file,os/fs,shada: Separate opening, closing, writing and reading files

Moves low-level functions handling to os/fs.c. Adds file.c with a proxy
interface.

Target: while leaving syscalls handling is os.c (partially handled by libuv),
add buffering for reading and writing to file.c.

1 files changed, 59 insertions, 0 deletions

diff --git a/src/nvim/file.h b/src/nvim/file.h
new file mode 100644
index 0000000000..0aa98e0def
--- /dev/null
+++ b/src/nvim/file.h
@@ -0,0 +1,59 @@
+#ifndef NVIM_FILE_H
+#define NVIM_FILE_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <fcntl.h>
+
+#include "nvim/func_attr.h"
+
+/// Structure used to read from/write to file
+typedef struct {
+  int fd;  ///< File descriptor.
+  bool eof;  ///< True if end of file was encountered.
+} FileDescriptor;
+
+/// file_open() flags
+typedef enum {
+  FILE_READ_ONLY = O_RDONLY,  ///< Open file read-only.
+  FILE_CREATE = O_CREAT,  ///< Create file if it does not exist yet.
+  FILE_WRITE_ONLY = O_WRONLY,  ///< Open file for writing only.
+#ifdef O_NOFOLLOW
+  FILE_NOSYMLINK = O_NOFOLLOW,  ///< Do not allow symbolic links.
+#else
+  FILE_NOSYMLINK = 0,
+#endif
+  FILE_CREATE_ONLY = O_CREAT|O_EXCL,  ///< Only create the file, failing
+                                      ///< if it already exists.
+  FILE_TRUNCATE = O_TRUNC,  ///< Truncate the file if it exists.
+} FileOpenFlags;
+
+/// Check whether end of file was encountered
+///
+/// @param[in]  fp  File to check.
+///
+/// @return true if it was, false if it was not or read operation was never
+///         performed.
+static inline bool file_eof(const FileDescriptor *const fp)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
+  FUNC_ATTR_ALWAYS_INLINE
+{
+  return fp->eof && rbuffer_size(fp->rv) == 0;
+}
+
+/// Return the file descriptor associated with the FileDescriptor structure
+///
+/// @param[in]  fp  File to check.
+///
+/// @return File descriptor.
+static inline int file_fd(const FileDescriptor *const fp)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
+  FUNC_ATTR_ALWAYS_INLINE
+{
+  return fp->fd;
+}
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "file.h.generated.h"
+#endif
+#endif  // NVIM_FILE_H