Question

I need to convert integer value into char array on bit layer. Let’s say int has 4 bytes and I need to split it into 4 chunks of length 1 byte as char array.

Example:

int a = 22445;
// this is in binary 00000000 00000000 1010111 10101101
...
//and the result I expect
char b[4];
b[0] = 0; //first chunk
b[1] = 0; //second chunk
b[2] = 87; //third chunk - in binary 1010111
b[3] = 173; //fourth chunk - 10101101

I need this conversion make really fast, if possible without any loops (some tricks with bit operations perhaps). The goal is thousands of such conversions in one second.

Answer 1

I’m not sure if I recommend this, but you can #include <stddef.h> and <sys/types.h> and write:

*(u32_t *)b = htonl((u32_t)a);

(The htonl is to ensure that the integer is in big-endian order before you store it.)