d3d11/tests: Introduce get_resource_data() helper function.

dlls/d3d11/tests/d3d11.c

@@ -716,24 +716,29 @@ static void get_texture_readback(ID3D11Texture2D *texture, unsigned int sub_reso
     ID3D11Device_Release(device);
 }
 
+static void *get_readback_data(struct resource_readback *rb, unsigned int x, unsigned int y, unsigned byte_width)
+{
+    return (BYTE *)rb->map_desc.pData + y * rb->map_desc.RowPitch + x * byte_width;
+}
+
 static DWORD get_readback_color(struct resource_readback *rb, unsigned int x, unsigned int y)
 {
-    return ((DWORD *)rb->map_desc.pData)[rb->map_desc.RowPitch * y / sizeof(DWORD) + x];
+    return *(DWORD *)get_readback_data(rb, x, y, sizeof(DWORD));
 }
 
 static float get_readback_float(struct resource_readback *rb, unsigned int x, unsigned int y)
 {
-    return ((float *)rb->map_desc.pData)[rb->map_desc.RowPitch * y / sizeof(float) + x];
+    return *(float *)get_readback_data(rb, x, y, sizeof(float));
 }
 
 static const struct vec4 *get_readback_vec4(struct resource_readback *rb, unsigned int x, unsigned int y)
 {
-    return &((const struct vec4 *)rb->map_desc.pData)[rb->map_desc.RowPitch * y / sizeof(struct vec4) + x];
+    return get_readback_data(rb, x, y, sizeof(struct vec4));
 }
 
 static const struct uvec4 *get_readback_uvec4(struct resource_readback *rb, unsigned int x, unsigned int y)
 {
-    return &((const struct uvec4 *)rb->map_desc.pData)[rb->map_desc.RowPitch * y / sizeof(struct uvec4) + x];
+    return get_readback_data(rb, x, y, sizeof(struct uvec4));
 }
 
 static void release_resource_readback(struct resource_readback *rb)