[client/host] added new asyncronous memory copy

This changes the method of the memory copy from the host application to
the guest. Instead of performing a full copy from the capture device
into shared memory, and then flagging the new frame, we instead set a
write pointer, flag the client that there is a new frame and then copy
in chunks of 1024 bytes until the entire frame is copied. The client
upon seeing the new frame flag begins to poll at high frequency the
write pointer and upon each update copies as much as it can into the
texture.

This should improve latency but also slightly increase CPU usage on the
client due to the high frequency polling.

c-host/platform/Windows/capture/NVFBC/src/nvfbc.c

@@ -23,6 +23,7 @@ Place, Suite 330, Boston, MA 02111-1307 USA
 #include "windows/debug.h"
 #include "windows/mousehook.h"
 #include "common/option.h"
+#include "common/framebuffer.h"
 #include <assert.h>
 #include <stdlib.h>
 #include <windows.h>
@@ -236,7 +237,7 @@ static CaptureResult nvfbc_capture()
   return CAPTURE_RESULT_OK;
 }
 
-static CaptureResult nvfbc_getFrame(CaptureFrame * frame)
+static CaptureResult nvfbc_waitFrame(CaptureFrame * frame)
 {
   if (!os_waitEvent(this->frameEvent, 1000))
     return CAPTURE_RESULT_TIMEOUT;
@@ -266,7 +267,16 @@ static CaptureResult nvfbc_getFrame(CaptureFrame * frame)
 #endif
 
   frame->format = this->grabInfo.bIsHDR ? CAPTURE_FMT_RGBA10 : CAPTURE_FMT_BGRA;
-  memcpy(frame->data, this->frameBuffer, frame->pitch * frame->height);
+  return CAPTURE_RESULT_OK;
+}
+
+static CaptureResult nvfbc_getFrame(FrameBuffer frame)
+{
+  framebuffer_write(
+    frame,
+    this->frameBuffer,
+    this->grabInfo.dwHeight * this->grabInfo.dwBufferWidth * 4
+  );
   return CAPTURE_RESULT_OK;
 }
 
@@ -310,6 +320,7 @@ struct CaptureInterface Capture_NVFBC =
   .free            = nvfbc_free,
   .getMaxFrameSize = nvfbc_getMaxFrameSize,
   .capture         = nvfbc_capture,
+  .waitFrame       = nvfbc_waitFrame,
   .getFrame        = nvfbc_getFrame,
   .getPointer      = nvfbc_getPointer
 };