javax.imageio.stream
Class MemoryCacheImageInputStream

java.lang.Object
  |
  +--javax.imageio.stream.ImageInputStreamImpl
        |
        +--javax.imageio.stream.MemoryCacheImageInputStream
All Implemented Interfaces:
DataInput, 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 inherited from class javax.imageio.stream.ImageInputStreamImpl
bitOffset, byteOrder, flushedPos, streamPos
 

 

Constructor Summary

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

 

Method Summary

 void close()
    Closes this MemoryCacheImageInputStream, freeing the cache.
 void flushBefore(long pos)
    Discards the initial portion of the stream prior to the indicated postion.
 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 integer 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, finalize, 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
 

 

Constructor Detail

 

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 Detail

 

read

public int read()
         throws IOException
Description copied from interface: ImageInputStream
Reads a single byte from the stream and returns it as an integer between 0 and 255. If the end of the stream is reached, -1 is returned.

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

Specified by:
read in interface ImageInputStream
Specified by:
read in class ImageInputStreamImpl
Returns:
a byte value from the stream, as an int, or -1 to indicate EOF.
Throws:
IOException - if an I/O error occurs.

 

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 postion. 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 file 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 ImageInputStream
Overrides:
close in class ImageInputStreamImpl
Throws:
IOException - if an I/O error occurs.