AVIOContextWrapper.cpp

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/**********************************************************************
 
  Audacity: A Digital Audio Editor
 
  AVIOContextWrapper.cpp
 
  Dmitry Vedenko
 
**********************************************************************/
 
#include "AVIOContextWrapper.h"
 
#include "FFmpegFunctions.h"
 
#define AVSEEK_FORCE 0x20000
#define AVSEEK_SIZE 0x10000
 
constexpr int BufferSize = 32 * 1024;
 
AVIOContextWrapper::AVIOContextWrapper(
   const FFmpegFunctions& ffmpeg) noexcept
    : mFFmpeg(ffmpeg)
{
}
 
AVIOContext* AVIOContextWrapper::GetWrappedValue() noexcept
{
   return mAVIOContext;
}
 
const AVIOContext* AVIOContextWrapper::GetWrappedValue() const noexcept
{
   return mAVIOContext;
}
 
AVIOContextWrapper::~AVIOContextWrapper()
{
   if (mAVIOContext == nullptr)
      return;
 
   if (mFFmpeg.avio_context_free != nullptr)
      mFFmpeg.avio_context_free(&mAVIOContext);
   else
      mFFmpeg.av_free(mAVIOContext);
}
 
AVIOContextWrapper::OpenResult
AVIOContextWrapper::Open(const wxString& fileName, bool forWriting)
{
   auto pFile = std::make_unique<wxFile>();
   if (!pFile->Open(fileName, forWriting ? wxFile::write : wxFile::read))
      return OpenResult::FileOpenFailed;
 
   unsigned char* buffer =
      static_cast<unsigned char*>(mFFmpeg.av_malloc(BufferSize));
 
   if (buffer == nullptr)
      return OpenResult::NoMemory;
 
   /*
    "The buffer must be allocated with av_malloc() and friends. It may be freed
    and replaced with a new buffer by libavformat. AVIOContext.buffer holds the
    buffer currently in use, which must be later freed with av_free()."
 
    See ~AVIOContextWrapperImpl() for the deallocation
    */
   mAVIOContext = mFFmpeg.avio_alloc_context(
      buffer, BufferSize,
      static_cast<int>(forWriting),
      this,
      FileRead, FileWrite, FileSeek
   );
 
   if (mAVIOContext == nullptr) {
      mFFmpeg.av_free(buffer);
      return OpenResult::NoMemory;
   }
 
   mpFile = move(pFile);
 
   return OpenResult::Success;
}
 
int AVIOContextWrapper::FileRead(void* opaque, uint8_t* buf, int size)
{
   AVIOContextWrapper* wrapper = static_cast<AVIOContextWrapper*>(opaque);
   
   if (wrapper == nullptr)
      return AUDACITY_AVERROR(EINVAL);
   
   return wrapper->Read(buf, size);
}
 
int AVIOContextWrapper::FileWrite(void* opaque, const uint8_t* buf, int size)
{
   AVIOContextWrapper* wrapper = static_cast<AVIOContextWrapper*>(opaque);
   if (!(wrapper && wrapper->mpFile))
      return {};
   return wrapper->mpFile->Write(buf, size);
}
 
int64_t AVIOContextWrapper::FileSeek(void* opaque, int64_t pos, int whence)
{
   AVIOContextWrapper* wrapper = static_cast<AVIOContextWrapper*>(opaque);
   if (!(wrapper && wrapper->mpFile))
      return {};
 
   wxSeekMode mode = wxFromStart;
 
   switch (whence & ~AVSEEK_FORCE)
   {
   case (SEEK_SET):
      mode = wxFromStart;
      break;
   case (SEEK_CUR):
      mode = wxFromCurrent;
      break;
   case (SEEK_END):
      mode = wxFromEnd;
      break;
   case (AVSEEK_SIZE):
      return wrapper->mpFile->Length();
   }
 
 
   return wrapper->mpFile->Seek(pos, mode);
}