text-io-fn.sml

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(* text-io-fn.sml
 *
 * COPYRIGHT (c) 1995 AT&T Bell Laboratories.
 *
 * This is the CML version of the TextIO functor.
 *)

functor TextIOFn (

    structure OSPrimIO : sig
        include OS_PRIM_IO
	val stdIn   : unit -> PrimIO.reader
	val stdOut  : unit -> PrimIO.writer
	val stdErr  : unit -> PrimIO.writer
	val strReader : string -> PrimIO.reader
      end
	where type PrimIO.array = TextPrimIO.array
	where type PrimIO.vector = TextPrimIO.vector
	where type PrimIO.elem = TextPrimIO.elem
	where type PrimIO.pos = TextPrimIO.pos
	where type PrimIO.reader = TextPrimIO.reader
	where type PrimIO.writer = TextPrimIO.writer

  ) : CML_TEXT_IO = struct

    structure PIO = OSPrimIO.PrimIO
    structure A = CharArray
    structure V = CharVector

    structure SV = SyncVar

  (* assign to an MVar *)
    fun mUpdate (mv, x) = ignore(SV.mSwap(mv, x))

  (* an element for initializing buffers *)
    val someElem = #"\000"

    val vecExtract = V.extract
    val vecSub = V.sub
    val arrUpdate = A.update
    val substringBase = Substring.base
    val empty = ""

    fun dummyCleaner () = ()

    structure StreamIO =
      struct
	type vector = V.vector
	type elem = V.elem
	type reader = PIO.reader
	type writer = PIO.writer
	type pos = PIO.pos

      (*** Functional input streams ***)
	datatype instream = ISTRM of (in_buffer * int)
	and in_buffer = IBUF of {
	    basePos : pos option,
	    more : more SV.mvar,	(* when this cell is empty, it means that *)
					(* there is an outstanding request to the *)
					(* server to extend the stream. *)
	    data : vector,
	    info : info
	  }
	and more
	  = MORE of in_buffer	(* forward link to additional data *)
	  | NOMORE		(* placeholder for forward link *)
	  | TERMINATED		(* termination of the stream *)

	and info = INFO of {
	    reader : reader,
	    readVec : int -> vector,
	    readVecEvt : int -> vector CML.event,
	    closed : bool ref,
	    getPos : unit -> pos option,
	    tail : more SV.mvar SV.mvar,
		(* points to the more cell of the last buffer *)
	    cleanTag : CleanIO.tag
	  }

	fun infoOfIBuf (IBUF{info, ...}) = info
	fun chunkSzOfIBuf buf = let
	      val INFO{reader=PIO.RD{chunkSize, ...}, ...} = infoOfIBuf buf
	      in
		chunkSize
	      end
	fun readVec (IBUF{info=INFO{readVec=f, ...}, ...}) = f

	fun inputExn (INFO{reader=PIO.RD{name, ...}, ...}, mlOp, exn) =
	      raise IO.Io{function=mlOp, name=name, cause=exn}

	datatype more_data = EOF | DATA of in_buffer

      (* extend the stream by a chunk.
       * Invariant: the more m-variable is empty on entry and full on exit.
       *)
	fun extendStream (readFn, mlOp, buf as IBUF{more, info, ...}) = (let
	      val INFO{getPos, tail, ...} = info
	      val basePos = getPos()
	      val chunk = readFn (chunkSzOfIBuf buf)
	      in
		if (V.length chunk = 0)
		  then (SV.mPut (more, NOMORE); EOF)
		  else let
		    val newMore = SV.mVar()
		    val buf' = IBUF{
			    basePos = basePos, data = chunk,
			    more = newMore, info = info
			  }
		    in
		    (* note that we do not fill the more cell until
		     * after the tail has been updated.  This ensures
		     * that someone attempting to access the tail will
		     * not acquire the lock until after we are done.
		     *)
		      mUpdate (tail, newMore);
		      SV.mPut (more, MORE buf');  (* releases lock!! *)
		      SV.mPut (newMore, NOMORE);
		      DATA buf'
		    end
	      end
		handle ex => (
		  SV.mPut (more, NOMORE);
		  inputExn(info, mlOp, ex)))

      (* get the next buffer in the stream, extending it if necessary.  If
       * the stream must be extended, we lock it by taking the value from the
       * more cell; the extendStream function is responsible for filling in
       * the cell.
       *)
	fun getBuffer (readFn, mlOp) (buf as IBUF{more, info, ...}) = let
	      fun get TERMINATED = EOF
		| get (MORE buf') = DATA buf'
		| get NOMORE = (case SV.mTake more
		     of NOMORE => extendStream (readFn, mlOp, buf)
		      | next => (SV.mPut(more, next); get next)
		    (* end case *))
	      in
		get (SV.mGet more)
	      end

      (* read a chunk that is at least the specified size *)
	fun readChunk buf = let
	      val INFO{readVec, reader=PIO.RD{chunkSize, ...}, ...} =
		     infoOfIBuf buf
	      in
		case (chunkSize - 1)
		 of 0 => (fn n => readVec n)
		  | k => (* round up to next multiple of chunkSize *)
		      (fn n => readVec(Int.quot(n+k, chunkSize) * chunkSize))
		(* end case *)
	      end

	fun generalizedInput getBuf = let
	      fun get (ISTRM(buf as IBUF{data, ...}, pos)) = let
		    val len = V.length data
		    in
		      if (pos < len)
			then (vecExtract(data, pos, NONE), ISTRM(buf, len))
			else (case (getBuf buf)
			   of EOF => (empty, ISTRM(buf, len))
			    | (DATA rest) => get (ISTRM(rest, 0))
			  (* end case *))
		    end
	      in
		get
	      end

      (* terminate an input stream *)
	fun terminate (info as INFO{tail, cleanTag, ...}) = let
	      val m = SV.mGet tail
	      in
		case SV.mTake m
		 of (m' as MORE _) => (SV.mPut(m, m'); terminate info)
		  | TERMINATED => SV.mPut(m, TERMINATED)
		  | _ => (
		      CleanIO.removeCleaner cleanTag;
		      SV.mPut(m, TERMINATED))
	        (* end case *)
	      end

      (* find the end of the stream *)
	fun findEOS (buf as IBUF{more, data, ...}) = (case (SV.mGet more)
	       of (MORE buf) => findEOS buf
		| _ => ISTRM(buf, V.length data)
	      (* end case *))

	fun input (strm as ISTRM(buf, _)) =
	      generalizedInput (getBuffer (readVec buf, "input")) strm
	fun input1 (ISTRM(buf, pos)) = let
	      val IBUF{data, more, ...} = buf
	      in
		if (pos < V.length data)
		  then SOME(vecSub(data, pos), ISTRM(buf, pos+1))
		  else let
		    fun get (MORE buf) = input1 (ISTRM(buf, 0))
		      | get TERMINATED = NONE
		      | get NOMORE = (case SV.mTake more
			   of NOMORE => (
				case extendStream (readVec buf, "input1", buf)
				 of EOF => NONE
				  | (DATA rest) => input1 (ISTRM(rest, 0))
				(* end case *))
			    | next => (SV.mPut(more, next); get next)
			  (* end case *))
		    in
		      get (SV.mGet more)
		    end
	      end
	fun inputN (ISTRM(buf, pos), n) = let
	      fun join (item, (list, strm)) = (item::list, strm)
	      fun inputList (buf as IBUF{data, ...}, i, n) = let
		    val len = V.length data
		    val remain = len-i
		    in
		      if (remain >= n)
			then ([vecExtract(data, i, SOME n)], ISTRM(buf, i+n))
		      else join (
			vecExtract(data, i, NONE),
			nextBuf(buf, n-remain))
		    end
	      and nextBuf (buf as IBUF{more, data, ...}, n) = let
		    fun get (MORE buf) = inputList (buf, 0, n)
		      | get TERMINATED = ([], ISTRM(buf, V.length data))
		      | get NOMORE = (case (SV.mTake more)
			   of NOMORE => (case extendStream (readVec buf, "inputN", buf)
				 of EOF => ([], ISTRM(buf, V.length data))
				  | (DATA rest) => inputList (rest, 0, n)
				(* end case *))
			    | next => (SV.mPut(more, next); get next)
			  (* end case *))
		    in
		      get (SV.mGet more)
		    end
	      val (data, strm) = inputList (buf, pos, n)
	      in
		(V.concat data, strm)
	      end

	fun inputAll (strm as ISTRM(buf, _)) = let
	      val INFO{reader=PIO.RD{avail, ...}, ...} = infoOfIBuf buf
 	    (* read a chunk that is as large as the available input.  Note
	     * that for systems that use CR-LF for #"\n", the size will be
	     * too large, but this should be okay.
	     *)
	      fun bigChunk _ = let
		    val delta = (case avail()
			   of NONE => chunkSzOfIBuf buf
			    | (SOME n) => n
			  (* end case *))
		    in
		      readChunk buf delta
		    end
	      val bigInput =
		    generalizedInput (getBuffer (bigChunk, "inputAll"))
	      fun loop (v, strm) =
		    if (V.length v = 0) then [] else v :: loop(bigInput strm)
	      val data = V.concat (loop (bigInput strm))
	      in
		(data, findEOS buf)
	      end

	fun input1Evt _ = raise Fail "input1Evt unimplemented"
	fun inputEvt _ = raise Fail "inputEvt unimplemented"
	fun inputNEvt _ = raise Fail "inputNEvt unimplemented"
	fun inputAllEvt _ = raise Fail "inputAllEvt unimplemented"
	fun inputLineEvt _ = raise Fail "inputLineEvt unimplemented"

      (* Return SOME k, if k <= amount characters can be read without blocking. *)
	fun canInput (strm as ISTRM(buf, pos), amount) = let
(******
	      val readVecNB = (case buf
		   of (IBUF{info as INFO{readVecNB=NONE, ...}, ...}) =>
			inputExn(info, "canInput", IO.NonblockingNotSupported)
		    | (IBUF{info=INFO{readVecNB=SOME f, ...}, ...}) => f
		  (* end case *))
******)
	      fun tryInput (buf as IBUF{data, ...}, i, n) = let
		    val len = V.length data
		    val remain = len - i
		    in
		      if (remain >= n)
			then SOME n
			else nextBuf (buf, n - remain)
		    end
	      and nextBuf (IBUF{more, ...}, n) = let
		    fun get (MORE buf) = tryInput (buf, 0, n)
		      | get TERMINATED = SOME(amount - n)
(******
		      | get NOMORE = (case SV.mTake more
			   of NOMORE => ((
				case extendStream (readVecNB, "canInput", buf)
				 of EOF => SOME(amount - n)
				  | (DATA b) => tryInput (b, 0, n)
				(* end case *))
				  handle IO.Io{cause=WouldBlock, ...} => SOME(amount - n))
			    | next => (SV.mPut(more, next); get next)
			  (* end case *))
******)
		      | get NOMORE = SOME(amount - n)
		    in
		      get (SV.mGet more)
		    end
	      in
		if (amount < 0)
		  then raise Size
		  else tryInput (buf, pos, amount)
	      end
(*** We need some kind of lock on the input stream to do this safely!!! ***)
	fun closeIn (ISTRM(buf, _)) = (case (infoOfIBuf buf)
	       of INFO{closed=ref true, ...} => ()
		| (info as INFO{closed, reader=PIO.RD{close, ...}, ...}) => (
		    terminate info;
		    closed := true;
		    close() handle ex => inputExn(info, "closeIn", ex))
	      (* end case *))
	fun endOfStream (ISTRM(buf as IBUF{more, ...}, pos)) = (
	      case SV.mTake more
	       of (next as MORE _) => (SV.mPut(more, next); false)
		| next => let
		    val IBUF{data, info=INFO{closed, ...}, ...} = buf
		    in
		      if (pos = V.length data)
			then (case (next, !closed)
			    of (NOMORE, false) => (
			        case extendStream (readVec buf, "endOfStream", buf)
			         of EOF => true
				  | _ => false
				(* end case *))
			     | _ => (SV.mPut(more, next); true)
			  (* end case *))
			else (SV.mPut(more, next); false)
		    end
	      (* end case *))
	fun mkInstream' (reader, optData) = let
	      val PIO.RD{readVec, readVecEvt, getPos, setPos, ...} = reader