1 files changed, 41 insertions, 0 deletions
diff --git a/stdio/vfprintf.c b/stdio/vfprintf.c
new file mode 100644
index 0000000..cd2c0a2
--- /dev/null
+++ b/stdio/vfprintf.c
@@ -0,0 +1,41 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=8 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/fmt/fmt.h"
+#include "libc/limits.h"
+#include "libc/stdio/stdio.h"
+#include "libc/sysv/errfuns.h"
+
+struct state {
+  FILE *f;
+  int n;
+};
+
+static noinstrument int vfprintfputchar(int c, struct state *st) {
+  st->n++;
+  return fputc(c, st->f);
+}
+
+int(vfprintf)(FILE *f, const char *fmt, va_list va) {
+  struct state st[1] = {{f, 0}};
+  if (__fmt(vfprintfputchar, st, fmt, va) != -1) {
+    return st->n;
+  } else {
+    return -1;
+  }
+}