Several common bit operations

The following conclusions are based on the computer platform 1 void main (unsigned int x) that uses the complement code to represent a negative number)
2 {
3 // determine whether the unsigned integer x is the power of 2
4 if (x & (x-1) // if a number is a power of 2, except the highest bit is 1, the other bits are 0 (binary representation, the same below)
5 printf ("False \ n ");
6 else
7 printf ("True \ n ");
8
9 // determine whether or not an unsigned integer is in the form of 2 ^ N-1 (Same principle as above)
10 if (x & (x + 1) // if it is 2 ^ n-1, the low position is all 1
11 printf ("False \ n ");
12 else
13 printf ("True \ n ");
14
15 // The integer can be the maximum power of 2 (?) Division: the number of digits at the rightmost of the result is 1.
16 // e.g.: 100-> 4
17 printf ("% d \ n", x & (-x); // set the remaining positions to 0
18
19 // describe the position with 0 at the rightmost (Same principle as above)
20 // e.g.: 111b-> 1000b, 10-> 1
21 printf ("% d \ n ",~ X & (x + 1); // set this position to 1 and the remaining positions to 0.
22
23 // identify the mask with the suffix 0 (0 consecutive positions 1 on the right side and 0 on the other positions)
24 // e.g.: 1100b-> 0011b
25 printf ("% d \ n ",~ X & (x-1); // or
26 printf ("% d \ n ",~ (X |-x); // or
27 printf ("% d \ n", (x &-x)-1 );
28
29 // identify the mask of 1 at the rightmost and with the suffix 0 (retain the 1 at the rightmost and set all 0 positions 1 after it)
30 // e.g.: 1100b-> 0111b
31 printf ("% d \ n", x ^ (x-1 ));
32
33 // spread the rightmost 1 digit to the right
34 // e.g.: 1100b-> 1111b
35 printf ("% d \ n", x | (x-1 ));
36
37 // set the rightmost consecutive 1 position to 0
38 // e.g.: 10110b-> 10000
39 printf ("% d \ n", (x | (x-1) + 1) & x );
40}

Calculate the number of 1 bits in x: 1int Count1 (int x)
2 {
3 int n = 0;
4 while (x)
5 {
6 n ++;
7 x & = X-1;
8}
9 return n;
10}

Obtain a larger number with the same number of 1 bits. Application: 1 unsigned snoob (unsigned x) in the bitstring representing the subset of the Set)
2 {
3 unsigned smallest, ripple, ones; // e.g.: x = XXX0 1111 0000
4 smallest = x &-x; // 0000 0001 0000
5 ripple = x + smallest; // XXX1 0000 0000
6 ones = x ^ ripple; // 0001 1111 0000
7 ones = (ones> 2)/smallest; // 0000 0000 0111
8 return ripple | ones; // XXX1 0000 0111
9}