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Tool that generates code for RPC between the Kurento Media Server and
remote libraries.
/*
* The MIT License
*
* Copyright 2012-2014 Zafar Khaja ([email protected]).
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
* */
package com.github.zafarkhaja.semver.expr;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.AND;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.DOT;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.EOL;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.HYPHEN;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.LEFT_PAREN;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.NOT;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.NUMERIC;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.OR;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.RIGHT_PAREN;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.STAR;
import static com.github.zafarkhaja.semver.expr.Lexer.Token.Type.TILDE;
import java.util.EnumSet;
import java.util.Iterator;
import com.github.zafarkhaja.semver.Parser;
import com.github.zafarkhaja.semver.Version;
import com.github.zafarkhaja.semver.expr.Lexer.Token;
import com.github.zafarkhaja.semver.util.Stream;
import com.github.zafarkhaja.semver.util.Stream.ElementType;
import com.github.zafarkhaja.semver.util.UnexpectedElementException;
/**
* A parser for the SemVer Expressions.
*
* @author Zafar Khaja ([email protected])
* @since 0.7.0
*/
public class ExpressionParser implements Parser {
/**
* The lexer instance used for tokenization of the input string.
*/
private final Lexer lexer;
/**
* The stream of tokens produced by the lexer.
*/
private Stream tokens;
/**
* Constructs a {@code ExpressionParser} instance with the corresponding lexer.
*
* @param lexer
* the lexer to use for tokenization of the input string
*/
ExpressionParser(Lexer lexer) {
this.lexer = lexer;
}
/**
* Creates and returns new instance of the {@code ExpressionParser} class.
*
*
* This method implements the Static Factory Method pattern.
*
*
* @return a new instance of the {@code ExpressionParser} class
*/
public static Parser newInstance() {
return new ExpressionParser(new Lexer());
}
/**
* Parses the SemVer Expressions.
*
* @param input
* a string representing the SemVer Expression
* @return the AST for the SemVer Expressions
* @throws LexerException
* when encounters an illegal character
* @throws UnexpectedTokenException
* when consumes a token of an unexpected type
*/
@Override
public Expression parse(String input) {
tokens = lexer.tokenize(input);
Expression expr = parseSemVerExpression();
consumeNextToken(EOL);
return expr;
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::= "(" ")"
* | "!" "(" ")"
* |
* |
* }
*
*
* @return the expression AST
*/
private Expression parseSemVerExpression() {
Expression expr;
if (tokens.positiveLookahead(NOT)) {
tokens.consume();
consumeNextToken(LEFT_PAREN);
expr = new Not(parseSemVerExpression());
consumeNextToken(RIGHT_PAREN);
} else if (tokens.positiveLookahead(LEFT_PAREN)) {
consumeNextToken(LEFT_PAREN);
expr = parseSemVerExpression();
consumeNextToken(RIGHT_PAREN);
} else {
expr = parseExpression();
}
return parseBooleanExpression(expr);
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::=
* |
* }
*
*
* @param expr
* the left-hand expression of the logical operators
* @return the expression AST
*/
private Expression parseBooleanExpression(Expression expr) {
if (tokens.positiveLookahead(AND)) {
tokens.consume();
expr = new And(expr, parseSemVerExpression());
} else if (tokens.positiveLookahead(OR)) {
tokens.consume();
expr = new Or(expr, parseSemVerExpression());
}
return expr;
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::=
* |
* |
* |
* }
*
*
* @return the expression AST
*/
private Expression parseExpression() {
if (tokens.positiveLookahead(TILDE)) {
return parseTildeExpression();
} else if (isVersionExpression()) {
return parseVersionExpression();
} else if (isRangeExpression()) {
return parseRangeExpression();
}
return parseComparisonExpression();
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::=
* |
* }
*
*
* @return the expression AST
*/
private Expression parseComparisonExpression() {
Token token = tokens.lookahead();
Expression expr;
switch (token.type) {
case EQUAL:
tokens.consume();
expr = new Equal(parseVersion());
break;
case NOT_EQUAL:
tokens.consume();
expr = new NotEqual(parseVersion());
break;
case GREATER:
tokens.consume();
expr = new Greater(parseVersion());
break;
case GREATER_EQUAL:
tokens.consume();
expr = new GreaterOrEqual(parseVersion());
break;
case LESS:
tokens.consume();
expr = new Less(parseVersion());
break;
case LESS_EQUAL:
tokens.consume();
expr = new LessOrEqual(parseVersion());
break;
default:
expr = new Equal(parseVersion());
}
return expr;
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::= "~"
* }
*
*
* @return the expression AST
*/
private Expression parseTildeExpression() {
consumeNextToken(TILDE);
int major = intOf(consumeNextToken(NUMERIC).lexeme);
if (!tokens.positiveLookahead(DOT)) {
return new GreaterOrEqual(versionOf(major, 0, 0));
}
consumeNextToken(DOT);
int minor = intOf(consumeNextToken(NUMERIC).lexeme);
if (!tokens.positiveLookahead(DOT)) {
return new And(new GreaterOrEqual(versionOf(major, minor, 0)),
new Less(versionOf(major + 1, 0, 0)));
}
consumeNextToken(DOT);
int patch = intOf(consumeNextToken(NUMERIC).lexeme);
return new And(new GreaterOrEqual(versionOf(major, minor, patch)),
new Less(versionOf(major, minor + 1, 0)));
}
/**
* Determines if the following version terminals are part of the {@literal
* } non-terminal.
*
* @return {@code true} if the following version terminals are part of the
* {@literal } non-terminal or {@code false} otherwise
*/
private boolean isVersionExpression() {
return isVersionFollowedBy(STAR);
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::= "." "*"
* | "." "." "*"
* }
*
*
* @return the expression AST
*/
private Expression parseVersionExpression() {
int major = intOf(consumeNextToken(NUMERIC).lexeme);
consumeNextToken(DOT);
if (tokens.positiveLookahead(STAR)) {
tokens.consume();
return new And(new GreaterOrEqual(versionOf(major, 0, 0)),
new Less(versionOf(major + 1, 0, 0)));
}
int minor = intOf(consumeNextToken(NUMERIC).lexeme);
consumeNextToken(DOT);
consumeNextToken(STAR);
return new And(new GreaterOrEqual(versionOf(major, minor, 0)),
new Less(versionOf(major, minor + 1, 0)));
}
/**
* Determines if the following version terminals are part of the {@literal
* } non-terminal.
*
* @return {@code true} if the following version terminals are part of the {@literal }
* non-terminal or {@code false} otherwise
*/
private boolean isRangeExpression() {
return isVersionFollowedBy(HYPHEN);
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::= "-"
* }
*
*
* @return the expression AST
*/
private Expression parseRangeExpression() {
Expression ge = new GreaterOrEqual(parseVersion());
consumeNextToken(HYPHEN);
Expression le = new LessOrEqual(parseVersion());
return new And(ge, le);
}
/**
* Parses the {@literal } non-terminal.
*
*
* {@literal
* ::=
* | "."
* | "." "."
* }
*
*
* @return the parsed version
*/
private Version parseVersion() {
int major = intOf(consumeNextToken(NUMERIC).lexeme);
int minor = 0;
if (tokens.positiveLookahead(DOT)) {
tokens.consume();
minor = intOf(consumeNextToken(NUMERIC).lexeme);
}
int patch = 0;
if (tokens.positiveLookahead(DOT)) {
tokens.consume();
patch = intOf(consumeNextToken(NUMERIC).lexeme);
}
return versionOf(major, minor, patch);
}
/**
* Determines if the version terminals are followed by the specified token type.
*
*
* This method is essentially a {@code lookahead(k)} method which allows to solve the grammar's
* ambiguities.
*
*
* @param type
* the token type to check
* @return {@code true} if the version terminals are followed by the specified token type or
* {@code false} otherwise
*/
private boolean isVersionFollowedBy(ElementType type) {
EnumSet expected = EnumSet.of(NUMERIC, DOT);
Iterator it = tokens.iterator();
Token lookahead = null;
while (it.hasNext()) {
lookahead = it.next();
if (!expected.contains(lookahead.type)) {
break;
}
}
return type.isMatchedBy(lookahead);
}
/**
* Creates a {@code Version} instance for the specified integers.
*
* @param major
* the major version number
* @param minor
* the minor version number
* @param patch
* the patch version number
* @return the version for the specified integers
*/
private Version versionOf(int major, int minor, int patch) {
return Version.forIntegers(major, minor, patch);
}
/**
* Returns a {@code int} representation of the specified string.
*
* @param value
* the string to convert into an integer
* @return the integer value of the specified string
*/
private int intOf(String value) {
return Integer.parseInt(value);
}
/**
* Tries to consume the next token in the stream.
*
* @param expected
* the expected types of the next token
* @return the next token in the stream
* @throws UnexpectedTokenException
* when encounters an unexpected token type
*/
private Token consumeNextToken(Token.Type... expected) {
try {
return tokens.consume(expected);
} catch (UnexpectedElementException e) {
throw new UnexpectedTokenException(e);
}
}
}