bufmgr.java

minibase diskmanger buffermanger

/*  File BufMgr,java */

package bufmgr;

import java.io.IOException;

import diskmgr.DiskMgrException;
import diskmgr.Page;
import global.GlobalConst;
import global.PageId;
import global.SystemDefs;

// *****************************************************

/** The buffer manager class, it allocates new pages for the
 * buffer pool, pins and unpins the frame, frees the frame
 * page, and uses the replacement algorithm to replace the
 * page.
 */
public class BufMgr implements GlobalConst {

	/** The hash table, only allocated once. */
	private BufHashTbl hashTable = new BufHashTbl();

	/** Total number of buffer frames in the buffer pool. */
	private int numBuffers;

	/** physical buffer pool. */
	private byte[][] bufPool; // default = byte[NUMBUF][MAX_SPACE];

	/** An array of Descriptors one per frame. */
	private FrameDesc[] frmeTable; // default = new FrameDesc[NUMBUF];

	/** The replacer object, which is only used in this class. */
	private Replacer replacer;

	/**
	 * Create a buffer manager object.
	 *
	 * @param numbufs number of buffers in the buffer pool.
	 * @param replacerArg name of the buffer replacement policy.
	 */
	public BufMgr(int numbufs, String replacerArg) {

		// type your code here
		// Note: readability of your code will be considered during marking

	}

	/** Check if this page is in buffer pool, otherwise
	 * find a frame for this page, read in and pin it.
	 * Also write out the old page if it's dirty before reading
	 * if emptyPage==TRUE, then actually no read is done to bring
	 * the page in.
	 *
	 * @param pin_pgid page number in the minibase.
	 * @param page the pointer poit to the page.
	 * @param emptyPage true (empty page); false (non-empty page)
	 *
	 * @exception ReplacerException if there is a replacer error.
	 * @exception HashOperationException if there is a hashtable error.
	 * @exception PageUnpinnedException if there is a page that is already unpinned.
	 * @exception InvalidFrameNumberException if there is an invalid frame number .
	 * @exception PageNotReadException if a page cannot be read.
	 * @exception BufferPoolExceededException if the buffer pool is full.
	 * @exception PagePinnedException if a page is left pinned .
	 * @exception BufMgrException other error occured in bufmgr layer
	 * @exception IOException if there is other kinds of I/O error.
	 */
	public void pinPage(PageId pin_pgid, Page page, boolean emptyPage)
			throws ReplacerException, HashOperationException,
			PageUnpinnedException, InvalidFrameNumberException,
			PageNotReadException, BufferPoolExceededException,
			PagePinnedException, BufMgrException, IOException {

		// type your code here
		// Note: readability of your code will be considered during marking

	}

	/**
	 * To unpin a page specified by a pageId.
	 *If pincount>0, decrement it and if it becomes zero,
	 * put it in a group of replacement candidates.
	 * if pincount=0 before this call, return error.
	 *
	 * @param PageId_in_a_DB page number in the minibase.
	 * @param dirty the dirty bit of the frame
	 *
	 * @exception ReplacerException if there is a replacer error.
	 * @exception PageUnpinnedException if there is a page that is already unpinned.
	 * @exception InvalidFrameNumberException if there is an invalid frame number .
	 * @exception HashEntryNotFoundException if there is no entry of page in the hash table.
	 */
	public void unpinPage(PageId PageId_in_a_DB, boolean dirty)
			throws ReplacerException, PageUnpinnedException,
			HashEntryNotFoundException, InvalidFrameNumberException {

		// type your code here
		// Note: readability of your code will be considered during marking

	}

	/** Call DB object to allocate a run of new pages and
	 * find a frame in the buffer pool for the first page
	 * and pin it. If buffer is full, ask DB to deallocate
	 * all these pages and return error (null if error).
	 *
	 * @param firstpage the address of the first page.
	 * @param howmany total number of allocated new pages.
	 * @return the first page id of the new pages.
	 *
	 * @exception BufferPoolExceededException if the buffer pool is full.
	 * @exception HashOperationException if there is a hashtable error.
	 * @exception ReplacerException if there is a replacer error.
	 * @exception HashEntryNotFoundException if there is no entry of page in the hash table.
	 * @exception InvalidFrameNumberException if there is an invalid frame number.
	 * @exception PageUnpinnedException if there is a page that is already unpinned.
	 * @exception PagePinnedException if a page is left pinned.
	 * @exception PageNotReadException if a page cannot be read.
	 * @exception IOException if there is other kinds of I/O error.
	 * @exception BufMgrException other error occured in bufmgr layer
	 * @exception DiskMgrException other error occured in diskmgr layer
	 */
	public PageId newPage(Page firstpage, int howmany)
			throws BufferPoolExceededException, HashOperationException,
			ReplacerException, HashEntryNotFoundException,
			InvalidFrameNumberException, PagePinnedException,
			PageUnpinnedException, PageNotReadException, BufMgrException,
			DiskMgrException, IOException {

		// type your code here
		// Note: readability of your code will be considered during marking

		return null; // replace it by your code

	}

	/** User should call this method if she needs to delete a page.
	 * this routine will call DB to deallocate the page.
	 *
	 * @param globalPageId the page number in the data base.
	 * @exception InvalidBufferException if buffer pool corrupted.
	 * @exception ReplacerException if there is a replacer error.
	 * @exception HashOperationException if there is a hash table error.
	 * @exception InvalidFrameNumberException if there is an invalid frame number.
	 * @exception PageNotReadException if a page cannot be read.
	 * @exception BufferPoolExceededException if the buffer pool is already full.
	 * @exception PagePinnedException if a page is left pinned.
	 * @exception PageUnpinnedException if there is a page that is already unpinned.
	 * @exception HashEntryNotFoundException if there is no entry
	 *            of page in the hash table.
	 * @exception IOException if there is other kinds of I/O error.
	 * @exception BufMgrException other error occured in bufmgr layer
	 * @exception DiskMgrException other error occured in diskmgr layer
	 */
	public void freePage(PageId globalPageId) throws InvalidBufferException,
			ReplacerException, HashOperationException,
			InvalidFrameNumberException, PageNotReadException,
			BufferPoolExceededException, PagePinnedException,
			PageUnpinnedException, HashEntryNotFoundException, BufMgrException,
			DiskMgrException, IOException {

		// type your code here
		// Note: readability of your code will be considered during marking

	}

	/** Added to flush a particular page of the buffer pool to disk
	 * @param pageid the page number in the database.
	 *
	 * @exception HashOperationException if there is a hashtable error.
	 * @exception PageUnpinnedException if there is a page that is already unpinned.
	 * @exception PagePinnedException if a page is left pinned.
	 * @exception PageNotFoundException if a page is not found.
	 * @exception BufMgrException other error occured in bufmgr layer
	 * @exception IOException if there is other kinds of I/O error.
	 */
	public void flushPage(PageId pageid) throws HashOperationException,
			PageUnpinnedException, PagePinnedException, PageNotFoundException,
			BufMgrException, IOException {

		// type your code here
		// Note: readability of your code will be considered during marking

	}

	/** Flushes all pages of the buffer pool to disk
	 * @exception HashOperationException if there is a hashtable error.
	 * @exception PageUnpinnedException if there is a page that is already unpinned.
	 * @exception PagePinnedException if a page is left pinned.
	 * @exception PageNotFoundException if a page is not found.
	 * @exception BufMgrException other error occured in bufmgr layer
	 * @exception IOException if there is other kinds of I/O error.
	 */
	public void flushAllPages() throws HashOperationException,
			PageUnpinnedException, PagePinnedException, PageNotFoundException,
			BufMgrException, IOException {

		// type your code here
		// Note: readability of your code will be considered during marking

	}

	/** Gets the total number of buffers.
	 *
	 * @return total number of buffer frames.
	 */
	public int getNumBuffers() {
		return numBuffers;
	}

	/** Gets the total number of unpinned buffer frames.
	 *
	 * @return total number of unpinned buffer frames.
	 */
	public int getNumUnpinnedBuffers() {
		return replacer.getNumUnpinnedBuffers();
	}

	/** A few routines currently need direct access to the FrameTable. */
	public FrameDesc[] frameTable() {
		return frmeTable;
	}

	/* The following code tells you how to call methods of DB class in BufMgr */
	private void write_page(PageId pageno, Page page) throws BufMgrException {

		try {
			SystemDefs.JavabaseDB.write_page(pageno, page);
		} catch (Exception e) {
			throw new BufMgrException(e, "BufMgr.java: write_page() failed");
		}

	} // end of write_page

	private void read_page(PageId pageno, Page page) throws BufMgrException {

		try {
			SystemDefs.JavabaseDB.read_page(pageno, page);
		} catch (Exception e) {
			throw new BufMgrException(e, "BufMgr.java: read_page() failed");
		}

	} // end of read_page

	private void allocate_page(PageId pageno, int num) throws BufMgrException {

		try {
			SystemDefs.JavabaseDB.allocate_page(pageno, num);
		} catch (Exception e) {
			throw new BufMgrException(e, "BufMgr.java: allocate_page() failed");
		}

	} // end of allocate_page

	private void deallocate_page(PageId pageno) throws BufMgrException {

		try {
			SystemDefs.JavabaseDB.deallocate_page(pageno);
		} catch (Exception e) {
			throw new BufMgrException(e,
					"BufMgr.java: deallocate_page() failed");
		}

	} // end of deallocate_page

}