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/*
 *     This file is part of mongowp.
 *
 *     mongowp is free software: you can redistribute it and/or modify
 *     it under the terms of the GNU Affero General Public License as published by
 *     the Free Software Foundation, either version 3 of the License, or
 *     (at your option) any later version.
 *
 *     mongowp 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 Affero General Public License for more details.
 *
 *     You should have received a copy of the GNU Affero General Public License
 *     along with mongowp. If not, see .
 *
 *     Copyright (c) 2014, 8Kdata Technology
 *     
 */


package com.eightkdata.mongowp.mongoserver.util;

import com.google.common.base.Charsets;
import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import io.netty.buffer.ByteBuf;
import org.bson.*;
import org.bson.codecs.BsonDocumentCodec;
import org.bson.codecs.DecoderContext;
import org.bson.codecs.EncoderContext;

/**
 *
 */
@SuppressFBWarnings(
        value="RV_RETURN_VALUE_IGNORED_NO_SIDE_EFFECT",
        justification = "It seems FindBugs considers ByteBuf methods are not side effect"
)
public class ByteBufUtil {
    public static final byte CSTRING_BYTE_TERMINATION = (byte) '\0';

    private static final BsonDocumentCodec BSON_CODEC = new BsonDocumentCodec();

    /**
     * A method that reads a C-string from a ByteBuf.
     * This method modified the internal state of the ByteBuf, advancing the read pointer to the position after the
     * cstring.
     *
     * @param buffer
     * @return The C-String as a String object or null if there was no C-String in the ByteBuf
     */
    public static String readCString(ByteBuf buffer) {
        int pos = buffer.bytesBefore(CSTRING_BYTE_TERMINATION);
        if(pos == -1) {
            return null;
        }
        byte[] bytes = new byte[pos];
        buffer.readBytes(bytes);
        buffer.readByte();  // Discard the termination byte

        return new String(bytes, Charsets.UTF_8);
    }

    public static BsonDocument readBsonDocument(ByteBuf buffer) {
        BsonReader reader = new BsonBinaryReader(new ByteBufBsonInputAdaptor(buffer));

        DecoderContext context = DecoderContext.builder().build();
        return BSON_CODEC.decode(reader, context);
    }

    public static void writeBsonDocument(ByteBuf buffer, BsonDocument bson) {
        BsonWriter writer = new BsonBinaryWriter(new ByteBufBsonOutputAdaptor(buffer));

        EncoderContext context = EncoderContext.builder().build();

        BSON_CODEC.encode(writer, bson, context);
    }
}