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 OFFSET_SHIFT 1
  14
  15 #define lstr_at(p, n) (*(char**)(((char*)(p))+(n >> OFFSET_SHIFT)))
  16
  17 #define str_at(p, n) (                                          \
  18                 (((n) & MPH_STRING_OFFSET_MASK) == MPH_STRING_OFFSET_ARRAY) \
  19                 ? (char*)(p) + (n >> OFFSET_SHIFT)                          \
  20                 : lstr_at(p, n)                                             \
  21 )
  22
  23 char* MPH_INTERNAL
  24 _mph_copy_structure_strings (
  25         void *to,         const mph_string_offset_t *to_offsets,
  26         const void *from, const mph_string_offset_t *from_offsets,
  27         size_t num_strings)
  28 {
  29         int i;
  30         size_t buflen;
  31         int len[MAX_OFFSETS];
  32         char *buf, *cur = NULL;
  33
  34         g_assert (num_strings < MAX_OFFSETS);
  35
  36         for (i = 0; i < num_strings; ++i) {
  37                 lstr_at (to, to_offsets[i]) = NULL;
  38         }
  39
  40         buflen = num_strings;
  41         for (i = 0; i < num_strings; ++i) {
  42                 len[i] = strlen (str_at(from, from_offsets[i]));
  43                 if (len[i] < INT_MAX - buflen)
  44                         buflen += len[i];
  45                 else
  46                         len[i] = -1;
  47         }
  48
  49         cur = buf = malloc (buflen);
  50         if (buf == NULL) {
  51                 return NULL;
  52         }
  53
  54         for (i = 0; i < num_strings; ++i) {
  55                 if (len[i] > 0) {
  56                         lstr_at (to, to_offsets[i]) =
  57                                 strcpy (cur, str_at (from, from_offsets[i]));
  58                         cur += (len[i] +1);
  59                 }
  60         }
  61
  62         return buf;
  63 }
  64
  65 #ifdef TEST
  66
  67 #include <stdio.h>
  68
  69 struct foo {
  70         char *a;
  71         int   b;
  72         char *c;
  73         char d[10];
  74 };
  75
  76 struct bar {
  77         int    b;
  78         char  *a;
  79         double d;
  80         char  *c;
  81         char  *e;
  82 };
  83
  84 int
  85 main ()
  86 {
  87         /* test copying foo to bar */
  88         struct foo f = {"hello", 42, "world", "!!"};
  89         struct bar b;
  90         mph_string_offset_t foo_offsets[] = {
  91                 MPH_STRING_OFFSET(struct foo, a, MPH_STRING_OFFSET_PTR),
  92                 MPH_STRING_OFFSET(struct foo, c, MPH_STRING_OFFSET_PTR),
  93                 MPH_STRING_OFFSET(struct foo, d, MPH_STRING_OFFSET_ARRAY)
  94         };
  95         mph_string_offset_t bar_offsets[] = {
  96                 MPH_STRING_OFFSET(struct bar, a, MPH_STRING_OFFSET_PTR),
  97                 MPH_STRING_OFFSET(struct bar, c, MPH_STRING_OFFSET_PTR),
  98                 MPH_STRING_OFFSET(struct bar, e, MPH_STRING_OFFSET_PTR)
  99         };
 100         char *buf;
 101
 102         buf = _mph_copy_structure_strings (&b, bar_offsets,
 103                         &f, foo_offsets, 3);
 104         printf ("b.a=%s\n", b.a);
 105         printf ("b.c=%s\n", b.c);
 106         printf ("b.e=%s\n", b.e);
 107
 108         return 0;
 109 }
 110 #endif
 111