Lexer.java
/* Copyright 2002-2023 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You 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.
*/
package org.orekit.utils.units;
import org.hipparchus.fraction.Fraction;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
/** Lexer for units.
* @author Luc Maisonobe
* @since 11.0
*/
class Lexer {
/** Unit specification to tokenize. */
private final CharSequence unitSpecification;
/** End index. */
private final int end;
/** Start index for next token. */
private int start;
/** Next to last token emitted. */
private Token nextToLast;
/** Last token emitted. */
private Token last;
/** Upcoming token (which was pushed back). */
private Token upcoming;
/** Build a lexer for a unit specification.
* @param unitSpecification unit specification to tokenize
*/
Lexer(final CharSequence unitSpecification) {
this.unitSpecification = unitSpecification;
this.end = unitSpecification.length();
this.start = 0;
this.last = null;
}
/** Get the complete unit specification.
* @return complete unit specification
*/
public String getUnitSpecification() {
return unitSpecification.toString();
}
/** Push back last returned token.
* <p>
* This can be called only once
* </p>
*/
public void pushBack() {
upcoming = last;
last = nextToLast;
}
/** Get next token.
* @return next token, or null if there are no more tokens
*/
public Token next() {
if (upcoming != null) {
nextToLast = last;
last = upcoming;
upcoming = null;
return last;
}
// skip whitespace
while (start < end && Character.isWhitespace(unitSpecification.charAt(start))) {
++start;
}
if (start >= end) {
// no more characters to analyze
nextToLast = last;
last = null;
return null;
}
// look for prefixed units
int current = start;
while (current < end &&
(Character.isLowerCase(unitSpecification.charAt(current)) ||
Character.isUpperCase(unitSpecification.charAt(current)) ||
unitSpecification.charAt(current) == '°' ||
unitSpecification.charAt(current) == '◦' ||
unitSpecification.charAt(current) == '′' ||
unitSpecification.charAt(current) == '\'' ||
unitSpecification.charAt(current) == '″' ||
unitSpecification.charAt(current) == '"' ||
unitSpecification.charAt(current) == '%' ||
unitSpecification.charAt(current) == '#')) {
++current;
}
if (current > start) {
return emit(current, TokenType.IDENTIFIER, 0, 1);
}
// look for power
if (start < end - 1 &&
unitSpecification.charAt(start) == '*' &&
unitSpecification.charAt(start + 1) == '*') {
// power indicator as **
return emit(start + 2, TokenType.POWER, 0, 1);
} else if (unitSpecification.charAt(start) == '^') {
// power indicator as ^
return emit(start + 1, TokenType.POWER, 0, 1);
} else if (convertSuperscript(start) != ' ' &&
last != null &&
last.getType() != TokenType.POWER) {
// virtual power indicator as we switch to superscript characters
return emit(start, TokenType.POWER, 0, 1);
}
// look for one character tokens
if (unitSpecification.charAt(start) == '*') {
return emit(start + 1, TokenType.MULTIPLICATION, 0, 1);
} else if (unitSpecification.charAt(start) == '×') {
return emit(start + 1, TokenType.MULTIPLICATION, 0, 1);
} else if (unitSpecification.charAt(start) == '.') {
return emit(start + 1, TokenType.MULTIPLICATION, 0, 1);
} else if (unitSpecification.charAt(start) == '·') {
return emit(start + 1, TokenType.MULTIPLICATION, 0, 1);
} else if (unitSpecification.charAt(start) == '/') {
return emit(start + 1, TokenType.DIVISION, 0, 1);
} else if (unitSpecification.charAt(start) == '⁄') {
return emit(start + 1, TokenType.DIVISION, 0, 1);
} else if (unitSpecification.charAt(start) == '(') {
return emit(start + 1, TokenType.OPEN, 0, 1);
} else if (unitSpecification.charAt(start) == ')') {
return emit(start + 1, TokenType.CLOSE, 0, 1);
} else if (unitSpecification.charAt(start) == '√') {
return emit(start + 1, TokenType.SQUARE_ROOT, 0, 1);
}
// look for special case "0.5" (used by CCSDS for square roots)
if (start < end - 2 &&
unitSpecification.charAt(start) == '0' &&
unitSpecification.charAt(start + 1) == '.' &&
unitSpecification.charAt(start + 2) == '5') {
// ½ written as decimal number
return emit(start + 3, TokenType.FRACTION, 1, 2);
}
// look for special case "1.5" (used by CCSDS for power 3/2)
if (start < end - 2 &&
unitSpecification.charAt(start) == '1' &&
unitSpecification.charAt(start + 1) == '.' &&
unitSpecification.charAt(start + 2) == '5') {
// 3/2 written as decimal number
return emit(start + 3, TokenType.FRACTION, 3, 2);
}
// look for unicode fractions
if (unitSpecification.charAt(start) == '¼') {
return emit(start + 1, TokenType.FRACTION, 1, 4);
} else if (unitSpecification.charAt(start) == '½') {
return emit(start + 1, TokenType.FRACTION, 1, 2);
} else if (unitSpecification.charAt(start) == '¾') {
return emit(start + 1, TokenType.FRACTION, 3, 4);
} else if (unitSpecification.charAt(start) == '⅐') {
return emit(start + 1, TokenType.FRACTION, 1, 7);
} else if (unitSpecification.charAt(start) == '⅑') {
return emit(start + 1, TokenType.FRACTION, 1, 9);
} else if (unitSpecification.charAt(start) == '⅒') {
return emit(start + 1, TokenType.FRACTION, 1, 10);
} else if (unitSpecification.charAt(start) == '⅓') {
return emit(start + 1, TokenType.FRACTION, 1, 3);
} else if (unitSpecification.charAt(start) == '⅔') {
return emit(start + 1, TokenType.FRACTION, 2, 3);
} else if (unitSpecification.charAt(start) == '⅕') {
return emit(start + 1, TokenType.FRACTION, 1, 5);
} else if (unitSpecification.charAt(start) == '⅖') {
return emit(start + 1, TokenType.FRACTION, 2, 5);
} else if (unitSpecification.charAt(start) == '⅗') {
return emit(start + 1, TokenType.FRACTION, 3, 5);
} else if (unitSpecification.charAt(start) == '⅘') {
return emit(start + 1, TokenType.FRACTION, 4, 5);
} else if (unitSpecification.charAt(start) == '⅙') {
return emit(start + 1, TokenType.FRACTION, 1, 6);
} else if (unitSpecification.charAt(start) == '⅚') {
return emit(start + 1, TokenType.FRACTION, 5, 6);
} else if (unitSpecification.charAt(start) == '⅛') {
return emit(start + 1, TokenType.FRACTION, 1, 8);
} else if (unitSpecification.charAt(start) == '⅜') {
return emit(start + 1, TokenType.FRACTION, 3, 8);
} else if (unitSpecification.charAt(start) == '⅝') {
return emit(start + 1, TokenType.FRACTION, 5, 8);
} else if (unitSpecification.charAt(start) == '⅞') {
return emit(start + 1, TokenType.FRACTION, 7, 8);
}
// it must be an integer, either as regular character or as superscript
final Converter converter = (convertSuperscript(start) == ' ') ?
this::noConvert :
this::convertSuperscript;
// manage sign, taking care of counting characters properly
final int sign;
final int numberStart;
if (converter.convert(start) == '+') {
sign = +1;
numberStart = start + 1;
} else if (converter.convert(start) == '-') {
sign = -1;
numberStart = start + 1;
} else {
sign = 1;
numberStart = start;
}
current = numberStart;
int value = 0;
while (current < end) {
final int c = converter.convert(current);
if (c >= '0' && c <= '9') {
value = value * 10 + (c - '0');
++current;
} else {
break;
}
}
if (current > numberStart) {
// there were some digits
return emit(current, TokenType.INTEGER, sign * value, 1);
}
throw generateException();
}
/** Generate an exception.
* @return generated exception
*/
public OrekitException generateException() {
return new OrekitException(OrekitMessages.UNKNOWN_UNIT, unitSpecification);
}
/** Emit one token.
* @param after index after token
* @param type token type
* @param numerator value of the token numerator
* @param denominator value of the token denominator
* @return new token
*/
private Token emit(final int after, final TokenType type, final int numerator, final int denominator) {
final CharSequence subString = unitSpecification.subSequence(start, after);
start = after;
nextToLast = last;
last = new Token(subString, type, numerator,
denominator == 1 ? null : new Fraction(numerator, denominator));
return last;
}
/** Convert a superscript character to regular digit or sign character.
* @param index character index
* @return regular digit or sign character, or ' ' if character is not a superscript
*/
private char convertSuperscript(final int index) {
// we can't do fancy stuff with code points
// superscripts for 1, 2 and 3 are not in the same range as others
switch (unitSpecification.charAt(index)) {
case '⁰' :
return '0';
case '¹' :
return '1';
case '²' :
return '2';
case '³' :
return '3';
case '⁴' :
return '4';
case '⁵' :
return '5';
case '⁶' :
return '6';
case '⁷' :
return '7';
case '⁸' :
return '8';
case '⁹' :
return '9';
case '⁺' :
return '+';
case '⁻' :
return '-';
default :
return ' ';
}
}
/** No-op converter.
* @param index character index
* @return character at index
*/
private char noConvert(final int index) {
return unitSpecification.charAt(index);
}
/** Character converter. */
private interface Converter {
/** Convert a character.
* @param index character index
* @return converted character
*/
char convert(int index);
}
}