Add missing Stdlib functions for older OCaml versions

Author: OlivierNicole

compiler/lib/link_js.ml

@@ -56,7 +56,14 @@ end = struct
 
   let open_ fname =
     let lines =
-      In_channel.input_all (open_in_bin fname) |> String.split_on_char ~sep:'\n'
+      (* If we are not on 32-bit hardware (where the max string length is too
+         small), read the entire file and split it in lines. This is faster
+         than reading it line by line. On 32 bits, we fall back to a
+         line-by-line read. *)
+      if Sys.word_size >= 64 then
+        In_channel.input_all (open_in_bin fname) |> String.split_on_char ~sep:'\n'
+      else
+        In_channel.input_lines (open_in_bin fname)
     in
     { lines; lnum = 0; fname; current = lines }
 

compiler/lib/stdlib.ml

@@ -1226,6 +1226,115 @@ module Fun = struct
         r
 end
 
+module In_channel = struct
+  include In_channel
+  [@@if ocaml_version >= (4, 14, 0)]
+
+  (* Read up to [len] bytes into [buf], starting at [ofs]. Return total bytes
+     read. *)
+  let read_upto ic buf ofs len =
+    let rec loop ofs len =
+      if len = 0 then ofs
+      else begin
+        let r = input ic buf ofs len in
+        if r = 0 then
+          ofs
+        else
+          loop (ofs + r) (len - r)
+      end
+    in
+    loop ofs len - ofs
+    [@@if ocaml_version < (4, 14, 0)]
+
+  (* Best effort attempt to return a buffer with >= (ofs + n) bytes of storage,
+     and such that it coincides with [buf] at indices < [ofs].
+
+     The returned buffer is equal to [buf] itself if it already has sufficient
+     free space.
+
+     The returned buffer may have *fewer* than [ofs + n] bytes of storage if this
+     number is > [Sys.max_string_length]. However the returned buffer will
+     *always* have > [ofs] bytes of storage. In the limiting case when [ofs = len
+     = Sys.max_string_length] (so that it is not possible to resize the buffer at
+     all), an exception is raised. *)
+
+  let ensure buf ofs n =
+    let len = Bytes.length buf in
+    if len >= ofs + n then buf
+    else begin
+      let new_len = ref len in
+      while !new_len < ofs + n do
+        new_len := 2 * !new_len + 1
+      done;
+      let new_len = !new_len in
+      let new_len =
+        if new_len <= Sys.max_string_length then
+          new_len
+        else if ofs < Sys.max_string_length then
+          Sys.max_string_length
+        else
+          failwith "In_channel.input_all: channel content \
+                    is larger than maximum string length"
+      in
+      let new_buf = Bytes.create new_len in
+      Bytes.blit ~src:buf ~src_pos:0 ~dst:new_buf ~dst_pos:0 ~len:ofs;
+      new_buf
+    end
+    [@@if ocaml_version < (4, 14, 0)]
+
+  let input_all ic =
+    let chunk_size = 65536 in (* IO_BUFFER_SIZE *)
+    let initial_size =
+      try
+        in_channel_length ic - pos_in ic
+      with Sys_error _ ->
+        -1
+    in
+    let initial_size = if initial_size < 0 then chunk_size else initial_size in
+    let initial_size =
+      if initial_size <= Sys.max_string_length then
+        initial_size
+      else
+        Sys.max_string_length
+    in
+    let buf = Bytes.create initial_size in
+    let nread = read_upto ic buf 0 initial_size in
+    if nread < initial_size then (* EOF reached, buffer partially filled *)
+      Bytes.sub_string buf ~pos:0 ~len:nread
+    else begin (* nread = initial_size, maybe EOF reached *)
+      match input_char ic with
+      | exception End_of_file ->
+          (* EOF reached, buffer is completely filled *)
+          Bytes.unsafe_to_string buf
+      | c ->
+          (* EOF not reached *)
+          let rec loop buf ofs =
+            let buf = ensure buf ofs chunk_size in
+            let rem = Bytes.length buf - ofs in
+            (* [rem] can be < [chunk_size] if buffer size close to
+               [Sys.max_string_length] *)
+            let r = read_upto ic buf ofs rem in
+            if r < rem then (* EOF reached *)
+              Bytes.sub_string buf ~pos:0 ~len:(ofs + r)
+            else (* r = rem *)
+              loop buf (ofs + rem)
+          in
+          let buf = ensure buf nread (chunk_size + 1) in
+          Bytes.set buf nread c;
+          loop buf (nread + 1)
+    end
+    [@@if ocaml_version < (4, 14, 0)]
+
+  let input_lines ic =
+    let rec aux acc =
+      match input_line ic with
+      | line -> aux (line :: acc)
+      | exception End_of_file -> acc
+    in
+    List.rev (aux [])
+  [@@if ocaml_version < (4, 14, 0)]
+end
+
 let generated_name = function
   | "param" | "match" | "switcher" -> true
   | s -> String.is_prefix ~prefix:"cst_" s