Introduce nvim namespace: Move files.

Move files from src/ to src/nvim/.
- src/nvim/ becomes the new root dir for nvim executable sources.
- src/libnvim/ is planned to become root dir of the neovim library.

src/nvim/os/os.h

@@ -0,0 +1,146 @@
+#ifndef NEOVIM_OS_OS_H
+#define NEOVIM_OS_OS_H
+#include <uv.h>
+
+#include "vim.h"
+
+/// Change to the given directory.
+///
+/// @return `0` on success, a libuv error code on failure.
+int os_chdir(const char *path);
+
+/// Get the name of current directory.
+///
+/// @param buf Buffer to store the directory name.
+/// @param len Length of `buf`.
+/// @return `OK` for success, `FAIL` for failure.
+int os_dirname(char_u *buf, size_t len);
+
+/// Check if the given path is a directory or not.
+///
+/// @return `true` if `fname` is a directory.
+bool os_isdir(const char_u *name);
+
+/// Check if the given path represents an executable file.
+///
+/// @return `true` if `name` is executable and
+///   - can be found in $PATH,
+///   - is relative to current dir or
+///   - is absolute.
+///
+/// @return `false` otherwise.
+bool os_can_exe(const char_u *name);
+
+/// Get the file permissions for a given file.
+///
+/// @return `-1` when `name` doesn't exist.
+int32_t os_getperm(const char_u *name);
+
+/// Set the permission of a file.
+///
+/// @return `OK` for success, `FAIL` for failure.
+int os_setperm(const char_u *name, int perm);
+
+/// Check if a file exists.
+///
+/// @return `true` if `name` exists.
+bool os_file_exists(const char_u *name);
+
+/// Check if a file is readonly.
+///
+/// @return `true` if `name` is readonly.
+bool os_file_is_readonly(const char *name);
+
+/// Check if a file is writable.
+///
+/// @return `0` if `name` is not writable,
+/// @return `1` if `name` is writable,
+/// @return `2` for a directory which we have rights to write into.
+int os_file_is_writable(const char *name);
+
+/// Get the size of a file in bytes.
+///
+/// @param[out] size pointer to an off_t to put the size into.
+/// @return `true` for success, `false` for failure.
+bool os_get_file_size(const char *name, off_t *size);
+
+/// Rename a file or directory.
+///
+/// @return `OK` for success, `FAIL` for failure.
+int os_rename(const char_u *path, const char_u *new_path);
+
+/// Make a directory.
+///
+/// @return `0` for success, non-zero for failure.
+int os_mkdir(const char *path, int32_t mode);
+
+/// Remove a directory.
+///
+/// @return `0` for success, non-zero for failure.
+int os_rmdir(const char *path);
+
+/// Remove a file.
+///
+/// @return `0` for success, non-zero for failure.
+int os_remove(const char *path);
+
+/// Get the total system physical memory in KiB.
+uint64_t os_get_total_mem_kib(void);
+const char *os_getenv(const char *name);
+int os_setenv(const char *name, const char *value, int overwrite);
+char *os_getenvname_at_index(size_t index);
+
+/// Get the process ID of the Neovim process.
+///
+/// @return the process ID.
+int64_t os_get_pid(void);
+
+/// Get the hostname of the machine runing Neovim.
+///
+/// @param hostname Buffer to store the hostname.
+/// @param len Length of `hostname`.
+void os_get_hostname(char *hostname, size_t len);
+
+int os_get_usernames(garray_T *usernames);
+int os_get_user_name(char *s, size_t len);
+int os_get_uname(uid_t uid, char *s, size_t len);
+char *os_get_user_directory(const char *name);
+
+/// Get stat information for a file.
+///
+/// @return OK on success, FAIL if an failure occured.
+int os_stat(const char_u *name, uv_stat_t *statbuf);
+
+/// Struct which encapsulates stat information.
+typedef struct {
+  // TODO(stefan991): make stat private
+  uv_stat_t stat;
+} FileInfo;
+
+/// Get the file information for a given path
+///
+/// @param file_descriptor File descriptor of the file.
+/// @param[out] file_info Pointer to a FileInfo to put the information in.
+/// @return `true` on sucess, `false` for failure.
+bool os_get_file_info(const char *path, FileInfo *file_info);
+
+/// Get the file information for a given path without following links
+///
+/// @param path Path to the file.
+/// @param[out] file_info Pointer to a FileInfo to put the information in.
+/// @return `true` on sucess, `false` for failure.
+bool os_get_file_info_link(const char *path, FileInfo *file_info);
+
+/// Get the file information for a given file descriptor
+///
+/// @param file_descriptor File descriptor of the file.
+/// @param[out] file_info Pointer to a FileInfo to put the information in.
+/// @return `true` on sucess, `false` for failure.
+bool os_get_file_info_fd(int file_descriptor, FileInfo *file_info);
+
+/// Compare the inodes of two FileInfos
+///
+/// @return `true` if the two FileInfos represent the same file.
+bool os_file_info_id_equal(FileInfo *file_info_1, FileInfo *file_info_2);
+
+#endif  // NEOVIM_OS_OS_H