bundles/org.simantics.databoard/src/org/simantics/databoard/units/internal/parser/UnitParser.java

   1 /*******************************************************************************
   2  *  Copyright (c) 2010 Association for Decentralized Information Management in
   3  *  Industry THTH ry.
   4  *  All rights reserved. This program and the accompanying materials
   5  *  are made available under the terms of the Eclipse Public License v1.0
   6  *  which accompanies this distribution, and is available at
   7  *  http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  *  Contributors:
  10  *      VTT Technical Research Centre of Finland - initial API and implementation
  11  *******************************************************************************/
  12 package org.simantics.databoard.units.internal.parser;
  13
  14 import org.simantics.databoard.units.internal.UnitParseException;
  15
  16 public abstract class UnitParser {
  17
  18         String string;
  19         int pos;
  20
  21         int nextChar;
  22         int sign;
  23
  24         public UnitParser() {
  25         }
  26
  27         void next() {
  28                 ++pos;
  29                 if(pos >= string.length())
  30                         nextChar = -1;
  31                 else
  32                         nextChar = string.charAt(pos);
  33         }
  34
  35         public void unit(String string, int sign) throws UnitParseException {
  36                 this.string = string;
  37                 this.pos = -1;
  38                 this.sign = sign;
  39                 next();
  40
  41                 expression();
  42                 expect(-1);
  43         }
  44
  45         /* Grammar
  46          *
  47          * unit_expression: unit_numerator [ "/" unit_denominator ]
  48          * unit_numerator: "1" | unit_factors | "(" unit_expression ")"
  49          * unit_denominator: unit_factor | "(" unit_expression ")"
  50          * unit_factors: unit_factor [ "." unit_factors ]
  51          * unit_factor: unit_operand [ unit_exponent ]
  52          * unit_exponent: [ "+" | "-" ] integer
  53          * unit_operand: unit_symbol | unit_prefix unit_symbol
  54          */
  55
  56         void expression() throws UnitParseException {
  57                 numerator();
  58                 if(nextChar == '/') {
  59                         next();
  60                         denominator();
  61                 }
  62         }
  63
  64         void numerator() throws UnitParseException {
  65                 if(nextChar == '1')
  66                         next();
  67                 else if(nextChar == '(') {
  68                         next();
  69                         expression();
  70                         skip(')');
  71                 }
  72                 else
  73                         factors();
  74         }
  75
  76         void denominator() throws UnitParseException {
  77                 sign = -sign;
  78                 if(nextChar == '(') {
  79                         next();
  80                         expression();
  81                         skip(')');
  82                 }
  83                 else
  84                         factor();
  85                 sign = -sign;
  86         }
  87
  88         void factors() throws UnitParseException {
  89                 while(true) {
  90                         factor();
  91                         if(nextChar == '.')
  92                                 next();
  93                         else
  94                             break;
  95                 }
  96         }
  97
  98         void factor() throws UnitParseException {
  99                 // Base
 100                 int factorBegin = pos;
 101                 while((nextChar >= 'a' && nextChar <= 'z') || (nextChar >= 'A' && nextChar <= 'Z') || (nextChar=='µ') || nextChar=='(' || nextChar==')' || nextChar=='%')
 102                         next();
 103                 int exponentBegin = pos;
 104                 if(factorBegin == exponentBegin)
 105                         throw new UnitParseException(string,
 106                                         "Expected base unit name, but got " + charName(nextChar) + " at position " + pos + ".");
 107                 String baseUnit = string.substring(factorBegin, exponentBegin);
 108
 109                 // Exponent
 110                 if(nextChar == '-' || nextChar == '+' || (nextChar >= '0' && nextChar <= '9')) {
 111                         next();
 112                         while(nextChar >= '0' && nextChar <= '9')
 113                                 next();
 114                 }
 115                 int exponentEnd = pos;
 116                 if(exponentEnd > exponentBegin) {
 117                         String exponentString = string.substring(exponentBegin, exponentEnd);
 118                         try {
 119                                 visit(baseUnit, sign * Integer.parseInt(exponentString));
 120                         } catch(NumberFormatException e) {
 121                                 throw new UnitParseException(string,
 122                                                 "Invalid exponent \"" + exponentString + "\" at position " + pos + ".");
 123                         }
 124                 }
 125                 else
 126                         visit(baseUnit, sign);
 127         }
 128
 129         private void skip(char c) throws UnitParseException {
 130                 expect(c);
 131                 next();
 132         }
 133
 134         private static String charName(int c) {
 135                 if(c >= 0)
 136                         return "'" + Character.toString((char)c) + "'";
 137                 else
 138                         return "end of unit";
 139         }
 140
 141         private void expect(int c) throws UnitParseException {
 142                 if(nextChar != c)
 143                         throw new UnitParseException(string,
 144                                         "Expected " + charName(c) + ", but got " + charName(nextChar) + " at position " + pos + ".");
 145         }
 146
 147         public abstract void visit(String baseUnit, int exponent);
 148
 149 }