Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.io.InputStream; import java.io.IOException; import java.io.Reader; import java.io.UTFDataFormatException; /** * @author Andy Clark, IBM * * @version $Id: UTF8Reader.java 515 2008-03-17 21:02:23Z jfrederic.clere@jboss.com $ */ public class UTF8Reader extends Reader { // // Constants // /** Default byte buffer size (2048). */ public static final int DEFAULT_BUFFER_SIZE = 2048; // debugging /** Debug read. */ private static final boolean DEBUG_READ = false; // // Data // /** Input stream. */ protected InputStream fInputStream; /** Byte buffer. */ protected byte[] fBuffer; /** Offset into buffer. */ protected int fOffset; /** Surrogate character. */ private int fSurrogate = -1; // // Constructors // /** * Constructs a UTF-8 reader from the specified input stream, * buffer size and MessageFormatter. * * @param inputStream The input stream. * @param size The initial buffer size. */ public UTF8Reader(InputStream inputStream, int size) { fInputStream = inputStream; fBuffer = new byte[size]; } // // Reader methods // /** * Read a single character. This method will block until a character is * available, an I/O error occurs, or the end of the stream is reached. * * Subclasses that intend to support efficient single-character input * should override this method. * * @return The character read, as an integer in the range 0 to 16383 * (<tt>0x00-0xffff</tt>), or -1 if the end of the stream has * been reached * * @exception IOException If an I/O error occurs */ public int read() throws IOException { // decode character int c = fSurrogate; if (fSurrogate == -1) { // NOTE: We use the index into the buffer if there are remaining // bytes from the last block read. -Ac int index = 0; // get first byte int b0 = index == fOffset ? fInputStream.read() : fBuffer[index++] & 0x00FF; if (b0 == -1) { return -1; } // UTF-8: [0xxx xxxx] // Unicode: [0000 0000] [0xxx xxxx] if (b0 < 0x80) { c = (char) b0; } // UTF-8: [110y yyyy] [10xx xxxx] // Unicode: [0000 0yyy] [yyxx xxxx] else if ((b0 & 0xE0) == 0xC0) { int b1 = index == fOffset ? fInputStream.read() : fBuffer[index++] & 0x00FF; if (b1 == -1) { expectedByte(2, 2); } if ((b1 & 0xC0) != 0x80) { invalidByte(2, 2, b1); } c = ((b0 << 6) & 0x07C0) | (b1 & 0x003F); } // UTF-8: [1110 zzzz] [10yy yyyy] [10xx xxxx] // Unicode: [zzzz yyyy] [yyxx xxxx] else if ((b0 & 0xF0) == 0xE0) { int b1 = index == fOffset ? fInputStream.read() : fBuffer[index++] & 0x00FF; if (b1 == -1) { expectedByte(2, 3); } if ((b1 & 0xC0) != 0x80) { invalidByte(2, 3, b1); } int b2 = index == fOffset ? fInputStream.read() : fBuffer[index++] & 0x00FF; if (b2 == -1) { expectedByte(3, 3); } if ((b2 & 0xC0) != 0x80) { invalidByte(3, 3, b2); } c = ((b0 << 12) & 0xF000) | ((b1 << 6) & 0x0FC0) | (b2 & 0x003F); } // UTF-8: [1111 0uuu] [10uu zzzz] [10yy yyyy] [10xx xxxx]* // Unicode: [1101 10ww] [wwzz zzyy] (high surrogate) // [1101 11yy] [yyxx xxxx] (low surrogate) // * uuuuu = wwww + 1 else if ((b0 & 0xF8) == 0xF0) { int b1 = index == fOffset ? fInputStream.read() : fBuffer[index++] & 0x00FF; if (b1 == -1) { expectedByte(2, 4); } if ((b1 & 0xC0) != 0x80) { invalidByte(2, 3, b1); } int b2 = index == fOffset ? fInputStream.read() : fBuffer[index++] & 0x00FF; if (b2 == -1) { expectedByte(3, 4); } if ((b2 & 0xC0) != 0x80) { invalidByte(3, 3, b2); } int b3 = index == fOffset ? fInputStream.read() : fBuffer[index++] & 0x00FF; if (b3 == -1) { expectedByte(4, 4); } if ((b3 & 0xC0) != 0x80) { invalidByte(4, 4, b3); } int uuuuu = ((b0 << 2) & 0x001C) | ((b1 >> 4) & 0x0003); if (uuuuu > 0x10) { invalidSurrogate(uuuuu); } int wwww = uuuuu - 1; int hs = 0xD800 | ((wwww << 6) & 0x03C0) | ((b1 << 2) & 0x003C) | ((b2 >> 4) & 0x0003); int ls = 0xDC00 | ((b2 << 6) & 0x03C0) | (b3 & 0x003F); c = hs; fSurrogate = ls; } // error else { invalidByte(1, 1, b0); } } // use surrogate else { fSurrogate = -1; } return c; } // read():int /** * Read characters into a portion of an array. This method will block * until some input is available, an I/O error occurs, or the end of the * stream is reached. * * @param ch Destination buffer * @param offset Offset at which to start storing characters * @param length Maximum number of characters to read * * @return The number of characters read, or -1 if the end of the * stream has been reached * * @exception IOException If an I/O error occurs */ public int read(char ch[], int offset, int length) throws IOException { // handle surrogate int out = offset; if (fSurrogate != -1) { ch[offset + 1] = (char) fSurrogate; fSurrogate = -1; length--; out++; } // read bytes int count = 0; if (fOffset == 0) { // adjust length to read if (length > fBuffer.length) { length = fBuffer.length; } // perform read operation count = fInputStream.read(fBuffer, 0, length); if (count == -1) { return -1; } count += out - offset; } // skip read; last character was in error // NOTE: Having an offset value other than zero means that there was // an error in the last character read. In this case, we have // skipped the read so we don't consume any bytes past the // error. By signalling the error on the next block read we // allow the method to return the most valid characters that // it can on the previous block read. -Ac else { count = fOffset; fOffset = 0; } // convert bytes to characters final int total = count; for (int in = 0; in < total; in++) { int b0 = fBuffer[in] & 0x00FF; // UTF-8: [0xxx xxxx] // Unicode: [0000 0000] [0xxx xxxx] if (b0 < 0x80) { ch[out++] = (char) b0; continue; } // UTF-8: [110y yyyy] [10xx xxxx] // Unicode: [0000 0yyy] [yyxx xxxx] if ((b0 & 0xE0) == 0xC0) { int b1 = -1; if (++in < total) { b1 = fBuffer[in] & 0x00FF; } else { b1 = fInputStream.read(); if (b1 == -1) { if (out > offset) { fBuffer[0] = (byte) b0; fOffset = 1; return out - offset; } expectedByte(2, 2); } count++; } if ((b1 & 0xC0) != 0x80) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fOffset = 2; return out - offset; } invalidByte(2, 2, b1); } int c = ((b0 << 6) & 0x07C0) | (b1 & 0x003F); ch[out++] = (char) c; count -= 1; continue; } // UTF-8: [1110 zzzz] [10yy yyyy] [10xx xxxx] // Unicode: [zzzz yyyy] [yyxx xxxx] if ((b0 & 0xF0) == 0xE0) { int b1 = -1; if (++in < total) { b1 = fBuffer[in] & 0x00FF; } else { b1 = fInputStream.read(); if (b1 == -1) { if (out > offset) { fBuffer[0] = (byte) b0; fOffset = 1; return out - offset; } expectedByte(2, 3); } count++; } if ((b1 & 0xC0) != 0x80) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fOffset = 2; return out - offset; } invalidByte(2, 3, b1); } int b2 = -1; if (++in < total) { b2 = fBuffer[in] & 0x00FF; } else { b2 = fInputStream.read(); if (b2 == -1) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fOffset = 2; return out - offset; } expectedByte(3, 3); } count++; } if ((b2 & 0xC0) != 0x80) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fBuffer[2] = (byte) b2; fOffset = 3; return out - offset; } invalidByte(3, 3, b2); } int c = ((b0 << 12) & 0xF000) | ((b1 << 6) & 0x0FC0) | (b2 & 0x003F); ch[out++] = (char) c; count -= 2; continue; } // UTF-8: [1111 0uuu] [10uu zzzz] [10yy yyyy] [10xx xxxx]* // Unicode: [1101 10ww] [wwzz zzyy] (high surrogate) // [1101 11yy] [yyxx xxxx] (low surrogate) // * uuuuu = wwww + 1 if ((b0 & 0xF8) == 0xF0) { int b1 = -1; if (++in < total) { b1 = fBuffer[in] & 0x00FF; } else { b1 = fInputStream.read(); if (b1 == -1) { if (out > offset) { fBuffer[0] = (byte) b0; fOffset = 1; return out - offset; } expectedByte(2, 4); } count++; } if ((b1 & 0xC0) != 0x80) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fOffset = 2; return out - offset; } invalidByte(2, 4, b1); } int b2 = -1; if (++in < total) { b2 = fBuffer[in] & 0x00FF; } else { b2 = fInputStream.read(); if (b2 == -1) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fOffset = 2; return out - offset; } expectedByte(3, 4); } count++; } if ((b2 & 0xC0) != 0x80) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fBuffer[2] = (byte) b2; fOffset = 3; return out - offset; } invalidByte(3, 4, b2); } int b3 = -1; if (++in < total) { b3 = fBuffer[in] & 0x00FF; } else { b3 = fInputStream.read(); if (b3 == -1) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fBuffer[2] = (byte) b2; fOffset = 3; return out - offset; } expectedByte(4, 4); } count++; } if ((b3 & 0xC0) != 0x80) { if (out > offset) { fBuffer[0] = (byte) b0; fBuffer[1] = (byte) b1; fBuffer[2] = (byte) b2; fBuffer[3] = (byte) b3; fOffset = 4; return out - offset; } invalidByte(4, 4, b2); } // decode bytes into surrogate characters int uuuuu = ((b0 << 2) & 0x001C) | ((b1 >> 4) & 0x0003); if (uuuuu > 0x10) { invalidSurrogate(uuuuu); } int wwww = uuuuu - 1; int zzzz = b1 & 0x000F; int yyyyyy = b2 & 0x003F; int xxxxxx = b3 & 0x003F; int hs = 0xD800 | ((wwww << 6) & 0x03C0) | (zzzz << 2) | (yyyyyy >> 4); int ls = 0xDC00 | ((yyyyyy << 6) & 0x03C0) | xxxxxx; // set characters ch[out++] = (char) hs; ch[out++] = (char) ls; count -= 2; continue; } // error if (out > offset) { fBuffer[0] = (byte) b0; fOffset = 1; return out - offset; } invalidByte(1, 1, b0); } return count; } // read(char[],int,int) /** * Skip characters. This method will block until some characters are * available, an I/O error occurs, or the end of the stream is reached. * * @param n The number of characters to skip * * @return The number of characters actually skipped * * @exception IOException If an I/O error occurs */ public long skip(long n) throws IOException { long remaining = n; final char[] ch = new char[fBuffer.length]; do { int length = ch.length < remaining ? ch.length : (int) remaining; int count = read(ch, 0, length); if (count > 0) { remaining -= count; } else { break; } } while (remaining > 0); long skipped = n - remaining; return skipped; } // skip(long):long /** * Tell whether this stream is ready to be read. * * @return True if the next read() is guaranteed not to block for input, * false otherwise. Note that returning false does not guarantee that the * next read will block. * * @exception IOException If an I/O error occurs */ public boolean ready() throws IOException { return false; } // ready() /** * Tell whether this stream supports the mark() operation. */ public boolean markSupported() { return false; } // markSupported() /** * Mark the present position in the stream. Subsequent calls to reset() * will attempt to reposition the stream to this point. Not all * character-input streams support the mark() operation. * * @param readAheadLimit Limit on the number of characters that may be * read while still preserving the mark. After * reading this many characters, attempting to * reset the stream may fail. * * @exception IOException If the stream does not support mark(), * or if some other I/O error occurs */ public void mark(int readAheadLimit) throws IOException { throw new IOException("operationNotSupported"); } /** * Reset the stream. If the stream has been marked, then attempt to * reposition it at the mark. If the stream has not been marked, then * attempt to reset it in some way appropriate to the particular stream, * for example by repositioning it to its starting point. Not all * character-input streams support the reset() operation, and some support * reset() without supporting mark(). * * @exception IOException If the stream has not been marked, * or if the mark has been invalidated, * or if the stream does not support reset(), * or if some other I/O error occurs */ public void reset() throws IOException { fOffset = 0; fSurrogate = -1; } // reset() /** * Close the stream. Once a stream has been closed, further read(), * ready(), mark(), or reset() invocations will throw an IOException. * Closing a previously-closed stream, however, has no effect. * * @exception IOException If an I/O error occurs */ public void close() throws IOException { fInputStream.close(); } // close() // // Private methods // /** Throws an exception for expected byte. */ private void expectedByte(int position, int count) throws UTFDataFormatException { throw new UTFDataFormatException("expectedByte"); } // expectedByte(int,int,int) /** Throws an exception for invalid byte. */ private void invalidByte(int position, int count, int c) throws UTFDataFormatException { throw new UTFDataFormatException("invalidByte"); } // invalidByte(int,int,int,int) /** Throws an exception for invalid surrogate bits. */ private void invalidSurrogate(int uuuuu) throws UTFDataFormatException { throw new UTFDataFormatException("invalidHighSurrogate"); } // invalidSurrogate(int) } // class UTF8Reader