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MemoryCacheImageOutputStream (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

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javax.imageio.stream
Class MemoryCacheImageOutputStream

java.lang.Object
  |
  +--javax.imageio.stream.ImageInputStreamImpl
        |
        +--javax.imageio.stream.ImageOutputStreamImpl
              |
              +--javax.imageio.stream.MemoryCacheImageOutputStream

All Implemented Interfaces:

DataInput, DataOutput, ImageInputStream, ImageOutputStream

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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.

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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)           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 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 the total length of the stream, if known.
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	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 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.

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read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Description copied from interface: ImageInputStream

Reads up to len bytes from the stream, and stores them into b starting at index off. The number of bytes read is returned. If no bytes can be read because the end of the stream has been 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

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.

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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 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.

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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 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.

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length

public long length()

Description copied from interface: ImageInputStream

Returns the total length of the stream, if known. Otherwise, -1 is returned.

Specified by:

length in interface ImageInputStream

Overrides:

length in class ImageInputStreamImpl

Returns:

a long containing the length of the stream, if known, or else -1.

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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()

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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()

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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()

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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.

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flushBefore

public void flushBefore(long pos)
                 throws IOException

Description copied from interface: ImageOutputStream

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.

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 to the destination.

Throws:

IOException - if an I/O error occurs.

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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.

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