Class FileCacheImageOutputStream

java.lang.Object

javax.imageio.stream.ImageInputStreamImpl

javax.imageio.stream.ImageOutputStreamImpl

javax.imageio.stream.FileCacheImageOutputStream

All Implemented Interfaces:

Closeable, DataInput, DataOutput, AutoCloseable, 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 declared in class ImageInputStreamImpl

bitOffset, byteOrder, flushedPos, streamPos

Constructor Summary

Constructors

Constructor	Description
FileCacheImageOutputStream(OutputStream stream, File cacheDir)	Constructs a FileCacheImageOutputStream that will write to a given outputStream.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes this FileCacheImageOutputStream.
void	flushBefore(long pos)	Flushes all data prior to the given position to the underlying destination, such as an OutputStream or File.
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 int 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 a sequence of bytes to the stream at the current position.
void	write(int b)	Writes a single byte to the stream at the current position.

Methods declared in class ImageOutputStreamImpl

flushBits, write, writeBit, writeBits, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeChars, writeDouble, writeDoubles, writeFloat, writeFloats, writeInt, writeInts, writeLong, writeLongs, writeShort, writeShorts, writeUTF

Methods declared in class ImageInputStreamImpl

checkClosed, finalize, flush, 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, setBitOffset, setByteOrder, skipBytes, skipBytes

Methods declared in class Object

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

Methods declared in interface 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 Details

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 cacheDir is 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 Details

read

public int read()
         throws IOException

Description copied from class: ImageInputStreamImpl

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 ImageInputStreamImpl

Returns:

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

Throws:

IOException - if the stream has been closed.

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: ImageOutputStream

Writes a single byte to the stream at the current position. The 24 high-order bits of b are ignored.

If the bit offset within the stream is non-zero, the remainder of the current byte is padded with 0s and written out first. The bit offset will be 0 after the write. Implementers can use the flushBits method of ImageOutputStreamImpl to guarantee this.

Parameters:

b - an int whose lower 8 bits are 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: ImageOutputStream

Writes a sequence of bytes to the stream at the current position. If len is 0, nothing is written. The byte b[off] is written first, then the byte b[off + 1], and so on.

If the bit offset within the stream is non-zero, the remainder of the current byte is padded with 0s and written out first. The bit offset will be 0 after the write. Implementers can use the flushBits method of ImageOutputStreamImpl to guarantee this.

Parameters:

b - an array of bytes to be written.

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.

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 FileCacheImageOutputStream. All pending data is flushed to the output, and the cache file is closed and removed. The destination OutputStream is not closed.

Throws:

IOException - if an error occurs.

flushBefore

public void flushBefore(long pos)
                 throws IOException

Flushes all data prior to the given position to the underlying destination, such as an OutputStream or File. Attempting to seek to the flushed portion of the stream will result in an IndexOutOfBoundsException.

Parameters:

pos - a long containing the length of the stream prefix that may be flushed to the destination.

Throws:

IOException - if an I/O error occurs.