package com.twelvemonkeys.io;
import com.twelvemonkeys.lang.Validate;
import java.io.IOException;
import java.io.InputStream;
/**
* Represents a cached seekable stream, that reads through a cache.
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haku $
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/AbstractCachedSeekableStream.java#2 $
*/
abstract class AbstractCachedSeekableStream extends SeekableInputStream {
/** The backing stream */
protected final InputStream stream;
/** The stream positon in the backing stream (stream) */
protected long streamPosition;
private StreamCache cache;
protected AbstractCachedSeekableStream(final InputStream pStream, final StreamCache pCache) {
Validate.notNull(pStream, "stream");
Validate.notNull(pCache, "cache");
stream = pStream;
cache = pCache;
}
protected final StreamCache getCache() {
return cache;
}
@Override
public int available() throws IOException {
long avail = streamPosition - position + stream.available();
return avail > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) avail;
}
public int read() throws IOException {
checkOpen();
int read;
if (position == streamPosition) {
// TODO: Read more bytes here!
// TODO: Use buffer if not in-memory cache? (See FileCacheSeekableStream overrides).
// Read a byte from the stream
read = stream.read();
if (read >= 0) {
streamPosition++;
cache.write(read);
}
}
else {
// ..or read byte from the cache
syncPosition();
read = cache.read();
}
// TODO: This field is not REALLY considered accessible.. :-P
if (read != -1) {
position++;
}
return read;
}
@Override
public int read(byte[] pBytes, int pOffset, int pLength) throws IOException {
checkOpen();
int length;
if (position == streamPosition) {
// Read bytes from the stream
length = stream.read(pBytes, pOffset, pLength);
if (length > 0) {
streamPosition += length;
cache.write(pBytes, pOffset, length);
}
}
else {
// ...or read bytes from the cache
syncPosition();
length = cache.read(pBytes, pOffset, pLength);
}
// TODO: This field is not REALLY considered accessible.. :-P
if (length > 0) {
position += length;
}
return length;
}
protected final void syncPosition() throws IOException {
if (cache.getPosition() != position) {
cache.seek(position); // Assure EOF is correctly thrown
}
}
public final boolean isCached() {
return true;
}
public abstract boolean isCachedMemory();
public abstract boolean isCachedFile();
protected void seekImpl(long pPosition) throws IOException {
if (streamPosition < pPosition) {
// Make sure we append at end of cache
if (cache.getPosition() != streamPosition) {
cache.seek(streamPosition);
}
// Read diff from stream into cache
long left = pPosition - streamPosition;
// TODO: Use fixed buffer, instead of allocating here...
int bufferLen = left > 1024 ? 1024 : (int) left;
byte[] buffer = new byte[bufferLen];
while (left > 0) {
int length = buffer.length < left ? buffer.length : (int) left;
int read = stream.read(buffer, 0, length);
if (read > 0) {
cache.write(buffer, 0, read);
streamPosition += read;
left -= read;
}
else if (read < 0) {
break;
}
}
}
else /*if (streamPosition >= pPosition) */ {
// Seek backwards into the cache
cache.seek(pPosition);
}
// System.out.println("pPosition: " + pPosition);
// System.out.println("position: " + position);
// System.out.println("streamPosition: " + streamPosition);
// System.out.println("cache.position: " + cache.getPosition());
// NOTE: If position == pPosition then we're good to go
}
protected void flushBeforeImpl(long pPosition) {
cache.flush(pPosition);
}
protected void closeImpl() throws IOException {
cache.flush(position);
cache = null;
stream.close();
}
/**
* An abstract stream cache.
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haku $
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/AbstractCachedSeekableStream.java#2 $
*/
public static abstract class StreamCache {
/**
* Creates a {@code StreamCache}.
*/
protected StreamCache() {
}
/**
* Writes a single byte at the current read/write position. The read/write position will be increased by one.
*
* @param pByte the byte value to write.
*
* @throws IOException if an I/O exception occurs in the cache backing mechanism.
*/
abstract void write(int pByte) throws IOException;
/**
* Writes a series of bytes at the current read/write position. The read/write position will be increased by
* {@code pLength}.
* <p/>
* This implementation invokes {@link #write(int)} {@code pLength} times.
* Subclasses may override this method for performance.
*
* @param pBuffer the bytes to write.
* @param pOffset the starting offset into the buffer.
* @param pLength the number of bytes to write from the buffer.
*
* @throws IOException if an I/O exception occurs in the cache backing mechanism.
*/
void write(final byte[] pBuffer, final int pOffset, final int pLength) throws IOException {
for (int i = 0; i < pLength; i++) {
write(pBuffer[pOffset + i]);
}
}
/**
* Reads a single byte a the current read/write position. The read/write position will be increased by one.
*
* @return the value read, or {@code -1} to indicate EOF.
*
* @throws IOException if an I/O exception occurs in the cache backing mechanism.
*/
abstract int read() throws IOException;
/**
* Writes a series of bytes at the current read/write position. The read/write position will be increased by
* {@code pLength}.
* <p/>
* This implementation invokes {@link #read()} {@code pLength} times.
* Subclasses may override this method for performance.
*
* @param pBuffer the bytes to write
* @param pOffset the starting offset into the buffer.
* @param pLength the number of bytes to write from the buffer.
* @return the number of bytes read, or {@code -1} to indicate EOF.
*
* @throws IOException if an I/O exception occurs in the cache backing mechanism.
*/
int read(final byte[] pBuffer, final int pOffset, final int pLength) throws IOException {
int count = 0;
for (int i = 0; i < pLength; i++) {
int read = read();
if (read >= 0) {
pBuffer[pOffset + i] = (byte) read;
count++;
}
else {
break;
}
}
return count;
}
/**
* Repositions the current cache read/write position to the given position.
*
* @param pPosition the new read/write position
*
* @throws IOException if an I/O exception occurs in the cache backing mechanism.
*/
abstract void seek(long pPosition) throws IOException;
/**
* Optionally flushes any data prior to the given position.
* <p/>
* Attempting to perform a seek operation, and/or a read or write operation to a position equal to or before
* the flushed position may result in exceptions or undefined behaviour.
* <p/>
* Subclasses should override this method for performance reasons, to avoid holding on to unnecessary resources.
* This implementation does nothing.
*
* @param pPosition the last position to flush.
*/
void flush(final long pPosition) {
}
/**
* Returns the current cache read/write position.
*
* @return the current cache read/write postion.
*
* @throws IOException if the position can't be determined because of a problem in the cache backing mechanism.
*/
abstract long getPosition() throws IOException;
}
}