netmkaddr.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>
#include <ctype.h>

/*
 *  make an address, add the defaults
 */
char *
netmkaddr(char *linear, char *defnet, char *defsrv)
{
	static char addr[256];
	char *cp;

	/*
	 *  dump network name
	 */
	cp = strchr(linear, '!');
	if(cp == 0){
		if(defnet==0){
			if(defsrv)
				snprint(addr, sizeof(addr), "net!%s!%s",
					linear, defsrv);
			else
				snprint(addr, sizeof(addr), "net!%s", linear);
		}
		else {
			if(defsrv)
				snprint(addr, sizeof(addr), "%s!%s!%s", defnet,
					linear, defsrv);
			else
				snprint(addr, sizeof(addr), "%s!%s", defnet,
					linear);
		}
		return addr;
	}

	/*
	 *  if there is already a service, use it
	 */
	cp = strchr(cp+1, '!');
	if(cp)
		return linear;

	/*
	 *  add default service
	 */
	if(defsrv == 0)
		return linear;
	snprint(addr, sizeof(addr), "%s!%s", linear, defsrv);

	return addr;
}