interpolate.c

   1 /*
   2  * Copyright 2006 Jon Loeliger
   3  */
   4
   5 #include "git-compat-util.h"
   6 #include "interpolate.h"
   7
   8
   9 void interp_set_entry(struct interp *table, int slot, const char *value)
  10 {
  11         char *oldval = table[slot].value;
  12         char *newval = NULL;
  13
  14         if (oldval)
  15                 free(oldval);
  16
  17         if (value)
  18                 newval = xstrdup(value);
  19
  20         table[slot].value = newval;
  21 }
  22
  23
  24 void interp_clear_table(struct interp *table, int ninterps)
  25 {
  26         int i;
  27
  28         for (i = 0; i < ninterps; i++) {
  29                 interp_set_entry(table, i, NULL);
  30         }
  31 }
  32
  33
  34 /*
  35  * Convert a NUL-terminated string in buffer orig
  36  * into the supplied buffer, result, whose length is reslen,
  37  * performing substitutions on %-named sub-strings from
  38  * the table, interps, with ninterps entries.
  39  *
  40  * Example interps:
  41  *    {
  42  *        { "%H", "example.org"},
  43  *        { "%port", "123"},
  44  *        { "%%", "%"},
  45  *    }
  46  *
  47  * Returns the length of the substituted string (not including the final \0).
  48  * Like with snprintf, if the result is >= reslen, then it overflowed.
  49  */
  50
  51 unsigned long interpolate(char *result, unsigned long reslen,
  52                 const char *orig,
  53                 const struct interp *interps, int ninterps)
  54 {
  55         const char *src = orig;
  56         char *dest = result;
  57         unsigned long newlen = 0;
  58         const char *name, *value;
  59         unsigned long namelen, valuelen;
  60         int i;
  61         char c;
  62
  63         while ((c = *src)) {
  64                 if (c == '%') {
  65                         /* Try to match an interpolation string. */
  66                         for (i = 0; i < ninterps; i++) {
  67                                 name = interps[i].name;
  68                                 namelen = strlen(name);
  69                                 if (strncmp(src, name, namelen) == 0)
  70                                         break;
  71                         }
  72
  73                         /* Check for valid interpolation. */
  74                         if (i < ninterps) {
  75                                 value = interps[i].value;
  76                                 if (!value) {
  77                                         src += namelen;
  78                                         continue;
  79                                 }
  80
  81                                 valuelen = strlen(value);
  82                                 if (newlen + valuelen < reslen) {
  83                                         /* Substitute. */
  84                                         memcpy(dest, value, valuelen);
  85                                         dest += valuelen;
  86                                 }
  87                                 newlen += valuelen;
  88                                 src += namelen;
  89                                 continue;
  90                         }
  91                 }
  92                 /* Straight copy one non-interpolation character. */
  93                 if (newlen + 1 < reslen)
  94                         *dest++ = *src;
  95                 src++;
  96                 newlen++;
  97         }
  98
  99         /* XXX: the previous loop always keep room for the ending NUL,
 100            we just need to check if there was room for a NUL in the first place */
 101         if (reslen > 0)
 102                 *dest = '\0';
 103         return newlen;
 104 }