FileCacheImageOutputStream (Java Platform SE 6) - JDK 5 Documentation v6.0, Java 2 SDK 英文文档

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Java™ Platform
Standard Ed. 6

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javax.imageio.stream
Class FileCacheImageOutputStream

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

All Implemented Interfaces:: DataInput, DataOutput, ImageInputStream, ImageOutputStream

public class FileCacheImageOutputStream
extends ImageOutputStreamImpl
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 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 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

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 `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 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 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.

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.

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 stream prefix that may be flushed.
Throws:: IOException - if an I/O error occurs.

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Standard Ed. 6

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For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

FileCacheImageOutputStream (Java Platform SE 6) - JDK 5 Documentation v6.0, Java 2 SDK 英文文档

javax.imageio.stream Class FileCacheImageOutputStream

FileCacheImageOutputStream

read

read

write

write

length

seek

isCached

isCachedFile

isCachedMemory

close

flushBefore

javax.imageio.stream
Class FileCacheImageOutputStream