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