Source Code Cross Referenced for NIOFileAdapter.java in  » Database-DBMS » db4o-6.4 » com » db4o » util » io » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Database DBMS » db4o 6.4 » com.db4o.util.io 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /* Copyright (C) 2004 - 2007  db4objects Inc.  http://www.db4o.com
002:
003:        This file is part of the db4o open source object database.
004:
005:        db4o is free software; you can redistribute it and/or modify it under
006:        the terms of version 2 of the GNU General Public License as published
007:        by the Free Software Foundation and as clarified by db4objects' GPL 
008:        interpretation policy, available at
009:        http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
010:        Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
011:        Suite 350, San Mateo, CA 94403, USA.
012:
013:        db4o is distributed in the hope that it will be useful, but WITHOUT ANY
014:        WARRANTY; without even the implied warranty of MERCHANTABILITY or
015:        FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
016:        for more details.
017:
018:        You should have received a copy of the GNU General Public License along
019:        with this program; if not, write to the Free Software Foundation, Inc.,
020:        59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
021:        package com.db4o.util.io;
022:
023:        import java.io.*;
024:        import java.lang.reflect.*;
025:        import java.nio.*;
026:        import java.nio.channels.*;
027:        import java.util.*;
028:
029:        import sun.nio.ch.*;
030:
031:        import com.db4o.*;
032:        import com.db4o.io.*;
033:
034:        public class NIOFileAdapter extends IoAdapter {
035:            private int hits = 0;
036:            private int misses = 0;
037:
038:            private int _pageSize;
039:            private FileChannel _channel;
040:            private MappedByteBuffer _page;
041:            private int _pageId;
042:            private long _position;
043:            private long _size;
044:            private boolean _dirty;
045:            private Map _id2Page;
046:            private LinkedList _lruPages;
047:            private int _lruLimit;
048:            private RandomAccessFile _file;
049:
050:            public NIOFileAdapter(int pageSize, int lruLimit) {
051:                _pageSize = pageSize;
052:                _lruLimit = lruLimit;
053:            }
054:
055:            private NIOFileAdapter(String filename, boolean lockFile,
056:                    long initialLength, boolean readOnly, int pageSize,
057:                    int lruLimit) throws Db4oIOException {
058:                _pageSize = pageSize;
059:                try {
060:                    _file = new RandomAccessFile(filename, readOnly ? "r"
061:                            : "rw");
062:                    _channel = _file.getChannel();
063:                    _size = _channel.size();
064:                } catch (IOException e) {
065:                    throw new Db4oIOException(e);
066:                }
067:                _page = null;
068:                _pageId = 0;
069:                _position = 0;
070:                _dirty = false;
071:                _id2Page = new HashMap();
072:                _lruPages = new LinkedList();
073:                _lruLimit = lruLimit;
074:            }
075:
076:            public void seek(long position) throws Db4oIOException {
077:                _position = position;
078:            }
079:
080:            public void close() throws Db4oIOException {
081:                for (Iterator pageiter = _id2Page.values().iterator(); pageiter
082:                        .hasNext();) {
083:                    MappedByteBuffer curpage = (MappedByteBuffer) pageiter
084:                            .next();
085:                    closePage(curpage);
086:                }
087:                _id2Page.clear();
088:                _lruPages.clear();
089:                _page = null;
090:                try {
091:                    _channel.close();
092:                    _file.close();
093:                } catch (IOException e) {
094:                    throw new Db4oIOException(e);
095:                }
096:                // System.err.println("Hits: "+hits+", Misses: "+misses);
097:            }
098:
099:            public void delete(String path) {
100:                new File(path).delete();
101:            }
102:
103:            public boolean exists(String path) {
104:                File existingFile = new File(path);
105:                return existingFile.exists() && existingFile.length() > 0;
106:            }
107:
108:            public long getLength() throws Db4oIOException {
109:                return _size;
110:            }
111:
112:            public int read(byte[] bytes, int length) throws Db4oIOException {
113:                if (length <= 0) {
114:                    return 0;
115:                }
116:                int alreadyRead = 0;
117:                int stillToRead = length;
118:                while (stillToRead > 0) {
119:                    forcePage();
120:                    try {
121:                        _page.position(pageOffset(_position));
122:                    } catch (IllegalArgumentException exc) {
123:                        return -1;
124:                    }
125:                    int hereToRead = (int) min(
126:                            _page.limit() - _page.position(), stillToRead);
127:                    if (hereToRead == 0) {
128:                        break;
129:                    }
130:                    _page.get(bytes, alreadyRead, hereToRead);
131:                    stillToRead -= hereToRead;
132:                    alreadyRead += hereToRead;
133:                    _position += hereToRead;
134:                }
135:                return (alreadyRead > 0 ? alreadyRead : -1);
136:            }
137:
138:            public void write(byte[] bytes, int length) throws Db4oIOException {
139:                if (length <= 0) {
140:                    return;
141:                }
142:                if (_position + length > _size) {
143:                    _size = _position + length;
144:                }
145:                int alreadyWritten = 0;
146:                int stillToWrite = length;
147:                while (stillToWrite > 0) {
148:                    forcePage();
149:                    int pageOffset = pageOffset(_position);
150:                    _page.limit((int) min(_pageSize, pageOffset + length));
151:                    _page.position(pageOffset);
152:                    int hereToWrite = (int) min(_page.capacity()
153:                            - _page.position(), stillToWrite);
154:                    _page.put(bytes, alreadyWritten, hereToWrite);
155:                    stillToWrite -= hereToWrite;
156:                    alreadyWritten += hereToWrite;
157:                    _position += hereToWrite;
158:                    _dirty = true;
159:                }
160:            }
161:
162:            public void sync() throws Db4oIOException {
163:                // FIXME internalSync(_page);
164:            }
165:
166:            private void internalSync(MappedByteBuffer page) {
167:                if (_dirty && page != null) {
168:                    page.flip();
169:                    page.force();
170:                }
171:            }
172:
173:            public void unlock() {
174:            }
175:
176:            public void lock() {
177:            }
178:
179:            private MappedByteBuffer page(int pageId) throws Db4oIOException {
180:                MappedByteBuffer page;
181:                try {
182:                    page = _channel.map(FileChannel.MapMode.READ_WRITE,
183:                            pagePosition(pageId), _pageSize);
184:                } catch (IOException e) {
185:                    throw new Db4oIOException(e);
186:                }
187:                page.limit(pageSize(pageId));
188:                return page;
189:            }
190:
191:            private long pagePosition(int pageId) {
192:                return (long) pageId * _pageSize;
193:            }
194:
195:            private int pageSize(int pageId) throws Db4oIOException {
196:                long sizeLeft = _size - pagePosition(pageId);
197:                return (sizeLeft > _pageSize ? _pageSize : (int) sizeLeft);
198:            }
199:
200:            private void forcePage() throws Db4oIOException {
201:                int pageId = pageId(_position);
202:                int pageOffset = pageOffset(_position);
203:                Integer pageIdKey = new Integer(pageId);
204:                if (_id2Page.containsKey(pageIdKey)) {
205:                    _lruPages.remove(pageIdKey);
206:                    _lruPages.addFirst(pageIdKey);
207:                    _page = (MappedByteBuffer) _id2Page.get(pageIdKey);
208:                    _page.limit(pageSize(pageId));
209:                    hits++;
210:                    return;
211:                }
212:                closePage();
213:                loadPage(pageId, pageOffset);
214:                if (_lruPages.size() == _lruLimit) {
215:                    Integer dropPageKey = (Integer) _lruPages.removeLast();
216:                    MappedByteBuffer page = (MappedByteBuffer) _id2Page
217:                            .remove(dropPageKey);
218:                    try {
219:                        Method unmap = FileChannelImpl.class
220:                                .getDeclaredMethod("unmap",
221:                                        new Class[] { MappedByteBuffer.class });
222:                        unmap.setAccessible(true);
223:                        unmap.invoke(null, new Object[] { page });
224:                    } catch (Exception exc) {
225:                        exc.printStackTrace();
226:                    }
227:                }
228:                Integer addedPageKey = new Integer(_pageId);
229:                _id2Page.put(addedPageKey, _page);
230:                _lruPages.addFirst(addedPageKey);
231:                _dirty = false;
232:                misses++;
233:            }
234:
235:            private void closePage() throws Db4oIOException {
236:                closePage(_page);
237:                _page = null;
238:            }
239:
240:            private void closePage(MappedByteBuffer page)
241:                    throws Db4oIOException {
242:                if (page != null) {
243:                    internalSync(page);
244:                }
245:            }
246:
247:            private void loadPage(int pageId, int pageOffset)
248:                    throws Db4oIOException {
249:                _page = page(pageId);
250:                _pageId = pageId;
251:                _dirty = false;
252:            }
253:
254:            private int pageId(long position) {
255:                return (int) (position / _pageSize);
256:            }
257:
258:            private int pageOffset(long position) {
259:                return (int) (position % _pageSize);
260:            }
261:
262:            private long min(long a, long b) {
263:                return (a > b ? b : a);
264:            }
265:
266:            public IoAdapter open(String path, boolean lockFile,
267:                    long initialLength, boolean readOnly)
268:                    throws Db4oIOException {
269:                return new NIOFileAdapter(path, lockFile, initialLength,
270:                        readOnly, _pageSize, _lruLimit);
271:            }
272:        }
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