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JDBC Type 4 driver for MySQL.
There is a newer version: 9.1.0
/*
 * Copyright (c) 2007, 2024, Oracle and/or its affiliates.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2.0, as published by
 * the Free Software Foundation.
 *
 * This program is designed to work with certain software that is licensed under separate terms, as designated in a particular file or component or in
 * included license documentation. The authors of MySQL hereby grant you an additional permission to link the program and your derivative works with the
 * separately licensed software that they have either included with the program or referenced in the documentation.
 *
 * Without limiting anything contained in the foregoing, this file, which is part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
 * version 1.0, a copy of which can be found at http://oss.oracle.com/licenses/universal-foss-exception.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0, for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

package com.mysql.cj.protocol.a.result;

import com.mysql.cj.exceptions.ExceptionInterceptor;
import com.mysql.cj.protocol.ColumnDefinition;
import com.mysql.cj.protocol.ValueDecoder;
import com.mysql.cj.protocol.a.NativeConstants.IntegerDataType;
import com.mysql.cj.protocol.a.NativeConstants.StringSelfDataType;
import com.mysql.cj.protocol.a.NativePacketPayload;
import com.mysql.cj.result.Row;
import com.mysql.cj.result.ValueFactory;

/**
 * A ResultSetRow implementation that holds one row packet (which is re-used by the driver, and thus saves memory allocations), and tries when possible to avoid
 * allocations to break out the results as individual byte[]s.
 *
 * (this isn't possible when doing things like reading floating point values).
 */
public class TextBufferRow extends AbstractBufferRow {

    public TextBufferRow(NativePacketPayload buf, ColumnDefinition cd, ExceptionInterceptor exceptionInterceptor, ValueDecoder valueDecoder) {
        super(exceptionInterceptor);

        this.rowFromServer = buf;
        this.homePosition = this.rowFromServer.getPosition();
        this.valueDecoder = valueDecoder;

        if (cd.getFields() != null) {
            setMetadata(cd);
        }
    }

    @Override
    protected int findAndSeekToOffset(int index) {
        if (index == 0) {
            this.lastRequestedIndex = 0;
            this.lastRequestedPos = this.homePosition;
            this.rowFromServer.setPosition(this.homePosition);

            return 0;
        }

        if (index == this.lastRequestedIndex) {
            this.rowFromServer.setPosition(this.lastRequestedPos);

            return this.lastRequestedPos;
        }

        int startingIndex = 0;

        if (index > this.lastRequestedIndex) {
            if (this.lastRequestedIndex >= 0) {
                startingIndex = this.lastRequestedIndex;
            } else {
                startingIndex = 0;
            }

            this.rowFromServer.setPosition(this.lastRequestedPos);
        } else {
            this.rowFromServer.setPosition(this.homePosition);
        }

        for (int i = startingIndex; i < index; i++) {
            this.rowFromServer.skipBytes(StringSelfDataType.STRING_LENENC);
        }

        this.lastRequestedIndex = index;
        this.lastRequestedPos = this.rowFromServer.getPosition();

        return this.lastRequestedPos;
    }

    @Override
    public byte[] getBytes(int index) {
        if (getNull(index)) {
            return null;
        }

        findAndSeekToOffset(index);
        return this.rowFromServer.readBytes(StringSelfDataType.STRING_LENENC);
    }

    @Override
    public boolean getNull(int columnIndex) {
        findAndSeekToOffset(columnIndex);
        this.wasNull = this.rowFromServer.readInteger(IntegerDataType.INT_LENENC) == NativePacketPayload.NULL_LENGTH;
        return this.wasNull;
    }

    @Override
    public Row setMetadata(ColumnDefinition f) {
        super.setMetadata(f);
        return this;
    }

    /**
     * Implementation of getValue() based on the underlying Buffer object. Delegate to superclass for decoding.
     */
    @Override
    public  T getValue(int columnIndex, ValueFactory vf) {
        findAndSeekToOffset(columnIndex);
        int length = (int) this.rowFromServer.readInteger(IntegerDataType.INT_LENENC);
        return getValueFromBytes(columnIndex, this.rowFromServer.getByteBuffer(), this.rowFromServer.getPosition(), length, vf);
    }

}