com.bigdata.rawstore.IAddressManager Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Sep 4, 2007
*/
package com.bigdata.rawstore;
/**
* An interface that encapsulates operations on opaque identifiers used to
* locate data within an {@link IRawStore}.
*
* @author Bryan Thompson
* @version $Id$
*/
public interface IAddressManager {
/**
* A null reference (0L).
*
* Note: It is a requirement that all implementations understand the value
* 0L as a null reference.
*/
public static final long NULL = 0L;
/**
* Converts a byte count and offset into a long integer.
*
* @param nbytes
* The byte count.
* @param offset
* The byte offset.
*
* @return The long integer.
*
* @exception IllegalArgumentException
* if the byte count is larger than can be represented by the
* address manager.
*
* @exception IllegalArgumentException
* if the byte offset is larger than can be represented by
* the address manager.
*/
public long toAddr(int nbytes,long offset);
/**
* The offset on the store at which the datum is stored. While this is often
* the offset of a byte into a file on disk, implementations MAY assign
* offsets using other strategies.
*
* @param addr
* The opaque identifier that is the within store locator for
* some datum.
*
* @return The offset of that datum.
*/
public long getOffset(long addr);
/**
* The length of the datum in bytes. This must be the actual length of the
* record on the disk, not the length of the caller's byte[]. This is
* necessary in order to support transparent checksums and/or compression
* for records in the {@link IRawStore}.
*
* @param addr
* The opaque identifier that is the within store locator for
* some datum.
*
* @return The offset of that datum.
*/
public int getByteCount(long addr);
// /**
// * Pack the address onto the output stream.
// *
// * @param out
// * The output stream.
// *
// * @param addr
// * The opaque identifier that is the within store locator for
// * some datum.
// *
// * @deprecated Address packing is not currently used by anything. While it
// * can produce somewhat more compact representations, it is
// * problematic in that it requires an awareness of the
// * {@link IAddressManager} at the point in the code where the
// * address is to be decoded. This is not always feasible and
// * other techniques are available to code the addresses more
// * efficiently, for example, the child addresses of a
// * {@link Node}.
// */
// public void packAddr(DataOutput out, long addr) throws IOException;
//
// /**
// * Unpack the address from the input stream.
// *
// * @param in
// * The input stream.
// *
// * @return The opaque identifier that is the within store locator for some
// * datum.
// *
// * @deprecated Address packing is not currently used by anything. While it
// * can produce somewhat more compact representations, it is
// * problematic in that it requires an awareness of the
// * {@link IAddressManager} at the point in the code where the
// * address is to be decoded. This is not always feasible and
// * other techniques are available to code the addresses more
// * efficiently, for example, the child addresses of a
// * {@link Node}.
// */
// public long unpackAddr(DataInput in) throws IOException;
/**
* A human readable representation of the address.
*
* @param addr
* The opaque identifier that is the within store locator for
* some datum.
*
* @return A human readable representation.
*/
public String toString(long addr);
/**
* Determine the unencoded physical address
*
* @param addr
* The encoded address
*
* @return an unencoded address offset
*/
public long getPhysicalAddress(long addr);
}