Module Unpack_one


If unpack_one : ('a, 'partial_unpack) unpack_one, then unpack_one buf ?pos ?len ?partial_unpack must unpack at most one value of type 'a from buf starting at pos, and not using more than len characters. unpack_one must returns one the following:

  • `Ok (value, n) -- unpacking succeeded and consumed n bytes, where 0 <= n <= len. It is possible to have n = 0, e.g. for sexp unpacking, which can only tell it has reached the end of an atom when it encounters the following punctuation character, which if it is left paren, is the start of the following sexp.
  • `Not_enough_data (p, n) -- unpacking encountered a valid proper prefix of a packed value, and consumed n bytes, where 0 <= n <= len. p is a "partial unpack" that can be supplied to a future call to unpack_one to continue unpacking.
  • `Invalid_data -- unpacking encountered an invalidly packed value.

A naive unpack_one that only succeeds on a fully packed value could lead to quadratic behavior if a packed value's bytes are input using a linear number of calls to feed.

type ('a, 'partial_unpack) unpacked = ?partial_unpack:'partial_unpack -> ?pos:int -> ?len:int -> Core_kernel.Bigstring.t -> [
| `Ok of 'a * int
| `Not_enough_data of 'partial_unpack * int
| `Invalid_data of Core_kernel.Error.t
type 'a t =
| T : ('a, _) unpacked -> 'a t
include Core_kernel.Monad.S with type 'a t := 'a t
type 'a t
include Monad_intf.S_without_syntax with type 'a t := 'a t
type 'a t

A monad is an abstraction of the concept of sequencing of computations. A value of type 'a monad represents a computation that returns a value of type 'a.

include Monad_intf.Infix with type 'a t := 'a t
type 'a t
val (>>=) : 'a t -> ('a -> 'b t) -> 'b t

t >>= f returns a computation that sequences the computations represented by two monad elements. The resulting computation first does t to yield a value v, and then runs the computation returned by f v.

val (>>|) : 'a t -> ('a -> 'b) -> 'b t

t >>| f is t >>= (fun a -> return (f a)).

module Monad_infix : Monad_intf.Infix with type 'a t := 'a t
val bind : 'a t -> ('a -> 'b t) -> 'b t

bind t f = t >>= f

val return : 'a -> 'a t

return v returns the (trivial) computation that returns v.

val map : 'a t -> f:('a -> 'b) -> 'b t

map t ~f is t >>| f.

val join : 'a t t -> 'a t

join t is t >>= (fun t' -> t').

val ignore_m : 'a t -> unit t

ignore_m t is map t ~f:(fun _ -> ()). ignore_m used to be called ignore, but we decided that was a bad name, because it shadowed the widely used Pervasives.ignore. Some monads still do let ignore = ignore_m for historical reasons.

val all : 'a t list -> 'a list t
val all_ignore : unit t list -> unit t
include Monad_intf.Syntax with type 'a t := 'a t
type 'a t
module Let_syntax : sig .. end
val create_bin_prot : 'a Bin_prot.Type_class.reader -> 'a t

create_bin_prot reader returns an unpacker that reads the "size-prefixed" bin_prot encoding, in which a value is encoded by first writing the length of the bin_prot data as a 64-bit int, and then writing the data itself. This encoding makes it trivial to know if enough data is available in the buffer, so there is no need to represent partially unpacked values, and hence 'partial_unpack = unit.

Beware that when unpacking sexps, one cannot tell if one is at the end of an atom until one hits punctuation. So, one should always feed a space (" ") to a sexp unpack buffer after feeding a batch of complete sexps, to ensure that the final sexp is unpacked.

val char : char t
module type Equal = sig .. end
expect t equal a returns an unpacker that unpacks using t and then returns `Ok if the unpacked value equals a, or `Invalid_data otherwise.
val expect : 'a t -> (module Equal with type t = 'a) -> 'a -> unit t

expect t equal a returns an unpacker that unpacks using t and then returns `Ok if the unpacked value equals a, or `Invalid_data otherwise.

val expect_char : char -> unit t

expect_char is expect char (module Char)

val newline : unit t