add a_strncpy functions

util.c

@@ -142,3 +142,29 @@ compute_new_value_from_arg(const char *arg, double current_value)
 
     return current_value;
 }
+
+/** \brief safe limited strcpy.
+ *
+ * Copies at most min(<tt>n-1</tt>, \c l) characters from \c src into \c dst,
+ * always adding a final \c \\0 in \c dst.
+ *
+ * \param[in]  dst      destination buffer.
+ * \param[in]  n        size of the buffer. Negative sizes are allowed.
+ * \param[in]  src      source string.
+ * \param[in]  l        maximum number of chars to copy.
+ *
+ * \return minimum of  \c src \e length and \c l.
+*/
+ssize_t a_strncpy(char *dst, ssize_t n, const char *src, ssize_t l)
+{
+    ssize_t len = MIN(a_strlen(src), l);
+
+    if (n > 0)
+    {
+        ssize_t dlen = MIN(n - 1, len);
+        memcpy(dst, src, dlen);
+        dst[dlen] = '\0';
+    }
+
+    return len; 
+} 

util.h

@@ -30,6 +30,11 @@
 /** \brief replace \c NULL strings with emtpy strings */ 
 #define NONULL(x)       (x ? x : "") 
 
+#undef MAX
+#undef MIN
+#define MAX(a,b) ((a) < (b) ? (b) : (a))
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+
 #define ssizeof(foo)            (ssize_t)sizeof(foo)
 #define countof(foo)            (ssizeof(foo) / ssizeof(foo[0]))
 
@@ -104,7 +109,6 @@ static inline ssize_t a_strlen(const char *s)
     return s ? strlen(s) : 0;
 }
 
-
 /** \brief \c NULL resistant strdup.
  *
  * the a_strdup() function returns a pointer to a new string, which is a
@@ -132,6 +136,8 @@ static inline int a_strcmp(const char *a, const char *b)
         return strcmp(NONULL(a), NONULL(b));
 }
 
+ssize_t a_strncpy(char *dst, ssize_t n, const char *src, ssize_t l) __attribute__((nonnull(1)));
+
 void die(const char *, ...) __attribute__ ((noreturn)) __attribute__ ((format(printf, 1, 2)));
 void eprint(const char *, ...) __attribute__ ((noreturn)) __attribute__ ((format(printf, 1, 2)));
 Bool xgettextprop(Display *, Window, Atom, char *, unsigned int);