SeekableXZInputStream (Grouper Installer 2.4.0-SNAPSHOT Java API.)

java.lang.Object
- java.io.InputStream
- - edu.internet2.middleware.grouperInstallerExt.org.tukaani.xz.SeekableInputStream
  - - edu.internet2.middleware.grouperInstallerExt.org.tukaani.xz.SeekableXZInputStream

All Implemented Interfaces:

Closeable, AutoCloseable
```
public class SeekableXZInputStream
extends SeekableInputStream
```
Decompresses a .xz file in random access mode. This supports decompressing concatenated .xz files.
Each .xz file consist of one or more Streams. Each Stream consist of zero or more Blocks. Each Stream contains an Index of Streams' Blocks. The Indexes from all Streams are loaded in RAM by a constructor of this class. A typical .xz file has only one Stream, and parsing its Index will need only three or four seeks.
To make random access possible, the data in a .xz file must be splitted into multiple Blocks of reasonable size. Decompression can only start at a Block boundary. When seeking to an uncompressed position that is not at a Block boundary, decompression starts at the beginning of the Block and throws away data until the target position is reached. Thus, smaller Blocks mean faster seeks to arbitrary uncompressed positions. On the other hand, smaller Blocks mean worse compression. So one has to make a compromise between random access speed and compression ratio.
Implementation note: This class uses linear search to locate the correct Stream from the data structures in RAM. It was the simplest to implement and should be fine as long as there aren't too many Streams. The correct Block inside a Stream is located using binary search and thus is fast even with a huge number of Blocks.
Memory usage

The amount of memory needed for the Indexes is taken into account when checking the memory usage limit. Each Stream is calculated to need at least 1 KiB of memory and each Block 16 bytes of memory, rounded up to the next kibibyte. So unless the file has a huge number of Streams or Blocks, these don't take significant amount of memory.
Creating random-accessible .xz files

When using XZOutputStream, a new Block can be started by calling its endBlock method. If you know that the decompressor will only need to seek to certain uncompressed positions, it can be a good idea to start a new Block at (some of) these positions (and only at these positions to get better compression ratio).
liblzma in XZ Utils supports starting a new Block with LZMA_FULL_FLUSH. XZ Utils 5.1.1alpha added threaded compression which creates multi-Block .xz files. XZ Utils 5.1.1alpha also added the option --block-size=SIZE to the xz command line tool. XZ Utils 5.1.2alpha added a partial implementation of --block-list=SIZES which allows specifying sizes of individual Blocks.

See Also:

SeekableFileInputStream, XZInputStream, XZOutputStream

Constructor Summary

Constructors
Constructor and Description
`SeekableXZInputStream(SeekableInputStream in)` Creates a new seekable XZ decompressor without a memory usage limit.
`SeekableXZInputStream(SeekableInputStream in, int memoryLimit)` Creates a new seekable XZ decomporessor with an optional memory usage limit.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`available()` Returns the number of uncompressed bytes that can be read without blocking.
`void`	`close()` Closes the stream and calls `in.close()`.
`int`	`getBlockCheckType(int blockNumber)` Gets integrity check type (Check ID) of the given Block.
`long`	`getBlockCompPos(int blockNumber)` Gets the position where the given compressed Block starts in the underlying .xz file.
`long`	`getBlockCompSize(int blockNumber)` Gets the compressed size of the given Block.
`int`	`getBlockCount()` Gets the number of Blocks in the .xz file.
`int`	`getBlockNumber(long pos)` Gets the number of the Block that contains the byte at the given uncompressed position.
`long`	`getBlockPos(int blockNumber)` Gets the uncompressed start position of the given Block.
`long`	`getBlockSize(int blockNumber)` Gets the uncompressed size of the given Block.
`int`	`getCheckTypes()` Gets the types of integrity checks used in the .xz file.
`int`	`getIndexMemoryUsage()` Gets the amount of memory in kibibytes (KiB) used by the data structures needed to locate the XZ Blocks.
`long`	`getLargestBlockSize()` Gets the uncompressed size of the largest XZ Block in bytes.
`int`	`getStreamCount()` Gets the number of Streams in the .xz file.
`long`	`length()` Gets the uncompressed size of this input stream.
`long`	`position()` Gets the current uncompressed position in this input stream.
`int`	`read()` Decompresses the next byte from this input stream.
`int`	`read(byte[] buf, int off, int len)` Decompresses into an array of bytes.
`void`	`seek(long pos)` Seeks to the specified absolute uncompressed position in the stream.
`void`	`seekToBlock(int blockNumber)` Seeks to the beginning of the given XZ Block.

Methods inherited from class edu.internet2.middleware.grouperInstallerExt.org.tukaani.xz.SeekableInputStream
skip

Methods inherited from class java.io.InputStream
mark, markSupported, read, reset

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - SeekableXZInputStream
```
public SeekableXZInputStream(SeekableInputStream in)
                      throws IOException
```
    Creates a new seekable XZ decompressor without a memory usage limit.
    
    Parameters:
    
    in - seekable input stream containing one or more XZ Streams; the whole input stream is used
    
    Throws:
    
    XZFormatException - input is not in the XZ format
    
    CorruptedInputException - XZ data is corrupt or truncated
    
    UnsupportedOptionsException - XZ headers seem valid but they specify options not supported by this implementation
    
    EOFException - less than 6 bytes of input was available from in, or (unlikely) the size of the underlying stream got smaller while this was reading from it
    
    IOException - may be thrown by in
  - SeekableXZInputStream
```
public SeekableXZInputStream(SeekableInputStream in,
                             int memoryLimit)
                      throws IOException
```
    Creates a new seekable XZ decomporessor with an optional memory usage limit.
    
    Parameters:
    
    in - seekable input stream containing one or more XZ Streams; the whole input stream is used
    
    memoryLimit - memory usage limit in kibibytes (KiB) or -1 to impose no memory usage limit
    
    Throws:
    
    XZFormatException - input is not in the XZ format
    
    CorruptedInputException - XZ data is corrupt or truncated
    
    UnsupportedOptionsException - XZ headers seem valid but they specify options not supported by this implementation
    
    MemoryLimitException - decoded XZ Indexes would need more memory than allowed by the memory usage limit
    
    EOFException - less than 6 bytes of input was available from in, or (unlikely) the size of the underlying stream got smaller while this was reading from it
    
    IOException - may be thrown by in
- Method Detail
  - getCheckTypes
```
public int getCheckTypes()
```
    Gets the types of integrity checks used in the .xz file. Multiple checks are possible only if there are multiple concatenated XZ Streams.
    The returned value has a bit set for every check type that is present. For example, if CRC64 and SHA-256 were used, the return value is (1 << XZ.CHECK_CRC64) | (1 << XZ.CHECK_SHA256).
  - getIndexMemoryUsage
```
public int getIndexMemoryUsage()
```
    Gets the amount of memory in kibibytes (KiB) used by the data structures needed to locate the XZ Blocks. This is usually useless information but since it is calculated for memory usage limit anyway, it is nice to make it available to too.
  - getLargestBlockSize
```
public long getLargestBlockSize()
```
    Gets the uncompressed size of the largest XZ Block in bytes. This can be useful if you want to check that the file doesn't have huge XZ Blocks which could make seeking to arbitrary offsets very slow. Note that huge Blocks don't automatically mean that seeking would be slow, for example, seeking to the beginning of any Block is always fast.
  - getStreamCount
```
public int getStreamCount()
```
    Gets the number of Streams in the .xz file.
    
    Since:
    
    1.3
  - getBlockCount
```
public int getBlockCount()
```
    Gets the number of Blocks in the .xz file.
    
    Since:
    
    1.3
  - getBlockPos
```
public long getBlockPos(int blockNumber)
```
    Gets the uncompressed start position of the given Block.
    
    Throws:
    
    IndexOutOfBoundsException - if blockNumber < 0 or blockNumber >= getBlockCount().
    
    Since:
    
    1.3
  - getBlockSize
```
public long getBlockSize(int blockNumber)
```
    Gets the uncompressed size of the given Block.
    
    Throws:
    
    IndexOutOfBoundsException - if blockNumber < 0 or blockNumber >= getBlockCount().
    
    Since:
    
    1.3
  - getBlockCompPos
```
public long getBlockCompPos(int blockNumber)
```
    Gets the position where the given compressed Block starts in the underlying .xz file. This information is rarely useful to the users of this class.
    
    Throws:
    
    IndexOutOfBoundsException - if blockNumber < 0 or blockNumber >= getBlockCount().
    
    Since:
    
    1.3
  - getBlockCompSize
```
public long getBlockCompSize(int blockNumber)
```
    Gets the compressed size of the given Block. This together with the uncompressed size can be used to calculate the compression ratio of the specific Block.
    
    Throws:
    
    IndexOutOfBoundsException - if blockNumber < 0 or blockNumber >= getBlockCount().
    
    Since:
    
    1.3
  - getBlockCheckType
```
public int getBlockCheckType(int blockNumber)
```
    Gets integrity check type (Check ID) of the given Block.
    
    Throws:
    
    IndexOutOfBoundsException - if blockNumber < 0 or blockNumber >= getBlockCount().
    
    Since:
    
    1.3
    
    See Also:
    
    getCheckTypes()
  - getBlockNumber
```
public int getBlockNumber(long pos)
```
    Gets the number of the Block that contains the byte at the given uncompressed position.
    
    Throws:
    
    IndexOutOfBoundsException - if pos < 0 or pos >= length().
    
    Since:
    
    1.3
  - read
```
public int read()
         throws IOException
```
    Decompresses the next byte from this input stream.
    
    Specified by:
    
    read in class InputStream
    
    Returns:
    
    the next decompressed byte, or -1 to indicate the end of the compressed stream
    
    Throws:
    
    CorruptedInputException
    
    UnsupportedOptionsException
    
    MemoryLimitException
    
    XZIOException - if the stream has been closed
    
    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 try to decompress len bytes of uncompressed data. Less than len bytes may be read only in the following situations:
    - The end of the compressed data was reached successfully.
    - An error is detected after at least one but less than len bytes have already been successfully decompressed. The next call with non-zero len will immediately throw the pending exception.
    - 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
    
    UnsupportedOptionsException
    
    MemoryLimitException
    
    XZIOException - if the stream has been closed
    
    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.
    
    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 Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Overrides:
    
    close in class InputStream
    
    Throws:
    
    IOException - if thrown by in.close()
  - length
```
public long length()
```
    Gets the uncompressed size of this input stream. If there are multiple XZ Streams, the total uncompressed size of all XZ Streams is returned.
    
    Specified by:
    
    length in class SeekableInputStream
  - position
```
public long position()
              throws IOException
```
    Gets the current uncompressed position in this input stream.
    
    Specified by:
    
    position in class SeekableInputStream
    
    Throws:
    
    XZIOException - if the stream has been closed
    
    IOException
  - seek
```
public void seek(long pos)
          throws IOException
```
    Seeks to the specified absolute uncompressed position in the stream. This only stores the new position, so this function itself is always very fast. The actual seek is done when read is called to read at least one byte.
    Seeking past the end of the stream is possible. In that case read will return -1 to indicate the end of the stream.
    
    Specified by:
    
    seek in class SeekableInputStream
    
    Parameters:
    
    pos - new uncompressed read position
    
    Throws:
    
    XZIOException - if pos is negative, or if stream has been closed
    
    IOException - if pos is negative or if a stream-specific I/O error occurs
  - seekToBlock
```
public void seekToBlock(int blockNumber)
                 throws IOException
```
    Seeks to the beginning of the given XZ Block.
    
    Throws:
    
    XZIOException - if blockNumber < 0 or blockNumber >= getBlockCount(), or if stream has been closed
    
    IOException
    
    Since:
    
    1.3

Class SeekableXZInputStream

Memory usage

Creating random-accessible .xz files

Constructor Summary

Method Summary

Methods inherited from class edu.internet2.middleware.grouperInstallerExt.org.tukaani.xz.SeekableInputStream

Methods inherited from class java.io.InputStream

Methods inherited from class java.lang.Object

Constructor Detail

SeekableXZInputStream

SeekableXZInputStream

Method Detail

getCheckTypes

getIndexMemoryUsage

getLargestBlockSize

getStreamCount

getBlockCount

getBlockPos

getBlockSize

getBlockCompPos

getBlockCompSize

getBlockCheckType

getBlockNumber

read

read

available

close

length

position

seek

seekToBlock