Source Code Cross Referenced for UTF8ByteBufferReader.java in  » Science » javolution-5.2 » javolution » io » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Science » javolution 5.2 » javolution.io 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Javolution - Java(TM) Solution for Real-Time and Embedded Systems
003:         * Copyright (C) 2005 - Javolution (http://javolution.org/)
004:         * All rights reserved.
005:         * 
006:         * Permission to use, copy, modify, and distribute this software is
007:         * freely granted, provided that this notice is preserved.
008:         */
009:        package javolution.io;
010:
011:        import j2me.lang.IllegalStateException;
012:        import j2me.io.CharConversionException;
013:        import j2me.nio.BufferUnderflowException;
014:        import j2me.nio.ByteBuffer;
015:
016:        import java.io.IOException;
017:        import java.io.Reader;
018:
019:        import javolution.lang.Reusable;
020:        import javolution.text.Appendable;
021:
022:        /**
023:         * <p> This class represents a UTF-8 <code>j2me.nio.ByteBuffer</code> reader.
024:         *     </p>
025:         *
026:         * <p> This reader can be used for efficient decoding of native byte 
027:         *     buffers (e.g. <code>MappedByteBuffer</code>), high-performance 
028:         *     messaging (no intermediate buffer), etc.</p>
029:         *     
030:         * <p> This reader supports surrogate <code>char</code> pairs (representing
031:         *     characters in the range [U+10000 .. U+10FFFF]). It can also be used
032:         *     to read characters unicodes (31 bits) directly
033:         *     (ref. {@link #read()}).</p>
034:         *
035:         * <p> Each invocation of one of the <code>read()</code> methods may cause one
036:         *     or more bytes to be read from the underlying byte buffer.
037:         *     The end of stream is reached when the byte buffer position and limit
038:         *     coincide.</p>
039:         *
040:         * @author  <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
041:         * @version 2.0, December 9, 2004
042:         * @see     UTF8ByteBufferWriter
043:         */
044:        public final class UTF8ByteBufferReader extends Reader implements 
045:                Reusable {
046:
047:            /**
048:             * Holds the byte buffer source.
049:             */
050:            private ByteBuffer _byteBuffer;
051:
052:            /**
053:             * Default constructor.
054:             */
055:            public UTF8ByteBufferReader() {
056:            }
057:
058:            /**
059:             * Sets the <code>ByteBuffer</code> to use for reading available bytes
060:             * from current buffer position.
061:             *
062:             * @param  byteBuffer the <code>ByteBuffer</code> source.
063:             * @return this UTF-8 reader.
064:             * @throws IllegalStateException if this reader is being reused and 
065:             *         it has not been {@link #close closed} or {@link #reset reset}.
066:             */
067:            public UTF8ByteBufferReader setInput(ByteBuffer byteBuffer) {
068:                if (_byteBuffer != null)
069:                    throw new IllegalStateException(
070:                            "Reader not closed or reset");
071:                _byteBuffer = byteBuffer;
072:                return this ;
073:            }
074:
075:            /**
076:             * Indicates if this stream is ready to be read.
077:             *
078:             * @return <code>true</code> if the byte buffer has remaining bytes to 
079:             *         read; <code>false</code> otherwise.
080:             * @throws  IOException if an I/O error occurs.
081:             */
082:            public boolean ready() throws IOException {
083:                if (_byteBuffer != null) {
084:                    return _byteBuffer.hasRemaining();
085:                } else {
086:                    throw new IOException("Reader closed");
087:                }
088:            }
089:
090:            /**
091:             * Closes and {@link #reset resets} this reader for reuse.
092:             *
093:             * @throws IOException if an I/O error occurs.
094:             */
095:            public void close() throws IOException {
096:                if (_byteBuffer != null) {
097:                    reset();
098:                }
099:            }
100:
101:            /**
102:             * Reads a single character.  This method does not block, <code>-1</code>
103:             * is returned if the buffer's limit has been reached.
104:             *
105:             * @return the 31-bits Unicode of the character read, or -1 if there is 
106:             *         no more remaining bytes to be read.
107:             * @throws IOException if an I/O error occurs (e.g. incomplete 
108:             *         character sequence being read).
109:             */
110:            public int read() throws IOException {
111:                if (_byteBuffer != null) {
112:                    if (_byteBuffer.hasRemaining()) {
113:                        byte b = _byteBuffer.get();
114:                        return (b >= 0) ? b : read2(b);
115:                    } else {
116:                        return -1;
117:                    }
118:                } else {
119:                    throw new IOException("Reader closed");
120:                }
121:            }
122:
123:            // Reads one full character, throws CharConversionException if limit reached.
124:            private int read2(byte b) throws IOException {
125:                try {
126:                    // Decodes UTF-8.
127:                    if ((b >= 0) && (_moreBytes == 0)) {
128:                        // 0xxxxxxx
129:                        return b;
130:                    } else if (((b & 0xc0) == 0x80) && (_moreBytes != 0)) {
131:                        // 10xxxxxx (continuation byte)
132:                        _code = (_code << 6) | (b & 0x3f); // Adds 6 bits to code.
133:                        if (--_moreBytes == 0) {
134:                            return _code;
135:                        } else {
136:                            return read2(_byteBuffer.get());
137:                        }
138:                    } else if (((b & 0xe0) == 0xc0) && (_moreBytes == 0)) {
139:                        // 110xxxxx
140:                        _code = b & 0x1f;
141:                        _moreBytes = 1;
142:                        return read2(_byteBuffer.get());
143:                    } else if (((b & 0xf0) == 0xe0) && (_moreBytes == 0)) {
144:                        // 1110xxxx
145:                        _code = b & 0x0f;
146:                        _moreBytes = 2;
147:                        return read2(_byteBuffer.get());
148:                    } else if (((b & 0xf8) == 0xf0) && (_moreBytes == 0)) {
149:                        // 11110xxx
150:                        _code = b & 0x07;
151:                        _moreBytes = 3;
152:                        return read2(_byteBuffer.get());
153:                    } else if (((b & 0xfc) == 0xf8) && (_moreBytes == 0)) {
154:                        // 111110xx
155:                        _code = b & 0x03;
156:                        _moreBytes = 4;
157:                        return read2(_byteBuffer.get());
158:                    } else if (((b & 0xfe) == 0xfc) && (_moreBytes == 0)) {
159:                        // 1111110x
160:                        _code = b & 0x01;
161:                        _moreBytes = 5;
162:                        return read2(_byteBuffer.get());
163:                    } else {
164:                        throw new CharConversionException(
165:                                "Invalid UTF-8 Encoding");
166:                    }
167:                } catch (BufferUnderflowException e) {
168:                    throw new CharConversionException("Incomplete Sequence");
169:                }
170:            }
171:
172:            private int _code;
173:
174:            private int _moreBytes;
175:
176:            /**
177:             * Reads characters into a portion of an array.  This method does not 
178:             * block.
179:             *
180:             * <p> Note: Characters between U+10000 and U+10FFFF are represented
181:             *     by surrogate pairs (two <code>char</code>).</p>
182:             *
183:             * @param  cbuf the destination buffer.
184:             * @param  off the offset at which to start storing characters.
185:             * @param  len the maximum number of characters to read
186:             * @return the number of characters read, or -1 if there is no more 
187:             *         byte remaining.
188:             * @throws IOException if an I/O error occurs.
189:             */
190:            public int read(char cbuf[], int off, int len) throws IOException {
191:                if (_byteBuffer == null)
192:                    throw new IOException("Reader closed");
193:                final int off_plus_len = off + len;
194:                int remaining = _byteBuffer.remaining();
195:                if (remaining <= 0)
196:                    return -1;
197:                for (int i = off; i < off_plus_len;) {
198:                    if (remaining-- > 0) {
199:                        byte b = _byteBuffer.get();
200:                        if (b >= 0) {
201:                            cbuf[i++] = (char) b; // Most common case.
202:                        } else {
203:                            if (i < off_plus_len - 1) { // Up to two 'char' can be read.
204:                                int code = read2(b);
205:                                remaining = _byteBuffer.remaining(); // Recalculates.
206:                                if (code < 0x10000) {
207:                                    cbuf[i++] = (char) code;
208:                                } else if (code <= 0x10ffff) { // Surrogates.
209:                                    cbuf[i++] = (char) (((code - 0x10000) >> 10) + 0xd800);
210:                                    cbuf[i++] = (char) (((code - 0x10000) & 0x3ff) + 0xdc00);
211:                                } else {
212:                                    throw new CharConversionException(
213:                                            "Cannot convert U+"
214:                                                    + Integer.toHexString(code)
215:                                                    + " to char (code greater than U+10FFFF)");
216:                                }
217:                            } else { // Not enough space in destination (go back).
218:                                _byteBuffer
219:                                        .position(_byteBuffer.position() - 1);
220:                                remaining++;
221:                                return i - off;
222:                            }
223:                        }
224:                    } else {
225:                        return i - off;
226:                    }
227:                }
228:                return len;
229:            }
230:
231:            /**
232:             * Reads characters into the specified appendable. This method does not 
233:             * block.
234:             *
235:             * <p> Note: Characters between U+10000 and U+10FFFF are represented
236:             *     by surrogate pairs (two <code>char</code>).</p>
237:             *
238:             * @param  dest the destination buffer.
239:             * @throws IOException if an I/O error occurs.
240:             */
241:            public void read(Appendable dest) throws IOException {
242:                if (_byteBuffer == null)
243:                    throw new IOException("Reader closed");
244:                while (_byteBuffer.hasRemaining()) {
245:                    byte b = _byteBuffer.get();
246:                    if (b >= 0) {
247:                        dest.append((char) b); // Most common case.
248:                    } else {
249:                        int code = read2(b);
250:                        if (code < 0x10000) {
251:                            dest.append((char) code);
252:                        } else if (code <= 0x10ffff) { // Surrogates.
253:                            dest
254:                                    .append((char) (((code - 0x10000) >> 10) + 0xd800));
255:                            dest
256:                                    .append((char) (((code - 0x10000) & 0x3ff) + 0xdc00));
257:                        } else {
258:                            throw new CharConversionException(
259:                                    "Cannot convert U+"
260:                                            + Integer.toHexString(code)
261:                                            + " to char (code greater than U+10FFFF)");
262:                        }
263:                    }
264:                }
265:            }
266:
267:            // Implements Reusable.
268:            public void reset() {
269:                _byteBuffer = null;
270:                _code = 0;
271:                _moreBytes = 0;
272:            }
273:
274:            /**
275:             * @deprecated Replaced by {@link #setInput(ByteBuffer)}
276:             */
277:            public UTF8ByteBufferReader setByteBuffer(ByteBuffer byteBuffer) {
278:                return this.setInput(byteBuffer);
279:            }
280:
281:        }
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