001: package com.quadcap.sql.file;
002:
003: /* Copyright 1999 - 2003 Quadcap Software. All rights reserved.
004: *
005: * This software is distributed under the Quadcap Free Software License.
006: * This software may be used or modified for any purpose, personal or
007: * commercial. Open Source redistributions are permitted. Commercial
008: * redistribution of larger works derived from, or works which bundle
009: * this software requires a "Commercial Redistribution License"; see
010: * http://www.quadcap.com/purchase.
011: *
012: * Redistributions qualify as "Open Source" under one of the following terms:
013: *
014: * Redistributions are made at no charge beyond the reasonable cost of
015: * materials and delivery.
016: *
017: * Redistributions are accompanied by a copy of the Source Code or by an
018: * irrevocable offer to provide a copy of the Source Code for up to three
019: * years at the cost of materials and delivery. Such redistributions
020: * must allow further use, modification, and redistribution of the Source
021: * Code under substantially the same terms as this license.
022: *
023: * Redistributions of source code must retain the copyright notices as they
024: * appear in each source code file, these license terms, and the
025: * disclaimer/limitation of liability set forth as paragraph 6 below.
026: *
027: * Redistributions in binary form must reproduce this Copyright Notice,
028: * these license terms, and the disclaimer/limitation of liability set
029: * forth as paragraph 6 below, in the documentation and/or other materials
030: * provided with the distribution.
031: *
032: * The Software is provided on an "AS IS" basis. No warranty is
033: * provided that the Software is free of defects, or fit for a
034: * particular purpose.
035: *
036: * Limitation of Liability. Quadcap Software shall not be liable
037: * for any damages suffered by the Licensee or any third party resulting
038: * from use of the Software.
039: */
040:
041: /**
042: * This interface models a page of data in a block file, either a main page
043: * (aka a Block) or a sub-page.
044: *
045: * @author Stan Bailes
046: */
047: public interface Page {
048: /**
049: * Return this page's block number
050: */
051: public long getPageNum();
052:
053: /**
054: * An artifact of the Cacheable interface implemented by the Block
055: * class, we need to keep track of which objects are actually being
056: * used so unused objects can be flushed from the cache to make room
057: * for new objects. At some point, we can get rid of this in favor
058: * of weak references.
059: */
060: public void decrRefCount();
061:
062: /**
063: * Read a range of bytes from the page.
064: *
065: * @param pos the offset in the page of the first byte to read
066: * @param pbuf the buffer into which the bytes are placed.
067: * @param offset the offset in <code>pbuf</code> where the first byte
068: * is placed.
069: * @param len the number of bytes to read
070: */
071: public int read(int pos, byte[] pbuf, int offset, int len);
072:
073: /**
074: * Write a range of bytes to the page.
075: *
076: * @param pos the offset in the page of the first byte to write
077: * @param pbuf the buffer from which the bytes are obtained
078: * @param offset the offset in <code>pbuf</code> of the first byte
079: * to write
080: * @param len the number of bytes to write
081: */
082: public int write(int pos, byte[] pbuf, int offset, int len);
083:
084: /**
085: * Read an integer (4-byte) value from the page.
086: *
087: * @param pos the offset in the page of the integer.
088: */
089: public int readInt(int pos);
090:
091: /**
092: * Write an integer (4-byte) value to the page.
093: *
094: * @param pos the offset in the page of the integer.
095: * @param val the integer value to write.
096: */
097: public void writeInt(int pos, int val);
098:
099: /**
100: * Read an long (8-byte) value from the page.
101: *
102: * @param pos the offset in the page of the long.
103: */
104: public long readLong(int pos);
105:
106: /**
107: * Write an long (8-byte) value to the page.
108: *
109: * @param pos the offset in the page of the long.
110: * @param val the long value to write.
111: */
112: public void writeLong(int pos, long val);
113:
114: /**
115: * Move the contents of the other page to this page, and zero out
116: * the other page.
117: */
118: public void takeData(Page p);
119:
120: /**
121: * Zero this page
122: */
123: public void clear();
124:
125: }
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