1 (** Mark objects as 'ancient' so they are taken out of the OCaml heap.
2 * $Id: ancient.mli,v 1.8 2006-10-13 12:28:20 rich Exp $
7 val mark : 'a -> 'a ancient
8 (** [mark obj] copies [obj] and all objects referenced
9 * by [obj] out of the OCaml heap. It returns the proxy
12 * The copy of [obj] accessed through the proxy MUST NOT be mutated.
14 * If [obj] represents a large object, then it is a good
15 * idea to call {!Gc.compact} after marking to recover the
19 val follow : 'a ancient -> 'a
20 (** Follow proxy link to out of heap object.
22 * @raise [Invalid_argument "deleted"] if the object has been deleted.
25 val delete : 'a ancient -> unit
26 (** [delete obj] deletes ancient object [obj].
28 * @raise [Invalid_argument "deleted"] if the object has been deleted.
30 * Forgetting to delete an ancient object results in a memory leak.
33 val is_ancient : 'a -> bool
34 (** [is_ancient ptr] returns true if [ptr] is an object on the ancient
38 val address_of : 'a -> nativeint
39 (** [address_of obj] returns the address of [obj], or [0n] if [obj]
43 (** {6 Shared memory mappings} *)
46 (** Memory descriptor handle. *)
48 val attach : Unix.file_descr -> nativeint -> md
49 (** [attach fd baseaddr] attaches to a new or existing file
50 * which may contain shared objects.
52 * Initially [fd] should be a read/writable, zero-length file
53 * (for example you could create this using {!Unix.openfile} and
54 * passing the flags [O_RDWR], [O_TRUNC], [O_CREAT]).
55 * One or more objects can then be shared in this file
56 * using {!Unix.share}.
58 * For new files, [baseaddr] specifies the virtual address to
59 * map the file. Specifying [Nativeint.zero] ([0n]) here lets [mmap(2)]
60 * choose this, but on some platforms (notably Linux/AMD64)
61 * [mmap] chooses very unwisely, tending to map the memory
62 * just before [libc] with hardly any headroom to grow. If
63 * you encounter this sort of problem (usually a segfault or
64 * illegal instruction inside libc), then look at [/proc/PID/maps]
65 * and choose a more suitable address.
67 * If the file was created previously, then the [baseaddr] is
68 * ignored. The underlying [mmalloc] library will map the
69 * file in at the same place as before.
72 val detach : md -> unit
73 (** [detach md] detaches from an existing file, and closes it.
76 val share : md -> int -> 'a -> 'a ancient
77 (** [share md key obj] does the same as {!Ancient.mark} except
78 * that instead of copying the object into local memory, it
79 * writes it into memory which is backed by the attached file.
81 * Shared mappings created this way may be shared between
82 * other OCaml processes which can access the underlying
83 * file. See {!Ancient.attach}, {!Ancient.detach}.
85 * More than one object can be stored in a file. The [key]
86 * parameter controls which object is written/overwritten by [share].
87 * If you do not wish to use this feature, just pass [0]
90 * Do not call {!Ancient.delete} on a mapping created like this.
91 * Instead, call {!Ancient.detach} and, if necessary, delete the
94 * Caution when sharing files/objects between processes:
95 * The underlying [mmalloc] library does not do any sort of
96 * locking, so all calls to [share] must ensure that they have
97 * exclusive access to the underlying file while in progress.
98 * (Other processes should not even call {!Ancient.get} while
99 * this is happening, but it seems safe to be just reading an
100 * ancient object from the file).
103 val get : md -> int -> 'a ancient
104 (** [get md key] returns the object indexed by [key] in the
107 * For details of the [key] parameter see {!Ancient.share}.
109 * You need to annotate the returned object with the correct
110 * type. As with the Marshal module, there is no type checking,
111 * and setting the wrong type will likely cause a segfault
112 * or undefined behaviour. Note that the returned object has
113 * type [sometype ancient], not just [sometype].
115 * @raises [Not_found] if no object is associated with the key.
118 (** {6 Additional information} *)
121 i_size : int; (** Allocated size, bytes. *)
123 (** Extra information fields. See {!Ancient.mark_info} and
124 * {!Ancient.share_info}.
127 val mark_info : 'a -> 'a ancient * info
128 (** Same as {!Ancient.mark}, but also returns some extra information. *)
130 val share_info : md -> int -> 'a -> 'a ancient * info
131 (** Same as {!Ancient.share}, but also returns some extra information. *)