1 5dc21454 2023-07-14 jrmu /*
 2 5dc21454 2023-07-14 jrmu  * 2-8. Write a function rightrot(x,n) that returns the value of the
 3 5dc21454 2023-07-14 jrmu  * integer x rotated to the right by n bit positions.
 4 5dc21454 2023-07-14 jrmu  */
 5 5dc21454 2023-07-14 jrmu 
 6 5dc21454 2023-07-14 jrmu #include <stdio.h>
 7 5dc21454 2023-07-14 jrmu 
 8 5dc21454 2023-07-14 jrmu unsigned setbits(unsigned x, int p, int n, unsigned y);
 9 5dc21454 2023-07-14 jrmu unsigned getbits(unsigned x, int p, int n);
10 5dc21454 2023-07-14 jrmu unsigned invert(unsigned x, int p, int n);
11 5dc21454 2023-07-14 jrmu unsigned rightrot(unsigned x, int n);
12 5dc21454 2023-07-14 jrmu 
13 5dc21454 2023-07-14 jrmu main()
14 5dc21454 2023-07-14 jrmu {
15 5dc21454 2023-07-14 jrmu 	printf("%u: %u\n", 0xf01abcde, rightrot(0xabcdef01, 12));
16 5dc21454 2023-07-14 jrmu 	printf("%u: %u\n", 0x468acf02, rightrot(0x12345678, 27));
17 5dc21454 2023-07-14 jrmu 	printf("%u: %u\n", 0xed497d59, rightrot(0x92fab3da, 9));
18 5dc21454 2023-07-14 jrmu 	printf("%u: %u\n", 0x1ef50dd4, rightrot(0x1ba83dea, 17));
19 5dc21454 2023-07-14 jrmu }
20 5dc21454 2023-07-14 jrmu /*
21 5dc21454 2023-07-14 jrmu a    b    c    d    e    f    0    1
22 5dc21454 2023-07-14 jrmu 1010 1011 1100 1101 1110 1111 0000 0001
23 5dc21454 2023-07-14 jrmu 1111 0000 0001 1010 1011 1100 1101 1110
24 5dc21454 2023-07-14 jrmu f    0    1    a    b    c    d    e
25 5dc21454 2023-07-14 jrmu 
26 5dc21454 2023-07-14 jrmu 1    2    3    4    5    6    7    8
27 5dc21454 2023-07-14 jrmu 0001 0010 0011 0100 0101 0110 0111 1000
28 5dc21454 2023-07-14 jrmu 0100 0110 1000 1010 1100 1111 0000 0010
29 5dc21454 2023-07-14 jrmu 4    6    8    a    c    f    0    2
30 5dc21454 2023-07-14 jrmu 
31 5dc21454 2023-07-14 jrmu 9    2    f    a    b    3    d    a
32 5dc21454 2023-07-14 jrmu 1001 0010 1111 1010 1011 0011 1101 1010
33 5dc21454 2023-07-14 jrmu 1110 1101 0100 1001 0111 1101 0101 1001
34 5dc21454 2023-07-14 jrmu e    d    4    9    7    d    5    9
35 5dc21454 2023-07-14 jrmu 
36 5dc21454 2023-07-14 jrmu 1    b    a    8    3    d    e    a
37 5dc21454 2023-07-14 jrmu 0001 1011 1010 1000 0011 1101 1110 1010
38 5dc21454 2023-07-14 jrmu 0001 1110 1111 0101 0000 1101 1101 0100
39 5dc21454 2023-07-14 jrmu 1    e    f    5    0    d    d    4
40 5dc21454 2023-07-14 jrmu  */
41 5dc21454 2023-07-14 jrmu unsigned rightrot(unsigned x, int n) {
42 5dc21454 2023-07-14 jrmu 	return (x >> n) | setbits(0,31,n,x);
43 5dc21454 2023-07-14 jrmu }
44 5dc21454 2023-07-14 jrmu 
45 5dc21454 2023-07-14 jrmu unsigned invert(unsigned x, int p, int n) {
46 5dc21454 2023-07-14 jrmu 	return setbits(x, p, n, ~getbits(x, p, n));
47 5dc21454 2023-07-14 jrmu }
48 5dc21454 2023-07-14 jrmu 
49 5dc21454 2023-07-14 jrmu unsigned setbits(unsigned x, int p, int n, unsigned y)
50 5dc21454 2023-07-14 jrmu {
51 5dc21454 2023-07-14 jrmu 	return ((x >> (p+1)) << (p+1)) | (getbits(y, n-1, n) << (p-n+1)) | (x & ~(~0 << (p-n+1)));
52 5dc21454 2023-07-14 jrmu }
53 5dc21454 2023-07-14 jrmu 
54 5dc21454 2023-07-14 jrmu unsigned getbits(unsigned x, int p, int n)
55 5dc21454 2023-07-14 jrmu {
56 5dc21454 2023-07-14 jrmu 	return (x >> (p+1-n)) & ~(~0 << n);
57 5dc21454 2023-07-14 jrmu }