Write an unsigned big-endian 32-bit integer
#include <uint32.h>
uint32 u;
void uint32_pack_big(char s[4],uint32 u);
uint32 is a 32-bit unsigned integer type, normally either unsigned int or unsigned long.
uint32_pack_big portably writes a uint32 u to s in big-endian (i.e. network) byte order.