Java™ Platform
Standard Ed. 6

javax.imageio.stream
Class MemoryCacheImageOutputStream

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

public class MemoryCacheImageOutputStream
extends ImageOutputStreamImpl

An implementation of ImageOutputStream that writes its output to a regular OutputStream. A memory buffer is used to cache at least the data between the discard position and the current write position. The only constructor takes an OutputStream, so this class may not be used for read/modify/write operations. Reading can occur only on parts of the stream that have already been written to the cache and not yet flushed.


Field Summary
 
Fields inherited from class javax.imageio.stream.ImageInputStreamImpl
bitOffset, byteOrder, flushedPos, streamPos
 
Constructor Summary
MemoryCacheImageOutputStream(OutputStream stream)
          Constructs a MemoryCacheImageOutputStream that will write to a given OutputStream.
 
Method Summary
 void close()
          Closes this MemoryCacheImageOutputStream.
 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 false since this ImageOutputStream does not maintain a file cache.
 boolean isCachedMemory()
          Returns true since this ImageOutputStream maintains 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 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 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, seek, 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, seek, setBitOffset, setByteOrder, skipBytes, skipBytes
 

Constructor Detail

MemoryCacheImageOutputStream

public MemoryCacheImageOutputStream(OutputStream stream)
Constructs a MemoryCacheImageOutputStream that will write to a given OutputStream.

Parameters:
stream - an OutputStream to write to.
Throws:
IllegalArgumentException - if stream is null.
Method Detail

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.

Specified by:
write in interface DataOutput
Specified by:
write in interface ImageOutputStream
Specified by:
write in class ImageOutputStreamImpl
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.

Specified by:
write in interface DataOutput
Specified by:
write in interface ImageOutputStream
Specified by:
write in class ImageOutputStreamImpl
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.

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 false since this ImageOutputStream does not maintain a file cache.

Specified by:
isCachedFile in interface ImageInputStream
Overrides:
isCachedFile in class ImageInputStreamImpl
Returns:
false.
See Also:
isCached(), isCachedMemory()

isCachedMemory

public boolean isCachedMemory()
Returns true since this ImageOutputStream maintains a main memory cache.

Specified by:
isCachedMemory in interface ImageInputStream
Overrides:
isCachedMemory in class ImageInputStreamImpl
Returns:
true.
See Also:
isCached(), isCachedFile()

close

public void close()
           throws IOException
Closes this MemoryCacheImageOutputStream. All pending data is flushed to the output, and the cache is released. The destination OutputStream is not closed.

Specified by:
close in interface ImageInputStream
Overrides:
close in class ImageInputStreamImpl
Throws:
IOException - if an I/O 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 stream prefix that may be flushed.
Throws:
IOException - if an I/O error occurs.

Java™ Platform
Standard Ed. 6

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