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 * Copyright (c) 1996, 2015, 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
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 */

package java.io;

/**
 * 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 not 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.
 *
 * @exception 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.
 * @param b Destination buffer
 * @param off Offset at which to start storing characters
 * @param len Maximum number of characters to read
 * @return The actual number of characters read, or -1 if
 * the end of the stream has been reached
 *
 * @exception IOException If an I/O error occurs
 * @exception IndexOutOfBoundsException {@inheritDoc}
 */
 public int read(char b[], int off, int len) throws IOException {
 synchronized (lock) {
 ensureOpen();
 if ((off < 0) || (off > b.length) || (len < 0) ||
 ((off + len) > b.length) || ((off + len) < 0)) {
 throw new IndexOutOfBoundsException();
 } else 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, b, off, len);
 pos += len;
 return len;
 }
 }

 /**
 * Skips characters. Returns the number of characters that were skipped.
 *
 * <p>The <code>n</code> parameter may be negative, even though the
 * <code>skip</code> method of the {@link Reader} superclass throws
 * an exception in this case. If <code>n</code> is negative, then
 * this method does nothing and returns <code>0</code>.
 *
 * @param n The number of characters to skip
 * @return The number of characters actually skipped
 * @exception IOException If the stream is closed, or an I/O error occurs
 */
 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 += n;
 return n;
 }
 }

 /**
 * Tells whether this stream is ready to be read. Character-array readers
 * are always ready to be read.
 *
 * @exception 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.
 *
 * @exception 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.
 *
 * @exception 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;
 }
 }
}