Class GzipCompressorInputStream

java.lang.Object
java.io.InputStream
org.apache.commons.compress.compressors.CompressorInputStream
org.apache.commons.compress.compressors.gzip.GzipCompressorInputStream
All Implemented Interfaces:
Closeable, AutoCloseable, InputStreamStatistics

public class GzipCompressorInputStream extends CompressorInputStream implements InputStreamStatistics
Input stream that decompresses .gz files.

This supports decompressing concatenated .gz files which is important when decompressing standalone .gz files.

GZIPInputStream doesn't decompress concatenated .gz files: it stops after the first member and silently ignores the rest. It doesn't leave the read position to point to the beginning of the next member, which makes it difficult workaround the lack of concatenation support.

Instead of using GZIPInputStream, this class has its own .gz container format decoder. The actual decompression is done with Inflater.

If you use the constructor GzipCompressorInputStream(in) or GzipCompressorInputStream(in, false) with some InputStream in then read() will return -1 as soon as the first internal member has been read completely. The stream in will be positioned at the start of the second gzip member if there is one.

If you use the constructor GzipCompressorInputStream(in, true) with some InputStream in then read() will return -1 once the stream in has been exhausted. The data read from a stream constructed this way will consist of the concatenated data of all gzip members contained inside in.

See Also:
  • "https://tools.ietf.org/html/rfc1952"
  • Field Details

  • Constructor Details

    • GzipCompressorInputStream

      public GzipCompressorInputStream(InputStream inputStream) throws IOException
      Constructs a new input stream that decompresses gzip-compressed data from the specified input stream.

      This is equivalent to GzipCompressorInputStream(inputStream, false) and thus will not decompress concatenated .gz files.

      Parameters:
      inputStream - the InputStream from which this object should be created of
      Throws:
      IOException - if the stream could not be created
    • GzipCompressorInputStream

      public GzipCompressorInputStream(InputStream inputStream, boolean decompressConcatenated) throws IOException
      Constructs a new input stream that decompresses gzip-compressed data from the specified input stream.

      If decompressConcatenated is false: This decompressor might read more input than it will actually use. If inputStream supports mark and reset, then the input position will be adjusted so that it is right after the last byte of the compressed stream. If mark isn't supported, the input position will be undefined.

      Parameters:
      inputStream - the InputStream from which this object should be created of
      decompressConcatenated - if true, decompress until the end of the input; if false, stop after the first .gz member
      Throws:
      IOException - if the stream could not be created
  • Method Details

    • getMetaData

      public GzipParameters getMetaData()
      Provides the stream's meta data - may change with each stream when decompressing concatenated streams.
      Returns:
      the stream's meta data
      Since:
      1.8
    • init

      private boolean init(boolean isFirstMember) throws IOException
      Throws:
      IOException
    • readToNull

      private static byte[] readToNull(DataInput inData) throws IOException
      Throws:
      IOException
    • read

      public int read() throws IOException
      Specified by:
      read in class InputStream
      Throws:
      IOException
    • read

      public int read(byte[] b, int off, int len) throws IOException
      Overrides:
      read in class InputStream
      Throws:
      IOException
      Since:
      1.1
    • matches

      public static boolean matches(byte[] signature, int length)
      Checks if the signature matches what is expected for a .gz file.
      Parameters:
      signature - the bytes to check
      length - the number of bytes to check
      Returns:
      true if this is a .gz stream, false otherwise
      Since:
      1.1
    • close

      public void close() throws IOException
      Closes the input stream (unless it is System.in).
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class InputStream
      Throws:
      IOException
      Since:
      1.2
    • getCompressedCount

      public long getCompressedCount()
      Specified by:
      getCompressedCount in interface InputStreamStatistics
      Returns:
      the amount of raw or compressed bytes read by the stream
      Since:
      1.17