1 files changed, 47 insertions, 0 deletions
diff --git a/stdio/fopenflags.c b/stdio/fopenflags.c
new file mode 100644
index 0000000..268ea61
--- /dev/null
+++ b/stdio/fopenflags.c
@@ -0,0 +1,47 @@
+/*-*- 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/calls/calls.h"
+#include "libc/stdio/stdio.h"
+#include "libc/sysv/consts/o.h"
+
+/**
+ * Turns stdio flags description string into bitmask.
+ */
+int fopenflags(const char *mode) {
+  unsigned omode, flags;
+  omode = flags = 0;
+  do {
+    if (*mode == 'r') {
+      omode = O_RDONLY;
+    } else if (*mode == 'w') {
+      omode = O_WRONLY;
+      flags |= O_CREAT | O_TRUNC;
+    } else if (*mode == 'a') {
+      omode = O_WRONLY;
+      flags |= O_CREAT | O_APPEND;
+    } else if (*mode == '+') {
+      omode = O_RDWR;
+    } else if (*mode == 'x') {
+      flags |= O_EXCL;
+    } else if (*mode == 'e') {
+      flags |= O_CLOEXEC;
+    }
+  } while (*mode++);
+  return omode | flags;
+}