getgr_r.c

#include "pwf.h"
#include <pthread.h>

#define FIX(x) (gr->gr_##x = gr->gr_##x-line+buf)

static int getgr_r(const char *name, gid_t gid, struct group *gr, char *buf, size_t size, struct group **res)
{
	FILE *f;
	char *line = 0;
	size_t len = 0;
	char **mem = 0;
	size_t nmem = 0;
	int rv = 0;
	size_t i;
	int cs;

	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);

	f = fopen("/etc/group", "rbe");
	if (!f) {
		rv = errno;
		goto done;
	}

	*res = 0;
	while (__getgrent_a(f, gr, &line, &len, &mem, &nmem)) {
		if (name && !strcmp(name, gr->gr_name)
		|| !name && gr->gr_gid == gid) {
			if (size < len + (nmem+1)*sizeof(char *) + 32) {
				rv = ERANGE;
				break;
			}
			*res = gr;
			buf += (16-(uintptr_t)buf)%16;
			gr->gr_mem = (void *)buf;
			buf += (nmem+1)*sizeof(char *);
			memcpy(buf, line, len);
			FIX(name);
			FIX(passwd);
			for (i=0; mem[i]; i++)
				gr->gr_mem[i] = mem[i]-line+buf;
			gr->gr_mem[i] = 0;
			break;
		}
	}
 	free(mem);
 	free(line);
	fclose(f);
done:
	pthread_setcancelstate(cs, 0);
	return rv;
}

int getgrnam_r(const char *name, struct group *gr, char *buf, size_t size, struct group **res)
{
	return getgr_r(name, 0, gr, buf, size, res);
}

int getgrgid_r(gid_t gid, struct group *gr, char *buf, size_t size, struct group **res)
{
	return getgr_r(0, gid, gr, buf, size, res);
}