/usr/lib/ocaml/batteries/batMarshal.mli is in libbatteries-ocaml-dev 2.4-1.
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(*
* BatMarshal - Extended marshaling operations
* Copyright (C) 1997 Xavier Leroy
* 2008 David Teller
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version,
* with the special exception on linking described in file LICENSE.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*)
(** Marshaling of data structures.
This module provides functions to encode arbitrary data structures
as sequences of bytes, which can then be written on a file or
sent over a pipe or network connection. The bytes can then
be read back later, possibly in another process, and decoded back
into a data structure. The format for the byte sequences
is compatible across all machines for a given version of OCaml.
Warning: marshaling is currently not type-safe. The type
of marshaled data is not transmitted along the value of the data,
making it impossible to check that the data read back possesses the
type expected by the context. In particular, the result type of
the [Marshal.from_*] functions is given as ['a], but this is
misleading: the returned OCaml value does not possess type ['a]
for all ['a]; it has one, unique type which cannot be determined
at compile-type. The programmer should explicitly give the expected
type of the returned value, using the following syntax:
- [(Marshal.from_channel chan : type)].
Anything can happen at run-time if the object in the file does not
belong to the given type.
The representation of marshaled values is not human-readable, and
uses bytes that are not printable characters. Therefore, input and
output channels used in conjunction with {!Marshal.output} and
{!Marshal.input} must be opened in binary mode, using e.g.
{!BatPervasives.open_out_bin} or
{!BatPervasives.open_in_bin}; channels opened in text
mode will cause unmarshaling errors on platforms where text
channels behave differently than binary channels, e.g. Windows.
@author Xavier Leroy (base module)
@author David Teller
*)
type extern_flags = Marshal.extern_flags =
No_sharing (** Don't preserve sharing *)
| Closures (** Send function closures *)
| Compat_32 (** Ensure 32-bit compatibility *)
# 63 "src/batMarshal.mliv"
(** The flags to the [Marshal.to_*] functions below. *)
val output: _ BatInnerIO.output -> ?sharing:bool -> ?closures:bool -> 'a -> unit
(** [output out v] writes the representation of [v] on [chan].
@param sharing If [true] (default value), circularities
and sharing inside the value [v] are detected and preserved
in the sequence of bytes produced. In particular, this
guarantees that marshaling always terminates. Sharing
between values marshaled by successive calls to
[output] is not detected, though. If [false], sharing is ignored.
This results in faster marshaling if [v] contains no shared
substructures, but may cause slower marshaling and larger
byte representations if [v] actually contains sharing,
or even non-termination if [v] contains cycles.
@param closures If [false] (default value) marshaling fails when
it encounters a functional value inside [v]: only ``pure'' data
structures, containing neither functions nor objects, can safely
be transmitted between different programs. If [true], functional
values will be marshaled as a position in the code of the
program. In this case, the output of marshaling can only be read
back in processes that run exactly the same program, with
exactly the same compiled code. (This is checked at
un-marshaling time, using an MD5 digest of the code transmitted
along with the code position.) *)
external to_bytes :
'a -> extern_flags list -> Bytes.t = "caml_output_value_to_string"
(** [Marshal.to_bytes v flags] returns a byte sequence containing
the representation of [v].
The [flags] argument has the same meaning as for
{!Marshal.output}.
@since 2.3.0
*)
external to_string :
'a -> extern_flags list -> string = "caml_output_value_to_string"
(** Same as [to_bytes] but return the result as a string instead of
a byte sequence. *)
val to_buffer : Bytes.t -> int -> int -> 'a -> extern_flags list -> int
(** [Marshal.to_buffer buff ofs len v flags] marshals the value [v],
storing its byte representation in the sequence [buff],
starting at index [ofs], and writing at most
[len] bytes. It returns the number of bytes
actually written to the sequence. If the byte representation
of [v] does not fit in [len] characters, the exception [Failure]
is raised. *)
val input : BatInnerIO.input -> 'a
(** [input inp] reads from [inp] the
byte representation of a structured value, as produced by
one of the [Marshal.to_*] functions, and reconstructs and
returns the corresponding value.*)
val from_bytes : Bytes.t -> int -> 'a
(** [Marshal.from_bytes buff ofs] unmarshals a structured value
like {!Marshal.from_channel} does, except that the byte
representation is not read from a channel, but taken from
the byte sequence [buff], starting at position [ofs].
The byte sequence is not mutated.
@since 2.3.0
*)
val from_string : string -> int -> 'a
(** Same as [from_bytes] but take a string as argument instead of a
byte sequence. *)
val header_size : int
(** The bytes representing a marshaled value are composed of
a fixed-size header and a variable-sized data part,
whose size can be determined from the header.
{!Marshal.header_size} is the size, in bytes, of the header.
{!Marshal.data_size}[ buff ofs] is the size, in bytes,
of the data part, assuming a valid header is stored in
[buff] starting at position [ofs].
Finally, {!Marshal.total_size} [buff ofs] is the total size,
in bytes, of the marshaled value.
Both {!Marshal.data_size} and {!Marshal.total_size} raise [Failure]
if [buff], [ofs] does not contain a valid header.
To read the byte representation of a marshaled value into
a byte sequence, the program needs to read first
{!Marshal.header_size} bytes into the sequence,
then determine the length of the remainder of the
representation using {!Marshal.data_size},
make sure the sequence is large enough to hold the remaining
data, then read it, and finally call {!Marshal.from_bytes}
to unmarshal the value. *)
val data_size : Bytes.t -> int -> int
(** See {!Marshal.header_size}.*)
val total_size : Bytes.t -> int -> int
(** See {!Marshal.header_size}.*)
(** {6 Deprecated} *)
val to_channel : _ BatInnerIO.output -> 'a -> extern_flags list -> unit
(** @deprecated Use {!output} instead *)
val from_channel : BatInnerIO.input -> 'a
(** @deprecated Use {!input} instead *)
|