Provided by: ocaml-man_4.14.1-1ubuntu1_all 
NAME
Stdlib.Marshal - no description
Module
Module Stdlib.Marshal
Documentation
Module Marshal
: (module Stdlib__Marshal)
type extern_flags =
| No_sharing (* Don't preserve sharing
*)
| Closures (* Send function closures
*)
| Compat_32 (* Ensure 32-bit compatibility
*)
The flags to the Marshal.to_* functions below.
val to_channel : out_channel -> 'a -> extern_flags list -> unit
Marshal.to_channel chan v flags writes the representation of v on channel chan . The flags
argument is a possibly empty list of flags that governs the marshaling behavior with
respect to sharing, functional values, and compatibility between 32- and 64-bit platforms.
If flags does not contain Marshal.No_sharing , 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 Marshal.to_channel is neither detected nor preserved, though. If
flags contains Marshal.No_sharing , 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.
If flags does not contain Marshal.Closures , 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 flags contains
Marshal.Closures , functional values will be marshaled as a the position in the code of
the program together with the values corresponding to the free variables captured in the
closure. 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.)
The exact definition of which free variables are captured in a closure is not specified
and can vary between bytecode and native code (and according to optimization flags). In
particular, a function value accessing a global reference may or may not include the
reference in its closure. If it does, unmarshaling the corresponding closure will create
a new reference, different from the global one.
If flags contains Marshal.Compat_32 , marshaling fails when it encounters an integer value
outside the range [-2{^30}, 2{^30}-1] of integers that are representable on a 32-bit
platform. This ensures that marshaled data generated on a 64-bit platform can be safely
read back on a 32-bit platform. If flags does not contain Marshal.Compat_32 , integer
values outside the range [-2{^30}, 2{^30}-1] are marshaled, and can be read back on a
64-bit platform, but will cause an error at un-marshaling time when read back on a 32-bit
platform. The Mashal.Compat_32 flag only matters when marshaling is performed on a 64-bit
platform; it has no effect if marshaling is performed on a 32-bit platform.
Raises Failure if chan is not in binary mode.
val to_bytes : 'a -> extern_flags list -> bytes
Marshal.to_bytes v flags returns a byte sequence containing the representation of v . The
flags argument has the same meaning as for Marshal.to_channel .
Since 4.02.0
val to_string : 'a -> extern_flags list -> string
Same as to_bytes but return the result as a string instead of a byte sequence.
val to_buffer : bytes -> 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 from_channel : in_channel -> 'a
Marshal.from_channel chan reads from channel chan the byte representation of a structured
value, as produced by one of the Marshal.to_* functions, and reconstructs and returns the
corresponding value.
Raises End_of_file if chan is already at the end of the file.
Raises Failure if the end of the file is reached during unmarshalling itself or if chan is
not in binary mode.
val from_bytes : bytes -> 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 4.02.0
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 -> int -> int
See Marshal.header_size .
val total_size : bytes -> int -> int
See Marshal.header_size .