misc.ml

(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
(*             Xavier Leroy, projet Cristal, INRIA Rocquencourt           *)
(*                                                                        *)
(*   Copyright 1996 Institut National de Recherche en Informatique et     *)
(*     en Automatique.                                                    *)
(*                                                                        *)
(*   All rights reserved.  This file is distributed under the terms of    *)
(*   the GNU Lesser General Public License version 2.1, with the          *)
(*   special exception on linking described in the file LICENSE.          *)
(*                                                                        *)
(**************************************************************************)

(* Errors *)

exception Fatal_error

let fatal_errorf fmt =
  Format.kfprintf
    (fun _ -> raise Fatal_error)
    Format.err_formatter
    ("@?>> Fatal error: " ^^ fmt ^^ "@.")

let fatal_error msg = fatal_errorf "%s" msg

(* Exceptions *)

let try_finally ?(always=(fun () -> ())) ?(exceptionally=(fun () -> ())) work =
  match work () with
    | result ->
      begin match always () with
        | () -> result
        | exception always_exn ->
          let always_bt = Printexc.get_raw_backtrace () in
          exceptionally ();
          Printexc.raise_with_backtrace always_exn always_bt
      end
    | exception work_exn ->
      let work_bt = Printexc.get_raw_backtrace () in
      begin match always () with
        | () ->
          exceptionally ();
          Printexc.raise_with_backtrace work_exn work_bt
        | exception always_exn ->
          let always_bt = Printexc.get_raw_backtrace () in
          exceptionally ();
          Printexc.raise_with_backtrace always_exn always_bt
      end

let reraise_preserving_backtrace e f =
  let bt = Printexc.get_raw_backtrace () in
  f ();
  Printexc.raise_with_backtrace e bt

type ref_and_value = R : 'a ref * 'a -> ref_and_value

let protect_refs =
  let set_refs l = List.iter (fun (R (r, v)) -> r := v) l in
  fun refs f ->
    let backup = List.map (fun (R (r, _)) -> R (r, !r)) refs in
    set_refs refs;
    Fun.protect ~finally:(fun () -> set_refs backup) f

(* List functions *)

let rec map_end f l1 l2 =
  match l1 with
    [] -> l2
  | hd::tl -> f hd :: map_end f tl l2

let rec map_left_right f = function
    [] -> []
  | hd::tl -> let res = f hd in res :: map_left_right f tl

let rec for_all2 pred l1 l2 =
  match (l1, l2) with
    ([], []) -> true
  | (hd1::tl1, hd2::tl2) -> pred hd1 hd2 && for_all2 pred tl1 tl2
  | (_, _) -> false

let rec replicate_list elem n =
  if n <= 0 then [] else elem :: replicate_list elem (n-1)

let rec list_remove x = function
    [] -> []
  | hd :: tl ->
      if hd = x then tl else hd :: list_remove x tl

let rec split_last = function
    [] -> assert false
  | [x] -> ([], x)
  | hd :: tl ->
      let (lst, last) = split_last tl in
      (hd :: lst, last)

module Stdlib = struct
  module List = struct
    type 'a t = 'a list

    let rec compare cmp l1 l2 =
      match l1, l2 with
      | [], [] -> 0
      | [], _::_ -> -1
      | _::_, [] -> 1
      | h1::t1, h2::t2 ->
        let c = cmp h1 h2 in
        if c <> 0 then c
        else compare cmp t1 t2

    let rec equal eq l1 l2 =
      match l1, l2 with
      | ([], []) -> true
      | (hd1 :: tl1, hd2 :: tl2) -> eq hd1 hd2 && equal eq tl1 tl2
      | (_, _) -> false

    let map2_prefix f l1 l2 =
      let rec aux acc l1 l2 =
        match l1, l2 with
        | [], _ -> (List.rev acc, l2)
        | _ :: _, [] -> raise (Invalid_argument "map2_prefix")
        | h1::t1, h2::t2 ->
          let h = f h1 h2 in
          aux (h :: acc) t1 t2
      in
      aux [] l1 l2

    let some_if_all_elements_are_some l =
      let rec aux acc l =
        match l with
        | [] -> Some (List.rev acc)
        | None :: _ -> None
        | Some h :: t -> aux (h :: acc) t
      in
      aux [] l

    let split_at n l =
      let rec aux n acc l =
        if n = 0
        then List.rev acc, l
        else
          match l with
          | [] -> raise (Invalid_argument "split_at")
          | t::q -> aux (n-1) (t::acc) q
      in
      aux n [] l

    let rec is_prefix ~equal t ~of_ =
      match t, of_ with
      | [], [] -> true
      | _::_, [] -> false
      | [], _::_ -> true
      | x1::t, x2::of_ -> equal x1 x2 && is_prefix ~equal t ~of_

    type 'a longest_common_prefix_result = {
      longest_common_prefix : 'a list;
      first_without_longest_common_prefix : 'a list;
      second_without_longest_common_prefix : 'a list;
    }

    let find_and_chop_longest_common_prefix ~equal ~first ~second =
      let rec find_prefix ~longest_common_prefix_rev l1 l2 =
        match l1, l2 with
        | elt1 :: l1, elt2 :: l2 when equal elt1 elt2 ->
          let longest_common_prefix_rev = elt1 :: longest_common_prefix_rev in
          find_prefix ~longest_common_prefix_rev l1 l2
        | l1, l2 ->
          { longest_common_prefix = List.rev longest_common_prefix_rev;
            first_without_longest_common_prefix = l1;
            second_without_longest_common_prefix = l2;
          }
      in
      find_prefix ~longest_common_prefix_rev:[] first second
  end

  module Option = struct
    type 'a t = 'a option

    let print print_contents ppf t =
      match t with
      | None -> Format.pp_print_string ppf "None"
      | Some contents ->
        Format.fprintf ppf "@[(Some@ %a)@]" print_contents contents
  end

  module Array = struct
    let exists2 p a1 a2 =
      let n = Array.length a1 in
      if Array.length a2 <> n then invalid_arg "Misc.Stdlib.Array.exists2";
      let rec loop i =
        if i = n then false
        else if p (Array.unsafe_get a1 i) (Array.unsafe_get a2 i) then true
        else loop (succ i) in
      loop 0

    let for_alli p a =
      let n = Array.length a in
      let rec loop i =
        if i = n then true
        else if p i (Array.unsafe_get a i) then loop (succ i)
        else false in
      loop 0

    let all_somes a =
      try
        Some (Array.map (function None -> raise_notrace Exit | Some x -> x) a)
      with
      | Exit -> None
  end

  module String = struct
    include String
    module Set = Set.Make(String)
    module Map = Map.Make(String)
    module Tbl = Hashtbl.Make(struct
      include String
      let hash = Hashtbl.hash
    end)

    let for_all f t =
      let len = String.length t in
      let rec loop i =
        i = len || (f t.[i] && loop (i + 1))
      in
      loop 0

    let print ppf t =
      Format.pp_print_string ppf t
  end

  external compare : 'a -> 'a -> int = "%compare"
end

(* File functions *)

let find_in_path path name =
  if not (Filename.is_implicit name) then
    if Sys.file_exists name then name else raise Not_found
  else begin
    let rec try_dir = function
      [] -> raise Not_found
    | dir::rem ->
        let fullname = Filename.concat dir name in
        if Sys.file_exists fullname then fullname else try_dir rem
    in try_dir path
  end

let find_in_path_rel path name =
  let rec simplify s =
    let open Filename in
    let base = basename s in
    let dir = dirname s in
    if dir = s then dir
    else if base = current_dir_name then simplify dir
    else concat (simplify dir) base
  in
  let rec try_dir = function
    [] -> raise Not_found
  | dir::rem ->
      let fullname = simplify (Filename.concat dir name) in
      if Sys.file_exists fullname then fullname else try_dir rem
  in try_dir path

let find_in_path_uncap path name =
  let uname = String.uncapitalize_ascii name in
  let rec try_dir = function
    [] -> raise Not_found
  | dir::rem ->
      let fullname = Filename.concat dir name
      and ufullname = Filename.concat dir uname in
      if Sys.file_exists ufullname then ufullname
      else if Sys.file_exists fullname then fullname
      else try_dir rem
  in try_dir path

let remove_file filename =
  try
    if Sys.file_exists filename
    then Sys.remove filename
  with Sys_error _msg ->
    ()

(* Expand a -I option: if it starts with +, make it relative to the standard
   library directory *)

let expand_directory alt s =
  if String.length s > 0 && s.[0] = '+'
  then Filename.concat alt
                       (String.sub s 1 (String.length s - 1))
  else s

let path_separator =
  match Sys.os_type with
  | "Win32" -> ';'
  | _ -> ':'

let split_path_contents ?(sep = path_separator) = function
  | "" -> []
  | s -> String.split_on_char sep s

(* Hashtable functions *)

let create_hashtable size init =
  let tbl = Hashtbl.create size in
  List.iter (fun (key, data) -> Hashtbl.add tbl key data) init;
  tbl

(* File copy *)

let copy_file ic oc =
  let buff = Bytes.create 0x1000 in
  let rec copy () =
    let n = input ic buff 0 0x1000 in
    if n = 0 then () else (output oc buff 0 n; copy())
  in copy()

let copy_file_chunk ic oc len =
  let buff = Bytes.create 0x1000 in
  let rec copy n =
    if n <= 0 then () else begin
      let r = input ic buff 0 (Int.min n 0x1000) in
      if r = 0 then raise End_of_file else (output oc buff 0 r; copy(n-r))
    end
  in copy len

let string_of_file ic =
  let b = Buffer.create 0x10000 in
  let buff = Bytes.create 0x1000 in
  let rec copy () =
    let n = input ic buff 0 0x1000 in
    if n = 0 then Buffer.contents b else
      (Buffer.add_subbytes b buff 0 n; copy())
  in copy()

let output_to_file_via_temporary ?(mode = [Open_text]) filename fn =
  let (temp_filename, oc) =
    Filename.open_temp_file
       ~mode ~perms:0o666 ~temp_dir:(Filename.dirname filename)
       (Filename.basename filename) ".tmp" in
    (* The 0o666 permissions will be modified by the umask.  It's just
       like what [open_out] and [open_out_bin] do.
       With temp_dir = dirname filename, we ensure that the returned
       temp file is in the same directory as filename itself, making
       it safe to rename temp_filename to filename later.
       With prefix = basename filename, we are almost certain that
       the first generated name will be unique.  A fixed prefix
       would work too but might generate more collisions if many
       files are being produced simultaneously in the same directory. *)
  match fn temp_filename oc with
  | res ->
      close_out oc;
      begin try
        Sys.rename temp_filename filename; res
      with exn ->
        remove_file temp_filename; raise exn
      end
  | exception exn ->
      close_out oc; remove_file temp_filename; raise exn

let protect_writing_to_file ~filename ~f =
  let outchan = open_out_bin filename in
  try_finally ~always:(fun () -> close_out outchan)
    ~exceptionally:(fun () -> remove_file filename)
    (fun () -> f outchan)

(* Integer operations *)

let rec log2 n =
  if n <= 1 then 0 else 1 + log2(n asr 1)

let align n a =
  if n >= 0 then (n + a - 1) land (-a) else n land (-a)

let no_overflow_add a b = (a lxor b) lor (a lxor (lnot (a+b))) < 0

let no_overflow_sub a b = (a lxor (lnot b)) lor (b lxor (a-b)) < 0

(* Taken from Hacker's Delight, chapter "Overflow Detection" *)
let no_overflow_mul a b =
  not ((a = min_int && b < 0) || (b <> 0 && (a * b) / b <> a))

let no_overflow_lsl a k =
  0 <= k && k < Sys.word_size - 1 && min_int asr k <= a && a <= max_int asr k

module Int_literal_converter = struct
  (* To convert integer literals, allowing max_int + 1 (PR#4210) *)
  let cvt_int_aux str neg of_string =
    if String.length str = 0 || str.[0]= '-'
    then of_string str
    else neg (of_string ("-" ^ str))
  let int s = cvt_int_aux s (~-) int_of_string
  let int32 s = cvt_int_aux s Int32.neg Int32.of_string
  let int64 s = cvt_int_aux s Int64.neg Int64.of_string
  let nativeint s = cvt_int_aux s Nativeint.neg Nativeint.of_string
end

(* String operations *)

let chop_extensions file =
  let dirname = Filename.dirname file and basename = Filename.basename file in
  try
    let pos = String.index basename '.' in
    let basename = String.sub basename 0 pos in
    if Filename.is_implicit file && dirname = Filename.current_dir_name then
      basename
    else
      Filename.concat dirname basename
  with Not_found -> file

let search_substring pat str start =
  let rec search i j =
    if j >= String.length pat then i
    else if i + j >= String.length str then raise Not_found
    else if str.[i + j] = pat.[j] then search i (j+1)
    else search (i+1) 0
  in search start 0

let replace_substring ~before ~after str =
  let rec search acc curr =
    match search_substring before str curr with
      | next ->
         let prefix = String.sub str curr (next - curr) in
         search (prefix :: acc) (next + String.length before)
      | exception Not_found ->
        let suffix = String.sub str curr (String.length str - curr) in
        List.rev (suffix :: acc)
  in String.concat after (search [] 0)

let rev_split_words s =
  let rec split1 res i =
    if i >= String.length s then res else begin
      match s.[i] with
        ' ' | '\t' | '\r' | '\n' -> split1 res (i+1)
      | _ -> split2 res i (i+1)
    end
  and split2 res i j =
    if j >= String.length s then String.sub s i (j-i) :: res else begin
      match s.[j] with
        ' ' | '\t' | '\r' | '\n' -> split1 (String.sub s i (j-i) :: res) (j+1)
      | _ -> split2 res i (j+1)
    end
  in split1 [] 0

let get_ref r =
  let v = !r in
  r := []; v

let set_or_ignore f opt x =
  match f x with
  | None -> ()
  | Some y -> opt := Some y

let fst3 (x, _, _) = x
let snd3 (_,x,_) = x
let thd3 (_,_,x) = x

let fst4 (x, _, _, _) = x
let snd4 (_,x,_, _) = x
let thd4 (_,_,x,_) = x
let for4 (_,_,_,x) = x


module LongString = struct
  type t = bytes array

  let create str_size =
    let tbl_size = str_size / Sys.max_string_length + 1 in
    let tbl = Array.make tbl_size Bytes.empty in
    for i = 0 to tbl_size - 2 do
      tbl.(i) <- Bytes.create Sys.max_string_length;
    done;
    tbl.(tbl_size - 1) <- Bytes.create (str_size mod Sys.max_string_length);
    tbl

  let length tbl =
    let tbl_size = Array.length tbl in
    Sys.max_string_length * (tbl_size - 1) + Bytes.length tbl.(tbl_size - 1)

  let get tbl ind =
    Bytes.get tbl.(ind / Sys.max_string_length) (ind mod Sys.max_string_length)

  let set tbl ind c =
    Bytes.set tbl.(ind / Sys.max_string_length) (ind mod Sys.max_string_length)
              c

  let blit src srcoff dst dstoff len =
    for i = 0 to len - 1 do
      set dst (dstoff + i) (get src (srcoff + i))
    done

  let blit_string src srcoff dst dstoff len =
    for i = 0 to len - 1 do
      set dst (dstoff + i) (String.get src (srcoff + i))
    done

  let output oc tbl pos len =
    for i = pos to pos + len - 1 do
      output_char oc (get tbl i)
    done

  let input_bytes_into tbl ic len =
    let count = ref len in
    Array.iter (fun str ->
      let chunk = Int.min !count (Bytes.length str) in
      really_input ic str 0 chunk;
      count := !count - chunk) tbl

  let input_bytes ic len =
    let tbl = create len in
    input_bytes_into tbl ic len;
    tbl
end


let edit_distance a b cutoff =
  let la, lb = String.length a, String.length b in
  let cutoff =
    (* using max_int for cutoff would cause overflows in (i + cutoff + 1);
       we bring it back to the (max la lb) worstcase *)
    Int.min (Int.max la lb) cutoff in
  if abs (la - lb) > cutoff then None
  else begin
    (* initialize with 'cutoff + 1' so that not-yet-written-to cases have
       the worst possible cost; this is useful when computing the cost of
       a case just at the boundary of the cutoff diagonal. *)
    let m = Array.make_matrix (la + 1) (lb + 1) (cutoff + 1) in
    m.(0).(0) <- 0;
    for i = 1 to la do
      m.(i).(0) <- i;
    done;
    for j = 1 to lb do
      m.(0).(j) <- j;
    done;
    for i = 1 to la do
      for j = Int.max 1 (i - cutoff - 1) to Int.min lb (i + cutoff + 1) do
        let cost = if a.[i-1] = b.[j-1] then 0 else 1 in
        let best =
          (* insert, delete or substitute *)
          Int.min (1 + Int.min m.(i-1).(j) m.(i).(j-1)) (m.(i-1).(j-1) + cost)
        in
        let best =
          (* swap two adjacent letters; we use "cost" again in case of
             a swap between two identical letters; this is slightly
             redundant as this is a double-substitution case, but it
             was done this way in most online implementations and
             imitation has its virtues *)
          if not (i > 1 && j > 1 && a.[i-1] = b.[j-2] && a.[i-2] = b.[j-1])
          then best
          else Int.min best (m.(i-2).(j-2) + cost)
        in
        m.(i).(j) <- best
      done;
    done;
    let result = m.(la).(lb) in
    if result > cutoff
    then None
    else Some result
  end

let spellcheck env name =
  let cutoff =
    match String.length name with
      | 1 | 2 -> 0
      | 3 | 4 -> 1
      | 5 | 6 -> 2
      | _ -> 3
  in
  let compare target acc head =
    match edit_distance target head cutoff with
      | None -> acc
      | Some dist ->
         let (best_choice, best_dist) = acc in
         if dist < best_dist then ([head], dist)
         else if dist = best_dist then (head :: best_choice, dist)
         else acc
  in
  let env = List.sort_uniq (fun s1 s2 -> String.compare s2 s1) env in
  fst (List.fold_left (compare name) ([], max_int) env)

let did_you_mean ppf get_choices =
  (* flush now to get the error report early, in the (unheard of) case
     where the search in the get_choices function would take a bit of
     time; in the worst case, the user has seen the error, she can
     interrupt the process before the spell-checking terminates. *)
  Format.fprintf ppf "@?";
  match get_choices () with
  | [] -> ()
  | choices ->
     let rest, last = split_last choices in
     Format.fprintf ppf "@\nHint: Did you mean %s%s%s?@?"
       (String.concat ", " rest)
       (if rest = [] then "" else " or ")
       last

let cut_at s c =
  let pos = String.index s c in
  String.sub s 0 pos, String.sub s (pos+1) (String.length s - pos - 1)

(* Color handling *)
module Color = struct
  (* use ANSI color codes, see https://en.wikipedia.org/wiki/ANSI_escape_code *)
  type color =
    | Black
    | Red
    | Green
    | Yellow
    | Blue
    | Magenta
    | Cyan
    | White
  ;;

  type style =
    | FG of color (* foreground *)
    | BG of color (* background *)
    | Bold
    | Reset

  let ansi_of_color = function
    | Black -> "0"
    | Red -> "1"
    | Green -> "2"
    | Yellow -> "3"
    | Blue -> "4"
    | Magenta -> "5"
    | Cyan -> "6"
    | White -> "7"

  let code_of_style = function
    | FG c -> "3" ^ ansi_of_color c
    | BG c -> "4" ^ ansi_of_color c
    | Bold -> "1"
    | Reset -> "0"

  let ansi_of_style_l l =
    let s = match l with
      | [] -> code_of_style Reset
      | [s] -> code_of_style s
      | _ -> String.concat ";" (List.map code_of_style l)
    in
    "\x1b[" ^ s ^ "m"


  type Format.stag += Style of style list
  type styles = {
    error: style list;
    warning: style list;
    loc: style list;
  }

  let default_styles = {
    warning = [Bold; FG Magenta];
    error = [Bold; FG Red];
    loc = [Bold];
  }

  let cur_styles = ref default_styles
  let get_styles () = !cur_styles
  let set_styles s = cur_styles := s

  (* map a tag to a style, if the tag is known.
     @raise Not_found otherwise *)
  let style_of_tag s = match s with
    | Format.String_tag "error" -> (!cur_styles).error
    | Format.String_tag "warning" -> (!cur_styles).warning
    | Format.String_tag "loc" -> (!cur_styles).loc
    | Style s -> s
    | _ -> raise Not_found

  let color_enabled = ref true

  (* either prints the tag of [s] or delegates to [or_else] *)
  let mark_open_tag ~or_else s =
    try
      let style = style_of_tag s in
      if !color_enabled then ansi_of_style_l style else ""
    with Not_found -> or_else s

  let mark_close_tag ~or_else s =
    try
      let _ = style_of_tag s in
      if !color_enabled then ansi_of_style_l [Reset] else ""
    with Not_found -> or_else s

  (* add color handling to formatter [ppf] *)
  let set_color_tag_handling ppf =
    let open Format in
    let functions = pp_get_formatter_stag_functions ppf () in
    let functions' = {functions with
      mark_open_stag=(mark_open_tag ~or_else:functions.mark_open_stag);
      mark_close_stag=(mark_close_tag ~or_else:functions.mark_close_stag);
    } in
    pp_set_mark_tags ppf true; (* enable tags *)
    pp_set_formatter_stag_functions ppf functions';
    ()

  external isatty : out_channel -> bool = "caml_sys_isatty"

  (* reasonable heuristic on whether colors should be enabled *)
  let should_enable_color () =
    let term = try Sys.getenv "TERM" with Not_found -> "" in
    term <> "dumb"
    && term <> ""
    && isatty stderr

  type setting = Auto | Always | Never

  let default_setting = Auto

  let setup =
    let first = ref true in (* initialize only once *)
    let formatter_l =
      [Format.std_formatter; Format.err_formatter; Format.str_formatter]
    in
    let enable_color = function
      | Auto -> should_enable_color ()
      | Always -> true
      | Never -> false
    in
    fun o ->
      if !first then (
        first := false;
        Format.set_mark_tags true;
        List.iter set_color_tag_handling formatter_l;
        color_enabled := (match o with
          | Some s -> enable_color s
          | None -> enable_color default_setting)
      );
      ()
end

module Error_style = struct
  type setting =
    | Contextual
    | Short

  let default_setting = Contextual
end

let normalise_eol s =
  let b = Buffer.create 80 in
    for i = 0 to String.length s - 1 do
      if s.[i] <> '\r' then Buffer.add_char b s.[i]
    done;
    Buffer.contents b

let delete_eol_spaces src =
  let len_src = String.length src in
  let dst = Bytes.create len_src in
  let rec loop i_src i_dst =
    if i_src = len_src then
      i_dst
    else
      match src.[i_src] with
      | ' ' | '\t' ->
        loop_spaces 1 (i_src + 1) i_dst
      | c ->
        Bytes.set dst i_dst c;
        loop (i_src + 1) (i_dst + 1)
  and loop_spaces spaces i_src i_dst =
    if i_src = len_src then
      i_dst
    else
      match src.[i_src] with
      | ' ' | '\t' ->
        loop_spaces (spaces + 1) (i_src + 1) i_dst
      | '\n' ->
        Bytes.set dst i_dst '\n';
        loop (i_src + 1) (i_dst + 1)
      | _ ->
        for n = 0 to spaces do
          Bytes.set dst (i_dst + n) src.[i_src - spaces + n]
        done;
        loop (i_src + 1) (i_dst + spaces + 1)
  in
  let stop = loop 0 0 in
  Bytes.sub_string dst 0 stop

let pp_two_columns ?(sep = "|") ?max_lines ppf (lines: (string * string) list) =
  let left_column_size =
    List.fold_left (fun acc (s, _) -> Int.max acc (String.length s)) 0 lines in
  let lines_nb = List.length lines in
  let ellipsed_first, ellipsed_last =
    match max_lines with
    | Some max_lines when lines_nb > max_lines ->
        let printed_lines = max_lines - 1 in (* the ellipsis uses one line *)
        let lines_before = printed_lines / 2 + printed_lines mod 2 in
        let lines_after = printed_lines / 2 in
        (lines_before, lines_nb - lines_after - 1)
    | _ -> (-1, -1)
  in
  Format.fprintf ppf "@[<v>";
  List.iteri (fun k (line_l, line_r) ->
    if k = ellipsed_first then Format.fprintf ppf "...@,";
    if ellipsed_first <= k && k <= ellipsed_last then ()
    else Format.fprintf ppf "%*s %s %s@," left_column_size line_l sep line_r
  ) lines;
  Format.fprintf ppf "@]"

(* showing configuration and configuration variables *)
let show_config_and_exit () =
  Config.print_config stdout;
  exit 0

let show_config_variable_and_exit x =
  match Config.config_var x with
  | Some v ->
      (* we intentionally don't print a newline to avoid Windows \r
         issues: bash only strips the trailing \n when using a command
         substitution $(ocamlc -config-var foo), so a trailing \r would
         remain if printing a newline under Windows and scripts would
         have to use $(ocamlc -config-var foo | tr -d '\r')
         for portability. Ugh. *)
      print_string v;
      exit 0
  | None ->
      exit 2

let get_build_path_prefix_map =
  let init = ref false in
  let map_cache = ref None in
  fun () ->
    if not !init then begin
      init := true;
      match Sys.getenv "BUILD_PATH_PREFIX_MAP" with
      | exception Not_found -> ()
      | encoded_map ->
        match Build_path_prefix_map.decode_map encoded_map with
          | Error err ->
              fatal_errorf
                "Invalid value for the environment variable \
                 BUILD_PATH_PREFIX_MAP: %s" err
          | Ok map -> map_cache := Some map
    end;
    !map_cache

let debug_prefix_map_flags () =
  if not Config.as_has_debug_prefix_map then
    []
  else begin
    match get_build_path_prefix_map () with
    | None -> []
    | Some map ->
      List.fold_right
        (fun map_elem acc ->
           match map_elem with
           | None -> acc
           | Some { Build_path_prefix_map.target; source; } ->
             (Printf.sprintf "--debug-prefix-map %s=%s"
                (Filename.quote source)
                (Filename.quote target)) :: acc)
        map
        []
  end

let print_if ppf flag printer arg =
  if !flag then Format.fprintf ppf "%a@." printer arg;
  arg


type filepath = string
type modname = string
type crcs = (modname * Digest.t option) list

type alerts = string Stdlib.String.Map.t

module Magic_number = struct
  type native_obj_config = {
    flambda : bool;
  }
  let native_obj_config = {
    flambda = Config.flambda;
  }

  type version = int

  type kind =
    | Exec
    | Cmi | Cmo | Cma
    | Cmx of native_obj_config | Cmxa of native_obj_config
    | Cmxs
    | Cmt
    | Ast_impl | Ast_intf

  (* please keep up-to-date, this is used for sanity checking *)
  let all_native_obj_configs = [
      {flambda = true};
      {flambda = false};
    ]
  let all_kinds = [
    Exec;
    Cmi; Cmo; Cma;
  ]
  @ List.map (fun conf -> Cmx conf) all_native_obj_configs
  @ List.map (fun conf -> Cmxa conf) all_native_obj_configs
  @ [
    Cmt;
    Ast_impl; Ast_intf;
  ]

  type raw = string
  type info = {
    kind: kind;
    version: version;
  }

  type raw_kind = string

  let parse_kind : raw_kind -> kind option = function
    | "Caml1999X" -> Some Exec
    | "Caml1999I" -> Some Cmi
    | "Caml1999O" -> Some Cmo
    | "Caml1999A" -> Some Cma
    | "Caml1999y" -> Some (Cmx {flambda = true})
    | "Caml1999Y" -> Some (Cmx {flambda = false})
    | "Caml1999z" -> Some (Cmxa {flambda = true})
    | "Caml1999Z" -> Some (Cmxa {flambda = false})

    (* Caml2007D and Caml2012T were used instead of the common Caml1999 prefix
       between the introduction of those magic numbers and October 2017
       (8ba70ff194b66c0a50ffb97d41fe9c4bdf9362d6).

       We accept them here, but will always produce/show kind prefixes
       that follow the current convention, Caml1999{D,T}. *)
    | "Caml2007D" | "Caml1999D" -> Some Cmxs
    | "Caml2012T" | "Caml1999T" -> Some Cmt

    | "Caml1999M" -> Some Ast_impl
    | "Caml1999N" -> Some Ast_intf
    | _ -> None

  (* note: over time the magic kind number has changed for certain kinds;
     this function returns them as they are produced by the current compiler,
     but [parse_kind] accepts older formats as well. *)
  let raw_kind : kind -> raw = function
    | Exec -> "Caml1999X"
    | Cmi -> "Caml1999I"
    | Cmo -> "Caml1999O"
    | Cma -> "Caml1999A"
    | Cmx config ->
       if config.flambda
       then "Caml1999y"
       else "Caml1999Y"
    | Cmxa config ->
       if config.flambda
       then "Caml1999z"
       else "Caml1999Z"
    | Cmxs -> "Caml1999D"
    | Cmt -> "Caml1999T"
    | Ast_impl -> "Caml1999M"
    | Ast_intf -> "Caml1999N"

  let string_of_kind : kind -> string = function
    | Exec -> "exec"
    | Cmi -> "cmi"
    | Cmo -> "cmo"
    | Cma -> "cma"
    | Cmx _ -> "cmx"
    | Cmxa _ -> "cmxa"
    | Cmxs -> "cmxs"
    | Cmt -> "cmt"
    | Ast_impl -> "ast_impl"
    | Ast_intf -> "ast_intf"

  let human_description_of_native_obj_config : native_obj_config -> string =
    fun[@warning "+9"] {flambda} ->
      if flambda then "flambda" else "non flambda"

  let human_name_of_kind : kind -> string = function
    | Exec -> "executable"
    | Cmi -> "compiled interface file"
    | Cmo -> "bytecode object file"
    | Cma -> "bytecode library"
    | Cmx config ->
       Printf.sprintf "native compilation unit description (%s)"
         (human_description_of_native_obj_config config)
    | Cmxa config ->
       Printf.sprintf "static native library (%s)"
         (human_description_of_native_obj_config config)
    | Cmxs -> "dynamic native library"
    | Cmt -> "compiled typedtree file"
    | Ast_impl -> "serialized implementation AST"
    | Ast_intf -> "serialized interface AST"

  let kind_length = 9
  let version_length = 3
  let magic_length =
    kind_length + version_length

  type parse_error =
    | Truncated of string
    | Not_a_magic_number of string

  let explain_parse_error kind_opt error =
       Printf.sprintf
         "We expected a valid %s, but the file %s."
         (Option.fold ~none:"object file" ~some:human_name_of_kind kind_opt)
         (match error with
            | Truncated "" -> "is empty"
            | Truncated _ -> "is truncated"
            | Not_a_magic_number _ -> "has a different format")

  let parse s : (info, parse_error) result =
    if String.length s = magic_length then begin
      let raw_kind = String.sub s 0 kind_length in
      let raw_version = String.sub s kind_length version_length in
      match parse_kind raw_kind with
      | None -> Error (Not_a_magic_number s)
      | Some kind ->
          begin match int_of_string raw_version with
          | exception _ -> Error (Truncated s)
          | version -> Ok { kind; version }
          end
    end
    else begin
      (* a header is "truncated" if it starts like a valid magic number,
         that is if its longest segment of length at most [kind_length]
         is a prefix of [raw_kind kind] for some kind [kind] *)
      let sub_length = Int.min kind_length (String.length s) in
      let starts_as kind =
        String.sub s 0 sub_length = String.sub (raw_kind kind) 0 sub_length
      in
      if List.exists starts_as all_kinds then Error (Truncated s)
      else Error (Not_a_magic_number s)
    end

  let read_info ic =
    let header = Buffer.create magic_length in
    begin
      try Buffer.add_channel header ic magic_length
      with End_of_file -> ()
    end;
    parse (Buffer.contents header)

  let raw { kind; version; } =
    Printf.sprintf "%s%03d" (raw_kind kind) version

  let current_raw kind =
    let open Config in
    match[@warning "+9"] kind with
      | Exec -> exec_magic_number
      | Cmi -> cmi_magic_number
      | Cmo -> cmo_magic_number
      | Cma -> cma_magic_number
      | Cmx config ->
         (* the 'if' guarantees that in the common case
            we return the "trusted" value from Config. *)
         let reference = cmx_magic_number in
         if config = native_obj_config then reference
         else
           (* otherwise we stitch together the magic number
              for a different configuration by concatenating
              the right magic kind at this configuration
              and the rest of the current raw number for our configuration. *)
           let raw_kind = raw_kind kind in
           let len = String.length raw_kind in
           raw_kind ^ String.sub reference len (String.length reference - len)
      | Cmxa config ->
         let reference = cmxa_magic_number in
         if config = native_obj_config then reference
         else
           let raw_kind = raw_kind kind in
           let len = String.length raw_kind in
           raw_kind ^ String.sub reference len (String.length reference - len)
      | Cmxs -> cmxs_magic_number
      | Cmt -> cmt_magic_number
      | Ast_intf -> ast_intf_magic_number
      | Ast_impl -> ast_impl_magic_number

  (* it would seem more direct to define current_version with the
     correct numbers and current_raw on top of it, but for now we
     consider the Config.foo values to be ground truth, and don't want
     to trust the present module instead. *)
  let current_version kind =
    let raw = current_raw kind in
    try int_of_string (String.sub raw kind_length version_length)
    with _ -> assert false

  type 'a unexpected = { expected : 'a; actual : 'a }
  type unexpected_error =
    | Kind of kind unexpected
    | Version of kind * version unexpected

  let explain_unexpected_error = function
    | Kind { actual; expected } ->
        Printf.sprintf "We expected a %s (%s) but got a %s (%s) instead."
          (human_name_of_kind expected) (string_of_kind expected)
          (human_name_of_kind actual) (string_of_kind actual)
    | Version (kind, { actual; expected }) ->
        Printf.sprintf "This seems to be a %s (%s) for %s version of OCaml."
          (human_name_of_kind kind) (string_of_kind kind)
          (if actual < expected then "an older" else "a newer")

  let check_current expected_kind { kind; version } : _ result =
    if kind <> expected_kind then begin
      let actual, expected = kind, expected_kind in
      Error (Kind { actual; expected })
    end else begin
      let actual, expected = version, current_version kind in
      if actual <> expected
      then Error (Version (kind, { actual; expected }))
      else Ok ()
    end

  type error =
    | Parse_error of parse_error
    | Unexpected_error of unexpected_error

  let read_current_info ~expected_kind ic =
    match read_info ic with
      | Error err -> Error (Parse_error err)
      | Ok info ->
         let kind = Option.value ~default:info.kind expected_kind in
         match check_current kind info with
           | Error err -> Error (Unexpected_error err)
           | Ok () -> Ok info
end