Module java.desktop

Package javax.imageio.stream

Class ImageInputStreamImpl

java.lang.Object

javax.imageio.stream.ImageInputStreamImpl

All Implemented Interfaces:

Closeable, DataInput, AutoCloseable, ImageInputStream

Direct Known Subclasses:

FileCacheImageInputStream, FileImageInputStream, ImageOutputStreamImpl, MemoryCacheImageInputStream

public abstract class ImageInputStreamImpl
extends Object
implements ImageInputStream

An abstract class implementing the ImageInputStream interface. This class is designed to reduce the number of methods that must be implemented by subclasses.

In particular, this class handles most or all of the details of byte order interpretation, buffering, mark/reset, discarding, closing, and disposing.

Field Summary

Fields

Modifier and Type	Field	Description
protected int	bitOffset	The current bit offset within the stream.
protected ByteOrder	byteOrder	The byte order of the stream as an instance of the enumeration class java.nio.ByteOrder, where ByteOrder.BIG_ENDIAN indicates network byte order and ByteOrder.LITTLE_ENDIAN indicates the reverse order.
protected long	flushedPos	The position prior to which data may be discarded.
protected long	streamPos	The current read position within the stream.

Constructor Summary

Constructors

Constructor	Description
ImageInputStreamImpl()	Constructs an ImageInputStreamImpl.

Method Summary

Modifier and Type	Method	Description
protected void	checkClosed()	Throws an IOException if the stream has been closed.
protected void	finalize()	Deprecated. The finalize method has been deprecated.
boolean	isCached()	Default implementation returns false.
boolean	isCachedFile()	Default implementation returns false.
boolean	isCachedMemory()	Default implementation returns false.
long	length()	Returns -1L to indicate that the stream has unknown length.
void	mark()	Pushes the current stream position onto a stack of marked positions.
abstract int	read()	Reads a single byte from the stream and returns it as an int between 0 and 255.
int	read(byte[] b)	A convenience method that calls read(b, 0, b.length).
abstract 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	reset()	Resets the current stream byte and bit positions from the stack of marked positions.
int	skipBytes(int n)	Advances the current stream position by calling seek(getStreamPosition() + n).
long	skipBytes(long n)	Advances the current stream position by calling seek(getStreamPosition() + n).

Methods declared in interface javax.imageio.stream.ImageInputStream

close, flush, flushBefore, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, readBit, readBits, readBoolean, readByte, readBytes, readChar, readDouble, readFloat, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedInt, readUnsignedShort, readUTF, seek, setBitOffset, setByteOrder

Methods declared in class java.lang.Object

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

Field Detail

byteOrder

protected ByteOrder byteOrder

The byte order of the stream as an instance of the enumeration class java.nio.ByteOrder, where ByteOrder.BIG_ENDIAN indicates network byte order and ByteOrder.LITTLE_ENDIAN indicates the reverse order. By default, the value is ByteOrder.BIG_ENDIAN.

streamPos

protected long streamPos

The current read position within the stream. Subclasses are responsible for keeping this value current from any method they override that alters the read position.

bitOffset

protected int bitOffset

The current bit offset within the stream. Subclasses are responsible for keeping this value current from any method they override that alters the bit offset.

flushedPos

protected long flushedPos

The position prior to which data may be discarded. Seeking to a smaller position is not allowed. flushedPos will always be >= 0.

Constructor Detail

ImageInputStreamImpl

public ImageInputStreamImpl()

Constructs an ImageInputStreamImpl.

Method Detail

checkClosed

protected final void checkClosed()
                          throws IOException

Throws an IOException if the stream has been closed. Subclasses may call this method from any of their methods that require the stream not to be closed.

Throws:

IOException - if the stream is closed.

read

public abstract int read()
                  throws IOException

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

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)
         throws IOException

A convenience method that calls read(b, 0, b.length).

The bit offset within the stream is reset to zero before the read occurs.

Specified by:

read in interface ImageInputStream

Parameters:

b - an array of bytes to be written to.

Returns:

the number of bytes actually read, or -1 to indicate EOF.

Throws:

NullPointerException - if b is null.

IOException - if an I/O error occurs.

read

public abstract int read(byte[] b,
                         int off,
                         int len)
                  throws IOException

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

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:

IndexOutOfBoundsException - if off is negative, len is negative, or off + len is greater than b.length.

NullPointerException - if b is null.

IOException - if an I/O error occurs.

length

public long length()

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

Returns:

-1L to indicate unknown length.

skipBytes

public int skipBytes(int n)
              throws IOException

Advances the current stream position by calling seek(getStreamPosition() + n).

The bit offset is reset to zero.

Specified by:

skipBytes in interface DataInput

Specified by:

skipBytes in interface ImageInputStream

Parameters:

n - the number of bytes to seek forward.

Returns:

an int representing the number of bytes skipped.

Throws:

IOException - if getStreamPosition throws an IOException when computing either the starting or ending position.

skipBytes

public long skipBytes(long n)
               throws IOException

Advances the current stream position by calling seek(getStreamPosition() + n).

The bit offset is reset to zero.

Specified by:

skipBytes in interface ImageInputStream

Parameters:

n - the number of bytes to seek forward.

Returns:

a long representing the number of bytes skipped.

Throws:

IOException - if getStreamPosition throws an IOException when computing either the starting or ending position.

mark

public void mark()

Pushes the current stream position onto a stack of marked positions.

Specified by:

mark in interface ImageInputStream

reset

public void reset()
           throws IOException

Resets the current stream byte and bit positions from the stack of marked positions.

An IOException will be thrown if the previous marked position lies in the discarded portion of the stream.

Specified by:

reset in interface ImageInputStream

Throws:

IOException - if an I/O error occurs.

isCached

public boolean isCached()

Default implementation returns false. Subclasses should override this if they cache data.

Specified by:

isCached in interface ImageInputStream

Returns:

true if this ImageInputStream caches data.

See Also:

ImageInputStream.isCachedMemory(), ImageInputStream.isCachedFile()

isCachedMemory

public boolean isCachedMemory()

Default implementation returns false. Subclasses should override this if they cache data in main memory.

Specified by:

isCachedMemory in interface ImageInputStream

Returns:

true if this ImageInputStream caches data in main memory.

See Also:

ImageInputStream.isCached(), ImageInputStream.isCachedFile()

isCachedFile

public boolean isCachedFile()

Default implementation returns false. Subclasses should override this if they cache data in a temporary file.

Specified by:

isCachedFile in interface ImageInputStream

Returns:

true if this ImageInputStream caches data in a temporary file.

See Also:

ImageInputStream.isCached(), ImageInputStream.isCachedMemory()

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 Object

Throws:

Throwable - if an error occurs during superclass finalization.

See Also:

WeakReference, PhantomReference