Package com.mckoi.util

Class PagedInputStream

java.lang.Object

java.io.InputStream

com.mckoi.util.PagedInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public abstract class PagedInputStream
extends java.io.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	Description
PagedInputStream(int page_size, long total_size)	Constructs the input stream.

Method Summary

Modifier and Type	Method	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, readAllBytes, readNBytes, transferTo

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 java.io.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:

java.io.IOException

read

public int read()
         throws java.io.IOException

Specified by:

read in class java.io.InputStream

Throws:

java.io.IOException

read

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

Overrides:

read in class java.io.InputStream

Throws:

java.io.IOException

skip

public long skip(long n)
          throws java.io.IOException

Overrides:

skip in class java.io.InputStream

Throws:

java.io.IOException

available

public int available()
              throws java.io.IOException

Overrides:

available in class java.io.InputStream

Throws:

java.io.IOException

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Overrides:

close in class java.io.InputStream

Throws:

java.io.IOException

mark

public void mark(int limit)

Overrides:

mark in class java.io.InputStream

reset

public void reset()

Overrides:

reset in class java.io.InputStream

markSupported

public boolean markSupported()

Overrides:

markSupported in class java.io.InputStream