Seeing the project name EAStdC I thought for a moment this would be the C counterpart to EASTL (e.g. a modern replacement for the C standard library), but alas,

Seeing the project name EAStdC I thought for a moment this would be the C counterpart to EASTL (e.g. a modern replacement for the C standard library), but alas, it's all written in C++ and intended to be used from C++ (e.g. no C interfaces). For anyone interested in this sort of stuff and isn't yet aware of the 'bit twiddling hacks' collection: https://graphics.stanford.edu/~seander/bithacks.html https://graphics.stanford.edu/~seander/bithacks.html Also regarding the bit counting function: inline int CountBits(uint32_t x) // Branchless version { #if defined(EASTDC_SSE_POPCNT) return _mm_popcnt_u32(x); #else x = x - ((x >> 1) & 0x55555555); x = (x & 0x33333333) + ((x >> 2) & 0x33333333); x = (x + (x >> 4)) & 0x0F0F0F0F; return (int)((x * 0x01010101) >> 24); #endif } Some compilers go as far as detecting the 'bit twiddling' version and replace that with a popcnt instruction: https://www.godbolt.org/z/bExMvfzEx https://www.godbolt.org/z/bExMvfzEx