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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.search.yql;
import org.antlr.v4.runtime.misc.Interval;
import org.antlr.v4.runtime.CharStream;
/**
* This class supports case-insensitive lexing by wrapping an existing
* {@link CharStream} and forcing the lexer to see only lowercase characters.
* Grammar literals should then be only lower case such as 'begin'. The text of the character
* stream is unaffected. Example: input 'BeGiN' would match lexer rule
* 'begin', but getText() would return 'BeGiN'.
* It is based on https://github.com/antlr/antlr4/blob/master/doc/resources/CaseChangingCharStream.java
*/
class CaseInsensitiveCharStream implements CharStream {
final CharStream stream;
/**
* Constructs a new CaseChangingCharStream wrapping the given {@link CharStream} forcing
* all characters lower case.
* @param stream The stream to wrap.
*/
CaseInsensitiveCharStream(CharStream stream) {
this.stream = stream;
}
@Override
public String getText(Interval interval) {
return stream.getText(interval);
}
@Override
public void consume() {
stream.consume();
}
@Override
public int LA(int i) {
int c = stream.LA(i);
if (c <= 0) {
return c;
}
return Character.toLowerCase(c);
}
@Override
public int mark() {
return stream.mark();
}
@Override
public void release(int marker) {
stream.release(marker);
}
@Override
public int index() {
return stream.index();
}
@Override
public void seek(int index) {
stream.seek(index);
}
@Override
public int size() {
return stream.size();
}
@Override
public String getSourceName() {
return stream.getSourceName();
}
}
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