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/* Copyright (c) 2001-2024, The HSQL Development Group
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the HSQL Development Group nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.hsqldb.lib;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.Objects;
/**
* An input stream that reads US-ASCII values from a Reader, in compliance
* with the Java US_ASCII Charset encoder, including
*
* utf-16-surrogate-pairs.
*
* @author Campbell Burnet (campbell-burnet@users dot sourceforge.net)
* @version 2.7.1
* @since 2.7.1
*/
public class AsciiInputStream extends InputStream {
/**
* is 7;
*/
public static final int ASCII_BITS = 7;
/**
* is 0b01111111
*/
public static final int ASCII_MASK = 0b01111111;
/**
* is 2^7 - 1 (127)
*/
public static final int ASCII_MAX = 127;
/**
* is 2^7 (128)
*/
public static final int NON_ASCII_MIN = 128;
/**
* is '?'
*/
public static final int NON_ASCII_REPLACEMENT = '?';
private boolean hasNextChar = false;
private int nextChar = 0;
private final Reader reader;
/**
* Constructs a new instance for the given reader.
*
* @param reader from which to read
*/
public AsciiInputStream(final Reader reader) {
this.reader = Objects.requireNonNull(reader, "reader must not be null");
}
@Override
public void close() throws IOException {
reader.close();
}
/**
* Reads the next byte of data from the input stream. The value byte is
* returned as an {@code int} in the range {@code 0} to
* {@link #ASCII_MAX}. If no byte is available because the end of the stream
* has been reached, the value {@code -1} is returned. This method
* blocks until input data is available, the end of the stream is detected,
* or an exception is thrown.
*
* UTF-16 characters above {@link #ASCII_MAX} produce a
* {@link #NON_ASCII_REPLACEMENT} value when read.
*
* Surrogate pairs are correctly counted as a single character and produce a
* single {@link #NON_ASCII_REPLACEMENT} value when read.
*
* @return the next byte of data, or {@code -1} if the end of the
* stream is reached.
* @exception IOException if an I/O error occurs.
*/
public synchronized int read() throws IOException {
if (hasNextChar) {
hasNextChar = false;
return nextChar;
}
final int c = reader.read();
if (c < 0) {
return -1;
}
if (Character.isHighSurrogate((char) c)) {
final int nc = reader.read();
hasNextChar = !Character.isLowSurrogate((char) nc);
if (hasNextChar) {
nextChar = nc < NON_ASCII_MIN
? nc & ASCII_MASK
: NON_ASCII_REPLACEMENT;
}
}
return c < NON_ASCII_MIN
? c & ASCII_MASK
: NON_ASCII_REPLACEMENT;
}
}