/*
* @(#)ByteArrayImageInputStream.java
*
* Copyright (c) 2008-2011 Werner Randelshofer, Immensee, Switzerland.
* All rights reserved.
*
* You may not use, copy or modify this file, except in compliance with the
* license agreement you entered into with Werner Randelshofer.
* For details see accompanying license terms.
*/
package ch.randelshofer.media.io;
import java.io.IOException;
import java.nio.ByteOrder;
/**
* A {@code ByteArrayImageInputStream} 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 ByteArrayImageInputStream} has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an {@code IOException}.
*
* @author Werner Randelshofer, Hausmatt 10, CH-6405 Immensee
* @version $Id: ByteArrayImageInputStream.java 134 2011-12-02 16:23:00Z werner $
*/
public class ByteArrayImageInputStream extends ImageInputStreamImpl2 {
/**
* An array of bytes that was provided
* by the creator of the stream. Elements <code>buf[0]</code>
* through <code>buf[count-1]</code> are the
* only bytes that can ever be read from the
* stream; element <code>buf[streamPos]</code> is
* the next byte to be read.
*/
protected byte buf[];
/**
* 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</code>.
* It is one greater than the position of
* the last byte within <code>buf</code> that
* can ever be read from the input stream buffer.
*/
protected int count;
/** The offset to the start of the array. */
private final int arrayOffset;
public ByteArrayImageInputStream(byte[] buf) {
this(buf, ByteOrder.BIG_ENDIAN);
}
public ByteArrayImageInputStream(byte[] buf, ByteOrder byteOrder) {
this(buf, 0, buf.length, byteOrder);
}
public ByteArrayImageInputStream(byte[] buf, int offset, int length, ByteOrder byteOrder) {
this.buf = buf;
this.streamPos = offset;
this.count = Math.min(offset + length, buf.length);
this.arrayOffset = offset;
this.byteOrder = byteOrder;
}
/**
* Reads the next byte of data from this input stream. The value
* byte is returned as an <code>int</code> in the range
* <code>0</code> to <code>255</code>. If no byte is available
* because the end of the stream has been reached, the value
* <code>-1</code> is returned.
* <p>
* This <code>read</code> method
* cannot block.
*
* @return the next byte of data, or <code>-1</code> if the end of the
* stream has been reached.
*/
@Override
public synchronized int read() {
flushBits();
return (streamPos < count) ? (buf[(int)(streamPos++)] & 0xff) : -1;
}
/**
* Reads up to <code>len</code> bytes of data into an array of bytes
* from this input stream.
* If <code>streamPos</code> equals <code>count</code>,
* then <code>-1</code> is returned to indicate
* end of file. Otherwise, the number <code>k</code>
* of bytes read is equal to the smaller of
* <code>len</code> and <code>count-streamPos</code>.
* If <code>k</code> is positive, then bytes
* <code>buf[streamPos]</code> through <code>buf[streamPos+k-1]</code>
* are copied into <code>b[off]</code> through
* <code>b[off+k-1]</code> in the manner performed
* by <code>System.arraycopy</code>. The
* value <code>k</code> is added into <code>streamPos</code>
* and <code>k</code> is returned.
* <p>
* This <code>read</code> method cannot block.
*
* @param b the buffer into which the data is read.
* @param off the start offset in the destination array <code>b</code>
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of
* the stream has been reached.
* @exception NullPointerException If <code>b</code> is <code>null</code>.
* @exception IndexOutOfBoundsException If <code>off</code> is negative,
* <code>len</code> is negative, or <code>len</code> is greater than
* <code>b.length - off</code>
*/
@Override
public synchronized int read(byte b[], int off, int len) {
flushBits();
if (b == null) {
throw new NullPointerException();
} else if (off < 0 || len < 0 || len > b.length - off) {
throw new IndexOutOfBoundsException();
}
if (streamPos >= count) {
return -1;
}
if (streamPos + len > count) {
len = (int)(count - streamPos);
}
if (len <= 0) {
return 0;
}
System.arraycopy(buf, (int)streamPos, b, off, len);
streamPos += len;
return len;
}
/**
* Skips <code>n</code> 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</code>
* of bytes to be skipped is equal to the smaller
* of <code>n</code> and <code>count-streamPos</code>.
* The value <code>k</code> is added into <code>streamPos</code>
* and <code>k</code> is returned.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
*/
public synchronized long skip(long n) {
if (streamPos + n > count) {
n = count - streamPos;
}
if (n < 0) {
return 0;
}
streamPos += n;
return n;
}
/**
* Returns the number of remaining bytes that can be read (or skipped over)
* from this input stream.
* <p>
* The value returned is <code>count - streamPos</code>,
* 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 (int)(count - streamPos);
}
/**
* Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an <tt>IOException</tt>.
* <p>
*/
@Override
public void close() {
// does nothing!!
}
@Override
public long getStreamPosition() throws IOException {
checkClosed();
return streamPos-arrayOffset;
}
@Override
public void seek(long pos) throws IOException {
checkClosed();
flushBits();
// This test also covers pos < 0
if (pos < flushedPos) {
throw new IndexOutOfBoundsException("pos < flushedPos!");
}
this.streamPos = pos+arrayOffset;
}
private void flushBits() {
bitOffset=0;
}
@Override
public long length() {
return count-arrayOffset;
}
}