Fix #1888: add %I *printf specifier for IP address. Remove mg_ntoa, mg_straddr

src/fmt.c

@@ -1,5 +1,6 @@
 #include "fmt.h"
 #include "iobuf.h"
+#include "util.h"
 
 static void mg_pfn_iobuf_private(char ch, void *param, bool expand) {
   struct mg_iobuf *io = (struct mg_iobuf *) param;
@@ -309,6 +310,20 @@ size_t mg_vxprintf(void (*out)(char, void *), void *param, const char *fmt,
           n += scpy(out, param, (char *) &hex[p[j] & 15], 1);
         }
         n += scpy(out, param, (char *) &dquote, 1);
+      } else if (c == 'I') {
+        // Print IPv4 or IPv6 address
+        size_t len = (size_t) va_arg(*ap, int);  // Length 16 means IPv6 address
+        uint8_t *buf = va_arg(*ap, uint8_t *);   // Pointer to the IP address
+        if (len == 6) {
+          uint16_t *p = (uint16_t *) buf;
+          n += mg_xprintf(out, param, "%x:%x:%x:%x:%x:%x:%x:%x", mg_htons(p[0]),
+                          mg_htons(p[1]), mg_htons(p[2]), mg_htons(p[3]),
+                          mg_htons(p[4]), mg_htons(p[5]), mg_htons(p[6]),
+                          mg_htons(p[7]));
+        } else {
+          n += mg_xprintf(out, param, "%d.%d.%d.%d", (int) buf[0], (int) buf[1],
+                          (int) buf[2], (int) buf[3]);
+        }
       } else if (c == 'V') {
         // Print base64-encoded double-quoted string
         size_t len = (size_t) va_arg(*ap, int);