add fluid_align_ptr() for aligning pointers

src/utils/fluid_sys.h

@@ -602,4 +602,20 @@ void fluid_clear_fpe_i386(void);
 /* System control */
 void fluid_msleep(unsigned int msecs);
 
+/**
+ * Advances the given \c ptr to the next \c alignment byte boundary.
+ * Make sure you've allocated an extra of \c alignment bytes to avoid a buffer overflow.
+ * 
+ * @return Returned pointer is guarenteed to be aligned to \c alignment boundary and in range \f[ ptr <= returned_ptr < ptr + alignment \f].
+ */
+static FLUID_INLINE void* fluid_align_ptr(const void* ptr, unsigned int alignment)
+{
+    uintptr_t ptr_int = (uintptr_t)ptr;
+    unsigned int offset = ptr_int % alignment;
+    unsigned int add = offset == 0 ? 0 // is already aligned, dont advance, else buffer overrun
+                                   : alignment - offset; // advance the pointer to the next alignment boundary
+    ptr_int += add;
+    return (void*)ptr_int;
+}
+
 #endif /* _FLUID_SYS_H */

test/CMakeLists.txt

@@ -13,6 +13,7 @@ ADD_FLUID_TEST(test_sample_cache)
 ADD_FLUID_TEST(test_sfont_loading)
 ADD_FLUID_TEST(test_sample_rate_change)
 ADD_FLUID_TEST(test_preset_sample_loading)
+ADD_FLUID_TEST(test_pointer_alignment)
 
 if ( LIBSNDFILE_HASVORBIS )
     ADD_FLUID_TEST(test_sf3_sfont_loading)

test/test_pointer_alignment.c

@@ -0,0 +1,31 @@
+
+#include "test.h"
+#include "utils/fluid_sys.h"
+
+
+// test for fluid_align_ptr()
+int main(void)
+{
+    unsigned int align;
+    uintptr_t ptr, aligned_ptr;
+    
+    for(align = 32; align <= 4*1024u; align <<= 1)
+    {
+        for(ptr = 0; ptr <= (align<<10); ptr++)
+        {
+            char* tmp = fluid_align_ptr((char*)ptr, align);
+            aligned_ptr = (uintptr_t)tmp;
+            
+            // pointer must be aligned properly
+            TEST_ASSERT(aligned_ptr % align == 0);
+            
+            // aligned pointer must not be smaller than ptr
+            TEST_ASSERT(aligned_ptr >= ptr);
+            
+            // aligned pointer must not be bigger than alignment
+            TEST_ASSERT(aligned_ptr < ptr + align);
+        }
+    }
+    
+    return EXIT_SUCCESS;
+}