add xargvlen

app/src/util/str_util.c

@@ -10,6 +10,18 @@
 # include <tchar.h>
 #endif
 
+size_t
+xargvlen(const char *const *argv, size_t *n_args) {
+    size_t i, len = 0;
+    for (i = 0; argv[i]; i++) {
+        len += strlen(argv[i]);
+        if(i != 0) len += 1; /* extra for space */
+    }
+    if (n_args) *n_args = i;
+
+    return len;
+}
+
 size_t
 xstrncpy(char *dest, const char *src, size_t n) {
     size_t i;

app/src/util/str_util.h

@@ -6,6 +6,10 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+// returns the flat buffer size large enough to store all argv elements (excluding nul terminator) plus separating spaces
+size_t
+xargvlen(const char * const argv[], size_t *n_args);
+
 // like strncpy, except:
 //  - it copies at most n-1 chars
 //  - the dest string is nul-terminated