pdf.js/src/core/ps_parser.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.
 */

import { error, isSpace } from '../shared/util';
import { EOF } from './primitives';

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 = Object.create(null);

  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;
    this.nextChar();

    this.strBuf = [];
  }
  PostScriptLexer.prototype = {
    nextChar: function PostScriptLexer_nextChar() {
      return (this.currentChar = this.stream.getByte());
    },
    getToken: function PostScriptLexer_getToken() {
      var comment = false;
      var ch = this.currentChar;

      // skip comments
      while (true) {
        if (ch < 0) {
          return EOF;
        }

        if (comment) {
          if (ch === 0x0A || ch === 0x0D) {
            comment = false;
          }
        } else if (ch === 0x25) { // '%'
          comment = true;
        } else if (!isSpace(ch)) {
          break;
        }
        ch = this.nextChar();
      }
      switch (ch | 0) {
        case 0x30: case 0x31: case 0x32: case 0x33: case 0x34: // '0'-'4'
        case 0x35: case 0x36: case 0x37: case 0x38: case 0x39: // '5'-'9'
        case 0x2B: case 0x2D: case 0x2E: // '+', '-', '.'
          return new PostScriptToken(PostScriptTokenTypes.NUMBER,
                                     this.getNumber());
        case 0x7B: // '{'
          this.nextChar();
          return PostScriptToken.LBRACE;
        case 0x7D: // '}'
          this.nextChar();
          return PostScriptToken.RBRACE;
      }
      // operator
      var strBuf = this.strBuf;
      strBuf.length = 0;
      strBuf[0] = String.fromCharCode(ch);

      while ((ch = this.nextChar()) >= 0 && // and 'A'-'Z', 'a'-'z'
             ((ch >= 0x41 && ch <= 0x5A) || (ch >= 0x61 && ch <= 0x7A))) {
        strBuf.push(String.fromCharCode(ch));
      }
      var str = strBuf.join('');
      switch (str.toLowerCase()) {
        case 'if':
          return PostScriptToken.IF;
        case 'ifelse':
          return PostScriptToken.IFELSE;
        default:
          return PostScriptToken.getOperator(str);
      }
    },
    getNumber: function PostScriptLexer_getNumber() {
      var ch = this.currentChar;
      var strBuf = this.strBuf;
      strBuf.length = 0;
      strBuf[0] = String.fromCharCode(ch);

      while ((ch = this.nextChar()) >= 0) {
        if ((ch >= 0x30 && ch <= 0x39) || // '0'-'9'
            ch === 0x2D || ch === 0x2E) { // '-', '.'
          strBuf.push(String.fromCharCode(ch));
        } else {
          break;
        }
      }
      var value = parseFloat(strBuf.join(''));
      if (isNaN(value)) {
        error('Invalid floating point number: ' + value);
      }
      return value;
    }
  };
  return PostScriptLexer;
})();

export {
  PostScriptLexer,
  PostScriptParser,
};