/*
* Copyright (c) 2012, the Dart project authors.
*
* Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
*
* 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 com.google.dart.engine.scanner;
/**
* Instances of the class {@code Token} represent a token that was scanned from the input. Each
* token knows which token follows it, acting as the head of a linked list of tokens.
*
* @coverage dart.engine.parser
*/
public class Token {
/**
* The type of the token.
*/
private final TokenType type;
/**
* The offset from the beginning of the file to the first character in the token.
*/
private int offset;
/**
* The previous token in the token stream.
*/
private Token previous;
/**
* The next token in the token stream.
*/
private Token next;
/**
* Initialize a newly created token to have the given type and offset.
*
* @param type the type of the token
* @param offset the offset from the beginning of the file to the first character in the token
*/
public Token(TokenType type, int offset) {
this.type = type;
this.offset = offset;
}
/**
* Return a newly created token that is a copy of this token but that is not a part of any token
* stream.
*
* @return a newly created token that is a copy of this token
*/
public Token copy() {
return new Token(type, offset);
}
/**
* Return the offset from the beginning of the file to the character after last character of the
* token.
*
* @return the offset from the beginning of the file to the first character after last character
* of the token
*/
public int getEnd() {
return offset + getLength();
}
/**
* Return the number of characters in the node's source range.
*
* @return the number of characters in the node's source range
*/
public int getLength() {
return getLexeme().length();
}
/**
* Return the lexeme that represents this token.
*
* @return the lexeme that represents this token
*/
public String getLexeme() {
return type.getLexeme();
}
/**
* Return the next token in the token stream.
*
* @return the next token in the token stream
*/
public Token getNext() {
return next;
}
/**
* Return the offset from the beginning of the file to the first character in the token.
*
* @return the offset from the beginning of the file to the first character in the token
*/
public int getOffset() {
return offset;
}
/**
* Return the first comment in the list of comments that precede this token, or {@code null} if
* there are no comments preceding this token. Additional comments can be reached by following the
* token stream using {@link #getNext()} until {@code null} is returned.
*
* @return the first comment in the list of comments that precede this token
*/
public Token getPrecedingComments() {
return null;
}
/**
* Return the previous token in the token stream.
*
* @return the previous token in the token stream
*/
public Token getPrevious() {
return previous;
}
/**
* Return the type of the token.
*
* @return the type of the token
*/
public TokenType getType() {
return type;
}
/**
* Return {@code true} if this token represents an operator.
*
* @return {@code true} if this token represents an operator
*/
public boolean isOperator() {
return type.isOperator();
}
/**
* Return {@code true} if this token is a synthetic token. A synthetic token is a token that was
* introduced by the parser in order to recover from an error in the code.
*
* @return {@code true} if this token is a synthetic token
*/
public boolean isSynthetic() {
return getLength() == 0;
}
/**
* Return {@code true} if this token represents an operator that can be defined by users.
*
* @return {@code true} if this token represents an operator that can be defined by users
*/
public boolean isUserDefinableOperator() {
return type.isUserDefinableOperator();
}
/**
* Return {@code true} if this token has any one of the given types.
*
* @param types the types of token that are being tested for
* @return {@code true} if this token has any of the given types
*/
public boolean matchesAny(TokenType... types) {
for (TokenType type : types) {
if (this.type == type) {
return true;
}
}
return false;
}
/**
* Set the next token in the token stream to the given token. This has the side-effect of setting
* this token to be the previous token for the given token.
*
* @param token the next token in the token stream
* @return the token that was passed in
*/
public Token setNext(Token token) {
next = token;
token.setPrevious(this);
return token;
}
/**
* Set the next token in the token stream to the given token without changing which token is the
* previous token for the given token.
*
* @param token the next token in the token stream
* @return the token that was passed in
*/
public Token setNextWithoutSettingPrevious(Token token) {
next = token;
return token;
}
/**
* Set the offset from the beginning of the file to the first character in the token to the given
* offset.
*
* @param offset the offset from the beginning of the file to the first character in the token
*/
public void setOffset(int offset) {
this.offset = offset;
}
@Override
public String toString() {
return getLexeme();
}
/**
* Return the value of this token. For keyword tokens, this is the keyword associated with the
* token, for other tokens it is the lexeme associated with the token.
*
* @return the value of this token
*/
public Object value() {
return type.getLexeme();
}
/**
* Apply (add) the given delta to this token's offset.
*
* @param delta the amount by which the offset is to be adjusted
*/
protected void applyDelta(int delta) {
offset += delta;
}
/**
* Copy a linked list of comment tokens identical to the given comment tokens.
*
* @param token the first token in the list, or {@code null} if there are no tokens to be copied
* @return the tokens that were created
*/
protected Token copyComments(Token token) {
if (token == null) {
return null;
}
Token head = token.copy();
Token tail = head;
token = token.getNext();
while (token != null) {
tail = tail.setNext(token.copy());
token = token.getNext();
}
return head;
}
/**
* Set the previous token in the token stream to the given token.
*
* @param previous the previous token in the token stream
*/
private void setPrevious(Token previous) {
this.previous = previous;
}
}