Package org.apache.accumulo.core.file.rfile.bcfile

Enum Compression.Algorithm

  • All Implemented Interfaces:
    Serializable, Comparable<Compression.Algorithm>
    Enclosing class:
    Compression
    public static enum Compression.Algorithm
extends Enum<Compression.Algorithm>
    Compression algorithms. There is a static initializer, below the values defined in the enumeration, that calls the initializer of all defined codecs within the Algorithm enum. This promotes a model of the following call graph of initialization by the static initializer, followed by calls to getCodec() and createCompressionStream/DecompressionStream. In some cases, the compression and decompression call methods will include a different buffer size for the stream. Note that if the compressed buffer size requested in these calls is zero, we will not set the buffer size for that algorithm. Instead, we will use the default within the codec. The buffer size is configured in the Codec by way of a Hadoop Configuration reference. One approach may be to use the same Configuration object, but when calls are made to createCompressionStream and DecompressionStream, with non default buffer sizes, the configuration object must be changed. In this case, concurrent calls to createCompressionStream and DecompressionStream would mutate the configuration object beneath each other, requiring synchronization to avoid undesirable activity via co-modification. To avoid synchronization entirely, we will create Codecs with their own Configuration object and cache them for re-use. A default codec will be statically created, as mentioned above to ensure we always have a codec available at loader initialization. There is a Guava cache defined within Algorithm that allows us to cache Codecs for re-use. Since they will have their own configuration object and thus do not need to be mutable, there is no concern for using them concurrently; however, the Guava cache exists to ensure a maximal size of the cache and efficient and concurrent read/write access to the cache itself. To provide Algorithm specific details and to describe what is in code: LZO will always have the default LZO codec because the buffer size is never overridden within it. GZ will use the default GZ codec for the compression stream, but can potentially use a different codec instance for the decompression stream if the requested buffer size does not match the default GZ buffer size of 32k. Snappy will use the default Snappy codec with the default buffer size of 64k for the compression stream, but will use a cached codec if the buffer size differs from the default.

    • Method Detail

      • values

        public static Compression.Algorithm[] values()
        Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows: 
        for (Compression.Algorithm c : Compression.Algorithm.values())
    System.out.println(c);
        Returns:
        an array containing the constants of this enum type, in the order they are declared

      • valueOf

        public static Compression.Algorithm valueOf​(String name)
        Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
        Parameters:
        name - the name of the enum constant to be returned.
        Returns:
        the enum constant with the specified name
        Throws:
        IllegalArgumentException - if this enum type has no constant with the specified name
        NullPointerException - if the argument is null

      • createDecompressionStream

        public abstract InputStream createDecompressionStream​(InputStream downStream,
                                                      org.apache.hadoop.io.compress.Decompressor decompressor,
                                                      int downStreamBufferSize)
                                               throws IOException
        Throws:
        IOException

      • isSupported

        public abstract boolean isSupported()

      • getCompressor

        public org.apache.hadoop.io.compress.Compressor getCompressor()

      • returnCompressor

        public void returnCompressor​(org.apache.hadoop.io.compress.Compressor compressor)

      • getDecompressor

        public org.apache.hadoop.io.compress.Decompressor getDecompressor()

      • returnDecompressor

        public void returnDecompressor​(org.apache.hadoop.io.compress.Decompressor decompressor)

      • getName

        public String getName()