uk.co.caprica.vlcj.media.callback.AbstractCallbackMedia Maven / Gradle / Ivy
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/*
* This file is part of VLCJ.
*
* VLCJ is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* VLCJ is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with VLCJ. If not, see
* This implementation mostly encapsulates the native callbacks using template methods, with the exception of the
* {@link #onRead(Pointer, int)} method. This particular method is used to read data and populate the native buffer. The
* reason this method exposes a native {@link Pointer} is so sub-classes can access the native buffer as efficiently as
* possible.
*
* In most cases it is likely preferable to deal instead with a Java byte array buffer, for this purpose the
* {@link DefaultCallbackMedia} sub-class should be used instead of this class.
*/
public abstract class AbstractCallbackMedia implements CallbackMedia {
/**
* Native API success indicator.
*/
private static final int SUCCESS = 0;
/**
* Native API error indicator.
*/
private static final int ERROR = -1;
/**
* Native API end-of-stream indicator.
*/
private static final int END_OF_STREAM = 0;
/**
* Is the media seekable?
*/
private final boolean seekable;
/**
* Native media open callback.
*/
private final Open open;
/**
* Native media read callback.
*/
private final Read read;
/**
* Native media seek callback.
*/
private final Seek seek;
/**
* Native media close callback.
*/
private final Close close;
/**
* Native opaque data.
*
* Currently unused.
*/
private final Pointer opaque;
/**
* Create a new media instance.
*
* @param seekable true if the media is seekable; false if it is not
*/
public AbstractCallbackMedia(boolean seekable) {
this.seekable = seekable;
this.open = new Open();
this.read = new Read();
this.seek = seekable ? new Seek() : null;
this.close = new Close();
this.opaque = null;
}
/**
* Is the media seekable?
*
* @return true if the media is seekable; false if it is not
*/
public final boolean isSeekable() {
return seekable;
}
/**
* Get the size of the media, if known.
*
* @return size of the media, or 0 if the size is not known
*/
protected abstract long onGetSize();
/**
* Open the media.
*
* @return true if the media was opened; false if it was not
*/
protected abstract boolean onOpen();
/**
* Read media data.
*
* It is allowable for implementations to block in this method waiting for IO, but care must be taken not
* to block indefinitely otherwise the native media player can not be stopped.
*
* @param buffer buffer to write into
* @param bufferSize capacity of the buffer to write into
* @return number of bytes read, or -1 if the end of the stream was reached
* @throws IOException if an error occurs
*/
protected abstract int onRead(Pointer buffer, int bufferSize) throws IOException;
/**
* Seek to a specific offset within the media.
*
* @param offset offset within the media to seek to
* @return true if the seek was successful; false on error
*/
protected abstract boolean onSeek(long offset);
/**
* Close the media.
*/
protected abstract void onClose();
/**
* Implementation of native media open callback.
*/
private class Open implements libvlc_media_open_cb {
@Override
public int open(Pointer opaque, PointerByReference datap, LongByReference sizep) {
sizep.setValue(onGetSize());
return onOpen() ? SUCCESS : ERROR;
}
}
/**
* Implementation of native media read callback.
*/
private class Read implements libvlc_media_read_cb {
@Override
public size_t read(Pointer opaque, Pointer buf, size_t len) {
int result;
try {
int bytesRead = onRead(buf, len.intValue());
result = bytesRead >= 0 ? bytesRead : END_OF_STREAM;
}
catch (IOException e) {
result = ERROR;
}
return new size_t(result);
}
}
/**
* Implementation of native media seek callback.
*/
private class Seek implements libvlc_media_seek_cb {
@Override
public int seek(Pointer opaque, long offset) {
return onSeek(offset) ? SUCCESS : ERROR;
}
}
/**
* Implementation of native media close callback.
*/
private class Close implements libvlc_media_close_cb {
@Override
public void close(Pointer opaque) {
onClose();
}
}
@Override
public final libvlc_media_open_cb getOpen() {
return open;
}
@Override
public final libvlc_media_read_cb getRead() {
return read;
}
@Override
public final libvlc_media_seek_cb getSeek() {
return seek;
}
@Override
public final libvlc_media_close_cb getClose() {
return close;
}
@Override
public final Pointer getOpaque() {
return opaque;
}
}