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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.prelude.query.parser;
import java.util.List;
/**
* An iterator-like view of a list of tokens, but typed, random-accessible
* and with more convenience methods
*
* @author bratseth
*/
final class TokenPosition {
private List<Token> tokenList;
private int position = 0;
/**
* Creates an empty token position which must be {@link #initialize initialized}
* before use
*/
public TokenPosition() {}
/**
* Initializes this token position. Must be done once or more before use
*
* @param tokens a list of tokens, which is not modified, and not used
* outside the calling thread
*/
public void initialize(List<Token> tokens) {
this.tokenList = tokens;
position = 0;
}
/**
* Returns the current token without changing the position.
* Returns null (no exception) if there are no more tokens.
*/
public Token current() {
return current(0);
}
/**
* Returns the current token without changing the position,
* and without ignoring spaces.
* Returns null (no exception) if there are no more tokens.
*/
public Token currentNoIgnore() {
return currentNoIgnore(0);
}
/**
* Returns the token at <code>offset</code> steps from here.
* Null (no exception) if there is no token at that position
*/
public Token current(int offset) {
int i = position + offset;
while (i < tokenList.size()) {
Token token = tokenList.get(i++);
if (token.kind != Token.Kind.SPACE) {
return token;
}
}
return null;
}
/**
* Returns the token at <code>offset</code> steps from here,
* without ignoring spaces.
* Null (no exception) if there is no token at that position
*/
public Token currentNoIgnore(int offset) {
if (tokenList.size() <= position + offset) {
return null;
}
return tokenList.get(position + offset);
}
/**
* Returns whether the current token is of the given kind.
* False also if there is no token at the current position
*/
public boolean currentIs(Token.Kind kind) {
Token current = current();
if (current == null) {
return false;
}
return current.kind == kind;
}
/**
* Returns whether the current token is of the given kind,
* without skipping spaces.
* False also if there is no token at the current position
*/
public boolean currentIsNoIgnore(Token.Kind kind) {
Token current = currentNoIgnore();
if (current == null) {
return false;
}
return current.kind == kind;
}
/** Returns whether more tokens are available */
public boolean hasNext() {
return tokenList.size() > (position + 1);
}
/**
* Returns the current token and increases the position by one.
* Returns null (no exception) if there are no more tokens
*/
public Token next() {
// Go to the next-non-space. Then set token, then increase position by one
while (position < tokenList.size()) {
Token current = tokenList.get(position++);
if (current.kind != Token.Kind.SPACE) {
return current;
}
}
return null;
}
/** Skips past the current token */
public void skip() {
next();
}
/** Skips to the next token, even if the next is a space */
public void skipNoIgnore() {
position++;
}
/** Sets the position */
public void setPosition(int position) {
this.position = position;
}
/** Returns the current position */
public int getPosition() {
return position;
}
/**
* Skips one or more tokens of the given kind
*
* @return true if at least one was skipped, false if there was none
*/
public boolean skipMultiple(Token.Kind kind) {
boolean skipped = false;
while (hasNext() && current().kind == kind) {
skipped = true;
skip();
}
return skipped;
}
/**
* Skips one or more tokens of the given kind, without ignoring spaces
*
* @return true if at least one was skipped, false if there was none
*/
public boolean skipMultipleNoIgnore(Token.Kind kind) {
boolean skipped = false;
while (hasNext() && currentNoIgnore().kind == kind) {
skipped = true;
skip();
}
return skipped;
}
/**
* Skips one or zero items of the given kind.
*
* @return true if one item was skipped, false if none was, or if there are no more tokens
*/
public boolean skip(Token.Kind kind) {
Token current = current();
if (current == null || current.kind != kind) {
return false;
}
skip();
return true;
}
/**
* Skips one or zero items of the given kind, without ignoring spaces
*
* @return true if one item was skipped, false if none was or if there are no more tokens
*/
public boolean skipNoIgnore(Token.Kind kind) {
Token current = currentNoIgnore();
if (current == null || current.kind != kind) return false;
skipNoIgnore();
return true;
}
@Override
public String toString() {
return "token " + current();
}
}
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