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(* Example code for the updated foreign-function interface.
Copyright David C.J. Matthews 2015
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License version 2.1 as published by the Free Software Foundation.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*)
open Foreign;
val mylib = loadLibrary "Foreign";
(* Example of creating a conversion for a datatype. *)
datatype intTree = NullTree | Node of {left: intTree, right: intTree, valu: int};
(* The corresponding C structure is
typedef struct _tree {
struct _tree *left, *right;
int nValue;
} *tree;
*)
local
(* Start with the C structure. *)
val treeNode = cStruct3(cPointer, cPointer, cInt)
val {store=storeStruct, load=loadStruct, ctype = {size = sizeStruct, ...}, ... } =
breakConversion treeNode
in
(* The following function builds a C data structure from an ML datatype. *)
fun treeMake NullTree = Memory.null
| treeMake(Node{left, right, valu}) =
let
val mem = Memory.malloc sizeStruct
in
ignore(storeStruct(mem, (treeMake left, treeMake right, valu)));
mem
end
fun treeClear a =
if a = Memory.null
then ()
else
let
val (left, right, _) = loadStruct a
in
treeClear left; treeClear right; Memory.free a
end
fun treeStore(addr, tree) =
let
val mem = treeMake tree
in
Memory.setAddress(addr, 0w0, mem);
(* The store function returns a function that frees the memory. *)
fn () => treeClear mem
end
(* The inverse of treeStore. We don't actually use this in this example. *)
fun treeGet a =
if a = Memory.null
then NullTree
else
let
val (left, right, valu) = loadStruct a
in
Node{left=treeGet left, right=treeGet right, valu = valu }
end
fun treeLoad v = treeGet(Memory.getAddress(v, 0w0))
end;
(* Build a conversion out of this. *)
val cTree: intTree conversion =
makeConversion { load = treeLoad, store = treeStore, ctype = LowLevel.cTypePointer };
val sumTree = buildCall1 (getSymbol mylib "SumTree", cTree, cInt);
val aTree = Node{left=Node{left=NullTree, right=NullTree, valu=4},
right=Node{
left= Node{left=NullTree, right=NullTree, valu=3},
right=NullTree, valu=5},
valu = 7};
sumTree aTree;
(* Example of returning a structure. *)
val returnR2 = buildCall2 (getSymbol mylib "ReturnR2", (cInt, cInt), cStruct2(cInt, cInt));
returnR2(5,6);
(* Example of passing and returning strings. *)
val dupNString = buildCall2 (getSymbol mylib "DupNString", (cInt, cString), cString);
dupNString (4, "hi");
(* Example of a callback function. *)
fun f (i, j) = (PolyML.print(i, j); i+j);
val fAsCFunction = buildClosure2(f, (cInt, cInt), cInt);
val doAdd =
buildCall2 (getSymbol mylib "MakeCallback", (cInt, cFunction: (int*int->int) closure conversion), cInt);
doAdd(4, fAsCFunction);
fun myCallback(a: int, b: char, c: real, d: real, e: int, f: Memory.voidStar) =
(
PolyML.print(a, b, c, d, e);
99.0
);
local
val myCallbackC =
buildClosure6(myCallback, (cInt, cChar, cDouble, cFloat, cShort, cPointer), cDouble)
val MakeCallback2 =
buildCall1(getSymbol mylib "MakeCallback2", cFunction, cDouble)
in
val returnR3 = MakeCallback2 myCallbackC
end;
let
val f = buildClosure1(fn i => print(Int.toString i), cInt, cVoid)
val doit = buildCall2(getSymbol mylib "MakeCallback3", (cFunction, cInt), cVoid)
in
doit(f, 2)
end;
(* Call-by-reference. *)
val r = ref 6;
val updateArg =
buildCall2 (getSymbol mylib "UpdateArg", (cInt, cStar cInt), cVoid);
updateArg(5, r); (* Adds its first argument to the ref. *)
!r;
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