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 ImageInputStreamImpl

bitOffset, byteOrder, flushedPos, streamPos

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
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.
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 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

Modifier and Type	Method	Description
protected final void	checkClosed()	Throws an IOException if the stream has been closed.
void	flush()	Discards the initial position of the stream prior to the current stream position.
void	flushBefore(long pos)	Discards the initial portion of the stream prior to the indicated position.
int	getBitOffset()	Returns the current bit offset, as an integer between 0 and 7, inclusive.
ByteOrder	getByteOrder()	Returns the byte order with which data values will be read from this stream as an instance of the java.nio.ByteOrder enumeration.
long	getFlushedPosition()	Returns the earliest position in the stream to which seeking may be performed.
long	getStreamPosition()	Returns the current byte position of the stream.
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.
int	read(byte[] b)	A convenience method that calls read(b, 0, b.length).
int	readBit()	Reads a single bit from the stream and returns it as an int with the value 0 or 1.
long	readBits(int numBits)	Reads a bitstring from the stream and returns it as a long, with the first bit read becoming the most significant bit of the output.
boolean	readBoolean()	Reads a byte from the stream and returns a boolean value of true if it is nonzero, false if it is zero.
byte	readByte()	Reads a byte from the stream and returns it as a byte value.
void	readBytes(IIOByteBuffer buf, int len)	Reads up to len bytes from the stream, and modifies the supplied IIOByteBuffer to indicate the byte array, offset, and length where the data may be found.
char	readChar()	Equivalent to readUnsignedShort, except that the result is returned using the char datatype.
double	readDouble()	Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a double.
float	readFloat()	Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a float.
void	readFully(byte[] b)	Reads b.length bytes from the stream, and stores them into b starting at index 0.
void	readFully(byte[] b, int off, int len)	Reads len bytes from the stream, and stores them into b starting at index off.
void	readFully(char[] c, int off, int len)	Reads len chars (unsigned 16-bit integers) from the stream according to the current byte order, and stores them into c starting at index off.
void	readFully(double[] d, int off, int len)	Reads len doubles (64-bit IEEE double-precision floats) from the stream according to the current byte order, and stores them into d starting at index off.
void	readFully(float[] f, int off, int len)	Reads len floats (32-bit IEEE single-precision floats) from the stream according to the current byte order, and stores them into f starting at index off.
void	readFully(int[] i, int off, int len)	Reads len ints (signed 32-bit integers) from the stream according to the current byte order, and stores them into i starting at index off.
void	readFully(long[] l, int off, int len)	Reads len longs (signed 64-bit integers) from the stream according to the current byte order, and stores them into l starting at index off.
void	readFully(short[] s, int off, int len)	Reads len shorts (signed 16-bit integers) from the stream according to the current byte order, and stores them into s starting at index off.
int	readInt()	Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as an int.
String	readLine()	Reads the next line of text from the input stream.
long	readLong()	Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a long.
short	readShort()	Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, and returns the result as a short value.
int	readUnsignedByte()	Reads a byte from the stream, and (conceptually) converts it to an int, masks it with 0xff in order to strip off any sign-extension bits, and returns it as a byte value.
long	readUnsignedInt()	Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the result to a long, masks it with 0xffffffffL in order to strip off any sign-extension bits, and returns the result as an unsigned long value.
int	readUnsignedShort()	Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the resulting value to an int, masks it with 0xffff in order to strip off any sign-extension buts, and returns the result as an unsigned int value.
String	readUTF()	Reads in a string that has been encoded using a modified UTF-8 format.
void	reset()	Resets the current stream byte and bit positions from the stack of marked positions.
void	seek(long pos)	Sets the current stream position to the desired location.
void	setBitOffset(int bitOffset)	Sets the bit offset to an integer between 0 and 7, inclusive.
void	setByteOrder(ByteOrder byteOrder)	Sets the desired byte order for future reads of data values from this stream.
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 class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
String	toString()	Returns a string representation of the object.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

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.