Added variadic string append function strb_appendv().

Author: obilaniu

src/util/strb.c

@@ -43,25 +43,29 @@ int strb_grow(strb *sb, size_t n) {
   return 0;
 }
 
-void strb_appendf(strb *sb, const char *f, ...) {
-  va_list ap;
-  int s;
+void strb_appendv(strb *sb, const char *f, va_list ap) {
+  va_list apSave;
+  int     s;
 
-  va_start(ap, f);
 #ifdef _MSC_VER
-  s = _vscprintf(f, ap);
+  /**
+   * va_copy() is a C99 novelty that a particular company should have started
+   * supporting a long time ago, to their undying shame.
+   */
+  
+  apSave = ap;
+  s = _vscprintf(f, apSave);
 #else
-  s = vsnprintf(NULL, 0, f, ap);
+  va_copy(apSave, ap);
+  s = vsnprintf(NULL, 0, f, apSave);
 #endif
-  va_end(ap);
-
+  va_end(apSave);
+  
   if (s < 0) { strb_seterror(sb); return; }
   s += 1;
 
   if (strb_ensure(sb, s)) return;
-  va_start(ap, f);
   s = vsnprintf(sb->s+sb->l, s, f, ap);
-  va_end(ap);
   sb->l += s;
 }
 
@@ -100,3 +104,11 @@ int strb_write(int fd, strb *sb) {
   }
   return 0;
 }
+
+void strb_appendf(strb *sb, const char *f, ...) {
+  va_list ap;
+  va_start(ap, f);
+  strb_appendv(sb, f, ap);
+  va_end(ap);
+}
+

src/util/strb.h

@@ -2,6 +2,7 @@
 #define STRB_H
 
 #include "private_config.h"
+#include <stdarg.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -187,6 +188,17 @@ void strb_read(strb *sb, int fd, size_t sz);
  */
 int strb_write(int fd, strb *sb);
 
+/*
+ * Appends the result of a sprintf using the format string `f` and
+ * following variadic arguments list, excluding terminating nul.
+ *
+ * Unlike sprintf, this function makes sure not to run off the end of
+ * memory and behaves like asprintf in that respect.
+ *
+ * A format error will place the strb in error mode.
+ */
+void strb_appendv(strb *, const char *f, va_list ap);
+
 /*
  * Returns a C string from the content of the strb.
  *