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#include <stdio.h>
const unsigned int tab32[32] = {
0, 9, 1, 10, 13, 21, 2, 29,
11, 14, 16, 18, 22, 25, 3, 30,
8, 12, 20, 28, 15, 17, 24, 7,
19, 27, 23, 6, 26, 5, 4, 31};
unsigned int log2_32(unsigned int value)
{
value |= value >> 1;
value |= value >> 2;
value |= value >> 4;
value |= value >> 8;
value |= value >> 16;
return tab32[(value * 0x07C4ACDD) >> 27];
}
int main()
{
unsigned int value = 311;
unsigned int bin = 0;
if (value > 0)
bin = log2_32( (value + 9) / 10 );
printf("value: %u, bin: %u", value, bin);
return 0;
}
