support/x-struct-str.c

   1 /*
   2  * A helper routine to copy the strings between differing structures.
   3  */
   4
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <limits.h>
   8
   9 #include "mph.h"
  10
  11 #define MAX_OFFSETS 10
  12
  13 #define str_at(p, n) (*(char**)(((char*)p)+n))
  14
  15 char* MPH_INTERNAL
  16 _mph_copy_structure_strings (
  17         void *to,         const size_t *to_offsets,
  18         const void *from, const size_t *from_offsets,
  19         size_t num_strings)
  20 {
  21         int i;
  22         size_t buflen;
  23         int len[MAX_OFFSETS];
  24         char *buf, *cur = NULL;
  25
  26         g_assert (num_strings < MAX_OFFSETS);
  27
  28         for (i = 0; i < num_strings; ++i) {
  29                 str_at (to, to_offsets[i]) = NULL;
  30         }
  31
  32         buflen = num_strings;
  33         for (i = 0; i < num_strings; ++i) {
  34                 len[i] = strlen (str_at(from, from_offsets[i]));
  35                 if (len[i] < INT_MAX - buflen)
  36                         buflen += len[i];
  37                 else
  38                         len[i] = -1;
  39         }
  40
  41         cur = buf = malloc (buflen);
  42         if (buf == NULL) {
  43                 return NULL;
  44         }
  45
  46         for (i = 0; i < num_strings; ++i) {
  47                 if (len[i] > 0) {
  48                         str_at (to, to_offsets[i]) =
  49                                 strcpy (cur, str_at (from, from_offsets[i]));
  50                         cur += (len[i] +1);
  51                 }
  52         }
  53
  54         return buf;
  55 }
  56
  57 #ifdef TEST
  58
  59 #include <stdio.h>
  60
  61 struct foo {
  62         char *a;
  63         int   b;
  64         char *c;
  65 };
  66
  67 struct bar {
  68         int    b;
  69         char  *a;
  70         double d;
  71         char  *c;
  72 };
  73
  74 int
  75 main ()
  76 {
  77         /* test copying foo to bar */
  78         struct foo f = {"hello", 42, "world"};
  79         struct bar b;
  80         size_t foo_offsets[] = {offsetof(struct foo, a), offsetof(struct foo, c)};
  81         size_t bar_offsets[] = {offsetof(struct bar, a), offsetof(struct bar, c)};
  82         char *buf;
  83
  84         buf = _mph_copy_structure_strings (&b, bar_offsets,
  85                         &f, foo_offsets, 2);
  86         printf ("b.a=%s\n", b.a);
  87         printf ("b.c=%s\n", b.c);
  88
  89         return 0;
  90 }
  91 #endif
  92