-(** Mark objects as 'ancient' so they are taken out of the OCaml heap.
- * $Id: ancient.mli,v 1.3 2006-09-27 18:39:44 rich Exp $
- *)
+(** Mark objects as 'ancient' so they are taken out of the OCaml heap. *)
type 'a ancient
* Forgetting to delete an ancient object results in a memory leak.
*)
+val is_ancient : 'a -> bool
+ (** [is_ancient ptr] returns true if [ptr] is an object on the ancient
+ * heap.
+ *)
+
+val address_of : 'a -> nativeint
+ (** [address_of obj] returns the address of [obj], or [0n] if [obj]
+ * is not a block.
+ *)
+
(** {6 Shared memory mappings} *)
type md
(** Memory descriptor handle. *)
-val attach : Unix.file_descr -> md
- (** [attach fd] attaches to a new or existing file which may contain
- * shared objects.
+val attach : Unix.file_descr -> nativeint -> md
+ (** [attach fd baseaddr] attaches to a new or existing file
+ * which may contain shared objects.
*
* Initially [fd] should be a read/writable, zero-length file
- * (see {!Unix.openfile}). One or more objects can then be
- * shared in this file using {!Unix.share}.
+ * (for example you could create this using {!Unix.openfile} and
+ * passing the flags [O_RDWR], [O_TRUNC], [O_CREAT]).
+ * One or more objects can then be shared in this file
+ * using {!Unix.share}.
+ *
+ * For new files, [baseaddr] specifies the virtual address to
+ * map the file. Specifying [Nativeint.zero] ([0n]) here lets [mmap(2)]
+ * choose this, but on some platforms (notably Linux/AMD64)
+ * [mmap] chooses very unwisely, tending to map the memory
+ * just before [libc] with hardly any headroom to grow. If
+ * you encounter this sort of problem (usually a segfault or
+ * illegal instruction inside libc), then look at [/proc/PID/maps]
+ * and choose a more suitable address.
+ *
+ * If the file was created previously, then the [baseaddr] is
+ * ignored. The underlying [mmalloc] library will map the
+ * file in at the same place as before.
*)
val detach : md -> unit
* other OCaml processes which can access the underlying
* file. See {!Ancient.attach}, {!Ancient.detach}.
*
- * More than one object can be stored in a file. They are
- * indexed using integers in the range [0..1023] (the limit
- * is hard-coded in [mmalloc/mmprivate.h]). The [key] parameter
- * controls which object is written/overwritten by [share].
+ * More than one object can be stored in a file. The [key]
+ * parameter controls which object is written/overwritten by [share].
* If you do not wish to use this feature, just pass [0]
* as the key.
*
* The underlying [mmalloc] library does not do any sort of
* locking, so all calls to [share] must ensure that they have
* exclusive access to the underlying file while in progress.
+ * (Other processes should not even call {!Ancient.get} while
+ * this is happening, but it seems safe to be just reading an
+ * ancient object from the file).
*)
val get : md -> int -> 'a ancient
(** [get md key] returns the object indexed by [key] in the
* attached file.
*
- * The key is in the range [0..1023] (the limit is hard-coded in
- * [mmalloc/mmprivate.h]).
+ * For details of the [key] parameter see {!Ancient.share}.
*
* You need to annotate the returned object with the correct
* type. As with the Marshal module, there is no type checking,
* and setting the wrong type will likely cause a segfault
- * or undefined behaviour.
+ * or undefined behaviour. Note that the returned object has
+ * type [sometype ancient], not just [sometype].
*
* @raises [Not_found] if no object is associated with the key.
*)
+
+(** {6 Additional information} *)
+
+type info = {
+ i_size : int; (** Allocated size, bytes. *)
+}
+ (** Extra information fields. See {!Ancient.mark_info} and
+ * {!Ancient.share_info}.
+ *)
+
+val mark_info : 'a -> 'a ancient * info
+ (** Same as {!Ancient.mark}, but also returns some extra information. *)
+
+val share_info : md -> int -> 'a -> 'a ancient * info
+ (** Same as {!Ancient.share}, but also returns some extra information. *)
+