dynbuf: add Curl_dyn_vaddf

Closes #6004

docs/DYNBUF.md

@@ -42,6 +42,12 @@ Append a C string to the end of the buffer.
 
 Append a `printf()`-style string to the end of the buffer.
 
+## vaddf
+
+    CURLcode Curl_dyn_vaddf(struct dynbuf *s, const char *fmt, va_list ap);
+
+Append a `vprintf()`-style string to the end of the buffer.
+
 ## reset
 
     void Curl_dyn_reset(struct dynbuf *s);

lib/dynbuf.c

@@ -177,24 +177,22 @@ CURLcode Curl_dyn_add(struct dynbuf *s, const char *str)
 }
 
 /*
- * Append a string printf()-style
+ * Append a string vprintf()-style
  */
-CURLcode Curl_dyn_addf(struct dynbuf *s, const char *fmt, ...)
+CURLcode Curl_dyn_vaddf(struct dynbuf *s, const char *fmt, va_list ap)
 {
-  va_list ap;
 #ifdef BUILDING_LIBCURL
   int rc;
-  va_start(ap, fmt);
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
   rc = Curl_dyn_vprintf(s, fmt, ap);
-  va_end(ap);
 
   if(!rc)
     return CURLE_OK;
 #else
   char *str;
-  va_start(ap, fmt);
   str = vaprintf(fmt, ap); /* this allocs a new string to append */
-  va_end(ap);
 
   if(str) {
     CURLcode result = dyn_nappend(s, (unsigned char *)str, strlen(str));
@@ -207,7 +205,21 @@ CURLcode Curl_dyn_addf(struct dynbuf *s, const char *fmt, ...)
   return CURLE_OUT_OF_MEMORY;
 }
 
-
+/*
+ * Append a string printf()-style
+ */
+CURLcode Curl_dyn_addf(struct dynbuf *s, const char *fmt, ...)
+{
+  CURLcode result;
+  va_list ap;
+  DEBUGASSERT(s);
+  DEBUGASSERT(s->init == DYNINIT);
+  DEBUGASSERT(!s->leng || s->bufr);
+  va_start(ap, fmt);
+  result = Curl_dyn_vaddf(s, fmt, ap);
+  va_end(ap);
+  return result;
+}
 
 /*
  * Returns a pointer to the buffer.

lib/dynbuf.h

@@ -29,6 +29,7 @@
 #define Curl_dyn_add(a,b) curlx_dyn_add(a,b)
 #define Curl_dyn_addn(a,b,c) curlx_dyn_addn(a,b,c)
 #define Curl_dyn_addf curlx_dyn_addf
+#define Curl_dyn_vaddf curlx_dyn_vaddf
 #define Curl_dyn_free(a) curlx_dyn_free(a)
 #define Curl_dyn_ptr(a) curlx_dyn_ptr(a)
 #define Curl_dyn_uptr(a) curlx_dyn_uptr(a)
@@ -56,6 +57,8 @@ CURLcode Curl_dyn_add(struct dynbuf *s, const char *str)
   WARN_UNUSED_RESULT;
 CURLcode Curl_dyn_addf(struct dynbuf *s, const char *fmt, ...)
   WARN_UNUSED_RESULT;
+CURLcode Curl_dyn_vaddf(struct dynbuf *s, const char *fmt, va_list ap)
+  WARN_UNUSED_RESULT;
 void Curl_dyn_reset(struct dynbuf *s);
 CURLcode Curl_dyn_tail(struct dynbuf *s, size_t trail);
 char *Curl_dyn_ptr(const struct dynbuf *s);
@@ -80,4 +83,5 @@ int Curl_dyn_vprintf(struct dynbuf *dyn, const char *format, va_list ap_save);
 #define DYN_PROXY_CONNECT_HEADERS 16384
 #define DYN_QLOG_NAME       1024
 #define DYN_H1_TRAILER      4096
+#define DYN_PINGPPONG_CMD   (64*1024)
 #endif