add reopen

Signed-off-by: Mattias Andrée <maandree@member.fsf.org>

1 files changed, 43 insertions, 4 deletions

diff --git a/include/fcntl.h b/include/fcntl.h
index 1c13b8d..422d408 100644
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -52,10 +52,49 @@ int creat(const char*, mode_t)
   __deprecated("Use 'open' instead.");
 
 
-
+#if defined(__SLIBC_SOURCE)
+/**
+ * Reopen a file via its file descriptor. The old file descriptor
+ * is closed and replace with the new open file descriptor.
+ * 
+ * This function call is different from the `dup` function-family
+ * in two ways: (1) you can select news flags, for example, if
+ * `fd` was read-only, the new file descriptor can be write-only,
+ * and (2) the file descriptor is not duplicated, the file is
+ * reopened.
+ * 
+ * This function is useful if you want to reopen a file you do
+ * now know the pathname, you do not want to create a new string
+ * with the pathname, or if the the file no longer has a pathname
+ * because it has been unlinked.
+ * 
+ * Because the file is reopened, the file position is reset and
+ * is not shared with any duplicates of `fd`, unlike a call to
+ * dup(3). it is visible to the filesystem as a new open file
+ * descriptor and is distinguished from the duplocates of `fd`,
+ * and all file locks associated with `fd` are lost, except for
+ * on the duplicates of `fd`, which means that you can create
+ * new locks without removing locks from the duplicates of `fd`.
+ * 
+ * This is a slibc extension.
+ * 
+ * @etymology  (Reopen) file!
+ * 
+ * @param   fd     The file descriptor.
+ * @param   oflag  How the file shall be opened, see open(3).
+ *                 `O_CREAT` is not allowed.
+ * @return         Zero on success, -1 on error.
+ * 
+ * @throws  EINVAL  `oflag` contains `O_CREAT`.
+ * @throws  EINVAL  `fd` is negative.
+ * @throws          Any error specified for open(3).
+ * @throws          Any error specified for dup2(3).
+ * 
+ * @since  Always.
+ */
+int reopen(int, int);
 #endif
 
-/*
-  TODO int reopen(int fd, int oflag); 0, on success, -1 on error
-*/
+
+#endif