(*
Copyright (c) 2013, Simon Cruanes
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modification, are permitted provided that the following conditions are met:

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*)

(** {1 Hash combinators}

Combination of hashes based on the Murmur Hash (64 bits). See
{{: https://sites.google.com/site/murmurhash/MurmurHash2_64.cpp?attredirects=0} this page}
*)

(** {2 Definitions} *)

type t = int
(** A hash value is a positive integer *)

type state = int64
(** State required by the hash function *)

type 'a hash_fun = 'a -> state -> state
(** Hash function for values of type ['a], merging a fingerprint of the
    value into the state of type [t] *)

val init : state
(** Initial value *)

val finish : state -> int
(** Extract a usable hash value *)

val apply : 'a hash_fun -> 'a -> int
(** Apply a hash function to a value *)

(** {2 Basic Combinators} *)

val bool_ : bool hash_fun
val char_ : char hash_fun
val int_ : int hash_fun
val string_ : string hash_fun
val int32_ : int32 hash_fun
val int64_ : int64 hash_fun
val nativeint_ : nativeint hash_fun

val list_ : 'a hash_fun -> 'a list hash_fun
(** Hash a list. Each element is hashed using [f]. *)

val array_ : 'a hash_fun -> 'a array hash_fun

val opt : 'a hash_fun -> 'a option hash_fun
val pair : 'a hash_fun -> 'b hash_fun -> ('a * 'b) hash_fun
val triple : 'a hash_fun -> 'b hash_fun -> 'c hash_fun -> ('a * 'b * 'c) hash_fun

val if_ : bool -> 'a hash_fun -> 'a hash_fun -> 'a hash_fun
(** Decide which hash function to use depending on the boolean *)

type 'a sequence = ('a -> unit) -> unit
type 'a gen = unit -> 'a option
type 'a klist = unit -> [`Nil | `Cons of 'a * 'a klist]

val seq : 'a hash_fun -> 'a sequence hash_fun
val gen : 'a hash_fun -> 'a gen hash_fun
val klist : 'a hash_fun -> 'a klist hash_fun