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CharArrayReader.java
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/*
* Copyright (c) 1996, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.io;
import java.nio.CharBuffer;
import java.util.Objects;
/**
* This class implements a character buffer that can be used as a
* character-input stream.
*
* @author Herb Jellinek
* @since 1.1
*/
public class CharArrayReader extends Reader {
/** The character buffer. */
protected char[] buf;
/** The current buffer position. */
protected int pos;
/** The position of mark in buffer. */
protected int markedPos = 0;
/**
* The index of the end of this buffer. There is no valid
* data at or beyond this index.
*/
protected int count;
/**
* Creates a CharArrayReader from the specified array of chars.
* @param buf Input buffer (not copied)
*/
public CharArrayReader(char[] buf) {
this.buf = buf;
this.pos = 0;
this.count = buf.length;
}
/**
* Creates a CharArrayReader from the specified array of chars.
*
* <p> The resulting reader will start reading at the given
* {@code offset}. The total number of {@code char} values that can be
* read from this reader will be either {@code length} or
* {@code buf.length-offset}, whichever is smaller.
*
* @throws IllegalArgumentException
* If {@code offset} is negative or greater than
* {@code buf.length}, or if {@code length} is negative, or if
* the sum of these two values is negative.
*
* @param buf Input buffer (not copied)
* @param offset Offset of the first char to read
* @param length Number of chars to read
*/
public CharArrayReader(char[] buf, int offset, int length) {
if ((offset < 0) || (offset > buf.length) || (length < 0) ||
((offset + length) < 0)) {
throw new IllegalArgumentException();
}
this.buf = buf;
this.pos = offset;
this.count = Math.min(offset + length, buf.length);
this.markedPos = offset;
}
/** Checks to make sure that the stream has not been closed */
private void ensureOpen() throws IOException {
if (buf == null)
throw new IOException("Stream closed");
}
/**
* Reads a single character.
*
* @throws IOException If an I/O error occurs
*/
public int read() throws IOException {
synchronized (lock) {
ensureOpen();
if (pos >= count)
return -1;
else
return buf[pos++];
}
}
/**
* Reads characters into a portion of an array.
*
* <p> If {@code len} is zero, then no characters are read and {@code 0} is
* returned; otherwise, there is an attempt to read at least one character.
* If no character is available because the stream is at its end, the value
* {@code -1} is returned; otherwise, at least one character is read and
* stored into {@code cbuf}.
*
* @param cbuf {@inheritDoc}
* @param off {@inheritDoc}
* @param len {@inheritDoc}
*
* @return {@inheritDoc}
*
* @throws IndexOutOfBoundsException {@inheritDoc}
* @throws IOException {@inheritDoc}
*/
public int read(char[] cbuf, int off, int len) throws IOException {
synchronized (lock) {
ensureOpen();
Objects.checkFromIndexSize(off, len, cbuf.length);
if (len == 0) {
return 0;
}
if (pos >= count) {
return -1;
}
int avail = count - pos;
if (len > avail) {
len = avail;
}
if (len <= 0) {
return 0;
}
System.arraycopy(buf, pos, cbuf, off, len);
pos += len;
return len;
}
}
@Override
public int read(CharBuffer target) throws IOException {
synchronized (lock) {
ensureOpen();
if (pos >= count) {
return -1;
}
int avail = count - pos;
int len = Math.min(avail, target.remaining());
target.put(buf, pos, len);
pos += len;
return len;
}
}
/**
* Skips characters. If the stream is already at its end before this method
* is invoked, then no characters are skipped and zero is returned.
*
* <p>The {@code n} parameter may be negative, even though the
* {@code skip} method of the {@link Reader} superclass throws
* an exception in this case. If {@code n} is negative, then
* this method does nothing and returns {@code 0}.
*
* @param n {@inheritDoc}
*
* @return {@inheritDoc}
*
* @throws IOException {@inheritDoc}
*/
public long skip(long n) throws IOException {
synchronized (lock) {
ensureOpen();
long avail = count - pos;
if (n > avail) {
n = avail;
}
if (n < 0) {
return 0;
}
pos += (int) n;
return n;
}
}
/**
* Tells whether this stream is ready to be read. Character-array readers
* are always ready to be read.
*
* @throws IOException If an I/O error occurs
*/
public boolean ready() throws IOException {
synchronized (lock) {
ensureOpen();
return (count - pos) > 0;
}
}
/**
* Tells whether this stream supports the mark() operation, which it does.
*/
public boolean markSupported() {
return true;
}
/**
* Marks the present position in the stream. Subsequent calls to reset()
* will reposition the stream to this point.
*
* @param readAheadLimit Limit on the number of characters that may be
* read while still preserving the mark. Because
* the stream's input comes from a character array,
* there is no actual limit; hence this argument is
* ignored.
*
* @throws IOException If an I/O error occurs
*/
public void mark(int readAheadLimit) throws IOException {
synchronized (lock) {
ensureOpen();
markedPos = pos;
}
}
/**
* Resets the stream to the most recent mark, or to the beginning if it has
* never been marked.
*
* @throws IOException If an I/O error occurs
*/
public void reset() throws IOException {
synchronized (lock) {
ensureOpen();
pos = markedPos;
}
}
/**
* Closes the stream and releases any system resources associated with
* it. Once the stream has been closed, further read(), ready(),
* mark(), reset(), or skip() invocations will throw an IOException.
* Closing a previously closed stream has no effect. This method will block
* while there is another thread blocking on the reader.
*/
public void close() {
synchronized (lock) {
buf = null;
}
}
}