- java.lang.Object
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- javax.imageio.stream.ImageInputStreamImpl
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- javax.imageio.stream.ImageOutputStreamImpl
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- javax.imageio.stream.FileCacheImageOutputStream
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- All Implemented Interfaces:
- Closeable, DataInput, DataOutput, AutoCloseable, ImageInputStream, ImageOutputStream
public class FileCacheImageOutputStream extends ImageOutputStreamImpl
An implementation ofImageOutputStream
that writes its output to a regularOutputStream
. A file is used to cache data until it is flushed to the output stream.
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Field Summary
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Fields inherited from class javax.imageio.stream.ImageInputStreamImpl
bitOffset, byteOrder, flushedPos, streamPos
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Constructor Summary
Constructors Constructor and Description FileCacheImageOutputStream(OutputStream stream, File cacheDir)
Constructs aFileCacheImageOutputStream
that will write to a givenoutputStream
.
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Method Summary
Methods Modifier and Type Method and Description void
close()
Closes thisFileCacheImageOutputStream
.void
flushBefore(long pos)
Discards the initial portion of the stream prior to the indicated postion.boolean
isCached()
Returnstrue
since thisImageOutputStream
caches data in order to allow seeking backwards.boolean
isCachedFile()
Returnstrue
since thisImageOutputStream
maintains a file cache.boolean
isCachedMemory()
Returnsfalse
since thisImageOutputStream
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 anint
between 0 and 255.int
read(byte[] b, int off, int len)
Reads up tolen
bytes from the stream, and stores them intob
starting at indexoff
.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
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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
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Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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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
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Constructor Detail
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FileCacheImageOutputStream
public FileCacheImageOutputStream(OutputStream stream, File cacheDir) throws IOException
Constructs aFileCacheImageOutputStream
that will write to a givenoutputStream
.A temporary file is used as a cache. If
cacheDir
is non-null
and is a directory, the file will be created there. If it isnull
, the system-dependent default temporary-file directory will be used (see the documentation forFile.createTempFile
for details).- Parameters:
stream
- anOutputStream
to write to.cacheDir
- aFile
indicating where the cache file should be created, ornull
to use the system directory.- Throws:
IllegalArgumentException
- ifstream
isnull
.IllegalArgumentException
- ifcacheDir
is non-null
but is not a directory.IOException
- if a cache file cannot be created.
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Method Detail
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read
public int read() throws IOException
Description copied from class:ImageInputStreamImpl
Reads a single byte from the stream and returns it as anint
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 interfaceImageInputStream
- Specified by:
read
in classImageInputStreamImpl
- Returns:
- the value of the next byte in the stream, or
-1
if EOF is reached. - Throws:
IOException
- if the stream has been closed.
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read
public int read(byte[] b, int off, int len) throws IOException
Description copied from class:ImageInputStreamImpl
Reads up tolen
bytes from the stream, and stores them intob
starting at indexoff
. 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 interfaceImageInputStream
- Specified by:
read
in classImageInputStreamImpl
- Parameters:
b
- an array of bytes to be written to.off
- the starting position withinb
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 ofb
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
method offlushBits
to guarantee this.ImageOutputStreamImpl
- Specified by:
write
in interfaceDataOutput
- Specified by:
write
in interfaceImageOutputStream
- Specified by:
write
in classImageOutputStreamImpl
- Parameters:
b
- anint
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. Iflen
is 0, nothing is written. The byteb[off]
is written first, then the byteb[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
method offlushBits
to guarantee this.ImageOutputStreamImpl
- Specified by:
write
in interfaceDataOutput
- Specified by:
write
in interfaceImageOutputStream
- Specified by:
write
in classImageOutputStreamImpl
- Parameters:
b
- an array ofbyte
s to be written.off
- the start offset in the data.len
- the number ofbyte
s to write.- Throws:
IOException
- if an I/O error occurs.
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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 interfaceImageInputStream
- Overrides:
length
in classImageInputStreamImpl
- Returns:
- -1L to indicate unknown length.
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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; anEOFException
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 interfaceImageInputStream
- Overrides:
seek
in classImageInputStreamImpl
- Parameters:
pos
- along
containing the desired file pointer position.- Throws:
IndexOutOfBoundsException
- ifpos
is smaller than the flushed position.IOException
- if any other I/O error occurs.
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isCached
public boolean isCached()
Returnstrue
since thisImageOutputStream
caches data in order to allow seeking backwards.- Specified by:
isCached
in interfaceImageInputStream
- Overrides:
isCached
in classImageInputStreamImpl
- Returns:
true
.- See Also:
isCachedMemory()
,isCachedFile()
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isCachedFile
public boolean isCachedFile()
Returnstrue
since thisImageOutputStream
maintains a file cache.- Specified by:
isCachedFile
in interfaceImageInputStream
- Overrides:
isCachedFile
in classImageInputStreamImpl
- Returns:
true
.- See Also:
isCached()
,isCachedMemory()
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isCachedMemory
public boolean isCachedMemory()
Returnsfalse
since thisImageOutputStream
does not maintain a main memory cache.- Specified by:
isCachedMemory
in interfaceImageInputStream
- Overrides:
isCachedMemory
in classImageInputStreamImpl
- Returns:
false
.- See Also:
isCached()
,isCachedFile()
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close
public void close() throws IOException
Closes thisFileCacheImageOutputStream
. All pending data is flushed to the output, and the cache file is closed and removed. The destinationOutputStream
is not closed.- Specified by:
close
in interfaceCloseable
- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceImageInputStream
- Overrides:
close
in classImageInputStreamImpl
- Throws:
IOException
- if an error occurs.
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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 anIndexOutOfBoundsException
.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 interfaceImageInputStream
- Specified by:
flushBefore
in interfaceImageOutputStream
- Overrides:
flushBefore
in classImageInputStreamImpl
- Parameters:
pos
- along
containing the length of the stream prefix that may be flushed.- Throws:
IOException
- if an I/O error occurs.
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