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; /** * A simple ASCII byte reader. This is an optimized reader for reading * byte streams that only contain 7-bit ASCII characters. * * @author Andy Clark, IBM * * @version $Id: ASCIIReader.java 793 2008-09-27 17:44:11Z remy.maucherat@jboss.com $ */ public class ASCIIReader extends Reader { // // Constants // /** Default byte buffer size (2048). */ public static final int DEFAULT_BUFFER_SIZE = 2048; // // Data // /** Input stream. */ protected InputStream fInputStream; /** Byte buffer. */ protected byte[] fBuffer; // // Constructors // /** * Constructs an ASCII reader from the specified input stream * and buffer size. * * @param inputStream The input stream. * @param size The initial buffer size. */ public ASCIIReader(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. * * <p> 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 127 * (<tt>0x00-0x7f</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 { int b0 = fInputStream.read(); if (b0 > 0x80) { throw new IOException("invalidASCII"); } return b0; } // 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 { if (length > fBuffer.length) { length = fBuffer.length; } int count = fInputStream.read(fBuffer, 0, length); for (int i = 0; i < count; i++) { int b0 = (0xff & fBuffer[i]); // Convert to unsigned if (b0 > 0x80) { throw new IOException("invalidASCII"); } ch[offset + i] = (char) 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 { return fInputStream.skip(n); } // 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 fInputStream.markSupported(); } // 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 { fInputStream.mark(readAheadLimit); } // mark(int) /** * 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 { fInputStream.reset(); } // 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() } // class ASCIIReader