javax.imageio.stream
Class FileCacheImageInputStream

java.lang.Object
  |
  +--javax.imageio.stream.ImageInputStreamImpl
        |
        +--javax.imageio.stream.FileCacheImageInputStream

All Implemented Interfaces:

DataInput, ImageInputStream

public class FileCacheImageInputStream

extends ImageInputStreamImpl

An implementation of ImageInputStream that gets its input from a regular InputStream. A file is used to cache previously read data.

Field Summary

Fields inherited from class javax.imageio.stream.ImageInputStreamImpl

bitOffset, byteOrder, flushedPos, streamPos

Constructor Summary

FileCacheImageInputStream(InputStream stream, File cacheDir)
Constructs a FileCacheImageInputStream that will read from a given InputStream.

Method Summary

void	close() Closes this FileCacheImageInputStream, closing and removing the cache file.
boolean	isCached() Returns true since this ImageInputStream caches data in order to allow seeking backwards.
boolean	isCachedFile() Returns true since this ImageInputStream maintains a file cache.
boolean	isCachedMemory() Returns false since this ImageInputStream does not maintain a main memory cache.
int	read() Reads a single byte from the stream and returns it as an integer between 0 and 255.
int	read(byte[] b, int off, int len) Reads up to len bytes from the stream, and stores them into b starting at index off.

Methods inherited from class javax.imageio.stream.ImageInputStreamImpl

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

Methods inherited from class java.lang.Object

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

Constructor Detail

FileCacheImageInputStream

public FileCacheImageInputStream(InputStream stream,
                                 File cacheDir)
                          throws IOException

Constructs a FileCacheImageInputStream that will read from a given InputStream.

A temporary file is used as a cache. If cacheDiris non-null and is a directory, the file will be created there. If it is null, the system-dependent default temporary-file directory will be used (see the documentation for File.createTempFile for details).

Parameters:

stream - an InputStream to read from.

cacheDir - a File indicating where the cache file should be created, or null to use the system directory.

Throws:

IllegalArgumentException - if stream is null.

IOException - if a cache file cannot be created.

Method Detail

read

public int read()
         throws IOException

Description copied from interface: ImageInputStream

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

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

Specified by:

read in interface ImageInputStream

Specified by:

read in class ImageInputStreamImpl

Returns:

a byte value from the stream, as an int, or -1 to indicate EOF.

Throws:

IOException - if an I/O error occurs.

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Description copied from class: ImageInputStreamImpl

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 ImageInputStreamImpl

Parameters:

b - an array of bytes to be written to.

off - the starting position within b to write to.

len - 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.

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 ImageInputStreamImpl

Returns:

true.

See Also:

isCachedMemory(), isCachedFile()

isCachedFile

public boolean isCachedFile()

Returns true since this ImageInputStream maintains a file cache.

Specified by:

isCachedFile in interface ImageInputStream

Overrides:

isCachedFile in class ImageInputStreamImpl

Returns:

true.

See Also:

isCached(), isCachedMemory()

isCachedMemory

public boolean isCachedMemory()

Returns false since this ImageInputStream does not maintain a main memory cache.

Specified by:

isCachedMemory in interface ImageInputStream

Overrides:

isCachedMemory in class ImageInputStreamImpl

Returns:

false.

See Also:

isCached(), isCachedFile()

close

public void close()
           throws IOException

Closes this FileCacheImageInputStream, closing and removing the cache file. The source InputStream is not closed.

Specified by:

close in interface ImageInputStream

Overrides:

close in class ImageInputStreamImpl

Throws:

IOException - if an error occurs.