viirya commented on a change in pull request #3250: URL: https://github.com/apache/hadoop/pull/3250#discussion_r684484896
########## File path: hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/compress/zlib/BuiltInGzipCompressor.java ########## @@ -0,0 +1,251 @@ +/* + * 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.hadoop.io.compress.zlib; + +import java.io.IOException; +import java.util.zip.Checksum; +import java.util.zip.Deflater; +import java.util.zip.GZIPOutputStream; + +import org.apache.hadoop.conf.Configuration; +import org.apache.hadoop.io.compress.Compressor; +import org.apache.hadoop.io.compress.DoNotPool; +import org.apache.hadoop.util.DataChecksum; + +/** + * A {@link Compressor} based on the popular gzip compressed file format. + * http://www.gzip.org/ + */ +@DoNotPool +public class BuiltInGzipCompressor implements Compressor { + + /** + * Fixed ten-byte gzip header. See {@link GZIPOutputStream}'s source for + * details. + */ + private static final byte[] GZIP_HEADER = new byte[]{ + 0x1f, (byte) 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}; + + // The trailer will be overwritten based on crc and output size. + private static final byte[] GZIP_TRAILER = new byte[]{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}; + + private static final int GZIP_HEADER_LEN = GZIP_HEADER.length; + private static final int GZIP_TRAILER_LEN = GZIP_TRAILER.length; + + private Deflater deflater; + + private int headerOff = 0; + private int trailerOff = 0; + + private int numExtraBytesWritten = 0; + + private int currentBufLen = 0; + + private final Checksum crc = DataChecksum.newCrc32(); + + private BuiltInGzipDecompressor.GzipStateLabel state; + + public BuiltInGzipCompressor(Configuration conf) { init(conf); } + + @Override + public boolean finished() { + // Only if the trailer is also written, it is thought as finished. + return deflater.finished() && state == BuiltInGzipDecompressor.GzipStateLabel.FINISHED; + } + + @Override + public boolean needsInput() { + if (state == BuiltInGzipDecompressor.GzipStateLabel.INFLATE_STREAM) { + return deflater.needsInput(); + } + + return false; + } + + @Override + public int compress(byte[] b, int off, int len) throws IOException { + int compressedBytesWritten = 0; + + if (currentBufLen <= 0) { + return compressedBytesWritten; + } + + // If we are not within uncompressed data yet, output the header. + if (state != BuiltInGzipDecompressor.GzipStateLabel.INFLATE_STREAM && + state != BuiltInGzipDecompressor.GzipStateLabel.TRAILER_CRC) { + int outputHeaderSize = writeHeader(b, off, len); + numExtraBytesWritten += outputHeaderSize; + + compressedBytesWritten += outputHeaderSize; + + if (outputHeaderSize == len) { + return compressedBytesWritten; + } + + off += outputHeaderSize; + len -= outputHeaderSize; + } + + if (state == BuiltInGzipDecompressor.GzipStateLabel.INFLATE_STREAM) { + // now compress it into b[] + int deflated = deflater.deflate(b, off, len); + + compressedBytesWritten += deflated; + off += deflated; + len -= deflated; + + // All current input are processed. Going to output trailer. + if (deflater.finished()) { + state = BuiltInGzipDecompressor.GzipStateLabel.TRAILER_CRC; + fillTrailer(); + } else { + return compressedBytesWritten; + } + } + + int outputTrailerSize = writeTrailer(b, off, len); + numExtraBytesWritten += outputTrailerSize; + + compressedBytesWritten += outputTrailerSize; + + return compressedBytesWritten; + } + + @Override + public long getBytesRead() { + return deflater.getTotalIn(); + } + + @Override + public long getBytesWritten() { + return numExtraBytesWritten + deflater.getTotalOut(); + } + + @Override + public void end() { + deflater.end(); + } + + @Override + public void finish() { + deflater.finish(); + } + + private void init(Configuration conf) { + ZlibCompressor.CompressionLevel level = ZlibFactory.getCompressionLevel(conf); + ZlibCompressor.CompressionStrategy strategy = ZlibFactory.getCompressionStrategy(conf); + + // 'true' (nowrap) => Deflater will handle raw deflate stream only + deflater = new Deflater(level.compressionLevel(), true); + deflater.setStrategy(strategy.compressionStrategy()); + + state = BuiltInGzipDecompressor.GzipStateLabel.HEADER_BASIC; + } + + @Override + public void reinit(Configuration conf) { + init(conf); + crc.reset(); + numExtraBytesWritten = 0; + currentBufLen = 0; + headerOff = trailerOff = 0; + } + + @Override + public void reset() { + deflater.reset(); + state = BuiltInGzipDecompressor.GzipStateLabel.HEADER_BASIC; + crc.reset(); + numExtraBytesWritten = 0; + currentBufLen = 0; + headerOff = trailerOff = 0; + } + + @Override + public void setDictionary(byte[] b, int off, int len) { + deflater.setDictionary(b, off, len); + } + + @Override + public void setInput(byte[] b, int off, int len) { + if (b == null) { + throw new NullPointerException(); + } + if (off < 0 || len < 0 || off > b.length - len) { + throw new ArrayIndexOutOfBoundsException(); + } + + deflater.reset(); + crc.reset(); + + deflater.setInput(b, off, len); + crc.update(b, off, len); // CRC-32 is on uncompressed data + currentBufLen = len; + } + + private int writeHeader(byte[] b, int off, int len) { + if (len <= 0) { + return 0; + } + + int n = Math.min(len, GZIP_HEADER_LEN - headerOff); + System.arraycopy(GZIP_HEADER, headerOff, b, off, n); + headerOff += n; + + // Completes header output. + if (headerOff == GZIP_HEADER_LEN) { + state = BuiltInGzipDecompressor.GzipStateLabel.INFLATE_STREAM; + } + + return n; + } + + private void fillTrailer() { + if (state == BuiltInGzipDecompressor.GzipStateLabel.TRAILER_CRC) { + int streamCrc = (int) crc.getValue(); + GZIP_TRAILER[0] = (byte) (streamCrc & 0x000000ff); + GZIP_TRAILER[1] = (byte) ((streamCrc & 0x0000ff00) >> 8); + GZIP_TRAILER[2] = (byte) ((streamCrc & 0x00ff0000) >> 16); + GZIP_TRAILER[3] = (byte) ((streamCrc & 0xff000000) >> 24); + + GZIP_TRAILER[4] = (byte) (currentBufLen & 0x000000ff); Review comment: Actually because the decompressor will check crc and size in the trailer, if this size is incorrect, we will see error immediately. -- This is an automated message from the Apache Git Service. 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