[O_DIRECT] Rather than overloading the existing Unixext.openfile function, create a Unixext.Direct namespace

Signed-off-by: David Scott <[email protected]>

Author: David Scott

stdext/Makefile

@@ -77,7 +77,7 @@ stdext.cma: $(foreach obj,$(STDEXT_OBJS),$(obj).cmo)
 stdext_stubs.a: unixext_stubs.o zerocheck_stub.o 
 	ocamlmklib -o stdext_stubs $+
 
-libstdext_stubs.a: unixext_open_stubs.o unixext_stubs.o zerocheck_stub.o 
+libstdext_stubs.a: unixext_open_stubs.o unixext_write_stubs.o unixext_stubs.o zerocheck_stub.o
 	ar rcs $@ $+
 	ocamlmklib -o stdext_stubs $+
 

stdext/unixext.ml

@@ -195,26 +195,26 @@ let execv_get_output cmd args =
 		Unix.close pipe_entrance;
 		pid, pipe_exit
 
-(** Copy all data from an in_channel to an out_channel,
- * returning the total number of bytes *)
-let copy_file ?limit ifd ofd =
+let copy_file_internal ?limit reader writer =
 	let buffer = String.make 65536 '\000' in
 	let buffer_len = Int64.of_int (String.length buffer) in
 	let finished = ref false in
 	let total_bytes = ref 0L in
 	let limit = ref limit in
 	while not(!finished) do
 		let requested = min (Opt.default buffer_len !limit) buffer_len in
-		let num = Unix.read ifd buffer 0 (Int64.to_int requested) in
+		let num = reader buffer 0 (Int64.to_int requested) in
 		let num64 = Int64.of_int num in
 
 		limit := Opt.map (fun x -> Int64.sub x num64) !limit;
-		ignore_int (Unix.write ofd buffer 0 num);
+		ignore_int (writer buffer 0 num);
 		total_bytes := Int64.add !total_bytes num64;
 		finished := num = 0 || !limit = Some 0L;
 	done;
 	!total_bytes
 
+let copy_file ?limit ifd ofd = copy_file_internal ?limit (Unix.read ifd) (Unix.write ofd)
+
 let file_exists file_path =
 	try Unix.access file_path [Unix.F_OK]; true
 	with _ -> false
@@ -638,19 +638,27 @@ type statvfs_t = {
 
 external statvfs : string -> statvfs_t = "stub_statvfs"
 
-type open_flag =
-	| O_DIRECT (* new *)
-	| O_RDONLY
-	| O_WRONLY
-	| O_RDWR
-	| O_NONBLOCK
-	| O_APPEND
-	| O_CREAT
-	| O_TRUNC
-	| O_EXCL
-	| O_NOCTTY
-	| O_DSYNC
-	| O_SYNC
-	| O_RSYNC
-
-external openfile : string -> open_flag list -> Unix.file_perm -> Unix.file_descr = "stub_stdext_unix_open"
+module Direct = struct
+	type t = Unix.file_descr
+
+	external openfile : string -> Unix.open_flag list -> Unix.file_perm -> t = "stub_stdext_unix_open_direct"
+
+	let close = Unix.close
+
+	let with_openfile path flags perms f =
+		let t = openfile path flags perms in
+		finally (fun () -> f t) (fun () -> close t)
+
+	external unsafe_write : t -> string -> int -> int -> int = "stub_stdext_unix_write"
+
+	let write fd buf ofs len =
+		if ofs < 0 || len < 0 || ofs > String.length buf - len
+		then invalid_arg "Unix.write"
+		else unsafe_write fd buf ofs len
+
+	let copy_from_fd ?limit socket fd = copy_file_internal ?limit (Unix.read socket) (write fd)
+
+	let fsync x = fsync x
+
+	let lseek fd x cmd = Unix.LargeFile.lseek fd x cmd
+end

stdext/unixext.mli

@@ -156,20 +156,31 @@ type statvfs_t = {
 
 val statvfs : string -> statvfs_t
 
-type open_flag =
-	| O_DIRECT (* new *)
-	| O_RDONLY
-	| O_WRONLY
-	| O_RDWR
-	| O_NONBLOCK
-	| O_APPEND
-	| O_CREAT
-	| O_TRUNC
-	| O_EXCL
-	| O_NOCTTY
-	| O_DSYNC
-	| O_SYNC
-	| O_RSYNC
-
-external openfile : string -> open_flag list -> Unix.file_perm -> Unix.file_descr = "stub_stdext_unix_open"
-(** [openfile name flags perm] behaves the same as [Unix.openfile] but includes the O_DIRECT flag *)
+module Direct : sig
+	(** Perform I/O in O_DIRECT mode using 4KiB page-aligned buffers *)
+
+	type t
+	(** represents a file open in O_DIRECT mode *)
+
+	val openfile : string -> Unix.open_flag list -> Unix.file_perm -> t
+	(** [openfile name flags perm] behaves the same as [Unix.openfile] but includes the O_DIRECT flag *)
+
+	val close : t -> unit
+	(** [close t] closes [t], a file open in O_DIRECT mode *)
+
+	val with_openfile : string -> Unix.open_flag list -> Unix.file_perm -> (t -> 'a) -> 'a
+	(** [with_openfile name flags perm f] opens [name], applies the result to [f] and closes *)
+
+	val write : t -> string -> int -> int -> int
+	(** [write t buf ofs len] writes [len] bytes at offset [ofs] from buffer [buf] to
+		[t] using page-aligned buffers. *)
+
+	val copy_from_fd : ?limit:int64 -> Unix.file_descr -> t -> int64
+	(** [copy_from_fd ?limit fd t] copies from [fd] to [t] up to [limit] *)
+
+	val fsync : t -> unit
+	(** [fsync t] commits all outstanding writes, throwing an error if necessary. *)
+
+	val lseek : t -> int64 -> Unix.seek_command -> int64
+	(** [lseek t offset command]: see Unix.LargeFile.lseek *)
+end

stdext/unixext_open_stubs.c

@@ -37,18 +37,17 @@
 #endif
 
 static int open_flag_table[] = {
-  O_DIRECT,
   O_RDONLY, O_WRONLY, O_RDWR, O_NONBLOCK, O_APPEND, O_CREAT, O_TRUNC, O_EXCL,
   O_NOCTTY, O_DSYNC, O_SYNC, O_RSYNC
 };
 
-CAMLprim value stub_stdext_unix_open(value path, value flags, value perm)
+CAMLprim value stub_stdext_unix_open_direct(value path, value flags, value perm)
 {
   CAMLparam3(path, flags, perm);
   int ret, cv_flags;
   char * p;
 
-  cv_flags = convert_flag_list(flags, open_flag_table);
+  cv_flags = convert_flag_list(flags, open_flag_table) | O_DIRECT;
   p = stat_alloc(string_length(path) + 1);
   strcpy(p, String_val(path));
   /* open on a named FIFO can block (PR#1533) */