Class BlockSourceFromPageManager

java.lang.Object
org.aksw.commons.io.binseach.BlockSourceFromPageManager
All Implemented Interfaces:
BlockSource
public class BlockSourceFromPageManager extends Object implements BlockSource
A block source mainly for testing the rest of the block-based machinery, such as binary search. TODO Can we align block source and page manager? Pages are backed by ByteBuffers and the assumption is, that no form of lazy loading is necessary. The prime use case is memory mapped io, where ranges of file contents are made accessible via a ByteBuffer. Hence, a Page only has a 'new buffer' method, which provides a mere duplicate on the buffer associated with the page. Closing the page implicitly invalidates all buffers. The PageNavigator provides a continuous view over a range of pages. In contrast, blocks need to be sequentially read. Our abstraction makes it possible to both only read as much data as necessary as well as view a sequence of blocks as a continuous segment. E.g. when performing binary search, only the first record of a block has to be decoded in order to examine the key. The main difference between block and page is: Pages provide access to the data using newBuffer: ByteBuffer - whereas blocks provide a newChannel: Seekable method. Seekable is a subclass of Channel. Now the gap is: Channels have a close method, ByteBuffers don't. Under this perspective, closing the channels opened from a block is not necessary, as closing the block invalidates the channels and unclosed channels do not keep the block open. Blocks are created from the underlying buffer by chunking it into equal sizes
Author:
raven