/*
 * Copyright (c) 1994, 2018, 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;

import java.util.Arrays;
import java.util.Objects;

/**
 * A {@code ByteArrayInputStream} contains
 * an internal buffer that contains bytes that
 * may be read from the stream. An internal
 * counter keeps track of the next byte to
 * be supplied by the {@code read} method.
 * <p>
 * Closing a {@code ByteArrayInputStream} has no effect. The methods in
 * this class can be called after the stream has been closed without
 * generating an {@code IOException}.
 *
 * @author Arthur van Hoff
 * @see java.io.StringBufferInputStream
 * @since 1.0
 */
public class ByteArrayInputStream extends InputStream {

 /**
 * An array of bytes that was provided
 * by the creator of the stream. Elements {@code buf[0]}
 * through {@code buf[count-1]} are the
 * only bytes that can ever be read from the
 * stream; element {@code buf[pos]} is
 * the next byte to be read.
 */
 protected byte buf[];

 /**
 * The index of the next character to read from the input stream buffer.
 * This value should always be nonnegative
 * and not larger than the value of {@code count}.
 * The next byte to be read from the input stream buffer
 * will be {@code buf[pos]}.
 */
 protected int pos;

 /**
 * The currently marked position in the stream.
 * ByteArrayInputStream objects are marked at position zero by
 * default when constructed. They may be marked at another
 * position within the buffer by the {@code mark()} method.
 * The current buffer position is set to this point by the
 * {@code reset()} method.
 * <p>
 * If no mark has been set, then the value of mark is the offset
 * passed to the constructor (or 0 if the offset was not supplied).
 *
 * @since 1.1
 */
 protected int mark = 0;

 /**
 * The index one greater than the last valid character in the input
 * stream buffer.
 * This value should always be nonnegative
 * and not larger than the length of {@code buf}.
 * It is one greater than the position of
 * the last byte within {@code buf} that
 * can ever be read from the input stream buffer.
 */
 protected int count;

 /**
 * Creates a {@code ByteArrayInputStream}
 * so that it uses {@code buf} as its
 * buffer array.
 * The buffer array is not copied.
 * The initial value of {@code pos}
 * is {@code 0} and the initial value
 * of {@code count} is the length of
 * {@code buf}.
 *
 * @param buf the input buffer.
 */
 public ByteArrayInputStream(byte buf[]) {
 this.buf = buf;
 this.pos = 0;
 this.count = buf.length;
 }

 /**
 * Creates {@code ByteArrayInputStream}
 * that uses {@code buf} as its
 * buffer array. The initial value of {@code pos}
 * is {@code offset} and the initial value
 * of {@code count} is the minimum of {@code offset+length}
 * and {@code buf.length}.
 * The buffer array is not copied. The buffer's mark is
 * set to the specified offset.
 *
 * @param buf the input buffer.
 * @param offset the offset in the buffer of the first byte to read.
 * @param length the maximum number of bytes to read from the buffer.
 */
 public ByteArrayInputStream(byte buf[], int offset, int length) {
 this.buf = buf;
 this.pos = offset;
 this.count = Math.min(offset + length, buf.length);
 this.mark = offset;
 }

 /**
 * Reads the next byte of data from this input stream. The value
 * byte is returned as an {@code int} in the range
 * {@code 0} to {@code 255}. If no byte is available
 * because the end of the stream has been reached, the value
 * {@code -1} is returned.
 * <p>
 * This {@code read} method
 * cannot block.
 *
 * @return the next byte of data, or {@code -1} if the end of the
 * stream has been reached.
 */
 public synchronized int read() {
 return (pos < count) ? (buf[pos++] & 0xff) : -1;
 }

 /**
 * Reads up to {@code len} bytes of data into an array of bytes from this
 * input stream. If {@code pos} equals {@code count}, then {@code -1} is
 * returned to indicate end of file. Otherwise, the number {@code k} of
 * bytes read is equal to the smaller of {@code len} and {@code count-pos}.
 * If {@code k} is positive, then bytes {@code buf[pos]} through
 * {@code buf[pos+k-1]} are copied into {@code b[off]} through
 * {@code b[off+k-1]} in the manner performed by {@code System.arraycopy}.
 * The value {@code k} is added into {@code pos} and {@code k} is returned.
 * <p>
 * This {@code read} method cannot block.
 *
 * @param b the buffer into which the data is read.
 * @param off the start offset in the destination array {@code b}
 * @param len the maximum number of bytes read.
 * @return the total number of bytes read into the buffer, or
 * {@code -1} if there is no more data because the end of
 * the stream has been reached.
 * @throws NullPointerException If {@code b} is {@code null}.
 * @throws IndexOutOfBoundsException If {@code off} is negative,
 * {@code len} is negative, or {@code len} is greater than
 * {@code b.length - off}
 */
 public synchronized int read(byte b[], int off, int len) {
 Objects.checkFromIndexSize(off, len, b.length);

 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;
 }

 public synchronized byte[] readAllBytes() {
 byte[] result = Arrays.copyOfRange(buf, pos, count);
 pos = count;
 return result;
 }

 public int readNBytes(byte[] b, int off, int len) {
 int n = read(b, off, len);
 return n == -1 ? 0 : n;
 }

 public synchronized long transferTo(OutputStream out) throws IOException {
 int len = count - pos;
 out.write(buf, pos, len);
 pos = count;
 return len;
 }

 /**
 * Skips {@code n} bytes of input from this input stream. Fewer
 * bytes might be skipped if the end of the input stream is reached.
 * The actual number {@code k}
 * of bytes to be skipped is equal to the smaller
 * of {@code n} and {@code count-pos}.
 * The value {@code k} is added into {@code pos}
 * and {@code k} is returned.
 *
 * @param n the number of bytes to be skipped.
 * @return the actual number of bytes skipped.
 */
 public synchronized long skip(long n) {
 long k = count - pos;
 if (n < k) {
 k = n < 0 ? 0 : n;
 }

 pos += k;
 return k;
 }

 /**
 * Returns the number of remaining bytes that can be read (or skipped over)
 * from this input stream.
 * <p>
 * The value returned is {@code count - pos},
 * which is the number of bytes remaining to be read from the input buffer.
 *
 * @return the number of remaining bytes that can be read (or skipped
 * over) from this input stream without blocking.
 */
 public synchronized int available() {
 return count - pos;
 }

 /**
 * Tests if this {@code InputStream} supports mark/reset. The
 * {@code markSupported} method of {@code ByteArrayInputStream}
 * always returns {@code true}.
 *
 * @since 1.1
 */
 public boolean markSupported() {
 return true;
 }

 /**
 * Set the current marked position in the stream.
 * ByteArrayInputStream objects are marked at position zero by
 * default when constructed. They may be marked at another
 * position within the buffer by this method.
 * <p>
 * If no mark has been set, then the value of the mark is the
 * offset passed to the constructor (or 0 if the offset was not
 * supplied).
 *
 * <p> Note: The {@code readAheadLimit} for this class
 * has no meaning.
 *
 * @since 1.1
 */
 public void mark(int readAheadLimit) {
 mark = pos;
 }

 /**
 * Resets the buffer to the marked position. The marked position
 * is 0 unless another position was marked or an offset was specified
 * in the constructor.
 */
 public synchronized void reset() {
 pos = mark;
 }

 /**
 * Closing a {@code ByteArrayInputStream} has no effect. The methods in
 * this class can be called after the stream has been closed without
 * generating an {@code IOException}.
 */
 public void close() throws IOException {
 }

}