decimal-external.sml

(* -*- mode: sml; mode: font-lock; tab-width: 4; insert-tabs-mode: nil; indent-tabs-mode: nil -*- *)
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 * Copyright (c) 2007 Adobe Systems Inc., The Mozilla Foundation, Opera
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(* An implementation of decimal128 arithmetic (via an external helper program). *)

structure DecimalNative = struct
open DecimalParams

fun runOp (precision:int)
	  (mode:ROUNDING_MODE)
	  (operator:DECIMAL_OPERATOR)
	  (a:DEC)
	  (b:DEC option)
    : DEC =
    let
	val prog = "decimal"
	val precStr = Int.toString precision
	val modeStr = rmToString mode
	val (Dec aval) = a
    val operator = opToString operator
	val argv = case b of
		       NONE => [prog, precStr, modeStr, operator, aval]
		     | SOME (Dec bval) => [prog, precStr, modeStr, operator, aval, bval]

	val {infd, outfd} = Posix.IO.pipe ()
	val pid = Posix.Process.fork ()
    in
	case pid of
	    NONE =>
	    (Posix.IO.close infd;
	     trace ("query:" :: argv);
	     Posix.IO.dup2 {old=outfd, new=Posix.FileSys.stdout};
	     Posix.Process.execp (prog, argv))

	  | SOME child =>
	    let
		val _ = Posix.IO.close outfd
		val vec = Posix.IO.readVec (infd, 1024)
		fun getCharN (n:int) = Char.chr (Word8.toInt (Word8Vector.sub (vec, n)))
		val _ = Posix.Process.wait ()
        val _ = Posix.IO.close infd
		val res = CharVector.tabulate (Word8Vector.length vec, getCharN)
	    in
		if String.isPrefix "ERROR:" res
		then raise (DecimalException res)
		else (trace ["reply:", res];
		      (Dec (List.hd (String.tokens (fn c => not (Char.isGraph c)) res))))
	    end
    end

end