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With inspiration from other libraries
/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.runtime;
import org.antlr.v4.runtime.misc.Pair;
import java.util.List;
/**
* Provides an implementation of {@link TokenSource} as a wrapper around a list
* of {@link Token} objects.
*
* If the final token in the list is an {@link Token#EOF} token, it will be used
* as the EOF token for every call to {@link #nextToken} after the end of the
* list is reached. Otherwise, an EOF token will be created.
*/
public class ListTokenSource implements TokenSource {
/**
* The wrapped collection of {@link Token} objects to return.
*/
protected final List tokens;
/**
* The name of the input source. If this value is {@code null}, a call to
* {@link #getSourceName} should return the source name used to create the
* the next token in {@link #tokens} (or the previous token if the end of
* the input has been reached).
*/
private final String sourceName;
/**
* The index into {@link #tokens} of token to return by the next call to
* {@link #nextToken}. The end of the input is indicated by this value
* being greater than or equal to the number of items in {@link #tokens}.
*/
protected int i;
/**
* This field caches the EOF token for the token source.
*/
protected Token eofToken;
/**
* This is the backing field for {@link #getTokenFactory} and
* {@link setTokenFactory}.
*/
private TokenFactory _factory = CommonTokenFactory.DEFAULT;
/**
* Constructs a new {@link ListTokenSource} instance from the specified
* collection of {@link Token} objects.
*
* @param tokens The collection of {@link Token} objects to provide as a
* {@link TokenSource}.
* @exception NullPointerException if {@code tokens} is {@code null}
*/
public ListTokenSource(List tokens) {
this(tokens, null);
}
/**
* Constructs a new {@link ListTokenSource} instance from the specified
* collection of {@link Token} objects and source name.
*
* @param tokens The collection of {@link Token} objects to provide as a
* {@link TokenSource}.
* @param sourceName The name of the {@link TokenSource}. If this value is
* {@code null}, {@link #getSourceName} will attempt to infer the name from
* the next {@link Token} (or the previous token if the end of the input has
* been reached).
*
* @exception NullPointerException if {@code tokens} is {@code null}
*/
public ListTokenSource(List tokens, String sourceName) {
if (tokens == null) {
throw new NullPointerException("tokens cannot be null");
}
this.tokens = tokens;
this.sourceName = sourceName;
}
/**
* {@inheritDoc}
*/
@Override
public int getCharPositionInLine() {
if (i < tokens.size()) {
return tokens.get(i).getCharPositionInLine();
}
else if (eofToken != null) {
return eofToken.getCharPositionInLine();
}
else if (tokens.size() > 0) {
// have to calculate the result from the line/column of the previous
// token, along with the text of the token.
Token lastToken = tokens.get(tokens.size() - 1);
String tokenText = lastToken.getText();
if (tokenText != null) {
int lastNewLine = tokenText.lastIndexOf('\n');
if (lastNewLine >= 0) {
return tokenText.length() - lastNewLine - 1;
}
}
return lastToken.getCharPositionInLine() + lastToken.getStopIndex() - lastToken.getStartIndex() + 1;
}
// only reach this if tokens is empty, meaning EOF occurs at the first
// position in the input
return 0;
}
/**
* {@inheritDoc}
*/
@Override
public Token nextToken() {
if (i >= tokens.size()) {
if (eofToken == null) {
int start = -1;
if (tokens.size() > 0) {
int previousStop = tokens.get(tokens.size() - 1).getStopIndex();
if (previousStop != -1) {
start = previousStop + 1;
}
}
int stop = Math.max(-1, start - 1);
eofToken = _factory.create(new Pair(this, getInputStream()), Token.EOF, "EOF", Token.DEFAULT_CHANNEL, start, stop, getLine(), getCharPositionInLine());
}
return eofToken;
}
Token t = tokens.get(i);
if (i == tokens.size() - 1 && t.getType() == Token.EOF) {
eofToken = t;
}
i++;
return t;
}
/**
* {@inheritDoc}
*/
@Override
public int getLine() {
if (i < tokens.size()) {
return tokens.get(i).getLine();
}
else if (eofToken != null) {
return eofToken.getLine();
}
else if (tokens.size() > 0) {
// have to calculate the result from the line/column of the previous
// token, along with the text of the token.
Token lastToken = tokens.get(tokens.size() - 1);
int line = lastToken.getLine();
String tokenText = lastToken.getText();
if (tokenText != null) {
for (int i = 0; i < tokenText.length(); i++) {
if (tokenText.charAt(i) == '\n') {
line++;
}
}
}
// if no text is available, assume the token did not contain any newline characters.
return line;
}
// only reach this if tokens is empty, meaning EOF occurs at the first
// position in the input
return 1;
}
/**
* {@inheritDoc}
*/
@Override
public CharStream getInputStream() {
if (i < tokens.size()) {
return tokens.get(i).getInputStream();
}
else if (eofToken != null) {
return eofToken.getInputStream();
}
else if (tokens.size() > 0) {
return tokens.get(tokens.size() - 1).getInputStream();
}
// no input stream information is available
return null;
}
/**
* {@inheritDoc}
*/
@Override
public String getSourceName() {
if (sourceName != null) {
return sourceName;
}
CharStream inputStream = getInputStream();
if (inputStream != null) {
return inputStream.getSourceName();
}
return "List";
}
/**
* {@inheritDoc}
*/
@Override
public void setTokenFactory(TokenFactory factory) {
this._factory = factory;
}
/**
* {@inheritDoc}
*/
@Override
public TokenFactory getTokenFactory() {
return _factory;
}
}