com.levigo.jadice.document.io
Class MemoryInputStream

java.lang.Object
  java.io.InputStream
      com.levigo.jadice.document.io.SeekableInputStream
          com.levigo.jadice.document.io.MemoryInputStream

All Implemented Interfaces:

Closeable, DataInput, ImageInputStream

public class MemoryInputStream
extends SeekableInputStream

A SeekableInputStream which decorates a plain InputStream with seekability by using an in-memory cache. Configurable: jadice.io.memoryInputStream.blocksize integer 2048 The block size to use when buffering input data in memory.

Field Summary

Fields inherited from class com.levigo.jadice.document.io.SeekableInputStream

bitOffset, byteOrder, flushedPos

Constructor Summary

MemoryInputStream(byte[] data)
Construct a new MemoryInputStream which reads from exactly one data block.

MemoryInputStream(InputStream is)
Constructs a new MemoryInputStream which wraps the given InputStream and uses the default block size of 2048 bytes.

MemoryInputStream(InputStream is, int blockSize)
Constructs a new MemoryInputStream which wraps the given InputStream and uses the given block size.

MemoryInputStream(InputStream is, int blockSize, boolean forcePrefetch)
Constructs a new MemoryInputStream which wraps the given InputStream and uses the given block size.

Method Summary

int	available()
void	close() Closes this seekable input stream.
protected void	finalize() Finalizes this object prior to garbage collection.
static int	getDefaultBlockSize() Get the default block size to use.
long	getSizeEstimate() A rough estimated size for this stream instance, which is used for internal cache management.
long	getStreamPosition()
boolean	isCached() Returns true since this ImageInputStream caches data in order to allow seeking backwards.
boolean	isCachedFile() Returns false since this ImageInputStream does not maintain a file cache.
boolean	isCachedMemory() Returns true since this ImageInputStream maintains a main memory cache.
long	length() Returns the length of this stream contents, if available.
int	read() Reads a single byte from the stream and returns it as an int between 0 and 255.
int	read(byte[] b) A convenience method that calls read(b, 0, b.length).
int	read(byte[] buffer, int offset, int length) Reads up to len bytes from the stream, and stores them into b starting at index off.
void	seek(long position) Sets the current stream position, measured from the beginning of this data stream, at which the next read occurs.
static void	setDefaultBlockSize(int defaultBlockSize) Set the default block size to use.

Methods inherited from class com.levigo.jadice.document.io.SeekableInputStream

checkClosed, flush, flushBefore, getBitOffset, getByteOrder, getFlushedPosition, mark, mark, readBit, readBits, readBoolean, readByte, readBytes, readChar, readDouble, readFloat, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readInt, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedInt, readUnsignedInt, readUnsignedShort, readUTF, reset, resetToInitialState, setBitOffset, setByteOrder, skip, skipBytes, skipBytes

Methods inherited from class java.io.InputStream

markSupported

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MemoryInputStream

public MemoryInputStream(InputStream is,
                         int blockSize)
                  throws IOException

Constructs a new MemoryInputStream which wraps the given InputStream and uses the given block size. The first block of data will be pre-fetched within this constructor call.

Parameters:

is - the input stream

blockSize - the used data block size in bytes. Caused by performance and memory reasons this value should be a multiple of 1024 greater than 1MB. If this value is smaller than 1024 bytes, a minimal block size of 1024 will be assumed.

Throws:

IOException

MemoryInputStream

public MemoryInputStream(InputStream is,
                         int blockSize,
                         boolean forcePrefetch)
                  throws IOException

Constructs a new MemoryInputStream which wraps the given InputStream and uses the given block size.

Parameters:

is - the input stream

blockSize - the used data block size in bytes. Caused by performance and memory reasons this value should be a multiple of 1024 greater than 1MB. If this value is smaller than 1024 bytes, a minimal block size of 1024 will be assumed.

forcePrefetch, - whether the first block of data should be pre-fetched or not.

Throws:

IOException

MemoryInputStream

public MemoryInputStream(InputStream is)
                  throws IOException

Constructs a new MemoryInputStream which wraps the given InputStream and uses the default block size of 2048 bytes.

Parameters:

is -

Throws:

IOException

MemoryInputStream

public MemoryInputStream(byte[] data)

Construct a new MemoryInputStream which reads from exactly one data block.

Parameters:

data -

Method Detail

read

public int read(byte[] b)
         throws IOException

Description copied from class: SeekableInputStream

A convenience method that calls read(b, 0, b.length).

The bit offset within the stream is reset to zero before the read occurs.

Specified by:

read in interface ImageInputStream

Overrides:

read in class SeekableInputStream

Parameters:

b - the byte buffer to fill up

Returns:

the number of bytes actually read, or -1 to indicate EOF.

Throws:

IOException - if an I/O error occurs.

See Also:

InputStream.read(byte[])

read

public int read(byte[] buffer,
                int offset,
                int length)
         throws IOException

Description copied from class: SeekableInputStream

Reads up to len bytes from the stream, and stores them into b starting at index off. If no bytes can be read because the end of the stream has been reached, -1 is returned.

The bit offset within the stream must be reset to zero before the read occurs.

Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.

Specified by:

read in interface ImageInputStream

Specified by:

read in class SeekableInputStream

Parameters:

buffer - an array of bytes to be written to.

offset - the starting position within b to write to.

length - the maximum number of bytes to read.

Returns:

the number of bytes actually read, or -1 to indicate EOF.

Throws:

IOException - if an I/O error occurs.

See Also:

InputStream.read(byte[], int, int)

read

public int read()
         throws IOException

Description copied from class: SeekableInputStream

Reads a single byte from the stream and returns it as an int between 0 and 255. If EOF is reached, -1 is returned.

Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.

The bit offset within the stream must be reset to zero before the read occurs.

Specified by:

read in interface ImageInputStream

Specified by:

read in class SeekableInputStream

Returns:

the value of the next byte in the stream, or -1 if EOF is reached.

Throws:

IOException - if the stream has been closed.

See Also:

InputStream.read()

seek

public void seek(long position)
          throws IOException

Description copied from class: SeekableInputStream

Sets the current stream position, measured from the beginning of this data stream, at which the next read occurs. The offset may be set beyond the end of this data stream. Setting the offset beyond the end does not change the data length, an EOFException will be thrown only if a read is performed. The bit offset is set to 0.

An IndexOutOfBoundsException will be thrown if pos is smaller than the flushed position (as returned by getflushedPosition).

It is legal to seek past the end of the file; an EOFException will be thrown only if a read is performed.

Specified by:

seek in interface ImageInputStream

Specified by:

seek in class SeekableInputStream

Parameters:

position - a long containing the desired file pointer position.

Throws:

IOException - if any other I/O error occurs.

See Also:

ImageInputStream.seek(long)

close

public void close()
           throws IOException

Description copied from class: SeekableInputStream

Closes this seekable input stream. Further attempts to read from it will throw IOExceptions. Additional attempts to SeekableInputStream.close(), however, have no effect.

Specified by:

close in interface Closeable

Specified by:

close in interface ImageInputStream

Overrides:

close in class SeekableInputStream

Throws:

IOException

See Also:

InputStream.close()

finalize

protected void finalize()
                 throws Throwable

Description copied from class: SeekableInputStream

Finalizes this object prior to garbage collection. The close method is called to close any open input source. This method should not be called from application code.

Overrides:

finalize in class SeekableInputStream

Throws:

Throwable - if an error occurs during superclass finalization.

See Also:

Object.finalize()

available

public int available()
              throws IOException

Overrides:

available in class InputStream

Throws:

IOException

See Also:

InputStream.available()

getStreamPosition

public long getStreamPosition()
                       throws IOException

Throws:

IOException

See Also:

ImageInputStream.getStreamPosition()

length

public long length()
            throws IOException

Description copied from class: SeekableInputStream

Returns the length of this stream contents, if available. Otherwise -1L will be returned.

Specified by:

length in interface ImageInputStream

Specified by:

length in class SeekableInputStream

Returns:

the length, measured in bytes or -1L if unknown.

Throws:

IOException - if an I/O error occurs.

See Also:

ImageInputStream.length()

isCached

public boolean isCached()

Returns true since this ImageInputStream caches data in order to allow seeking backwards.

Specified by:

isCached in interface ImageInputStream

Overrides:

isCached in class SeekableInputStream

Returns:

true.

See Also:

isCachedMemory(), isCachedFile()

isCachedFile

public boolean isCachedFile()

Returns false since this ImageInputStream does not maintain a file cache.

Specified by:

isCachedFile in interface ImageInputStream

Overrides:

isCachedFile in class SeekableInputStream

Returns:

false.

See Also:

isCached(), isCachedMemory()

isCachedMemory

public boolean isCachedMemory()

Returns true since this ImageInputStream maintains a main memory cache.

Specified by:

isCachedMemory in interface ImageInputStream

Overrides:

isCachedMemory in class SeekableInputStream

Returns:

true.

See Also:

isCached(), isCachedFile()

getSizeEstimate

public long getSizeEstimate()

Description copied from class: SeekableInputStream

A rough estimated size for this stream instance, which is used for internal cache management.

Specified by:

getSizeEstimate in class SeekableInputStream

Returns:

an estimated size

setDefaultBlockSize

public static void setDefaultBlockSize(int defaultBlockSize)

Set the default block size to use.

Parameters:

defaultBlockSize -

getDefaultBlockSize

public static int getDefaultBlockSize()

Get the default block size to use.

Returns:

the default block size.