com.mckoi.util

Class PagedInputStream

java.lang.Object

java.io.InputStream

com.mckoi.util.PagedInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public abstract class PagedInputStream
extends InputStream

An implementation of InputStream that reads data from an underlying representation in fixed sized pages. This object maintains a single buffer that is the size of a page. This implementation supports 'skip' and buffered access to the data.

The only method that needs to be implemented is the 'readPageContent' method.

Author:

Tobias Downer

Constructor Summary

Constructors

Constructor and Description
PagedInputStream(int page_size, long total_size) Constructs the input stream.

Method Summary

Modifier and Type	Method and Description
int	available()
void	close()
void	mark(int limit)
boolean	markSupported()
int	read()
int	read(byte[] read_buf, int off, int len)
protected abstract void	readPageContent(byte[] buf, long pos, int length) Reads the page at the given offset in the underlying data into the given byte[] array.
void	reset()
long	skip(long n)

Methods inherited from class java.io.InputStream

read

Methods inherited from class java.lang.Object

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

Constructor Detail

PagedInputStream

public PagedInputStream(int page_size,
                        long total_size)

Constructs the input stream.

Parameters:

page_size - the size of the pages when accessing the underlying stream.

total_size - the total size of the underlying data set.

Method Detail

readPageContent

protected abstract void readPageContent(byte[] buf,
                                        long pos,
                                        int length)
                                 throws IOException

Reads the page at the given offset in the underlying data into the given byte[] array. The 'pos' variable given is guarenteed to be a multiple of buffer_size. For example, the first access will be to pos = 0, the second access to pos = BUFFER_SIZE, the third access to pos = BUFFER_SIZE * 2, etc. 'length' will always be either BUFFER_SIZE or a value smaller than BUFFER_SIZE if the page containing the end of the stream is read.

Throws:

IOException

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

read

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

Overrides:

read in class InputStream

Throws:

IOException

skip

public long skip(long n)
          throws IOException

Overrides:

skip in class InputStream

Throws:

IOException

available

public int available()
              throws IOException

Overrides:

available in class InputStream

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class InputStream

Throws:

IOException

mark

public void mark(int limit)

Overrides:

mark in class InputStream

reset

public void reset()

Overrides:

reset in class InputStream

markSupported

public boolean markSupported()

Overrides:

markSupported in class InputStream