mediasink.cpp

流媒体传输协议的实现代码,非常有用.可以支持rtsp mms等流媒体传输协议

/**********
This library is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)

This library 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 Lesser General Public License for
more details.

You should have received a copy of the GNU Lesser General Public License
along with this library; if not, write to the Free Software Foundation, Inc.,
59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2004 Live Networks, Inc.  All rights reserved.
// Media Sinks
// Implementation

#include "MediaSink.hh"
#include "GroupsockHelper.hh"
#include <string.h>

////////// MediaSink //////////

MediaSink::MediaSink(UsageEnvironment& env)
  : Medium(env), fSource(NULL) {
}

MediaSink::~MediaSink() {
  stopPlaying();
}

Boolean MediaSink::isSink() const {
  return True;
}

Boolean MediaSink::lookupByName(UsageEnvironment& env, char const* sinkName,
				MediaSink*& resultSink) {
  resultSink = NULL; // unless we succeed

  Medium* medium;
  if (!Medium::lookupByName(env, sinkName, medium)) return False;

  if (!medium->isSink()) {
    env.setResultMsg(sinkName, " is not a media sink");
    return False;
  }

  resultSink = (MediaSink*)medium;
  return True;
}

Boolean MediaSink::sourceIsCompatibleWithUs(MediaSource& source) {
  // We currently support only framed sources.
  return source.isFramedSource();
}

Boolean MediaSink::startPlaying(MediaSource& source,
				afterPlayingFunc* afterFunc,
				void* afterClientData) {
  // Make sure we're not already being played:
  if (fSource != NULL) {
    envir().setResultMsg("This sink is already being played");
    return False;
  }

  // Make sure our source is compatible:
  if (!sourceIsCompatibleWithUs(source)) {
    envir().setResultMsg("MediaSink::startPlaying(): source is not compatible!");
    return False;
  }
  fSource = (FramedSource*)&source;

  fAfterFunc = afterFunc;
  fAfterClientData = afterClientData;
  return continuePlaying();
}

void MediaSink::stopPlaying() {
  // First, tell the source that we're no longer interested:
  if (fSource != NULL) fSource->stopGettingFrames();

  // Cancel any pending tasks:
  envir().taskScheduler().unscheduleDelayedTask(nextTask());
  nextTask() = NULL;

  fSource = NULL; // indicates that we can be played again
  fAfterFunc = NULL;
}

void MediaSink::onSourceClosure(void* clientData) {
  MediaSink* sink = (MediaSink*)clientData;
  sink->fSource = NULL; // indicates that we can be played again
  if (sink->fAfterFunc != NULL) {
    (*(sink->fAfterFunc))(sink->fAfterClientData);
  }
}

Boolean MediaSink::isRTPSink() const {
  return False; // default implementation
}

////////// OutPacketBuffer //////////

unsigned OutPacketBuffer::maxSize = 60000; // by default

OutPacketBuffer::OutPacketBuffer(unsigned preferredPacketSize,
				 unsigned maxPacketSize)
  : fPreferred(preferredPacketSize), fMax(maxPacketSize),
    fOverflowDataSize(0) {
  unsigned maxNumPackets = (maxSize + (maxPacketSize-1))/maxPacketSize;
  fLimit = maxNumPackets*maxPacketSize;
  fBuf = new unsigned char[fLimit];
  resetPacketStart();
  resetOffset();
  resetOverflowData();
}

OutPacketBuffer::~OutPacketBuffer() {
  delete[] fBuf;
}

void OutPacketBuffer::enqueue(unsigned char const* from, unsigned numBytes) {
  if (numBytes > totalBytesAvailable()) {
#ifdef DEBUG
    fprintf(stderr, "OutPacketBuffer::enqueue() warning: %d > %d\n", numBytes, totalBytesAvailable());
#endif
    numBytes = totalBytesAvailable();
  }

  if (curPtr() != from) memmove(curPtr(), from, numBytes);
  increment(numBytes);
}

void OutPacketBuffer::enqueueWord(unsigned word) {
  unsigned nWord = htonl(word);
  enqueue((unsigned char*)&nWord, 4);
}

void OutPacketBuffer::insert(unsigned char const* from, unsigned numBytes,
			     unsigned toPosition) {
  unsigned realToPosition = fPacketStart + toPosition;
  if (realToPosition + numBytes > fLimit) {
    if (realToPosition > fLimit) return; // we can't do this
    numBytes = fLimit - realToPosition;
  }

  memmove(&fBuf[realToPosition], from, numBytes);
  if (toPosition + numBytes > fCurOffset) {
    fCurOffset = toPosition + numBytes;
  }
}

void OutPacketBuffer::insertWord(unsigned word, unsigned toPosition) {
  unsigned nWord = htonl(word);
  insert((unsigned char*)&nWord, 4, toPosition);
}

void OutPacketBuffer::extract(unsigned char* to, unsigned numBytes,
			      unsigned fromPosition) {
  unsigned realFromPosition = fPacketStart + fromPosition;
  if (realFromPosition + numBytes > fLimit) { // sanity check
    if (realFromPosition > fLimit) return; // we can't do this
    numBytes = fLimit - realFromPosition;
  }

  memmove(to, &fBuf[realFromPosition], numBytes);
}

unsigned OutPacketBuffer::extractWord(unsigned fromPosition) {
  unsigned nWord;
  extract((unsigned char*)&nWord, 4, fromPosition);
  return ntohl(nWord);
}

void OutPacketBuffer::skipBytes(unsigned numBytes) {
  if (numBytes > totalBytesAvailable()) {
    numBytes = totalBytesAvailable();
  }

  increment(numBytes);
}

void OutPacketBuffer
::setOverflowData(unsigned overflowDataOffset,
		  unsigned overflowDataSize,
		  struct timeval const& presentationTime,
		  unsigned durationInMicroseconds) {
  fOverflowDataOffset = overflowDataOffset;
  fOverflowDataSize = overflowDataSize;
  fOverflowPresentationTime = presentationTime;
  fOverflowDurationInMicroseconds = durationInMicroseconds;
}

void OutPacketBuffer::useOverflowData() {
  enqueue(&fBuf[fPacketStart + fOverflowDataOffset], fOverflowDataSize);
  fCurOffset -= fOverflowDataSize; // undoes increment performed by "enqueue"
  resetOverflowData();
}

void OutPacketBuffer::adjustPacketStart(unsigned numBytes) { 
  fPacketStart += numBytes;
  if (fOverflowDataOffset >= numBytes) {
    fOverflowDataOffset -= numBytes;
  } else {
    fOverflowDataOffset = 0;
    fOverflowDataSize = 0; // an error otherwise
  }
}

void OutPacketBuffer::resetPacketStart() {
  if (fOverflowDataSize > 0) {
    fOverflowDataOffset += fPacketStart;
  }
  fPacketStart = 0;
}