Mega Code Archive
An optimized reader for reading byte streams that only contain 7-bit ASCII characters
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/*
* 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.
*
* 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
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