JavaTM 2 Platform
Standard Ed. 5.0

javax.imageio.stream
Class FileCacheImageOutputStream

java.lang.Object
  extended by javax.imageio.stream.ImageInputStreamImpl
      extended by javax.imageio.stream.ImageOutputStreamImpl
          extended by javax.imageio.stream.FileCacheImageOutputStream
All Implemented Interfaces:
DataInput, DataOutput, ImageInputStream, ImageOutputStream

public class FileCacheImageOutputStream
extends ImageOutputStreamImpl

An implementation of ImageOutputStream that writes its output to a regular OutputStream. A file is used to cache data until it is flushed to the output stream.


Field Summary
 
Fields inherited from class javax.imageio.stream.ImageInputStreamImpl
bitOffset, byteOrder, flushedPos, streamPos
 
Constructor Summary
FileCacheImageOutputStream(OutputStream stream, File cacheDir)
          Constructs a FileCacheImageOutputStream that will write to a given outputStream.
 
Method Summary
 void close()
          Closes this FileCacheImageOututStream.
 void flushBefore(long pos)
          Discards the initial portion of the stream prior to the indicated postion.
 boolean isCached()
          Returns true since this ImageOutputStream caches data in order to allow seeking backwards.
 boolean isCachedFile()
          Returns true since this ImageOutputStream maintains a file cache.
 boolean isCachedMemory()
          Returns false since this ImageOutputStream does not maintain a main memory cache.
 long length()
          Returns -1L to indicate that the stream has unknown length.
 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.
 void seek(long pos)
          Sets the current stream position and resets the bit offset to 0.
 void write(byte[] b, int off, int len)
          Writes len bytes from array b, in order, to the output stream.
 void write(int b)
          Writes to the output stream the eight low-order bits of the argument b.
 
Methods inherited from class javax.imageio.stream.ImageOutputStreamImpl
flushBits, write, writeBit, writeBits, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeChars, writeDouble, writeDoubles, writeFloat, writeFloats, writeInt, writeInts, writeLong, writeLongs, writeShort, writeShorts, writeUTF
 
Methods inherited from class javax.imageio.stream.ImageInputStreamImpl
checkClosed, finalize, flush, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, 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, setBitOffset, setByteOrder, skipBytes, skipBytes
 
Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface javax.imageio.stream.ImageInputStream
flush, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, 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, setBitOffset, setByteOrder, skipBytes, skipBytes
 

Constructor Detail

FileCacheImageOutputStream

public FileCacheImageOutputStream(OutputStream stream,
                                  File cacheDir)
                           throws IOException
Constructs a FileCacheImageOutputStream that will write to a given outputStream.

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 OutputStream to write to.
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.

write

public void write(int b)
           throws IOException
Description copied from interface: DataOutput
Writes to the output stream the eight low-order bits of the argument b. The 24 high-order bits of b are ignored.

Specified by:
write in interface DataOutput
Specified by:
write in interface ImageOutputStream
Specified by:
write in class ImageOutputStreamImpl
Parameters:
b - the byte to be written.
Throws:
IOException - if an I/O error occurs.

write

public void write(byte[] b,
                  int off,
                  int len)
           throws IOException
Description copied from interface: DataOutput
Writes len bytes from array b, in order, to the output stream. If b is null, a NullPointerException is thrown. If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown. If len is zero, then no bytes are written. Otherwise, the byte b[off] is written first, then b[off+1], and so on; the last byte written is b[off+len-1].

Specified by:
write in interface DataOutput
Specified by:
write in interface ImageOutputStream
Specified by:
write in class ImageOutputStreamImpl
Parameters:
b - the data.
off - the start offset in the data.
len - the number of bytes to write.
Throws:
IOException - if an I/O error occurs.

length

public long length()
Description copied from class: ImageInputStreamImpl
Returns -1L to indicate that the stream has unknown length. Subclasses must override this method to provide actual length information.

Specified by:
length in interface ImageInputStream
Overrides:
length in class ImageInputStreamImpl
Returns:
-1L to indicate unknown length.

seek

public void seek(long pos)
          throws IOException
Sets the current stream position and resets the bit offset to 0. It is legal to seek past the end of the file; an EOFException will be thrown only if a read is performed. The file length will not be increased until a write is performed.

Specified by:
seek in interface ImageInputStream
Overrides:
seek in class ImageInputStreamImpl
Parameters:
pos - a long containing the desired file pointer position.
Throws:
IndexOutOfBoundsException - if pos is smaller than the flushed position.
IOException - if any other I/O error occurs.

isCached

public boolean isCached()
Returns true since this ImageOutputStream 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 ImageOutputStream 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 ImageOutputStream 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 FileCacheImageOututStream. All pending data is flushed to the output, and the cache file is closed and removed. The destination OutputStream is not closed.

Specified by:
close in interface ImageInputStream
Overrides:
close in class ImageInputStreamImpl
Throws:
IOException - if an error occurs.

flushBefore

public void flushBefore(long pos)
                 throws IOException
Description copied from interface: ImageInputStream
Discards the initial portion of the stream prior to the indicated postion. Attempting to seek to an offset within the flushed portion of the stream will result in an IndexOutOfBoundsException.

Calling flushBefore may allow classes implementing this interface to free up resources such as memory or disk space that are being used to store data from the stream.

Specified by:
flushBefore in interface ImageInputStream
Specified by:
flushBefore in interface ImageOutputStream
Overrides:
flushBefore in class ImageInputStreamImpl
Parameters:
pos - a long containing the length of the file prefix that may be flushed.
Throws:
IOException - if an I/O 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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