Class MemoryCacheImageInputStream

All Implemented Interfaces:
Closeable, DataInput, AutoCloseable, ImageInputStream 

public class MemoryCacheImageInputStream
extends ImageInputStreamImpl

An implementation of ImageInputStream that gets its input from a regular InputStream. A memory buffer is used to cache at least the data between the discard position and the current read position.

In general, it is preferable to use a FileCacheImageInputStream when reading from a regular InputStream. This class is provided for cases where it is not possible to create a writable temporary file.

Fields

Fields inherited from class javax.imageio.stream.ImageInputStreamImpl

bitOffset, byteOrder, flushedPos, streamPos

Constructors

Constructor and Description
MemoryCacheImageInputStream(InputStream stream)

Constructs a MemoryCacheImageInputStream that will read from a given InputStream.

Methods

Modifier and Type Method and Description
void close()

Closes this MemoryCacheImageInputStream, freeing the cache.
protected void finalize()

Finalizes this object prior to garbage collection.
void flushBefore(long pos)

Discards the initial portion of the stream prior to the indicated position.
boolean isCached()

Returns true since this ImageInputStream caches data in order to allow seeking backwards.
boolean isCachedFile()

Returns false since this ImageInputStream does not maintain a file cache.
boolean isCachedMemory()

Returns true since this ImageInputStream maintains a main memory cache.
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.

Methods inherited from class javax.imageio.stream.ImageInputStreamImpl

checkClosed, flush, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, length, 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

Constructors

MemoryCacheImageInputStream

public MemoryCacheImageInputStream(InputStream stream)

Constructs a MemoryCacheImageInputStream that will read from a given InputStream.

Parameters:
stream - an InputStream to read from.
Throws:
IllegalArgumentException - if stream is null.

Methods

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.

flushBefore

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.

Specified by:
flushBefore in interface ImageInputStream
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.

isCached

public boolean isCached()

Returns true since this ImageInputStream 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 ImageInputStream 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 ImageInputStream 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 MemoryCacheImageInputStream, freeing the cache. The source InputStream is not closed.

Specified by:
close in interface Closeable
Specified by:
close in interface AutoCloseable
Specified by:
close in interface ImageInputStream
Overrides:
close in class ImageInputStreamImpl
Throws:
IOException - if an I/O error occurs.

finalize

protected void finalize()
                 throws Throwable

Finalizes this object prior to garbage collection. The close method is called to close any open input source. This method should not be called from application code.

Overrides:
finalize in class ImageInputStreamImpl
Throws:
Throwable - if an error occurs during superclass finalization.
See Also:
WeakReference, PhantomReference

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/javase/8/docs/api/javax/imageio/stream/MemoryCacheImageInputStream.html