Bit Operation

* Bit Operations
~, &, |, ^, << and >>.

* Examples
- Check whether the system is big endian or little endian
Why does this solution not work?
int i = 1;
char c = (char)i; /* c == 1 no matter what endianness */
return c;
- Get/clear the lowest bit of 1 (or 0 by using ~x as input)
x & -x; and x & (x-1);
- Get the index of lowest/highest bit of 1
k = 0;
if ((x & 0x1) != 0) return k;
do { ++k;} while (((x >>= 1) & 0x1) == 0) and
while (x >>= 1) ++k;
- Calculate the number of '1' in the one integer
while (x != 0)
{ x = x & (x-1); ++count; }
- Check whether the integer is the power of 2
The number of '1' in the integer is one.
- Get the next power of 2
unsigned int n = 1U << highestOne(x);
if (n == x) return n;
return n << 1;
- Reverse the bits order in one integer
x = ((x & m) << n) | ((x & ~m) >> n); /* m is masking code and n is swapping number */
- Reverse two bits in one word: swap2(x, k1, k2)
- Arithmetic Rotation
x = (x << r) | (x >> (BITNUM - r));
- Circular Block Shifting
x = (1 << n) - 1;
x = x << p | (x >> (BITNUM - p));
- Max(0, x) and Min(0, x)
return x & ~(x >> (BITNUM - 1)); and
return x & (x >> (BITNUM - 1))
- Overflow for signed num
addition: ~(a^b)&(a^s)&0x80000000
subtraction: (a^b)&(a^s)&0x80000000