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/*
* Copyright (c) 1994, 2021, 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.
*
* 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.
*
* 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.
*
* 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.
*
* Unlike the {@link InputStream#read(byte[],int,int) overridden method}
* of {@code InputStream}, this method returns {@code -1} instead of zero
* if the end of the stream has been reached and {@code len == 0}.
*
* 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.
*
* 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.
*
* 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).
*
*
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 {
}
}