, Domain_2i), Domain_2i+1)
          var domain_2i = domain[i][0];
          var domain_2i_1 = domain[i][1];
          var xi = Math.min(Math.max(x[i], domain_2i), domain_2i_1);

          // e_i = Interpolate(x_i', Domain_2i, Domain_2i+1,
          //                   Encode_2i, Encode_2i+1)
          var e = interpolate(xi, domain_2i, domain_2i_1,
                              encode[i][0], encode[i][1]);

          // e_i' = min(max(e_i, 0), Size_i - 1)
          var size_i = size[i];
          e = Math.min(Math.max(e, 0), size_i - 1);

          // Adjusting the cube: N and vertex sample index
          var e0 = e < size_i - 1 ? Math.floor(e) : e - 1; // e1 = e0 + 1;
          var n0 = e0 + 1 - e; // (e1 - e) / (e1 - e0);
          var n1 = e - e0; // (e - e0) / (e1 - e0);
          var offset0 = e0 * k;
          var offset1 = offset0 + k; // e1 * k
          for (var j = 0; j < cubeVertices; j++) {
            if (j & pos) {
              cubeN[j] *= n1;
              cubeVertex[j] += offset1;
            } else {
              cubeN[j] *= n0;
              cubeVertex[j] += offset0;
            }
          }

          k *= size_i;
          pos <<= 1;
        }

        var y = new Float64Array(n);
        for (var j = 0; j < n; ++j) {
          // Sum all cube vertices' samples portions
          var rj = 0;
          for (var i = 0; i < cubeVertices; i++)
            rj += samples[cubeVertex[i] + j] * cubeN[i];

          // r_j' = Interpolate(r_j, 0, 2^BitsPerSample - 1,
          //                    Decode_2j, Decode_2j+1)
          rj = interpolate(rj, 0, 1, decode[j][0], decode[j][1]);

          // y_j = min(max(r_j, range_2j), range_2j+1)
          y[j] = Math.min(Math.max(rj, range[j][0]), range[j][1]);
        }

        return y;
      };
    },

    constructInterpolated: function PDFFunction_constructInterpolated(str,
                                                                      dict) {
      var c0 = dict.get('C0') || [0];
      var c1 = dict.get('C1') || [1];
      var n = dict.get('N');

      if (!isArray(c0) || !isArray(c1))
        error('Illegal dictionary for interpolated function');

      var length = c0.length;
      var diff = [];
      for (var i = 0; i < length; ++i)
        diff.push(c1[i] - c0[i]);

      return [CONSTRUCT_INTERPOLATED, c0, diff, n];
    },

    constructInterpolatedFromIR:
      function PDFFunction_constructInterpolatedFromIR(IR) {
      var c0 = IR[1];
      var diff = IR[2];
      var n = IR[3];

      var length = diff.length;

      return function constructInterpolatedFromIRResult(args) {
        var x = n == 1 ? args[0] : Math.pow(args[0], n);

        var out = [];
        for (var j = 0; j < length; ++j)
          out.push(c0[j] + (x * diff[j]));

        return out;

      };
    },

    constructStiched: function PDFFunction_constructStiched(fn, dict, xref) {
      var domain = dict.get('Domain');

      if (!domain)
        error('No domain');

      var inputSize = domain.length / 2;
      if (inputSize != 1)
        error('Bad domain for stiched function');

      var fnRefs = dict.get('Functions');
      var fns = [];
      for (var i = 0, ii = fnRefs.length; i < ii; ++i)
        fns.push(PDFFunction.getIR(xref, xref.fetchIfRef(fnRefs[i])));

      var bounds = dict.get('Bounds');
      var encode = dict.get('Encode');

      return [CONSTRUCT_STICHED, domain, bounds, encode, fns];
    },

    constructStichedFromIR: function PDFFunction_constructStichedFromIR(IR) {
      var domain = IR[1];
      var bounds = IR[2];
      var encode = IR[3];
      var fnsIR = IR[4];
      var fns = [];

      for (var i = 0, ii = fnsIR.length; i < ii; i++) {
        fns.push(PDFFunction.fromIR(fnsIR[i]));
      }

      return function constructStichedFromIRResult(args) {
        var clip = function constructStichedFromIRClip(v, min, max) {
          if (v > max)
            v = max;
          else if (v < min)
            v = min;
          return v;
        };

        // clip to domain
        var v = clip(args[0], domain[0], domain[1]);
        // calulate which bound the value is in
        for (var i = 0, ii = bounds.length; i < ii; ++i) {
          if (v < bounds[i])
            break;
        }

        // encode value into domain of function
        var dmin = domain[0];
        if (i > 0)
          dmin = bounds[i - 1];
        var dmax = domain[1];
        if (i < bounds.length)
          dmax = bounds[i];

        var rmin = encode[2 * i];
        var rmax = encode[2 * i + 1];

        var v2 = rmin + (v - dmin) * (rmax - rmin) / (dmax - dmin);

        // call the appropropriate function
        return fns[i]([v2]);
      };
    },

    constructPostScript: function PDFFunction_constructPostScript(fn, dict,
                                                                  xref) {
      var domain = dict.get('Domain');
      var range = dict.get('Range');

      if (!domain)
        error('No domain.');

      if (!range)
        error('No range.');

      var lexer = new PostScriptLexer(fn);
      var parser = new PostScriptParser(lexer);
      var code = parser.parse();

      return [CONSTRUCT_POSTSCRIPT, domain, range, code];
    },

    constructPostScriptFromIR: function PDFFunction_constructPostScriptFromIR(
                                          IR) {
      var domain = IR[1];
      var range = IR[2];
      var code = IR[3];
      var numOutputs = range.length / 2;
      var evaluator = new PostScriptEvaluator(code);
      // Cache the values for a big speed up, the cache size is limited though
      // since the number of possible values can be huge from a PS function.
      var cache = new FunctionCache();
      return function constructPostScriptFromIRResult(args) {
        var initialStack = [];
        for (var i = 0, ii = (domain.length / 2); i < ii; ++i) {
          initialStack.push(args[i]);
        }

        var key = initialStack.join('_');
        if (cache.has(key))
          return cache.get(key);

        var stack = evaluator.execute(initialStack);
        var transformed = [];
        for (i = numOutputs - 1; i >= 0; --i) {
          var out = stack.pop();
          var rangeIndex = 2 * i;
          if (out < range[rangeIndex])
            out = range[rangeIndex];
          else if (out > range[rangeIndex + 1])
            out = range[rangeIndex + 1];
          transformed[i] = out;
        }
        cache.set(key, transformed);
        return transformed;
      };
    }
  };
})();

var FunctionCache = (function FunctionCacheClosure() {
  // Of 10 PDF's with type4 functions the maxium number of distinct values seen
  // was 256. This still may need some tweaking in the future though.
  var MAX_CACHE_SIZE = 1024;
  function FunctionCache() {
    this.cache = {};
    this.total = 0;
  }
  FunctionCache.prototype = {
    has: function FunctionCache_has(key) {
      return key in this.cache;
    },
    get: function FunctionCache_get(key) {
      return this.cache[key];
    },
    set: function FunctionCache_set(key, value) {
      if (this.total < MAX_CACHE_SIZE) {
        this.cache[key] = value;
        this.total++;
      }
    }
  };
  return FunctionCache;
})();

var PostScriptStack = (function PostScriptStackClosure() {
  var MAX_STACK_SIZE = 100;
  function PostScriptStack(initialStack) {
    this.stack = initialStack || [];
  }

  PostScriptStack.prototype = {
    push: function PostScriptStack_push(value) {
      if (this.stack.length >= MAX_STACK_SIZE)
        error('PostScript function stack overflow.');
      this.stack.push(value);
    },
    pop: function PostScriptStack_pop() {
      if (this.stack.length <= 0)
        error('PostScript function stack underflow.');
      return this.stack.pop();
    },
    copy: function PostScriptStack_copy(n) {
      if (this.stack.length + n >= MAX_STACK_SIZE)
        error('PostScript function stack overflow.');
      var stack = this.stack;
      for (var i = stack.length - n, j = n - 1; j >= 0; j--, i++)
        stack.push(stack[i]);
    },
    index: function PostScriptStack_index(n) {
      this.push(this.stack[this.stack.length - n - 1]);
    },
    // rotate the last n stack elements p times
    roll: function PostScriptStack_roll(n, p) {
      var stack = this.stack;
      var l = stack.length - n;
      var r = stack.length - 1, c = l + (p - Math.floor(p / n) * n), i, j, t;
      for (i = l, j = r; i < j; i++, j--) {
        t = stack[i]; stack[i] = stack[j]; stack[j] = t;
      }
      for (i = l, j = c - 1; i < j; i++, j--) {
        t = stack[i]; stack[i] = stack[j]; stack[j] = t;
      }
      for (i = c, j = r; i < j; i++, j--) {
        t = stack[i]; stack[i] = stack[j]; stack[j] = t;
      }
    }
  };
  return PostScriptStack;
})();
var PostScriptEvaluator = (function PostScriptEvaluatorClosure() {
  function PostScriptEvaluator(operators, operands) {
    this.operators = operators;
    this.operands = operands;
  }
  PostScriptEvaluator.prototype = {
    execute: function PostScriptEvaluator_execute(initialStack) {
      var stack = new PostScriptStack(initialStack);
      var counter = 0;
      var operators = this.operators;
      var length = operators.length;
      var operator, a, b;
      while (counter < length) {
        operator = operators[counter++];
        if (typeof operator == 'number') {
          // Operator is really an operand and should be pushed to the stack.
          stack.push(operator);
          continue;
        }
        switch (operator) {
          // non standard ps operators
          case 'jz': // jump if false
            b = stack.pop();
            a = stack.pop();
            if (!a)
              counter = b;
            break;
          case 'j': // jump
            a = stack.pop();
            counter = a;
            break;

          // all ps operators in alphabetical order (excluding if/ifelse)
          case 'abs':
            a = stack.pop();
            stack.push(Math.abs(a));
            break;
          case 'add':
            b = stack.pop();
            a = stack.pop();
            stack.push(a + b);
            break;
          case 'and':
            b = stack.pop();
            a = stack.pop();
            if (isBool(a) && isBool(b))
              stack.push(a && b);
            else
              stack.push(a & b);
            break;
          case 'atan':
            a = stack.pop();
            stack.push(Math.atan(a));
            break;
          case 'bitshift':
            b = stack.pop();
            a = stack.pop();
            if (a > 0)
              stack.push(a << b);
            else
              stack.push(a >> b);
            break;
          case 'ceiling':
            a = stack.pop();
            stack.push(Math.ceil(a));
            break;
          case 'copy':
            a = stack.pop();
            stack.copy(a);
            break;
          case 'cos':
            a = stack.pop();
            stack.push(Math.cos(a));
            break;
          case 'cvi':
            a = stack.pop() | 0;
            stack.push(a);
            break;
          case 'cvr':
            // noop
            break;
          case 'div':
            b = stack.pop();
            a = stack.pop();
            stack.push(a / b);
            break;
          case 'dup':
            stack.copy(1);
            break;
          case 'eq':
            b = stack.pop();
            a = stack.pop();
            stack.push(a == b);
            break;
          case 'exch':
            stack.roll(2, 1);
            break;
          case 'exp':
            b = stack.pop();
            a = stack.pop();
            stack.push(Math.pow(a, b));
            break;
          case 'false':
            stack.push(false);
            break;
          case 'floor':
            a = stack.pop();
            stack.push(Math.floor(a));
            break;
          case 'ge':
            b = stack.pop();
            a = stack.pop();
            stack.push(a >= b);
            break;
          case 'gt':
            b = stack.pop();
            a = stack.pop();
            stack.push(a > b);
            break;
          case 'idiv':
            b = stack.pop();
            a = stack.pop();
            stack.push((a / b) | 0);
            break;
          case 'index':
            a = stack.pop();
            stack.index(a);
            break;
          case 'le':
            b = stack.pop();
            a = stack.pop();
            stack.push(a <= b);
            break;
          case 'ln':
            a = stack.pop();
            stack.push(Math.log(a));
            break;
          case 'log':
            a = stack.pop();
            stack.push(Math.log(a) / Math.LN10);
            break;
          case 'lt':
            b = stack.pop();
            a = stack.pop();
            stack.push(a < b);
            break;
          case 'mod':
            b = stack.pop();
            a = stack.pop();
            stack.push(a % b);
            break;
          case 'mul':
            b = stack.pop();
            a = stack.pop();
            stack.push(a * b);
            break;
          case 'ne':
            b = stack.pop();
            a = stack.pop();
            stack.push(a != b);
            break;
          case 'neg':
            a = stack.pop();
            stack.push(-b);
            break;
          case 'not':
            a = stack.pop();
            if (isBool(a) && isBool(b))
              stack.push(a && b);
            else
              stack.push(a & b);
            break;
          case 'or':
            b = stack.pop();
            a = stack.pop();
            if (isBool(a) && isBool(b))
              stack.push(a || b);
            else
              stack.push(a | b);
            break;
          case 'pop':
            stack.pop();
            break;
          case 'roll':
            b = stack.pop();
            a = stack.pop();
            stack.roll(a, b);
            break;
          case 'round':
            a = stack.pop();
            stack.push(Math.round(a));
            break;
          case 'sin':
            a = stack.pop();
            stack.push(Math.sin(a));
            break;
          case 'sqrt':
            a = stack.pop();
            stack.push(Math.sqrt(a));
            break;
          case 'sub':
            b = stack.pop();
            a = stack.pop();
            stack.push(a - b);
            break;
          case 'true':
            stack.push(true);
            break;
          case 'truncate':
            a = stack.pop();
            a = a < 0 ? Math.ceil(a) : Math.floor(a);
            stack.push(a);
            break;
          case 'xor':
            b = stack.pop();
            a = stack.pop();
            if (isBool(a) && isBool(b))
              stack.push(a != b);
            else
              stack.push(a ^ b);
            break;
          default:
            error('Unknown operator ' + operator);
            break;
        }
      }
      return stack.stack;
    }
  };
  return PostScriptEvaluator;
})();

var PostScriptParser = (function PostScriptParserClosure() {
  function PostScriptParser(lexer) {
    this.lexer = lexer;
    this.operators = [];
    this.token = null;
    this.prev = null;
  }
  PostScriptParser.prototype = {
    nextToken: function PostScriptParser_nextToken() {
      this.prev = this.token;
      this.token = this.lexer.getToken();
    },
    accept: function PostScriptParser_accept(type) {
      if (this.token.type == type) {
        this.nextToken();
        return true;
      }
      return false;
    },
    expect: function PostScriptParser_expect(type) {
      if (this.accept(type))
        return true;
      error('Unexpected symbol: found ' + this.token.type + ' expected ' +
            type + '.');
    },
    parse: function PostScriptParser_parse() {
      this.nextToken();
      this.expect(PostScriptTokenTypes.LBRACE);
      this.parseBlock();
      this.expect(PostScriptTokenTypes.RBRACE);
      return this.operators;
    },
    parseBlock: function PostScriptParser_parseBlock() {
      while (true) {
        if (this.accept(PostScriptTokenTypes.NUMBER)) {
          this.operators.push(this.prev.value);
        } else if (this.accept(PostScriptTokenTypes.OPERATOR)) {
          this.operators.push(this.prev.value);
        } else if (this.accept(PostScriptTokenTypes.LBRACE)) {
          this.parseCondition();
        } else {
          return;
        }
      }
    },
    parseCondition: function PostScriptParser_parseCondition() {
      // Add two place holders that will be updated later
      var conditionLocation = this.operators.length;
      this.operators.push(null, null);

      this.parseBlock();
      this.expect(PostScriptTokenTypes.RBRACE);
      if (this.accept(PostScriptTokenTypes.IF)) {
        // The true block is right after the 'if' so it just falls through on
        // true else it jumps and skips the true block.
        this.operators[conditionLocation] = this.operators.length;
        this.operators[conditionLocation + 1] = 'jz';
      } else if (this.accept(PostScriptTokenTypes.LBRACE)) {
        var jumpLocation = this.operators.length;
        this.operators.push(null, null);
        var endOfTrue = this.operators.length;
        this.parseBlock();
        this.expect(PostScriptTokenTypes.RBRACE);
        this.expect(PostScriptTokenTypes.IFELSE);
        // The jump is added at the end of the true block to skip the false
        // block.
        this.operators[jumpLocation] = this.operators.length;
        this.operators[jumpLocation + 1] = 'j';

        this.operators[conditionLocation] = endOfTrue;
        this.operators[conditionLocation + 1] = 'jz';
      } else {
        error('PS Function: error parsing conditional.');
      }
    }
  };
  return PostScriptParser;
})();

var PostScriptTokenTypes = {
  LBRACE: 0,
  RBRACE: 1,
  NUMBER: 2,
  OPERATOR: 3,
  IF: 4,
  IFELSE: 5
};

var PostScriptToken = (function PostScriptTokenClosure() {
  function PostScriptToken(type, value) {
    this.type = type;
    this.value = value;
  }

  var opCache = {};

  PostScriptToken.getOperator = function PostScriptToken_getOperator(op) {
    var opValue = opCache[op];
    if (opValue)
      return opValue;

    return opCache[op] = new PostScriptToken(PostScriptTokenTypes.OPERATOR, op);
  };

  PostScriptToken.LBRACE = new PostScriptToken(PostScriptTokenTypes.LBRACE,
                                                '{');
  PostScriptToken.RBRACE = new PostScriptToken(PostScriptTokenTypes.RBRACE,
                                                '}');
  PostScriptToken.IF = new PostScriptToken(PostScriptTokenTypes.IF, 'IF');
  PostScriptToken.IFELSE = new PostScriptToken(PostScriptTokenTypes.IFELSE,
                                                'IFELSE');
  return PostScriptToken;
})();

var PostScriptLexer = (function PostScriptLexerClosure() {
  function PostScriptLexer(stream) {
    this.stream = stream;
  }
  PostScriptLexer.prototype = {
    getToken: function PostScriptLexer_getToken() {
      var s = '';
      var ch;
      var comment = false;
      var stream = this.stream;

      // skip comments
      while (true) {
        if (!(ch = stream.getChar()))
          return EOF;

        if (comment) {
          if (ch == '\x0a' || ch == '\x0d')
            comment = false;
        } else if (ch == '%') {
          comment = true;
        } else if (!Lexer.isSpace(ch)) {
          break;
        }
      }
      switch (ch) {
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
        case '+': case '-': case '.':
          return new PostScriptToken(PostScriptTokenTypes.NUMBER,
                                      this.getNumber(ch));
        case '{':
          return PostScriptToken.LBRACE;
        case '}':
          return PostScriptToken.RBRACE;
      }
      // operator
      var str = ch.toLowerCase();
      while (true) {
        ch = stream.lookChar();
        if (ch === null)
          break;
        ch = ch.toLowerCase();
        if (ch >= 'a' && ch <= 'z')
          str += ch;
        else
          break;
        stream.skip();
      }
      switch (str) {
        case 'if':
          return PostScriptToken.IF;
        case 'ifelse':
          return PostScriptToken.IFELSE;
        default:
          return PostScriptToken.getOperator(str);
      }
    },
    getNumber: function PostScriptLexer_getNumber(ch) {
      var str = ch;
      var stream = this.stream;
      while (true) {
        ch = stream.lookChar();
        if ((ch >= '0' && ch <= '9') || ch == '-' || ch == '.')
          str += ch;
        else
          break;
        stream.skip();
      }
      var value = parseFloat(str);
      if (isNaN(value))
        error('Invalid floating point number: ' + value);
      return value;
    }
  };
  return PostScriptLexer;
})();