D3D10/11 dyn buffer management

gistfile1.cpp

////////////////////////////////////////////////////////////////////////
//
//   Dynamic buffer (D3D11-specific code)
//

#define D3D1X_(id)         D3D11_##id
#define ID3D1X(id)         ID3D11##id
#define gdraw_D3D1X_(id)   gdraw_D3D11_##id
#define GDRAW_D3D1X_(id)   GDRAW_D3D11_##id

typedef ID3D11Device ID3D1XDevice;
typedef ID3D11DeviceContext ID3D1XContext;

static void report_d3d_error(HRESULT hr, char *call, char *context);

static void *map_buffer(ID3D1XContext *ctx, ID3D11Buffer *buf, bool discard)
{
   D3D11_MAPPED_SUBRESOURCE msr;
   HRESULT hr = ctx->Map(buf, 0, discard ? D3D11_MAP_WRITE_DISCARD : D3D11_MAP_WRITE_NO_OVERWRITE, 0, &msr);
   if (FAILED(hr)) {
      report_d3d_error(hr, "Map", "of buffer");
      return NULL;
   } else
      return msr.pData;
}

static void unmap_buffer(ID3D1XContext *ctx, ID3D11Buffer *buf)
{
   ctx->Unmap(buf, 0);
}

////////////////////////////////////////////////////////////////////////
//
//   Dynamic buffer (generic code)
//

struct DynBuffer
{
   ID3D1X(Buffer) *buffer;
   U32 size;      // size of buffer
   U32 write_pos; // start of most recently allocated chunk (=start offset for draw calls)
   U32 alloc_pos; // end of most recently allocated chunk (=start of next allocation)
};

static void *start_write_dyn(DynBuffer *buf, U32 size)
{
   U8 *ptr = NULL;

   if (size > buf->size) {
      IggyGDrawSendWarning(NULL, "GDraw dynamic vertex buffer usage of %d bytes in one call larger than buffer size %d", size, buf->size);
      return NULL;
   }

   // update statistics
   gdraw->dyn_maxalloc = RR_MAX(gdraw->dyn_maxalloc, size);

   // invariant: current alloc_pos is in [0,size]
   assert(buf->alloc_pos <= buf->size);

   // wrap around when less than "size" bytes left in buffer
   buf->write_pos = ((buf->size - buf->alloc_pos) < size) ? 0 : buf->alloc_pos;

   // discard buffer whenever the current write position is 0;
   // done this way so that if a DISCARD Map() were to fail, we would
   // just keep retrying the next time around.
   ptr = (U8 *) map_buffer(gdraw->d3d_context, buf->buffer, buf->write_pos == 0);
   if (ptr) {
      ptr += buf->write_pos; // we return pointer to write position in buffer
      buf->alloc_pos = buf->write_pos + size; // bump alloc position
      assert(buf->alloc_pos <= buf->size); // invariant again
   }
   // if map_buffer fails, it will have sent a warning

   return ptr;
}

static U32 end_write_dyn(DynBuffer *buf)
{
   unmap_buffer(gdraw->d3d_context, buf->buffer);
   return buf->write_pos;
}