/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name "TwelveMonkeys" nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.twelvemonkeys.io;
import java.io.IOException;
import java.io.InputStream;
import java.util.Stack;
/**
* Abstract base class for {@code InputStream}s implementing the {@code Seekable} interface.
* <p/>
* @see SeekableOutputStream
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/SeekableInputStream.java#4 $
*/
public abstract class SeekableInputStream extends InputStream implements Seekable {
// TODO: It's at the moment not possible to create subclasses outside this
// package, as there's no access to position. position needs to be
// updated from the read/read/read methods...
/** The stream position in this stream */
long position;
long flushedPosition;
boolean closed;
protected Stack<Long> markedPositions = new Stack<Long>();
/// InputStream overrides
@Override
public final int read(byte[] pBytes) throws IOException {
return read(pBytes, 0, pBytes != null ? pBytes.length : 1);
}
/**
* Implemented using {@code seek(currentPos + pLength)}.
*
* @param pLength the number of bytes to skip
* @return the actual number of bytes skipped (may be equal to or less
* than {@code pLength})
*
* @throws IOException if an I/O exception occurs during skip
*/
@Override
public final long skip(final long pLength) throws IOException {
long pos = position;
long wantedPosition = pos + pLength;
if (wantedPosition < flushedPosition) {
throw new IOException("position < flushedPosition");
}
// Stop at stream length for compatibility, even though it might be allowed
// to seek past end of stream
int available = available();
if (available > 0) {
seek(Math.min(wantedPosition, pos + available));
}
// TODO: Add optimization for streams with known length!
else {
// Slow mode...
int toSkip = (int) Math.max(Math.min(pLength, 512), -512);
while (toSkip > 0 && read() >= 0) {
toSkip--;
}
}
return position - pos;
}
@Override
public final void mark(int pLimit) {
mark();
// TODO: We don't really need to do this.. Is it a good idea?
try {
flushBefore(Math.max(position - pLimit, flushedPosition));
}
catch (IOException ignore) {
// Ignore, as it's not really critical
}
}
/**
* Returns {@code true}, as marking is always supported.
*
* @return {@code true}.
*/
@Override
public final boolean markSupported() {
return true;
}
/// Seekable implementation
public final void seek(long pPosition) throws IOException {
checkOpen();
// NOTE: This is correct according to javax.imageio (IndexOutOfBoundsException),
// but it's kind of inconsistent with reset that throws IOException...
if (pPosition < flushedPosition) {
throw new IndexOutOfBoundsException("position < flushedPosition");
}
seekImpl(pPosition);
position = pPosition;
}
protected abstract void seekImpl(long pPosition) throws IOException;
public final void mark() {
markedPositions.push(position);
}
@Override
public final void reset() throws IOException {
checkOpen();
if (!markedPositions.isEmpty()) {
long newPos = markedPositions.pop();
// NOTE: This is correct according to javax.imageio (IOException),
// but it's kind of inconsistent with seek that throws IndexOutOfBoundsException...
if (newPos < flushedPosition) {
throw new IOException("Previous marked position has been discarded");
}
seek(newPos);
}
else {
// TODO: To iron out some wrinkles due to conflicting contracts
// (InputStream and Seekable both declare reset),
// we might need to reset to the last marked position instead..
// However, that becomes REALLY confusing if that position is after
// the current position...
seek(0);
}
}
public final void flushBefore(long pPosition) throws IOException {
if (pPosition < flushedPosition) {
throw new IndexOutOfBoundsException("position < flushedPosition");
}
if (pPosition > getStreamPosition()) {
throw new IndexOutOfBoundsException("position > stream position");
}
checkOpen();
flushBeforeImpl(pPosition);
flushedPosition = pPosition;
}
/**
* Discards the initial portion of the stream prior to the indicated postion.
*
* @param pPosition the position to flush to
* @throws IOException if an I/O exception occurs during the flush operation
*
* @see #flushBefore(long)
*/
protected abstract void flushBeforeImpl(long pPosition) throws IOException;
public final void flush() throws IOException {
flushBefore(flushedPosition);
}
public final long getFlushedPosition() throws IOException {
checkOpen();
return flushedPosition;
}
public final long getStreamPosition() throws IOException {
checkOpen();
return position;
}
protected final void checkOpen() throws IOException {
if (closed) {
throw new IOException("closed");
}
}
@Override
public final void close() throws IOException {
checkOpen();
closed = true;
closeImpl();
}
protected abstract void closeImpl() throws IOException;
/**
* Finalizes this object prior to garbage collection. The
* {@code close} method is called to close any open input
* source. This method should not be called from application
* code.
*
* @exception Throwable if an error occurs during superclass
* finalization.
*/
@Override
protected void finalize() throws Throwable {
if (!closed) {
try {
close();
}
catch (IOException ignore) {
// Ignroe
}
}
super.finalize();
}
}