JavaTM 2 Platform
Standard Ed. 5.0

javax.imageio.stream
Class FileCacheImageInputStream

java.lang.Object
  extended by javax.imageio.stream.ImageInputStreamImpl
      extended by 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.
IllegalArgumentException - if cacheDir is non-null but is not a directory.
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.

JavaTM 2 Platform
Standard Ed. 5.0

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2004 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.


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