public class

FileCacheImageOutputStream

extends ImageOutputStreamImpl
java.lang.Object
   ↳ javax.imageio.stream.ImageInputStreamImpl
     ↳ javax.imageio.stream.ImageOutputStreamImpl
       ↳ javax.imageio.stream.FileCacheImageOutputStream

Class Overview

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.

Summary

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Inherited Fields
From class javax.imageio.stream.ImageInputStreamImpl
Public Constructors
FileCacheImageOutputStream(OutputStream stream, File cacheDir)
Constructs a FileCacheImageOutputStream that will write to a given outputStream.
Public Methods
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 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.
[Expand]
Inherited Methods
From class javax.imageio.stream.ImageOutputStreamImpl
From class javax.imageio.stream.ImageInputStreamImpl
From class java.lang.Object
From interface java.io.DataInput
From interface java.io.DataOutput
From interface javax.imageio.stream.ImageInputStream
From interface javax.imageio.stream.ImageOutputStream

Public Constructors

public FileCacheImageOutputStream (OutputStream stream, File cacheDir)

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.

Public Methods

public void close ()

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.

Throws
IOException if an error occurs.

public void flushBefore (long pos)

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.

Parameters
pos a long containing the length of the stream prefix that may be flushed.
Throws
IOException

public boolean isCached ()

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

Returns
  • true.

public boolean isCachedFile ()

Returns true since this ImageOutputStream maintains a file cache.

Returns
  • true.

public boolean isCachedMemory ()

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

Returns
  • false.

public long length ()

Returns -1L to indicate that the stream has unknown length. Subclasses must override this method to provide actual length information.

Returns
  • -1L to indicate unknown length.

public int read ()

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.

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

public 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. 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.

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

public void seek (long pos)

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.

public void write (byte[] b, int off, int len)

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

public void write (int b)

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