/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package java.io;
import java.util.Arrays;
/**
* A specialized {@link InputStream } for reading the contents of a byte array.
*
* @see ByteArrayOutputStream
*/
public class ByteArrayInputStream extends InputStream {
/**
* The {@code byte} array containing the bytes to stream over.
*/
protected byte[] buf;
/**
* The current position within the byte array.
*/
protected int pos;
/**
* The current mark position. Initially set to 0 or the <code>offset</code>
* parameter within the constructor.
*/
protected int mark;
/**
* The total number of bytes initially available in the byte array
* {@code buf}.
*/
protected int count;
/**
* Constructs a new {@code ByteArrayInputStream} on the byte array
* {@code buf}.
*
* @param buf
* the byte array to stream over.
*/
public ByteArrayInputStream(byte[] buf) {
this.mark = 0;
this.buf = buf;
this.count = buf.length;
}
/**
* Constructs a new {@code ByteArrayInputStream} on the byte array
* {@code buf} with the initial position set to {@code offset} and the
* number of bytes available set to {@code offset} + {@code length}.
*
* @param buf
* the byte array to stream over.
* @param offset
* the initial position in {@code buf} to start streaming from.
* @param length
* the number of bytes available for streaming.
*/
public ByteArrayInputStream(byte[] buf, int offset, int length) {
this.buf = buf;
pos = offset;
mark = offset;
count = offset + length > buf.length ? buf.length : offset + length;
}
/**
* Returns the number of remaining bytes.
*
* @return {@code count - pos}
*/
@Override
public synchronized int available() {
return count - pos;
}
/**
* Closes this stream and frees resources associated with this stream.
*
* @throws IOException
* if an I/O error occurs while closing this stream.
*/
@Override
public void close() throws IOException {
// Do nothing on close, this matches JDK behavior.
}
/**
* Sets a mark position in this ByteArrayInputStream. The parameter
* {@code readlimit} is ignored. Sending {@code reset()} will reposition the
* stream back to the marked position.
*
* @param readlimit
* ignored.
* @see #markSupported()
* @see #reset()
*/
@Override
public synchronized void mark(int readlimit) {
mark = pos;
}
/**
* Indicates whether this stream supports the {@code mark()} and
* {@code reset()} methods. Returns {@code true} since this class supports
* these methods.
*
* @return always {@code true}.
* @see #mark(int)
* @see #reset()
*/
@Override
public boolean markSupported() {
return true;
}
/**
* Reads a single byte from the source byte array and returns it as an
* integer in the range from 0 to 255. Returns -1 if the end of the source
* array has been reached.
*
* @return the byte read or -1 if the end of this stream has been reached.
*/
@Override
public synchronized int read() {
return pos < count ? buf[pos++] & 0xFF : -1;
}
/**
* Reads at most {@code len} bytes from this stream and stores
* them in byte array {@code b} starting at {@code offset}. This
* implementation reads bytes from the source byte array.
*
* @param buffer
* the byte array in which to store the bytes read.
* @param offset
* the initial position in {@code b} to store the bytes read from
* this stream.
* @param length
* the maximum number of bytes to store in {@code b}.
* @return the number of bytes actually read or -1 if no bytes were read and
* the end of the stream was encountered.
* @throws IndexOutOfBoundsException
* if {@code offset < 0} or {@code length < 0}, or if
* {@code offset + length} is greater than the size of
* {@code b}.
* @throws NullPointerException
* if {@code b} is {@code null}.
*/
@Override
public synchronized int read(byte[] buffer, int offset, int length) {
Arrays.checkOffsetAndCount(buffer.length, offset, length);
// Are there any bytes available?
if (this.pos >= this.count) {
return -1;
}
if (length == 0) {
return 0;
}
int copylen = this.count - pos < length ? this.count - pos : length;
System.arraycopy(this.buf, pos, buffer, offset, copylen);
pos += copylen;
return copylen;
}
/**
* Resets this stream to the last marked location. This implementation
* resets the position to either the marked position, the start position
* supplied in the constructor or 0 if neither has been provided.
*
* @see #mark(int)
*/
@Override
public synchronized void reset() {
pos = mark;
}
/**
* Skips {@code byteCount} bytes in this InputStream. Subsequent
* calls to {@code read} will not return these bytes unless {@code reset} is
* used. This implementation skips {@code byteCount} number of bytes in the
* target stream. It does nothing and returns 0 if {@code byteCount} is negative.
*
* @return the number of bytes actually skipped.
*/
@Override
public synchronized long skip(long byteCount) {
if (byteCount <= 0) {
return 0;
}
int temp = pos;
pos = this.count - pos < byteCount ? this.count : (int) (pos + byteCount);
return pos - temp;
}
}