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(* Example code for a C-library accessible from ML
using the CInterface structure.
Copyright David C.J. Matthews 1999-2009
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
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 CInterface;
val mylib = CInterface.load_lib "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 = STRUCT3(POINTER, POINTER, INT);
val (unMakeStruct, mkStruct, structType) = breakConversion TREENODE;
in
(* The following function builds a C data structure from an ML datatype. *)
fun tree2vol NullTree: vol = null
| tree2vol (Node{left, right, valu}) =
let
(* Construct a struct from the values. *)
val str = mkStruct(tree2vol left, tree2vol right, valu)
(* Allocate a struct on the heap. *)
val v = alloc 1 structType
in
(* Copy it over *)
assign structType v str;
(* Return the address of the heap area. *)
address v
end;
(* The inverse of tree2vol. We don't actually use this in this example. *)
fun vol2tree v =
if fromClong v = 0
then NullTree
else
let
val struc = deref v (* Get the structure itself from the pointer. *)
val (left, right, valu) = unMakeStruct struc
in
Node{left=vol2tree left, right=vol2tree right, valu = valu }
end
end;
(* Build a conversion out of this. *)
val TREE = mkConversion vol2tree tree2vol voidStar;
val sumTree = CInterface.call1 ( CInterface.load_sym mylib "SumTree") TREE INT;
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 = CInterface.call2 ( CInterface.load_sym mylib "ReturnR2")
(CInterface.INT, CInterface.INT) (STRUCT2(CInterface.INT, CInterface.INT));
(* This function crashes the old version. Now fixed. *)
returnR2(5,6);
(* Example of passing and returning strings. *)
val dupNString = CInterface.call2 (CInterface.load_sym mylib "DupNString") (CInterface.INT, CInterface.STRING)
CInterface.STRING;
dupNString (4, "hi");
(* Example of a callback function. *)
fun f (i, j) = (PolyML.print(i, j); i+j);
val doAdd = call2 (load_sym mylib "MakeCallback") (INT, FUNCTION2 (INT, INT) INT) INT;
doAdd(4, f);
(* Check that an exception is properly propagated. *)
(* This doesn't work if the library has been compiled with GCC. Foreign.c is C code
not C++ and the C++ exception mechanism won't propagate a C++ exception through
C code. *)
(* doAdd(4, fn _ => raise Fail "failed"); *)
(* int a, char b, double c, float d, short e, int *f *)
fun myCallback [v1, v2, v3, v4, v5, v6] =
let
val a = fromCint v1;
val b = fromCchar v2;
val c = fromCdouble v3;
val d = fromCfloat v4;
val e = fromCshort v5
(* f ? *)
in
PolyML.print(a, b, c, d, e);
toCdouble 99.0
end
| myCallback _ = toCint 1234;
val myCbVol = toCfunction [Cint, Cchar, Cdouble, Cfloat, Cshort, Cpointer Cint] Cdouble myCallback;
val returnR3 = call_sym (load_sym mylib "MakeCallback2") [(Cpointer Cint, myCbVol) ] Cdouble;
fromCdouble returnR3;
val doit = call2(load_sym mylib "MakeCallback3") (FUNCTION1 INT VOID, INT) VOID;
doit(fn i => print(Int.toString i), 2);
(* Test for finalisation. *)
val allocateIt = call0 (load_sym mylib "AllocateIt") () POINTER;
val v1 = allocateIt();
val v2 = allocateIt ();
val final = load_sym mylib "FreeIt";
setFinal final v1;
setFinal final v2;
(* Activating the finalisers requires a full GC. *)
val v1 = 0; (* The v1 object is no longer reachable. *)
PolyML.fullGC();
val v2 = 0; (* The v2 object is no longer reachable. *)
PolyML.fullGC();
|
