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Asynchronous PostgreSQL Java driver

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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,
 * 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.github.pgasync.impl.io;

import com.github.pgasync.impl.message.ErrorResponse;

import java.nio.ByteBuffer;

import static com.github.pgasync.impl.io.IO.getCString;

/**
 * See PostgreSQL message formats
 *
 *  * ErrorResponse (B)
 *  Byte1('E')
 *      Identifies the message as an error.
 *  Int32
 *      Length of message contents in bytes, including self.
 *  The message body consists of one or more identified fields, followed by a zero byte as a terminator. Fields can appear in any order. For each field there is the following:
 *  Byte1
 *      A code identifying the field type; if zero, this is the message terminator and no string follows. The presently defined field types are listed in Section 46.6. Since more field types might be added in future, frontends should silently ignore fields of unrecognized type.
 *  String
 *      The field value.
 * 
 *
 * @author Antti Laisi
 */
public class ErrorResponseDecoder implements Decoder {

    @Override
    public byte getMessageId() {
        return 'E';
    }

    @Override
    public ErrorResponse read(ByteBuffer buffer) {

        String level = null;
        String code = null;
        String message = null;

        byte[] field = new byte[255];
        for (byte type = buffer.get(); type != 0; type = buffer.get()) {
            String value = getCString(buffer, field);
            if (type == (byte) 'S') {
                level = value;
            } else if (type == 'C') {
                code = value;
            } else if (type == 'M') {
                message = value;
            }
        }

        return new ErrorResponse(level, code, message);
    }

}