How can I reorder the bytes of an integer? [duplicate]

Answer 1

You may want to have a look at this answer, which shows how to convert both ways, also with different byte sizes. This is one way to do it, but more efficient ways are discussed in the thread linked.

uint32_t num = 9;
uint32_t b0,b1,b2,b3,b4,b5,b6,b7;
uint32_t res = 0;

b0 = (num & 0xf) << 28;
b1 = (num & 0xf0) << 24;
b2 = (num & 0xf00) << 20;
b3 = (num & 0xf000) << 16;
b4 = (num & 0xf0000) << 12;
b5 = (num & 0xf00000) << 8;
b6 = (num & 0xf000000) << 4;
b7 = (num & 0xf0000000) << 4;

res = b0 + b1 + b2 + b3 + b4 + b5 + b6 + b7;

printf("%d\n", res);