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#include <limits.h>
#include <stdint.h>
#include "test.h"
const uint8_t pg_leftmost_one_pos[256] = {
0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7
};
static inline int pg_leftmost_one_pos64(uint64_t word)
{
int shift = 64 - 8;
while ((word >> shift) == 0) {
shift -= 8;
}
int pos = shift + pg_leftmost_one_pos[(word >> shift) & 255];
return pos;
}
static inline int pg_ceil_log2_64(uint64_t num)
{
if (num < 2)
return 0;
else
return pg_leftmost_one_pos64(num - 1) + 1;
}
static int my_log2(long num) {
if (num > LONG_MAX / 2)
num = LONG_MAX / 2;
// Assuming SIZEOF_LONG >= 8
return pg_ceil_log2_64(num);
}
static int next_pow2_int(long num) {
if (num > INT_MAX / 2)
num = INT_MAX / 2;
int log2 = my_log2(num);
return 1 << log2;
}
int main() {
long test_values[] = {1, 2, 3, 536870912, LONG_MAX};
for (int i = 0; i < sizeof(test_values) / sizeof(test_values[0]); ++i) {
printf("Input: %ld, next_pow2_int: %d\n", test_values[i], next_pow2_int(test_values[i]));
if (i == 0)
ASSERT(1, next_pow2_int(test_values[i]) );
else if (i == 1)
ASSERT(2, next_pow2_int(test_values[i]) );
else if (i == 2)
ASSERT(4, next_pow2_int(test_values[i]) );
else if (i == 3)
ASSERT(536870912, next_pow2_int(test_values[i]) );
else if (i == 4)
ASSERT(1073741824, next_pow2_int(test_values[i]) );
}
return 0;
}
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