Class LZMA2InputStream

java.lang.Object
java.io.InputStream
org.tukaani.xz.LZMA2InputStream
All Implemented Interfaces:
Closeable, AutoCloseable

public class LZMA2InputStream
extends InputStream
Decompresses a raw LZMA2 stream (no XZ headers).
  • Field Details

    • DICT_SIZE_MIN

      public static final int DICT_SIZE_MIN
      Smallest valid LZMA2 dictionary size.

      Very tiny dictionaries would be a performance problem, so the minimum is 4 KiB.

      See Also:
      Constant Field Values
    • DICT_SIZE_MAX

      public static final int DICT_SIZE_MAX
      Largest dictionary size supported by this implementation.

      The LZMA2 algorithm allows dictionaries up to one byte less than 4 GiB. This implementation supports only 16 bytes less than 2 GiB for raw LZMA2 streams, and for .xz files the maximum is 1.5 GiB. This limitation is due to Java using signed 32-bit integers for array indexing. The limitation shouldn't matter much in practice since so huge dictionaries are not normally used.

      See Also:
      Constant Field Values
  • Constructor Details

    • LZMA2InputStream

      public LZMA2InputStream​(InputStream in, int dictSize)
      Creates a new input stream that decompresses raw LZMA2 data from in.

      The caller needs to know the dictionary size used when compressing; the dictionary size isn't stored as part of a raw LZMA2 stream.

      Specifying a too small dictionary size will prevent decompressing the stream. Specifying a too big dictionary is waste of memory but decompression will work.

      There is no need to specify a dictionary bigger than the uncompressed size of the data even if a bigger dictionary was used when compressing. If you know the uncompressed size of the data, this might allow saving some memory.

      Parameters:
      in - input stream from which LZMA2-compressed data is read
      dictSize - LZMA2 dictionary size as bytes, must be in the range [DICT_SIZE_MIN, DICT_SIZE_MAX]
    • LZMA2InputStream

      public LZMA2InputStream​(InputStream in, int dictSize, byte[] presetDict)
      Creates a new LZMA2 decompressor using a preset dictionary.

      This is like LZMA2InputStream(InputStream, int) except that the dictionary may be initialized using a preset dictionary. If a preset dictionary was used when compressing the data, the same preset dictionary must be provided when decompressing.

      Parameters:
      in - input stream from which LZMA2-compressed data is read
      dictSize - LZMA2 dictionary size as bytes, must be in the range [DICT_SIZE_MIN, DICT_SIZE_MAX]
      presetDict - preset dictionary or null to use no preset dictionary
  • Method Details

    • getMemoryUsage

      public static int getMemoryUsage​(int dictSize)
      Gets approximate decompressor memory requirements as kibibytes for the given dictionary size.
      Parameters:
      dictSize - LZMA2 dictionary size as bytes, must be in the range [DICT_SIZE_MIN, DICT_SIZE_MAX]
      Returns:
      approximate memory requirements as kibibytes (KiB)
    • read

      public int read() throws IOException
      Decompresses the next byte from this input stream.

      Reading lots of data with read() from this input stream may be inefficient. Wrap it in java.io.BufferedInputStream if you need to read lots of data one byte at a time.

      Specified by:
      read in class InputStream
      Returns:
      the next decompressed byte, or -1 to indicate the end of the compressed stream
      Throws:
      CorruptedInputException
      XZIOException - if the stream has been closed
      EOFException - compressed input is truncated or corrupt
      IOException - may be thrown by in
    • read

      public int read​(byte[] buf, int off, int len) throws IOException
      Decompresses into an array of bytes.

      If len is zero, no bytes are read and 0 is returned. Otherwise this will block until len bytes have been decompressed, the end of the LZMA2 stream is reached, or an exception is thrown.

      Overrides:
      read in class InputStream
      Parameters:
      buf - target buffer for uncompressed data
      off - start offset in buf
      len - maximum number of uncompressed bytes to read
      Returns:
      number of bytes read, or -1 to indicate the end of the compressed stream
      Throws:
      CorruptedInputException
      XZIOException - if the stream has been closed
      EOFException - compressed input is truncated or corrupt
      IOException - may be thrown by in
    • available

      public int available() throws IOException
      Returns the number of uncompressed bytes that can be read without blocking. The value is returned with an assumption that the compressed input data will be valid. If the compressed data is corrupt, CorruptedInputException may get thrown before the number of bytes claimed to be available have been read from this input stream.

      In LZMA2InputStream, the return value will be non-zero when the decompressor is in the middle of an LZMA2 chunk. The return value will then be the number of uncompressed bytes remaining from that chunk. The return value can also be non-zero in the middle of an uncompressed chunk, but then the return value depends also on the available() method of the underlying InputStream.

      Overrides:
      available in class InputStream
      Returns:
      the number of uncompressed bytes that can be read without blocking
      Throws:
      IOException
    • close

      public void close() throws IOException
      Closes the stream and calls in.close(). If the stream was already closed, this does nothing.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class InputStream
      Throws:
      IOException - if thrown by in.close()