com.oceanbase.tools.sqlparser.util.CaseChangingCharStream Maven / Gradle / Ivy

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ob-sql-parser parses an SQL statement into a Java classes.

There is a newer version: 1.3.0

/*
 * Copyright (c) 2023 OceanBase.
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * 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.oceanbase.tools.sqlparser.util;

import org.antlr.v4.runtime.CharStream;
import org.antlr.v4.runtime.misc.Interval;

/**
 * https://github.com/parrt/antlr4/blob/case-insensitivity-doc/doc/resources/CaseChangingCharStream.java
 * 
 * This class supports case-insensitive lexing by wrapping an existing {@link CharStream} and
 * forcing the lexer to see either upper or lowercase characters. Grammar literals should then be
 * either upper or lower case such as 'BEGIN' or 'begin'. The text of the character stream is
 * unaffected. Example: input 'BeGiN' would match lexer rule 'BEGIN' if constructor parameter
 * upper=true but getText() would return 'BeGiN'.
 */
public class CaseChangingCharStream implements CharStream {

    final CharStream stream;
    final boolean upper;

    /**
     * Constructs a new CaseChangingCharStream wrapping the given {@link CharStream} forcing all
     * characters to upper case or lower case.
     *
     * @param stream The stream to wrap.
     * @param upper If true force each symbol to upper case, otherwise force to lower.
     */
    public CaseChangingCharStream(CharStream stream, boolean upper) {
        this.stream = stream;
        this.upper = upper;
    }

    @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;
        }
        if (upper) {
            return Character.toUpperCase(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();
    }
}