/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you 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 io.netty.handler.codec.compression;

import com.ning.compress.BufferRecycler;
import com.ning.compress.lzf.ChunkEncoder;
import com.ning.compress.lzf.LZFEncoder;
import com.ning.compress.lzf.util.ChunkEncoderFactory;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;

import static com.ning.compress.lzf.LZFChunk.*;

Compresses a ByteBuf using the LZF format. See original LZF package
and LZF format for full description.
/**
 * Compresses a {@link ByteBuf} using the LZF format.
 *
 * See original <a href="http://oldhome.schmorp.de/marc/liblzf.html">LZF package</a>
 * and <a href="https://github.com/ning/compress/wiki/LZFFormat">LZF format</a> for full description.
 */
public class LzfEncoder extends MessageToByteEncoder<ByteBuf> {
    
Minimum block size ready for compression. Blocks with length less than MIN_BLOCK_TO_COMPRESS will write as uncompressed. /**
     * Minimum block size ready for compression. Blocks with length
     * less than {@link #MIN_BLOCK_TO_COMPRESS} will write as uncompressed.
     */
    private static final int MIN_BLOCK_TO_COMPRESS = 16;

    
Underlying decoder in use.
/**
     * Underlying decoder in use.
     */
    private final ChunkEncoder encoder;

    
Object that handles details of buffer recycling.
/**
     * Object that handles details of buffer recycling.
     */
    private final BufferRecycler recycler;

    
Creates a new LZF encoder with the most optimal available methods for underlying data access. It will "unsafe" instance if one can be used on current JVM. It should be safe to call this constructor as implementations are dynamically loaded; however, on some non-standard platforms it may be necessary to use LzfEncoder(boolean) with true param. /**
     * Creates a new LZF encoder with the most optimal available methods for underlying data access.
     * It will "unsafe" instance if one can be used on current JVM.
     * It should be safe to call this constructor as implementations are dynamically loaded; however, on some
     * non-standard platforms it may be necessary to use {@link #LzfEncoder(boolean)} with {@code true} param.
     */
    public LzfEncoder() {
        this(false, MAX_CHUNK_LEN);
    }

    
Creates a new LZF encoder with specified encoding instance.
Params:
safeInstance –  If true encoder will use ChunkEncoder that only uses standard JDK access methods, and should work on all Java platforms and JVMs. Otherwise encoder will try to use highly optimized ChunkEncoder implementation that uses Sun JDK's Unsafe class (which may be included by other JDK's as well)./**
     * Creates a new LZF encoder with specified encoding instance.
     *
     * @param safeInstance
     *        If {@code true} encoder will use {@link ChunkEncoder} that only uses standard JDK access methods,
     *        and should work on all Java platforms and JVMs.
     *        Otherwise encoder will try to use highly optimized {@link ChunkEncoder} implementation that uses
     *        Sun JDK's {@link sun.misc.Unsafe} class (which may be included by other JDK's as well).
     */
    public LzfEncoder(boolean safeInstance) {
        this(safeInstance, MAX_CHUNK_LEN);
    }

    
Creates a new LZF encoder with specified total length of encoded chunk. You can configure it to encode
your data flow more efficient if you know the average size of messages that you send.
Params:
totalLength – 
       Expected total length of content to compress; only matters for outgoing messages that is smaller
       than maximum chunk size (64k), to optimize encoding hash tables./**
     * Creates a new LZF encoder with specified total length of encoded chunk. You can configure it to encode
     * your data flow more efficient if you know the average size of messages that you send.
     *
     * @param totalLength
     *        Expected total length of content to compress; only matters for outgoing messages that is smaller
     *        than maximum chunk size (64k), to optimize encoding hash tables.
     */
    public LzfEncoder(int totalLength) {
        this(false, totalLength);
    }

    
Creates a new LZF encoder with specified settings.
Params:
safeInstance –  If true encoder will use ChunkEncoder that only uses standard JDK access methods, and should work on all Java platforms and JVMs. Otherwise encoder will try to use highly optimized ChunkEncoder implementation that uses Sun JDK's Unsafe class (which may be included by other JDK's as well).
totalLength – 
       Expected total length of content to compress; only matters for outgoing messages that is smaller
       than maximum chunk size (64k), to optimize encoding hash tables./**
     * Creates a new LZF encoder with specified settings.
     *
     * @param safeInstance
     *        If {@code true} encoder will use {@link ChunkEncoder} that only uses standard JDK access methods,
     *        and should work on all Java platforms and JVMs.
     *        Otherwise encoder will try to use highly optimized {@link ChunkEncoder} implementation that uses
     *        Sun JDK's {@link sun.misc.Unsafe} class (which may be included by other JDK's as well).
     * @param totalLength
     *        Expected total length of content to compress; only matters for outgoing messages that is smaller
     *        than maximum chunk size (64k), to optimize encoding hash tables.
     */
    public LzfEncoder(boolean safeInstance, int totalLength) {
        super(false);
        if (totalLength < MIN_BLOCK_TO_COMPRESS || totalLength > MAX_CHUNK_LEN) {
            throw new IllegalArgumentException("totalLength: " + totalLength +
                    " (expected: " + MIN_BLOCK_TO_COMPRESS + '-' + MAX_CHUNK_LEN + ')');
        }

        encoder = safeInstance ?
                ChunkEncoderFactory.safeNonAllocatingInstance(totalLength)
              : ChunkEncoderFactory.optimalNonAllocatingInstance(totalLength);

        recycler = BufferRecycler.instance();
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception {
        final int length = in.readableBytes();
        final int idx = in.readerIndex();
        final byte[] input;
        final int inputPtr;
        if (in.hasArray()) {
            input = in.array();
            inputPtr = in.arrayOffset() + idx;
        } else {
            input = recycler.allocInputBuffer(length);
            in.getBytes(idx, input, 0, length);
            inputPtr = 0;
        }

        final int maxOutputLength = LZFEncoder.estimateMaxWorkspaceSize(length);
        out.ensureWritable(maxOutputLength);
        final byte[] output = out.array();
        final int outputPtr = out.arrayOffset() + out.writerIndex();
        final int outputLength = LZFEncoder.appendEncoded(encoder,
                        input, inputPtr, length,  output, outputPtr) - outputPtr;
        out.writerIndex(out.writerIndex() + outputLength);
        in.skipBytes(length);

        if (!in.hasArray()) {
            recycler.releaseInputBuffer(input);
        }
    }
}