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optimize fluid_align_ptr() for alignment powers of two

This commit is contained in:
derselbst 2018-05-04 16:40:45 +02:00
parent ab255b7178
commit 5280aae7ac
1 changed files with 7 additions and 3 deletions
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10
src/utils/fluid_sys.h
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@ -606,15 +606,19 @@ 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.
*
* @note \c alignment must be a power of two
* @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
unsigned int offset = ptr_int & (alignment-1);
unsigned int add = (alignment - offset) & (alignment-1); // advance the pointer to the next alignment boundary
ptr_int += add;
/* assert alignment is power of two */
FLUID_ASSERT(!(alignment == 0) && !(alignment & (alignment - 1)));
return (void*)ptr_int;
}