com.viaoa.image.jpg.ByteArrayImageInputStream Maven / Gradle / Ivy
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/*
* @(#)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 com.viaoa.image.jpg;
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.
*
* 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 buf[0]
* through buf[count-1] are the
* only bytes that can ever be read from the
* stream; element buf[streamPos] 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 buf.
* It is one greater than the position of
* the last byte within buf 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 int in the range
* 0 to 255. If no byte is available
* because the end of the stream has been reached, the value
* -1 is returned.
*
* This read method
* cannot block.
*
* @return the next byte of data, or -1 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 len bytes of data into an array of bytes
* from this input stream.
* If streamPos equals count,
* then -1 is returned to indicate
* end of file. Otherwise, the number k
* of bytes read is equal to the smaller of
* len and count-streamPos.
* If k is positive, then bytes
* buf[streamPos] through buf[streamPos+k-1]
* are copied into b[off] through
* b[off+k-1] in the manner performed
* by System.arraycopy. The
* value k is added into streamPos
* and k is returned.
*
* This read method cannot block.
*
* @param b the buffer into which the data is read.
* @param off the start offset in the destination array b
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end of
* the stream has been reached.
* @exception NullPointerException If b is null.
* @exception IndexOutOfBoundsException If off is negative,
* len is negative, or len is greater than
* b.length - off
*/
@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 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 k
* of bytes to be skipped is equal to the smaller
* of n and count-streamPos.
* The value k is added into streamPos
* and 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) {
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.
*
* The value returned is count - streamPos,
* 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 ByteArrayInputStream has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an IOException.
*
*/
@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;
}
}