iovec-wrapper: introduce iovw_put_string_fieldf()

src/basic/iovec-wrapper.c

@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <stdio.h>
+
 #include "alloc-util.h"
 #include "iovec-util.h"
 #include "iovec-wrapper.h"
@@ -84,6 +86,22 @@ int iovw_put_string_field_full(struct iovec_wrapper *iovw, bool replace, const c
         return r;
 }
 
+int iovw_put_string_fieldf_full(struct iovec_wrapper *iovw, bool replace, const char *field, const char *format, ...) {
+        _cleanup_free_ char *value = NULL;
+        va_list ap;
+        int r;
+
+        assert(format);
+
+        va_start(ap, format);
+        r = vasprintf(&value, format, ap);
+        va_end(ap);
+        if (r < 0)
+                return -ENOMEM;
+
+        return iovw_put_string_field_full(iovw, replace, field, value);
+}
+
 int iovw_put_string_field_free(struct iovec_wrapper *iovw, const char *field, char *value) {
         _cleanup_free_ _unused_ char *free_ptr = value;
 

src/basic/iovec-wrapper.h

@@ -40,6 +40,9 @@ static inline int iovw_put_string_field(struct iovec_wrapper *iovw, const char *
 static inline int iovw_replace_string_field(struct iovec_wrapper *iovw, const char *field, const char *value) {
         return iovw_put_string_field_full(iovw, true, field, value);
 }
+int iovw_put_string_fieldf_full(struct iovec_wrapper *iovw, bool replace, const char *field, const char *format, ...) _printf_(4, 5);
+#define iovw_put_string_fieldf(iovw, ...)     iovw_put_string_fieldf_full(iovw, false, __VA_ARGS__)
+#define iovw_replace_string_fieldf(iovw, ...) iovw_put_string_fieldf_full(iovw, true, __VA_ARGS__)
 int iovw_put_string_field_free(struct iovec_wrapper *iovw, const char *field, char *value);
 void iovw_rebase(struct iovec_wrapper *iovw, void *old, void *new);
 size_t iovw_size(const struct iovec_wrapper *iovw);