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.
bitOffset, byteOrder, flushedPos, streamPos 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).
stream - an OutputStream to write to.cacheDir - a File indicating where the cache file should be created, or null to use the system directory.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 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.
read in interface ImageInputStream
read in class ImageInputStreamImpl
-1 if EOF is reached.IOException - if the stream has been closed.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.
read in interface ImageInputStream
read in class ImageInputStreamImpl
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.-1 to indicate EOF.IOException - if an I/O error occurs.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.
write in interface DataOutput
write in interface ImageOutputStream
write in class ImageOutputStreamImpl
b - an int whose lower 8 bits are to be written.IOException - if an I/O error occurs.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.
write in interface DataOutput
write in interface ImageOutputStream
write in class ImageOutputStreamImpl
b - an array of bytes to be written.off - the start offset in the data.len - the number of bytes to write.IOException - if an I/O error occurs.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.
length in interface ImageInputStream
length in class ImageInputStreamImpl
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.
seek in interface ImageInputStream
seek in class ImageInputStreamImpl
pos - a long containing the desired file pointer position.IndexOutOfBoundsException - if pos is smaller than the flushed position.IOException - if any other I/O error occurs.public boolean isCached()
Returns true since this ImageOutputStream caches data in order to allow seeking backwards.
isCached in interface ImageInputStream
isCached in class ImageInputStreamImpl
true.isCachedMemory(), isCachedFile()
public boolean isCachedFile()
Returns true since this ImageOutputStream maintains a file cache.
isCachedFile in interface ImageInputStream
isCachedFile in class ImageInputStreamImpl
true.isCached(), isCachedMemory()
public boolean isCachedMemory()
Returns false since this ImageOutputStream does not maintain a main memory cache.
isCachedMemory in interface ImageInputStream
isCachedMemory in class ImageInputStreamImpl
false.isCached(), isCachedFile()
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.
close in interface Closeable
close in interface AutoCloseable
close in interface ImageInputStream
close in class ImageInputStreamImpl
IOException - if an error occurs.public void flushBefore(long pos)
throws IOException Description copied from interface: ImageInputStream
Discards the initial portion of the stream prior to the indicated position. 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.
flushBefore in interface ImageInputStream
flushBefore in interface ImageOutputStream
flushBefore in class ImageInputStreamImpl
pos - a long containing the length of the stream prefix that may be flushed.IOException - if an I/O error occurs.
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Documentation extracted from Debian's OpenJDK Development Kit package.
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