Class MemoryCacheImageInputStream

java.lang.Object

javax.imageio.stream.ImageInputStreamImpl

javax.imageio.stream.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.

Field Summary

Fields declared in class javax.imageio.stream.ImageInputStreamImpl

bitOffset, byteOrder, flushedPos, streamPos

Constructor Summary

Constructor	Description
`MemoryCacheImageInputStream(InputStream stream)`	Constructs a `MemoryCacheImageInputStream` that will read from a given `InputStream`.

Method Summary

Modifier and Type	Method	Description
`void`	`close()`	Closes this `MemoryCacheImageInputStream`, freeing the cache.
`protected void`	`finalize()`	Deprecated. The `finalize` method has been deprecated.
`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 declared in class javax.imageio.stream.ImageInputStreamImpl

checkClosed, flush, flushBefore, 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 declared in class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

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.

Method Details

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.

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.

Throws:: IOException - if an I/O error occurs.

finalize

@Deprecated(since="9") protected void finalize() throws Throwable

Deprecated.

The finalize method has been deprecated. Subclasses that override finalize in order to perform cleanup should be modified to use alternative cleanup mechanisms and to remove the overriding finalize method. When overriding the finalize method, its implementation must explicitly ensure that super.finalize() is invoked as described in Object.finalize(). See the specification for Object.finalize() for further information about migration options.

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:

© 1993, 2021, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/17/docs/api/java.desktop/javax/imageio/stream/MemoryCacheImageInputStream.html