Repository: commons-compress Updated Branches: refs/heads/master b8939bea3 -> 74b38da45
COMPRESS-271 non-functional skeleton of LZ4 block output stream Project: http://git-wip-us.apache.org/repos/asf/commons-compress/repo Commit: http://git-wip-us.apache.org/repos/asf/commons-compress/commit/74b38da4 Tree: http://git-wip-us.apache.org/repos/asf/commons-compress/tree/74b38da4 Diff: http://git-wip-us.apache.org/repos/asf/commons-compress/diff/74b38da4 Branch: refs/heads/master Commit: 74b38da45a6601a5f4d8c38e417c547024abaf4c Parents: b8939be Author: Stefan Bodewig <[email protected]> Authored: Wed Jan 18 06:41:23 2017 +0100 Committer: Stefan Bodewig <[email protected]> Committed: Wed Jan 18 06:41:23 2017 +0100 ---------------------------------------------------------------------- .../lz4/BlockLZ4CompressorInputStream.java | 8 +- .../lz4/BlockLZ4CompressorOutputStream.java | 144 +++++++++++++++++++ 2 files changed, 148 insertions(+), 4 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/commons-compress/blob/74b38da4/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorInputStream.java ---------------------------------------------------------------------- diff --git a/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorInputStream.java b/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorInputStream.java index bdefcb2..a93f10d 100644 --- a/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorInputStream.java +++ b/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorInputStream.java @@ -32,10 +32,10 @@ import org.apache.commons.compress.utils.ByteUtils; */ public class BlockLZ4CompressorInputStream extends AbstractLZ77CompressorInputStream { - private static final int WINDOW_SIZE = 1 << 16; - private static final int SIZE_BITS = 4; - private static final int COPY_SIZE_MASK = (1 << SIZE_BITS) - 1; - private static final int LITERAL_SIZE_MASK = COPY_SIZE_MASK << SIZE_BITS; + static final int WINDOW_SIZE = 1 << 16; + static final int SIZE_BITS = 4; + static final int COPY_SIZE_MASK = (1 << SIZE_BITS) - 1; + static final int LITERAL_SIZE_MASK = COPY_SIZE_MASK << SIZE_BITS; /** Copy-size part of the block starting byte. */ private int nextCopySize; http://git-wip-us.apache.org/repos/asf/commons-compress/blob/74b38da4/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorOutputStream.java ---------------------------------------------------------------------- diff --git a/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorOutputStream.java b/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorOutputStream.java new file mode 100644 index 0000000..79e1310 --- /dev/null +++ b/src/main/java/org/apache/commons/compress/compressors/lz4/BlockLZ4CompressorOutputStream.java @@ -0,0 +1,144 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF 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 org.apache.commons.compress.compressors.lz4; + +import java.io.IOException; +import java.io.OutputStream; + +import org.apache.commons.compress.compressors.CompressorOutputStream; +import org.apache.commons.compress.compressors.lz77support.LZ77Compressor; +import org.apache.commons.compress.compressors.lz77support.Parameters; +import org.apache.commons.compress.utils.ByteUtils; + +/** + * CompressorOutputStream for the LZ4 block format. + * + * @see <a href="http://lz4.github.io/lz4/lz4_Block_format.html";>LZ4 Block Format Description</a> + * @since 1.14 + */ +public class BlockLZ4CompressorOutputStream extends CompressorOutputStream { + + /* + + The LZ4 block format has a few properties that make it less + straight-forward than one would hope: + + * literal blocks and back-references must come in pairs (except + for the very last literal block), so consecutive literal + blocks created by the compressor must be merged into a single + block. + + * the start of a literal/back-reference pair contains the length + of the copy (at least some part of it) so we can't start + writing the literal before we know how long the next copy is + going to be. + + * there is a special rule for the final blocks + + > There are specific parsing rules to respect in order to remain + > compatible with assumptions made by the decoder : + > + > 1. The last 5 bytes are always literals + > + > 2. The last match must start at least 12 bytes before end of + > block. Consequently, a block with less than 13 bytes cannot be + > compressed. + + which means any back-reference may need to get rewritten as a + literal block unless we know the next block is at least of + length 5 and the sum of this block's length and offset and the + next block's length is at least twelve. + + */ + + private final LZ77Compressor compressor; + private final OutputStream os; + private final ByteUtils.ByteConsumer consumer; + + // used in one-arg write method + private final byte[] oneByte = new byte[1]; + + private boolean finished = false; + + /** + * Creates a new LZ4 output stream. + * + * @param os + * An OutputStream to read compressed data from + * + * @throws IOException if reading fails + */ + public BlockLZ4CompressorOutputStream(final OutputStream os) throws IOException { + this.os = os; + consumer = new ByteUtils.OutputStreamByteConsumer(os); + int maxLen = BlockLZ4CompressorInputStream.WINDOW_SIZE - 1; + compressor = new LZ77Compressor(new Parameters(BlockLZ4CompressorInputStream.WINDOW_SIZE, 4, maxLen, maxLen, + maxLen), + new LZ77Compressor.Callback() { + public void accept(LZ77Compressor.Block block) throws IOException { + //System.err.println(block); + if (block instanceof LZ77Compressor.LiteralBlock) { + addLiteralBlock((LZ77Compressor.LiteralBlock) block); + } else if (block instanceof LZ77Compressor.BackReference) { + addBackReference((LZ77Compressor.BackReference) block); + } else if (block instanceof LZ77Compressor.EOD) { + writeFinalLiteralBlock(); + } + } + }); + } + + @Override + public void write(int b) throws IOException { + oneByte[0] = (byte) (b & 0xff); + write(oneByte); + } + + @Override + public void write(byte[] data, int off, int len) throws IOException { + compressor.compress(data, off, len); + } + + @Override + public void close() throws IOException { + finish(); + os.close(); + } + + /** + * Compresses all remaining data and writes it to the stream, + * doesn't close the underlying stream. + * @throws IOException if an error occurs + */ + public void finish() throws IOException { + if (!finished) { + compressor.finish(); + finished = true; + } + } + + private void addLiteralBlock(LZ77Compressor.LiteralBlock block) throws IOException { + } + + private void addBackReference(LZ77Compressor.BackReference block) throws IOException { + } + + private void writeFinalLiteralBlock() throws IOException { + } +}
