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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.Bind;

import java.nio.ByteBuffer;

/**
 * See PostgreSQL message formats
 *  
 *  * Bind (F)
 *   Byte1('B')
 *       Identifies the message as a Bind command.
 *   Int32
 *       Length of message contents in bytes, including self.
 *   String
 *       The name of the destination portal (an empty string selects the unnamed portal).
 *   String
 *       The name of the source prepared statement (an empty string selects the unnamed prepared statement).
 *   Int16
 *       The number of parameter format codes that follow (denoted C below). This can be zero to indicate that there are no parameters or that the parameters all use the default format (text); or one, in which case the specified format code is applied to all parameters; or it can equal the actual number of parameters.
 *   Int16[C]
 *       The parameter format codes. Each must presently be zero (text) or one (binary).
 *   Int16
 *       The number of parameter values that follow (possibly zero). This must match the number of parameters needed by the query.
 *   Next, the following pair of fields appear for each parameter:
 *   Int32
 *       The length of the parameter value, in bytes (this count does not include itself). Can be zero. As a special case, -1 indicates a NULL parameter value. No value bytes follow in the NULL case.
 *   Byten
 *       The value of the parameter, in the format indicated by the associated format code. n is the above length.
 *   After the last parameter, the following fields appear:
 *   Int16
 *       The number of result-column format codes that follow (denoted R below). This can be zero to indicate that there are no result columns or that the result columns should all use the default format (text); or one, in which case the specified format code is applied to all result columns (if any); or it can equal the actual number of result columns of the query.
 *   Int16[R]
 *       The result-column format codes. Each must presently be zero (text) or one (binary).
 *
 *
 * @author Antti Laisi
 */
public class BindEncoder implements Encoder {

    @Override
    public Class getMessageType() {
        return Bind.class;
    }

    @Override
    public void write(Bind msg, ByteBuffer buffer) {
        buffer.put((byte) 'B');
        buffer.putInt(0);
        buffer.put((byte) 0); // portal
        buffer.put((byte) 0); // prepared statement
        buffer.putShort((short) 0); // number of format codes
        buffer.putShort((short) msg.getParams().length); // number of parameters
        for (byte[] param : msg.getParams()) {
            writeParameter(buffer, param);
        }
        buffer.putShort((short) 0);
        buffer.putInt(1, buffer.position() - 1);
    }

    void writeParameter(ByteBuffer buffer, byte[] param) {
        if (param == null) {
            buffer.putInt(-1);
            return;
        }
        buffer.putInt(param.length);
        buffer.put(param);
    }
}