ImagingComponent: Align the memory when allocating the buffer.

Essentially a reimplementation of cv::fastMalloc using std::align in C++11.

src/osvr/Common/ImagingComponent.cpp

@@ -31,9 +31,12 @@
 #include <osvr/Util/Verbosity.h>
 
 // Standard includes
+#include <stdlib.h>
 #include <sstream>
 #include <utility>
 
+#define OSVR_ALIGN_SIZE 16
+
 namespace osvr {
 namespace common {
     static inline uint32_t getBufferSize(OSVR_ImagingMetadata const &meta) {
@@ -67,14 +70,27 @@ namespace common {
 
             template <typename T>
             void allocateBuffer(T &, size_t bytes, std::true_type const &) {
-                m_imgBuf.reset(reinterpret_cast<OSVR_ImageBufferElement *>(malloc(bytes)));
+                // Allocate a memory pointed aligned to a boundary.
+                size_t space = bytes + sizeof(void*) + OSVR_ALIGN_SIZE;
+                void* buffer = malloc(space);
+                void* aligned = std::align(OSVR_ALIGN_SIZE, bytes, buffer, space);
+
+                // Store the buffer pointer for the delete call.
+                ((void **)aligned)[-1] = buffer;
+
+                m_imgBuf.reset(reinterpret_cast<OSVR_ImageBufferElement *>(aligned, deleteBuffer));
             }
 
             template <typename T>
             void allocateBuffer(T &, size_t, std::false_type const &) {
                 // Does nothing if we're serializing.
             }
 
+            static void deleteBuffer(void* p) {
+                if (p)
+                    free(((void **)p)[-1]);
+            }
+
             template <typename T> void processMessage(T &p) {
                 process(m_meta, p);
                 auto bytes = getBufferSize(m_meta);