(* Title: Pure/General/buffer.ML
Author: Markus Wenzel, TU Muenchen
Efficient text buffers.
*)
signature BUFFER =
sig
type T
val empty: T
val add: string -> T -> T
val markup: Markup.T -> (T -> T) -> T -> T
val content: T -> string
val chunks: T -> string list
val output: T -> BinIO.outstream -> unit
end;
structure Buffer: BUFFER =
struct
datatype T = Buffer of string list;
val empty = Buffer [];
fun add "" buf = buf
| add x (Buffer xs) = Buffer (x :: xs);
fun markup m body =
let val (bg, en) = Markup.output m
in add bg #> body #> add en end;
fun content (Buffer xs) = implode (rev xs);
(* chunks *)
local
val max_chunk = 4096;
fun add_chunk [] res = res
| add_chunk chunk res = implode chunk :: res;
fun rev_chunks [] _ chunk res = add_chunk chunk res
| rev_chunks (x :: xs) len chunk res =
let
val n = size x;
val len' = len + n;
in
if len' < max_chunk then rev_chunks xs len' (x :: chunk) res
else rev_chunks xs n [x] (add_chunk chunk res)
end;
in
fun chunks (Buffer xs) = rev_chunks xs 0 [] [];
fun output buf stream =
List.app (fn s => BinIO.output (stream, Byte.stringToBytes s)) (chunks buf);
end;
end;