move allocMatFromBuf function to farneback.cpp:

* it is the only place, where it is used
* no need to make this function public

modules/core/include/opencv2/core/cuda.hpp

@@ -314,8 +314,6 @@ The function does not reallocate memory if the matrix has proper attributes alre
  */
 CV_EXPORTS void ensureSizeIsEnough(int rows, int cols, int type, OutputArray arr);
 
-CV_EXPORTS GpuMat allocMatFromBuf(int rows, int cols, int type, GpuMat& mat);
-
 //! BufferPool management (must be called before Stream creation)
 CV_EXPORTS void setBufferPoolUsage(bool on);
 CV_EXPORTS void setBufferPoolConfig(int deviceId, size_t stackSize, int stackCount);

modules/core/src/cuda_gpu_mat.cpp

@@ -342,14 +342,6 @@ void cv::cuda::ensureSizeIsEnough(int rows, int cols, int type, OutputArray arr)
     }
 }
 
-GpuMat cv::cuda::allocMatFromBuf(int rows, int cols, int type, GpuMat& mat)
-{
-    if (!mat.empty() && mat.type() == type && mat.rows >= rows && mat.cols >= cols)
-        return mat(Rect(0, 0, cols, rows));
-
-    return mat = GpuMat(rows, cols, type);
-}
-
 #ifndef HAVE_CUDA
 
 GpuMat::Allocator* cv::cuda::GpuMat::defaultAllocator()

modules/cudaoptflow/src/farneback.cpp

@@ -95,6 +95,16 @@ namespace cv { namespace cuda { namespace device { namespace optflow_farneback
 
 }}}} // namespace cv { namespace cuda { namespace cudev { namespace optflow_farneback
 
+namespace
+{
+    GpuMat allocMatFromBuf(int rows, int cols, int type, GpuMat& mat)
+    {
+        if (!mat.empty() && mat.type() == type && mat.rows >= rows && mat.cols >= cols)
+            return mat(Rect(0, 0, cols, rows));
+
+        return mat = GpuMat(rows, cols, type);
+    }
+}
 
 void cv::cuda::FarnebackOpticalFlow::prepareGaussian(
         int n, double sigma, float *g, float *xg, float *xxg,