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QuestDB is high performance SQL time series database

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 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2024 QuestDB
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 *  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,
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package io.questdb.griffin.engine.functions.cast;

import io.questdb.cairo.CairoConfiguration;
import io.questdb.cairo.sql.Function;
import io.questdb.cairo.sql.Record;
import io.questdb.griffin.FunctionFactory;
import io.questdb.griffin.SqlExecutionContext;
import io.questdb.std.IntList;
import io.questdb.std.ObjList;
import io.questdb.std.str.StringSink;
import io.questdb.std.str.Utf8Sequence;

public class CastVarcharToCharFunctionFactory implements FunctionFactory {

    @Override
    public String getSignature() {
        return "cast(Øa)";
    }

    @Override
    public Function newInstance(
            int position,
            ObjList args,
            IntList argPositions,
            CairoConfiguration configuration,
            SqlExecutionContext sqlExecutionContext
    ) {
        return new Func(args.getQuick(0));
    }

    private static class Func extends AbstractCastToCharFunction {
        private final StringSink utf16Sink = new StringSink();

        public Func(Function arg) {
            super(arg);
        }

        @Override
        public char getChar(Record rec) {
            final Utf8Sequence value = arg.getVarcharA(rec);
            if (value == null) {
                return 0;
            }
            utf16Sink.clear();
            utf16Sink.put(value);
            return utf16Sink.length() > 0 ? utf16Sink.charAt(0) : 0;
        }

        @Override
        public boolean isThreadSafe() {
            return false;
        }
    }
}