Created
October 31, 2019 04:25
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int most_significant_bit_position(size_t value) { | |
// int count = 0; | |
// while (value != 0) { | |
// value >>= 1; | |
// count++; | |
// } | |
// return count; | |
assert(value > 0); | |
value = (uint64_t) value; | |
int count = 0; | |
printf("----\n"); | |
printf("value: %zx, count: %d\n", value, count); | |
if ((value & 0x00000000FFFFFFFF) == 0) { | |
count += 32; | |
value = value >> 32; | |
} | |
if ((value & 0x000000000000FFFF) == 0) { | |
count += 16; | |
value = value >> 16; | |
} | |
if ((value & 0x00000000000000FF) == 0) { | |
count += 8; | |
value = value >> 8; | |
} | |
if ((value & 0x000000000000000F) == 0) { | |
count += 4; | |
value = value >> 4; | |
} | |
if ((value & 0x0000000000000003) == 0) { | |
count += 2; | |
value = value >> 2; | |
} | |
if ((value & 0x0000000000000001) == 0) { | |
count += 1; | |
} | |
printf("value: %zx, count: %d\n", value, count); | |
printf("returning: 64-count: %d\n", 64-count); | |
return 64 - count; | |
} |
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