sys/src/libndb/csgetval.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <bio.h>
   4 #include <ndb.h>
   5 #include <ndbhf.h>
   6
   7 /*
   8  *  search for a tuple that has the given 'attr=val' and also 'rattr=x'.
   9  *  copy 'x' into 'buf' and return the whole tuple.
  10  *
  11  *  return 0 if not found.
  12  */
  13 char*
  14 csgetvalue(char *netroot, char *attr, char *val, char *rattr, Ndbtuple **pp)
  15 {
  16         Ndbtuple *t, *first, *last;
  17         char line[1024];
  18         int fd, n;
  19         char *rv;
  20
  21         if(pp != nil)
  22                 *pp = nil;
  23
  24         if(netroot)
  25                 snprint(line, sizeof(line), "%s/cs", netroot);
  26         else
  27                 strcpy(line, "/net/cs");
  28         fd = open(line, ORDWR);
  29         if(fd < 0)
  30                 return nil;
  31         seek(fd, 0, 0);
  32         snprint(line, sizeof(line), "!%s=%s %s=*", attr, val, rattr);
  33         if(write(fd, line, strlen(line)) < 0){
  34                 close(fd);
  35                 return nil;
  36         }
  37         seek(fd, 0, 0);
  38
  39         rv = nil;
  40         first = last = nil;
  41         for(;;){
  42                 n = read(fd, line, sizeof(line)-2);
  43                 if(n <= 0)
  44                         break;
  45                 line[n] = '\n';
  46                 line[n+1] = 0;
  47
  48                 t = _ndbparseline(line);
  49                 if(t == nil)
  50                         continue;
  51                 if(first != nil)
  52                         last->entry = t;
  53                 else
  54                         first = t;
  55                 do {
  56                         last = t;
  57                         if(rv == nil && strcmp(rattr, t->attr) == 0)
  58                                 rv = strdup(t->val);
  59                         t = t->entry;
  60                 } while(t != nil);
  61         }
  62         close(fd);
  63
  64         if(pp != nil){
  65                 setmalloctag(first, getcallerpc(&netroot));
  66                 *pp = first;
  67         } else
  68                 ndbfree(first);
  69
  70         return rv;
  71 }