Change semantics of interpolate to work like snprintf.

[git.git] / interpolate.c

diff --git a/interpolate.c b/interpolate.c
index 00826778fc3d760a9b001423cd9c26e7972c126f..3de583238d854675ae872047a2d2b7fb09a66969 100644 (file)
--- a/interpolate.c
+++ b/interpolate.c
@@ -44,9 +44,8 @@ void interp_clear_table(struct interp *table, int ninterps)
  *        { "%%", "%"},
  *    }
  *
- * Returns 0 on a successful substitution pass that fits in result,
- * Returns a number of bytes needed to hold the full substituted
- * string otherwise.
+ * Returns the length of the substituted string (not including the final \0).
+ * Like with snprintf, if the result is >= reslen, then it overflowed.
  */
 
 unsigned long interpolate(char *result, unsigned long reslen,
@@ -61,8 +60,6 @@ unsigned long interpolate(char *result, unsigned long reslen,
        int i;
        char c;
 
-        memset(result, 0, reslen);
-
        while ((c = *src)) {
                if (c == '%') {
                        /* Try to match an interpolation string. */
@@ -78,9 +75,9 @@ unsigned long interpolate(char *result, unsigned long reslen,
                                value = interps[i].value;
                                valuelen = strlen(value);
 
-                               if (newlen + valuelen + 1 < reslen) {
+                               if (newlen + valuelen < reslen) {
                                        /* Substitute. */
-                                       strncpy(dest, value, valuelen);
+                                       memcpy(dest, value, valuelen);
                                        dest += valuelen;
                                }
                                newlen += valuelen;
@@ -95,8 +92,9 @@ unsigned long interpolate(char *result, unsigned long reslen,
                newlen++;
        }
 
-       if (newlen + 1 < reslen)
-               return 0;
-       else
-               return newlen + 2;
+       /* XXX: the previous loop always keep room for the ending NUL,
+          we just need to check if there was room for a NUL in the first place */
+       if (reslen > 0)
+               *dest = '\0';
+       return newlen;
 }