Source file decompress_seq.ml

(* Copyright (c) 2012-2016, Simon Cruanes All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

   Redistributions of source code must retain the above copyright notice, this
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   form must reproduce the above copyright notice, this list of conditions and
   the following disclaimer in the documentation and/or other materials
   provided with the distribution.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
   LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   POSSIBILITY OF SUCH DAMAGE. *)

type 'a t = ('a -> unit) -> unit

let empty _ = ()
let cons x l k = k x ; l k
let snoc l x k = l k ; k x

module MList = struct
  type 'a node = Nil | Cons of 'a array * int ref * 'a node ref

  let of_seq_with seq k =
    let start = ref Nil in
    let chunk_size = ref 8 in
    (* XXX: fill the list. pref: tail-reference from previous node *)
    let prev, cur = (ref start, ref Nil) in
    seq (fun x ->
        k x ;
        (* callback *)
        match !cur with
        | Nil ->
            let n = !chunk_size in
            if n < 4096 then chunk_size := 2 * !chunk_size ;
            cur := Cons (Array.make n x, ref 1, ref Nil)
        | Cons (a, n, next) ->
            assert (!n < Array.length a) ;
            a.(!n) <- x ;
            incr n ;
            if !n = Array.length a then (
              !prev := !cur ;
              prev := next ;
              cur := Nil ) ) ;
    !prev := !cur ;
    !start

  let of_seq seq = of_seq_with seq (fun _ -> ())

  let rec iter f l =
    match l with
    | Nil -> ()
    | Cons (a, n, tl) ->
        for i = 0 to !n - 1 do
          f a.(i)
        done ;
        iter f !tl

  let to_seq l k = iter k l
end

let persistent seq =
  let l = MList.of_seq seq in
  MList.to_seq l

let fold f init seq =
  let r = ref init in
  seq (fun elt -> r := f !r elt) ;
  !r

exception Break

let fold_while f s seq =
  let state = ref s in
  let consume x =
    let acc, cont = f !state x in
    state := acc ;
    match cont with `Stop -> raise Break | `Continue -> ()
  in
  try seq consume ; !state with Break -> !state

let iter f seq = seq f
let concat s k = s (fun s' -> s' k)
let append s1 s2 k = s1 k ; s2 k
let to_queue q seq = seq (fun x -> Queue.push x q)
let of_queue q k = Queue.iter k q
let to_list seq = List.rev (fold (fun y x -> x :: y) [] seq)
let of_list l k = List.iter k l