#if defined(__GNUC__) && (__GNUC__ >= 5) #include "uint32.h" int umult32(uint32 a,uint32 b,uint32* c) { return !__builtin_mul_overflow(a,b,c); } #else #include "safemult.h" int umult32(uint32 a,uint32 b,uint32* c) { unsigned long long x=(unsigned long long)a*b; if (x>0xffffffff) return 0; *c=x&0xffffffff; return 1; } #endif #ifdef UNITTEST #include <assert.h> int main() { uint32 a; assert(umult32(4,0x80000000,&a)==0); assert(umult32(16,0x45000000,&a)==0); // make sure we don't fall for "if a*b<a && a*b<b" assert(umult32(5,10,&a)==1 && a==50); assert(umult32(6,0x10000000,&a)==1 && a==0x60000000); return 0; } #endif