#include <uint32.h> uint32 u;uint32 is a 32-bit unsigned integer type, normally either unsigned int or unsigned long.
#include <uint32.h> uint32_pack(s,u); uint32_unpack(s,&u); uint32 u; char s[4];uint32_pack finds integers u0, u1, u2, u3 between 0 and 255 inclusive such that u equals u0+256*u1+65536*u2+16777216*u3. It then stores u0 in s[0], u1 in s[1], u2 in s[2], and u3 in s[3].
uint32_unpack extracts u0 from s[0], u1 from s[1], u2 from s[2], and u3 from s[3]. It then sets u to u0+256*u1+65536*u2+16777216*u3.
#include <uint32.h> uint32_pack_big(s,u); uint32_unpack_big(s,&u); uint32 u; char s[4];uint32_pack_big finds integers u0, u1, u2, u3 between 0 and 255 inclusive such that u equals u0+256*u1+65536*u2+16777216*u3. It then stores u0 in s[3], u1 in s[2], u2 in s[1], and u3 in s[0].
uint32_unpack_big extracts u0 from s[3], u1 from s[2], u2 from s[1], and u3 from s[0]. It then sets u to u0+256*u1+65536*u2+16777216*u3.