1 /* ISC license. */
2
3 #include <unistd.h>
4 #include <sys/resource.h>
5
6 #include <skalibs/types.h>
7 #include <skalibs/strerr2.h>
8 #include <skalibs/djbunix.h>
9 #include <skalibs/exec.h>
10
11 #define USAGE "fdreserve n prog..."
12
13 #define MAXFDS 1024
14
doit(char * modif,unsigned int i,int fd)15 unsigned int doit (char *modif, unsigned int i, int fd)
16 {
17 unsigned int pos = 2 ;
18 modif[0] = 'F' ; modif[1] = 'D' ;
19 pos += uint_fmt(modif + pos, i) ;
20 modif[pos++] = '=' ;
21 pos += uint_fmt(modif + pos, (unsigned int)fd) ;
22 modif[pos++] = 0 ;
23 return pos ;
24 }
25
main(int argc,char const * const * argv)26 int main (int argc, char const *const *argv)
27 {
28 unsigned int n ;
29 PROG = "fdreserve" ;
30 if ((argc < 3) || !uint0_scan(argv[1], &n))
31 strerr_dieusage(100, USAGE) ;
32 {
33 struct rlimit lim ;
34 if (getrlimit(RLIMIT_NOFILE, &lim) < 0) strerr_diefu1sys(111, "getrlimit") ;
35 if (n > lim.rlim_cur) strerr_dief1x(100, "too many requested fds") ;
36 }
37 {
38 char modif[12 * n] ; /* enough for n times "FDaaaa=bbbb\0" */
39 unsigned int j = 0 ;
40 {
41 int fd[n >> 1][2] ;
42 unsigned int i = 0 ;
43 for (; i < (n>>1) ; i++)
44 if (pipe(fd[i]) < 0)
45 strerr_diefu1sys(111, "reserve fds") ;
46 if (n & 1)
47 {
48 int lastfd = openb_read("/dev/null") ;
49 if (lastfd < 0)
50 strerr_diefu1sys(111, "reserve last fd") ;
51 fd_close(lastfd) ;
52 j += doit(modif + j, n-1, lastfd) ;
53 }
54 for (i = 0 ; i < (n>>1) ; i++)
55 {
56 fd_close(fd[i][0]) ;
57 fd_close(fd[i][1]) ;
58 j += doit(modif + j, i<<1, fd[i][0]) ;
59 j += doit(modif + j, (i<<1)|1, fd[i][1]) ;
60 }
61 }
62 xmexec_n(argv+2, modif, j, n) ;
63 }
64 }
65