tcsgetval.c - plan9port - [fork] Plan 9 from user space
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tcsgetval.c (1752B)
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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 int n, linefound;
18 char line[1024];
19 int fd;
20 int oops = 0;
21 char *rv;
22
23 if(pp)
24 *pp = nil;
25 rv = nil;
26
27 if(netroot)
28 snprint(line, sizeof(line), "%s/cs", netroot);
29 else
30 strcpy(line, "/net/cs");
31 fd = open(line, ORDWR);
32 if(fd < 0)
33 return 0;
34 seek(fd, 0, 0);
35 snprint(line, sizeof(line), "!%s=%s %s=*", attr, val, rattr);
36 if(write(fd, line, strlen(line)) < 0){
37 close(fd);
38 return 0;
39 }
40 seek(fd, 0, 0);
41
42 first = last = 0;
43 linefound = 0;
44 for(;;){
45 n = read(fd, line, sizeof(line)-2);
46 if(n <= 0)
47 break;
48 line[n] = '\n';
49 line[n+1] = 0;
50
51 t = _ndbparseline(line);
52 if(t == 0)
53 continue;
54 if(first)
55 last->entry = t;
56 else
57 first = t;
58 last = t;
59
60 while(last->entry)
61 last = last->entry;
62
63 for(; t; t = t->entry){
64 if(linefound == 0){
65 if(strcmp(rattr, t->attr) == 0){
66 linefound = 1;
67 rv = strdup(t->val);
68 }
69 }
70 }
71 }
72 close(fd);
73
74 if(oops){
75 werrstr("buffer too short");
76 ndbfree(first);
77 return nil;
78 }
79
80 if(pp){
81 setmalloctag(first, getcallerpc(&netroot));
82 *pp = first;
83 } else
84 ndbfree(first);
85
86 return rv;
87 }
88
89 Ndbtuple*
90 csgetval(char *netroot, char *attr, char *val, char *rattr, char *buf)
91 {
92 Ndbtuple *t;
93 char *p;
94
95 p = csgetvalue(netroot, attr, val, rattr, &t);
96 if(p == nil){
97 if(buf != nil)
98 *buf = 0;
99 } else {
100 if(buf != nil){
101 strncpy(buf, p, Ndbvlen-1);
102 buf[Ndbvlen-1] = 0;
103 }
104 free(p);
105 }
106 return t;
107 }