src/basic/replace-var.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2012 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <errno.h>
  23 #include <stddef.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26
  27 #include "alloc-util.h"
  28 #include "macro.h"
  29 #include "replace-var.h"
  30 #include "string-util.h"
  31
  32 /*
  33  * Generic infrastructure for replacing @FOO@ style variables in
  34  * strings. Will call a callback for each replacement.
  35  */
  36
  37 static int get_variable(const char *b, char **r) {
  38         size_t k;
  39         char *t;
  40
  41         assert(b);
  42         assert(r);
  43
  44         if (*b != '@')
  45                 return 0;
  46
  47         k = strspn(b + 1, UPPERCASE_LETTERS "_");
  48         if (k <= 0 || b[k+1] != '@')
  49                 return 0;
  50
  51         t = strndup(b + 1, k);
  52         if (!t)
  53                 return -ENOMEM;
  54
  55         *r = t;
  56         return 1;
  57 }
  58
  59 char *replace_var(const char *text, char *(*lookup)(const char *variable, void*userdata), void *userdata) {
  60         char *r, *t;
  61         const char *f;
  62         size_t l;
  63
  64         assert(text);
  65         assert(lookup);
  66
  67         l = strlen(text);
  68         r = new(char, l+1);
  69         if (!r)
  70                 return NULL;
  71
  72         f = text;
  73         t = r;
  74         while (*f) {
  75                 _cleanup_free_ char *v = NULL, *n = NULL;
  76                 char *a;
  77                 int k;
  78                 size_t skip, d, nl;
  79
  80                 k = get_variable(f, &v);
  81                 if (k < 0)
  82                         goto oom;
  83                 if (k == 0) {
  84                         *(t++) = *(f++);
  85                         continue;
  86                 }
  87
  88                 n = lookup(v, userdata);
  89                 if (!n)
  90                         goto oom;
  91
  92                 skip = strlen(v) + 2;
  93
  94                 d = t - r;
  95                 nl = l - skip + strlen(n);
  96                 a = realloc(r, nl + 1);
  97                 if (!a)
  98                         goto oom;
  99
 100                 l = nl;
 101                 r = a;
 102                 t = r + d;
 103
 104                 t = stpcpy(t, n);
 105                 f += skip;
 106         }
 107
 108         *t = 0;
 109         return r;
 110
 111 oom:
 112         free(r);
 113         return NULL;
 114 }