Source Code Cross Referenced for BufferedRandomAccess.java in  » PDF » jPod » de » intarsys » tools » randomaccess » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » PDF » jPod » de.intarsys.tools.randomaccess 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright (c) 2007, intarsys consulting GmbH
003:         *
004:         * Redistribution and use in source and binary forms, with or without
005:         * modification, are permitted provided that the following conditions are met:
006:         *
007:         * - Redistributions of source code must retain the above copyright notice,
008:         *   this list of conditions and the following disclaimer.
009:         *
010:         * - Redistributions in binary form must reproduce the above copyright notice,
011:         *   this list of conditions and the following disclaimer in the documentation
012:         *   and/or other materials provided with the distribution.
013:         *
014:         * - Neither the name of intarsys nor the names of its contributors may be used
015:         *   to endorse or promote products derived from this software without specific
016:         *   prior written permission.
017:         *
018:         * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
019:         * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
020:         * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
021:         * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
022:         * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
023:         * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
024:         * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
025:         * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
026:         * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
027:         * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
028:         * POSSIBILITY OF SUCH DAMAGE.
029:         */
030:        package de.intarsys.tools.randomaccess;
031:
032:        import java.io.IOException;
033:
034:        /**
035:         * todo 1 length reply may be invalid
036:         */
037:        public class BufferedRandomAccess extends AbstractRandomAccess {
038:            private static int DEFAULT_BUFFER_SIZE = 4096;
039:
040:            /**
041:             * The buffer for the delegates data
042:             */
043:            private byte[] bytes;
044:
045:            /**
046:             * The relative index of the buffer's first byte in the delegates data
047:             */
048:            private long bytesOffset = 0;
049:
050:            /**
051:             * The number of valid bytes in the buffer
052:             */
053:            private int count = 0;
054:
055:            /**
056:             * The index into the buffer indicating the current byte
057:             */
058:            private int localOffset = 0;
059:
060:            /**
061:             * The buffered random access delegate
062:             */
063:            private IRandomAccess randomAccess;
064:
065:            /**
066:             * The total offset in the delegates data.
067:             * <p>
068:             * totalOffset = bufferOffset + localOffset; or count == 0 (invalid/empty
069:             * buffer);
070:             * 
071:             */
072:            private long totalOffset = 0;
073:
074:            private boolean closed = false;
075:
076:            /**
077:             * The length of the random access data
078:             */
079:            private long length;
080:
081:            /**
082:             * Flag if data in the buffer is currently changed.
083:             */
084:            private boolean bufferChanged = false;
085:
086:            public BufferedRandomAccess(IRandomAccess randomAccess)
087:                    throws IOException {
088:                this (randomAccess, DEFAULT_BUFFER_SIZE);
089:            }
090:
091:            public BufferedRandomAccess(IRandomAccess randomAccess,
092:                    int bufferSize) throws IOException {
093:                this .randomAccess = randomAccess;
094:                this .bytes = new byte[bufferSize];
095:                this .length = randomAccess.getLength();
096:            }
097:
098:            protected int basicRead(byte[] buffer, int start, int numBytes)
099:                    throws IOException {
100:                if (localOffset >= count) {
101:                    if (numBytes >= bytes.length) {
102:                        flushBuffer();
103:                        randomAccess.seek(totalOffset);
104:                        int readBytes = randomAccess.read(buffer, start,
105:                                numBytes);
106:                        if (readBytes > 0) {
107:                            totalOffset += readBytes;
108:                            localOffset = count;
109:                        }
110:                        return readBytes;
111:                    } else {
112:                        fillBuffer();
113:                        if (localOffset >= count) {
114:                            return -1;
115:                        }
116:                    }
117:                }
118:                int avail = count - localOffset;
119:                int cnt = (avail < numBytes) ? avail : numBytes;
120:                System.arraycopy(bytes, localOffset, buffer, start, cnt);
121:                localOffset += cnt;
122:                totalOffset += cnt;
123:                return cnt;
124:            }
125:
126:            /*
127:             * (non-Javadoc)
128:             * 
129:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#close()
130:             */
131:            public void close() throws IOException {
132:                if (isClosed()) {
133:                    return;
134:                }
135:                flushBuffer();
136:                randomAccess.close();
137:                setClosed(true);
138:            }
139:
140:            /*
141:             * (non-Javadoc)
142:             * 
143:             * @see de.intarsys.tools.randomaccess.IRandomAccess#flush()
144:             */
145:            public void flush() throws IOException {
146:                if (isClosed()) {
147:                    throw new IOException("random access closed");
148:                }
149:                flushBuffer();
150:                randomAccess.flush();
151:            }
152:
153:            protected void fillBuffer() throws IOException {
154:                flushBuffer();
155:                randomAccess.seek(totalOffset);
156:                count = randomAccess.read(bytes, 0, bytes.length);
157:            }
158:
159:            protected void flushBuffer() throws IOException {
160:                if (bufferChanged && (count > 0)) {
161:                    randomAccess.seek(bytesOffset);
162:                    randomAccess.write(bytes, 0, count);
163:                }
164:                bytesOffset = totalOffset;
165:                localOffset = 0;
166:                count = 0;
167:                bufferChanged = false;
168:            }
169:
170:            /*
171:             * (non-Javadoc)
172:             * 
173:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#getLength()
174:             */
175:            public long getLength() throws IOException {
176:                if (isClosed()) {
177:                    throw new IOException("random access closed");
178:                }
179:                return length;
180:            }
181:
182:            /*
183:             * (non-Javadoc)
184:             * 
185:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#getOffset()
186:             */
187:            public long getOffset() throws IOException {
188:                if (isClosed()) {
189:                    throw new IOException("random access closed");
190:                }
191:                return totalOffset;
192:            }
193:
194:            /*
195:             * (non-Javadoc)
196:             * 
197:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#isReadOnly()
198:             */
199:            public boolean isReadOnly() {
200:                return randomAccess.isReadOnly();
201:            }
202:
203:            /*
204:             * (non-Javadoc)
205:             * 
206:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#read()
207:             */
208:            public int read() throws IOException {
209:                if (isClosed()) {
210:                    throw new IOException("random access closed");
211:                }
212:                if (localOffset >= count) {
213:                    fillBuffer();
214:                    if (localOffset >= count) {
215:                        return -1;
216:                    }
217:                }
218:                totalOffset++;
219:                return bytes[localOffset++] & 0xff;
220:            }
221:
222:            /*
223:             * (non-Javadoc)
224:             * 
225:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#read(byte[])
226:             */
227:            public int read(byte[] buffer) throws IOException {
228:                if (isClosed()) {
229:                    throw new IOException("random access closed");
230:                }
231:                return read(buffer, 0, buffer.length);
232:            }
233:
234:            /*
235:             * (non-Javadoc)
236:             * 
237:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#read(byte[], int,
238:             *      int)
239:             */
240:            public int read(byte[] buffer, int start, int numBytes)
241:                    throws IOException {
242:                if (isClosed()) {
243:                    throw new IOException("random access closed");
244:                }
245:                if (numBytes == 0) {
246:                    return 0;
247:                }
248:                int totalByteCount = 0;
249:                while (totalByteCount < numBytes) {
250:                    int byteCount = basicRead(buffer, start + totalByteCount,
251:                            numBytes - totalByteCount);
252:                    if (byteCount <= 0) {
253:                        break;
254:                    }
255:                    totalByteCount += byteCount;
256:                }
257:                if (totalByteCount == 0) {
258:                    return -1;
259:                }
260:                return totalByteCount;
261:            }
262:
263:            /*
264:             * (non-Javadoc)
265:             * 
266:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#seek(long)
267:             */
268:            public void seek(long offset) throws IOException {
269:                if (isClosed()) {
270:                    throw new IOException("random access closed");
271:                }
272:                totalOffset = offset;
273:                long newLocalOffset = totalOffset - bytesOffset;
274:                if ((newLocalOffset < 0) || (newLocalOffset >= count)) {
275:                    flushBuffer();
276:                } else {
277:                    localOffset = (int) newLocalOffset;
278:                }
279:            }
280:
281:            public void seekBy(long delta) throws IOException {
282:                if (isClosed()) {
283:                    throw new IOException("random access closed");
284:                }
285:                totalOffset += delta;
286:                long newLocalOffset = localOffset + delta;
287:                if ((newLocalOffset < 0) || (newLocalOffset >= count)) {
288:                    flushBuffer();
289:                } else {
290:                    localOffset = (int) newLocalOffset;
291:                }
292:            }
293:
294:            /*
295:             * (non-Javadoc)
296:             * 
297:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#setLength(int)
298:             */
299:            public void setLength(long newLength) throws IOException {
300:                if (isClosed()) {
301:                    throw new IOException("random access closed");
302:                }
303:                if (newLength < (bytesOffset + bytes.length)) {
304:                    flushBuffer();
305:                }
306:                if (newLength < totalOffset) {
307:                    totalOffset = newLength;
308:                    bytesOffset = newLength;
309:                }
310:                length = newLength;
311:                randomAccess.setLength(newLength);
312:            }
313:
314:            /*
315:             * (non-Javadoc)
316:             * 
317:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#write(byte[])
318:             */
319:            public void write(byte[] buffer) throws IOException {
320:                if (isClosed()) {
321:                    throw new IOException("random access closed");
322:                }
323:                write(buffer, 0, buffer.length);
324:            }
325:
326:            /*
327:             * (non-Javadoc)
328:             * 
329:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#write(byte[], int,
330:             *      int)
331:             */
332:            public void write(byte[] buffer, int start, int numBytes)
333:                    throws IOException {
334:                if (isClosed()) {
335:                    throw new IOException("random access closed");
336:                }
337:                if (numBytes >= bytes.length) {
338:                    // greater than local buffer size -> write directly
339:                    flushBuffer();
340:                    randomAccess.seek(totalOffset);
341:                    randomAccess.write(buffer, start, numBytes);
342:                    totalOffset += numBytes;
343:                    bytesOffset = totalOffset;
344:                    if (totalOffset > length) {
345:                        length = totalOffset;
346:                    }
347:                    return;
348:                }
349:                if (numBytes > (bytes.length - localOffset)) {
350:                    // greater than rest of buffer -> flush and fill new one
351:                    flushBuffer();
352:                }
353:                System.arraycopy(buffer, start, bytes, localOffset, numBytes);
354:                bufferChanged = true;
355:                totalOffset += numBytes;
356:                localOffset += numBytes;
357:                if (totalOffset > length) {
358:                    length = totalOffset;
359:                }
360:                if (localOffset >= count) {
361:                    count = localOffset;
362:                }
363:            }
364:
365:            /*
366:             * (non-Javadoc)
367:             * 
368:             * @see de.intarsys.tools.randomaccess.IRandomAccessData#write(int)
369:             */
370:            public void write(int b) throws IOException {
371:                if (isClosed()) {
372:                    throw new IOException("random access closed");
373:                }
374:                if (localOffset >= bytes.length) {
375:                    flushBuffer();
376:                }
377:                bufferChanged = true;
378:                if (localOffset == count) {
379:                    count++;
380:                }
381:                totalOffset++;
382:                if (totalOffset > length) {
383:                    length = totalOffset;
384:                }
385:                bytes[localOffset++] = (byte) b;
386:            }
387:
388:            protected boolean isClosed() {
389:                return closed;
390:            }
391:
392:            protected void setClosed(boolean closed) {
393:                this.closed = closed;
394:            }
395:        }
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