Merge pull request #621 from talex5/stat-docs

Document File.Stat record fields

lib_eio/core/eio__core.mli

@@ -433,6 +433,9 @@ module Exn : sig
       This is similar to {!Fmt.exn}, but can do a better job on {!Io} exceptions
       because it can format them directly without having to convert to a string first. *)
 
+  val pp_err : err Fmt.t
+  (** [pp_err] formats an error code. *)
+
   (** Extensible backend-specific exceptions. *)
   module Backend : sig
     type t = ..

lib_eio/file.ml

@@ -16,6 +16,16 @@ module Stat = struct
     | `Socket
   ]
 
+  let pp_kind ppf = function
+    | `Unknown -> Fmt.string ppf "unknown"
+    | `Fifo -> Fmt.string ppf "fifo"
+    | `Character_special -> Fmt.string ppf "character special file"
+    | `Directory -> Fmt.string ppf "directory"
+    | `Block_device -> Fmt.string ppf "block device"
+    | `Regular_file -> Fmt.string ppf "regular file"
+    | `Symbolic_link -> Fmt.string ppf "symbolic link"
+    | `Socket -> Fmt.string ppf "socket"
+
   type t = {
     dev : Int64.t;
     ino : Int64.t;
@@ -30,6 +40,22 @@ module Stat = struct
     mtime : float;
     ctime : float;
   }
+
+  let pp ppf t =
+    Fmt.record [
+      Fmt.field "dev" (fun t -> t.dev) Fmt.int64;
+      Fmt.field "ino" (fun t -> t.ino) Fmt.int64;
+      Fmt.field "kind" (fun t -> t.kind) pp_kind;
+      Fmt.field "perm" (fun t -> t.perm) (fun ppf i -> Fmt.pf ppf "0o%o" i);
+      Fmt.field "nlink" (fun t -> t.nlink) Fmt.int64;
+      Fmt.field "uid" (fun t -> t.uid) Fmt.int64;
+      Fmt.field "gid" (fun t -> t.gid) Fmt.int64;
+      Fmt.field "rdev" (fun t -> t.rdev) Fmt.int64;
+      Fmt.field "size" (fun t -> t.size) Optint.Int63.pp;
+      Fmt.field "atime" (fun t -> t.atime) Fmt.float;
+      Fmt.field "mtime" (fun t -> t.mtime) Fmt.float;
+      Fmt.field "ctime" (fun t -> t.ctime) Fmt.float;
+    ] ppf t 
 end
 
 type ro_ty = [`File | Flow.source_ty | Resource.close_ty]

lib_eio/file.mli

@@ -1,6 +1,6 @@
 open Std
 
-(** Tranditional Unix permissions. *)
+(** Traditional Unix permissions. *)
 module Unix_perm : sig
   type t = int
   (** This is the same as {!Unix.file_perm}, but avoids a dependency on [Unix]. *)
@@ -21,21 +21,27 @@ module Stat : sig
   ]
   (** Kind of file from st_mode. **)
 
+  val pp_kind : kind Fmt.t
+  (** Pretty printer for {! kind}. *)
+
   type t = {
-    dev : Int64.t;
+    dev : Int64.t;              (** Device containing the filesystem where the file resides. *)
-    ino : Int64.t;
+    ino : Int64.t;              (** Inode number. *)
-    kind : kind;
+    kind : kind;                (** File type. *)
-    perm : Unix_perm.t;
+    perm : Unix_perm.t;         (** Permissions (mode). *)
-    nlink : Int64.t;
+    nlink : Int64.t;            (** Number of hard links. *)
-    uid : Int64.t;
+    uid : Int64.t;              (** User ID of owner. *)
-    gid : Int64.t;
+    gid : Int64.t;              (** Group ID of owner. *)
-    rdev : Int64.t;
+    rdev : Int64.t;             (** Device's ID (if this is a device). *)
-    size : Optint.Int63.t;
+    size : Optint.Int63.t;      (** Total size in bytes. *)
-    atime : float;
+    atime : float;              (** Last access time. *)
-    mtime : float;
+    mtime : float;              (** Last modification time. *)
-    ctime : float;
+    ctime : float;              (** Creation time. *)
   }
   (** Like stat(2). *)
+
+  val pp : t Fmt.t
+  (** Pretty printer for {! t}. *)
 end
 
 type ro_ty = [`File | Flow.source_ty | Resource.close_ty]

lib_eio/fs.ml

@@ -42,8 +42,8 @@ type create = [
 
 type dir_ty = [`Dir]
 type 'a dir = ([> dir_ty] as 'a) r
-
 (** Note: use the functions in {!Path} to access directories. *)
+
 module Pi = struct
   module type DIR = sig
     type t
@@ -60,6 +60,7 @@ module Pi = struct
     val mkdir : t -> perm:File.Unix_perm.t -> path -> unit
     val open_dir : t -> sw:Switch.t -> path -> [`Close | dir_ty] r
     val read_dir : t -> path -> string list
+    val stat : t -> follow:bool -> string -> File.Stat.t
     val unlink : t -> path -> unit
     val rmdir : t -> path -> unit
     val rename : t -> path -> _ dir -> path -> unit

lib_eio/path.ml

@@ -61,6 +61,14 @@ let read_dir t =
     let bt = Printexc.get_raw_backtrace () in
     Exn.reraise_with_context ex bt "reading directory %a" pp t
 
+let stat ~follow t =
+  let (Resource.T (dir, ops), path) = t in
+  let module X = (val (Resource.get ops Fs.Pi.Dir)) in
+  try X.stat ~follow dir path
+  with Exn.Io _ as ex ->
+    let bt = Printexc.get_raw_backtrace () in
+    Exn.reraise_with_context ex bt "examining %a" pp t
+
 let with_open_in path fn =
   Switch.run @@ fun sw -> fn (open_in ~sw path)
 

lib_eio/path.mli

@@ -128,6 +128,14 @@ val read_dir : _ t -> string list
 
     Note: The special Unix entries "." and ".." are not included in the results. *)
 
+(** {2 Metadata} *)
+
+val stat : follow:bool -> _ t -> File.Stat.t
+(** [stat ~follow t] returns metadata about the file [t].
+
+    If [t] is a symlink, the information returned is about the target if [follow = true],
+    otherwise it is about the link itself. *)
+
 (** {1 Other} *)
 
 val unlink : _ t -> unit

lib_eio_linux/eio_linux.ml

@@ -526,6 +526,34 @@ end = struct
   let unlink t path = Low_level.unlink ~rmdir:false t.fd path
   let rmdir t path = Low_level.unlink ~rmdir:true t.fd path
 
+  let float_of_time s ns =
+    let s = Int64.to_float s in
+    let f = s +. (float ns /. 1e9) in
+    (* It's possible that we might round up to the next second.
+       Since some algorithms only care about the seconds part,
+       make sure the integer part is always [s]: *)
+    if floor f = s then f
+    else Float.pred f
+
+  let stat t ~follow path =
+    let module X = Uring.Statx in
+    let x = X.create () in
+    Low_level.statx_confined ~follow ~mask:X.Mask.basic_stats t.fd path x;
+    { Eio.File.Stat.
+      dev    = X.dev x;
+      ino    = X.ino x;
+      kind   = X.kind x;
+      perm   = X.perm x;
+      nlink  = X.nlink x;
+      uid    = X.uid x;
+      gid    = X.gid x;
+      rdev   = X.rdev x;
+      size   = X.size x |> Optint.Int63.of_int64;
+      atime  = float_of_time (X.atime_sec x) (X.atime_nsec x);
+      mtime  = float_of_time (X.mtime_sec x) (X.mtime_nsec x);
+      ctime  = float_of_time (X.ctime_sec x) (X.ctime_nsec x);
+    }
+
   let rename t old_path t2 new_path =
     match get_dir_fd_opt t2 with
     | Some fd2 -> Low_level.rename t.fd old_path fd2 new_path

lib_eio_linux/low_level.ml

@@ -350,25 +350,43 @@ let getrandom { Cstruct.buffer; off; len } =
   in
   loop 0
 
-(* [with_parent_dir dir path fn] runs [fn parent (basename path)],
+(* [with_parent_dir_fd dir path fn] runs [fn parent (basename path)],
-   where [parent] is a path FD for [path]'s parent, resolved using [Resolve.beneath]. *)
+   where [parent] is a path FD for [path]'s parent, resolved using [Resolve.beneath].
-let with_parent_dir op dir path fn =
+
+   If [basename path] is ".." then we treat it as if path had "/." on the end,
+   to avoid the special case.
+
+   todo: Optimise this by doing [fn AT_FDCWD path] if [dir = Fs].
+*)
+let with_parent_dir_fd dir path fn =
   let dir_path = Filename.dirname path in
   let leaf = Filename.basename path in
   Switch.run (fun sw ->
-      let parent =
       match dir with
-        | FD d when dir_path = "." -> d
+      | _ when leaf = ".." ->
+        let fd =
+          openat ~sw ~seekable:false dir path   (* Open the full path *)
+            ~access:`R
+            ~flags:Uring.Open_flags.(cloexec + path + directory)
+            ~perm:0
+        in
+        fn fd "."
+      | FD d when dir_path = "." -> fn d leaf
       | _ ->
+        let parent =
           openat ~sw ~seekable:false dir dir_path
             ~access:`R
             ~flags:Uring.Open_flags.(cloexec + path + directory)
             ~perm:0
         in
-      Fd.use_exn op parent @@ fun parent ->
         fn parent leaf
     )
 
+let with_parent_dir op dir path fn =
+  with_parent_dir_fd dir path @@ fun parent leaf ->
+  Fd.use_exn op parent @@ fun parent ->
+  fn parent leaf
+
 let statx ?fd ~mask path buf flags =
   let res =
     match fd with
@@ -379,6 +397,23 @@ let statx ?fd ~mask path buf flags =
   in
   if res <> 0 then raise @@ Err.wrap_fs (Uring.error_of_errno res) "statx" path
 
+let statx_confined ~mask ~follow fd path buf =
+  let module X = Uring.Statx in
+  let flags = if follow then X.Flags.empty else X.Flags.symlink_nofollow in
+  match fd with
+  | Fs -> statx ~mask path buf flags
+  | Cwd | FD _ when not follow ->
+    with_parent_dir_fd fd path @@ fun parent leaf ->
+    statx ~mask ~fd:parent leaf buf flags
+  | Cwd | FD _ ->
+    Switch.run @@ fun sw ->
+    let fd = openat ~sw ~seekable:false fd (if path = "" then "." else path)
+        ~access:`R
+        ~flags:Uring.Open_flags.(cloexec + path)
+        ~perm:0
+    in
+    statx ~fd ~mask "" buf Uring.Statx.Flags.(flags + empty_path)
+
 let mkdir_beneath ~perm dir path =
   (* [mkdir] is really an operation on [path]'s parent. Get a reference to that first: *)
   with_parent_dir "mkdir" dir path @@ fun parent leaf ->

lib_eio_posix/flow.ml

@@ -2,12 +2,7 @@ open Eio.Std
 
 module Fd = Eio_unix.Fd
 
-module Impl = struct
+let float_of_time s ns =
-  type tag = [`Generic | `Unix]
-
-  type t = Eio_unix.Fd.t
-
-  let float_of_time s ns =
   let s = Int64.to_float s in
   let f = s +. (float ns /. 1e9) in
   (* It's possible that we might round up to the next second.
@@ -16,10 +11,7 @@ module Impl = struct
   if floor f = s then f
   else Float.pred f
 
-  let stat t =
+let eio_of_stat x =
-    try
-      let x = Low_level.create_stat () in
-      Low_level.fstat ~buf:x t;
   { Eio.File.Stat.
     dev    = Low_level.dev x;
     ino    = Low_level.ino x;
@@ -34,6 +26,17 @@ module Impl = struct
     mtime  = float_of_time (Low_level.mtime_sec x) (Low_level.mtime_nsec x);
     ctime  = float_of_time (Low_level.ctime_sec x) (Low_level.ctime_nsec x);
   }
+
+module Impl = struct
+  type tag = [`Generic | `Unix]
+
+  type t = Eio_unix.Fd.t
+
+  let stat t =
+    try
+      let x = Low_level.create_stat () in
+      Low_level.fstat ~buf:x t;
+      eio_of_stat x
     with Unix.Unix_error (code, name, arg) -> raise @@ Err.wrap code name arg
 
   let single_write t bufs =

lib_eio_posix/fs.ml

@@ -137,6 +137,16 @@ end = struct
     with_parent_dir t path @@ fun dirfd path ->
     Err.run (Low_level.unlink ?dirfd ~dir:true) path
 
+  let stat t ~follow path =
+    let buf = Low_level.create_stat () in
+    if follow then (
+      Err.run (Low_level.fstatat ~buf ~follow:true) (resolve t path);
+    ) else (
+      with_parent_dir t path @@ fun dirfd path ->
+      Err.run (Low_level.fstatat ~buf ?dirfd ~follow:false) path;
+    );
+    Flow.eio_of_stat buf
+
   let read_dir t path =
     (* todo: need fdopendir here to avoid races *)
     let path = resolve t path in

lib_eio_windows/fs.ml

@@ -145,6 +145,15 @@ end = struct
     with_parent_dir t path @@ fun dirfd path ->
     Err.run (Low_level.unlink ?dirfd ~dir:true) path
 
+  let stat t ~follow path =
+    Switch.run @@ fun sw ->
+    let open Low_level in
+    let flags = Low_level.Flags.Open.(generic_read + synchronise) in
+    let dis = Flags.Disposition.open_if in
+    let create = Flags.Create.non_directory in
+    let fd = Err.run (openat ~sw ~nofollow:(not follow) (resolve t path) flags dis) create in
+    Flow.Impl.stat fd
+
   let read_dir t path =
     (* todo: need fdopendir here to avoid races *)
     let path = resolve t path in
@@ -153,7 +162,7 @@ end = struct
 
   let rename t old_path new_dir new_path =
     match Handler.as_posix_dir new_dir with
-    | None -> invalid_arg "Target is not an eio_posix directory!"
+    | None -> invalid_arg "Target is not an eio_windows directory!"
     | Some new_dir ->
       with_parent_dir t old_path @@ fun old_dir old_path ->
       with_parent_dir new_dir new_path @@ fun new_dir new_path ->

tests/fs.md

@@ -520,6 +520,22 @@ Unconfined:
 ```
 
 # Stat
+
+```ocaml
+let try_stat path =
+  let stat ~follow =
+    match Eio.Path.stat ~follow path with
+    | info -> Fmt.str "@[<h>%a@]" Eio.File.Stat.pp_kind info.kind
+    | exception Eio.Io (e, _) -> Fmt.str "@[<h>%a@]" Eio.Exn.pp_err e
+  in
+  let a = stat ~follow:false in
+  let b = stat ~follow:true in
+  if a = b then
+    traceln "%a -> %s" Eio.Path.pp path a
+  else
+    traceln "%a -> %s / %s" Eio.Path.pp path a b
+```
+
 ```ocaml
 # run @@ fun env ->
   let cwd = Eio.Stdenv.cwd env in
@@ -533,6 +549,32 @@ Unconfined:
 - : unit = ()
 ```
 
+Fstatat:
+
+```ocaml
+# run @@ fun env ->
+  let cwd = Eio.Stdenv.cwd env in
+  Switch.run @@ fun sw ->
+  try_mkdir (cwd / "stat_subdir2");
+  Unix.symlink "stat_subdir2" "symlink";
+  Unix.symlink "missing" "broken-symlink";
+  try_stat (cwd / "stat_subdir2");
+  try_stat (cwd / "symlink");
+  try_stat (cwd / "broken-symlink");
+  try_stat cwd;
+  try_stat (cwd / "..");
+  Unix.symlink ".." "parent-symlink";
+  try_stat (cwd / "parent-symlink");
++mkdir <cwd:stat_subdir2> -> ok
++<cwd:stat_subdir2> -> directory
++<cwd:symlink> -> symbolic link / directory
++<cwd:broken-symlink> -> symbolic link / Fs Not_found _
++<cwd> -> directory
++<cwd:..> -> Fs Permission_denied _
++<cwd:parent-symlink> -> symbolic link / Fs Permission_denied _
+- : unit = ()
+```
+
 # pread/pwrite
 
 Check reading and writing vectors at arbitrary offsets: