Batteries user guide : Batteries.Marshal

# Module Batteries.Marshal

    module Marshal: BatMarshal

    type extern_flags = Marshal.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 output : 'b BatInnerIO.output -> ?sharing:bool -> ?closures:bool -> 'a -> unit

`output out v` writes the representation of `v` on `chan`.
`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.
`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.)

    val to_bytes : 'a -> extern_flags list -> Bytes.t

`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

    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.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`.

###### Deprecated

    val to_channel : 'b BatInnerIO.output -> 'a -> extern_flags list -> unit

Deprecated.Use `BatMarshal.output` instead

    val from_channel : BatInnerIO.input -> 'a

Deprecated.Use `BatMarshal.input` instead