org.apache.batik.ext.awt.image.codec.util
Class MemoryCacheSeekableStream

java.lang.Object
  extended by java.io.InputStream
      extended by org.apache.batik.ext.awt.image.codec.util.SeekableStream
          extended by org.apache.batik.ext.awt.image.codec.util.MemoryCacheSeekableStream
All Implemented Interfaces:
Closeable, DataInput

public final class MemoryCacheSeekableStream
extends SeekableStream

A subclass of SeekableStream that may be used to wrap a regular InputStream. Seeking backwards is supported by means of an in-memory cache. For greater efficiency, FileCacheSeekableStream should be used in circumstances that allow the creation of a temporary file.

The mark() and reset() methods are supported.

This class is not a committed part of the JAI API. It may be removed or changed in future releases of JAI.


Field Summary
 
Fields inherited from class org.apache.batik.ext.awt.image.codec.util.SeekableStream
markPos
 
Constructor Summary
MemoryCacheSeekableStream(InputStream src)
          Constructs a MemoryCacheSeekableStream that takes its source data from a regular InputStream.
 
Method Summary
 boolean canSeekBackwards()
          Returns true since all MemoryCacheSeekableStream instances support seeking backwards.
 long getFilePointer()
          Returns the current offset in this file.
 int read()
          Reads the next byte of data from the input stream.
 int read(byte[] b, int off, int len)
          Reads up to len bytes of data from the input stream into an array of bytes.
 void seek(long pos)
          Sets the file-pointer offset, measured from the beginning of this file, at which the next read occurs.
 
Methods inherited from class org.apache.batik.ext.awt.image.codec.util.SeekableStream
finalize, mark, markSupported, readBoolean, readByte, readChar, readCharLE, readDouble, readDoubleLE, readFloat, readFloatLE, readFully, readFully, readInt, readIntLE, readLine, readLong, readLongLE, readShort, readShortLE, readUnsignedByte, readUnsignedInt, readUnsignedIntLE, readUnsignedShort, readUnsignedShortLE, readUTF, reset, skipBytes, wrapInputStream
 
Methods inherited from class java.io.InputStream
available, close, read, skip
 
Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

MemoryCacheSeekableStream

public MemoryCacheSeekableStream(InputStream src)
Constructs a MemoryCacheSeekableStream that takes its source data from a regular InputStream. Seeking backwards is supported by means of an in-memory cache.

Method Detail

canSeekBackwards

public boolean canSeekBackwards()
Returns true since all MemoryCacheSeekableStream instances support seeking backwards.

Overrides:
canSeekBackwards in class SeekableStream

getFilePointer

public long getFilePointer()
Returns the current offset in this file.

Specified by:
getFilePointer in class SeekableStream
Returns:
the offset from the beginning of the file, in bytes, at which the next read occurs.

seek

public void seek(long pos)
          throws IOException
Sets the file-pointer offset, measured from the beginning of this file, at which the next read occurs.

Specified by:
seek in class SeekableStream
Parameters:
pos - the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.
Throws:
IOException - if pos is less than 0 or if an I/O error occurs.

read

public int read()
         throws IOException
Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

Specified by:
read in class SeekableStream
Returns:
the next byte of data, or -1 if the end of the stream is reached.
Throws:
IOException - if an I/O error occurs.

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException
Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read, possibly zero. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

Specified by:
read in class SeekableStream
Parameters:
b - the buffer into which the data is read.
off - the start offset in array b at which the data is written.
len - the maximum number of bytes to read.
Returns:
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
Throws:
IOException - if an I/O error occurs.


Copyright © 2008 Apache Software Foundation. All Rights Reserved.