[m-rev.] For review: Java implementation of builtin library

[James Goddard]

Estimated hours taken: 4
Branches: main

Implement some library procedures for the Java back-end.

library/builtin.m:
	Implement the following functions:
		cc_cast/1
		cc_cast_io/1

	Partially implemented - This procedure serves as little more than
	a place-holder for the moment.  (See comment in deep_copy()).
		copy/2


Index: builtin.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/builtin.m,v
retrieving revision 1.100
diff -u -d -r1.100 builtin.m
--- builtin.m	1 Dec 2003 13:17:10 -0000	1.100
+++ builtin.m	20 Jan 2004 01:18:51 -0000
@@ -398,6 +398,19 @@
 "
 	Y = X;
 ").
+:- pragma foreign_proc("Java",
+	cc_cast(X :: (pred(out) is cc_multi)) = (Y :: out(pred(out) is det)),
+	[will_not_call_mercury, thread_safe],
+"
+	Y = X;
+").
+:- pragma foreign_proc("Java",
+	cc_cast(X :: (pred(out) is cc_nondet)) =
+		(Y :: out(pred(out) is semidet)),
+	[will_not_call_mercury, thread_safe],
+"
+	Y = X;
+").
 
 :- pragma promise_pure(promise_only_solution_io/4).
 promise_only_solution_io(Pred, X) -->
@@ -425,6 +438,13 @@
 "
 	Y = X;
 ").
+:- pragma foreign_proc("Java", 
+	cc_cast_io(X :: (pred(out, di, uo) is cc_multi)) =
+		(Y :: out(pred(out, di, uo) is det)),
+	[will_not_call_mercury, thread_safe],
+"
+	Y = X;
+").
 
 %-----------------------------------------------------------------------------%
 
@@ -618,6 +638,57 @@
 
 ").
 
+:- pragma foreign_code("Java",
+"
+public static java.lang.Object
+deep_copy(java.lang.Object original) {
+	java.lang.Object clone;
+
+	if (original == null) {
+		return null;
+	}
+
+	java.lang.Class cls = original.getClass();
+
+	if (cls.getName().equals(""java.lang.String"")) {
+		return new java.lang.String((java.lang.String) original);
+	}
+
+	if (cls.isArray()) {
+		int length = java.lang.reflect.Array.getLength(original);
+		clone = java.lang.reflect.Array.newInstance(
+				cls.getComponentType(), length);
+		for (int i = 0; i < length; i++) {
+			java.lang.Object X, Y;
+			X = java.lang.reflect.Array.get(original, i);
+			Y = deep_copy(X);
+			java.lang.reflect.Array.set(clone, i, Y);
+		}
+		return clone;
+	}
+
+	/*
+	** XXX Two possible approaches are possible here:
+	**
+	** 1. Get all mercury objects to implement the Serializable interface.
+	**    Then this whole function could be replaced with code that writes
+	**    the Object out via an ObjectOutputStream into a byte array (or
+	**    something), then reads it back in again, thus creating a copy.
+	** 2. Call cls.getConstructors(), then iterate through the resulting
+	**    array until one of them allows instantiation with all parameters
+	**    set to 0 or null (or some sort of recursive call that attempts to
+	**    instantiate the parameters).
+	**    This approach is of course not guaranteed to work all the time.
+	**    Then we can just copy the fields across using Reflection.
+	**
+	** For now, we're just throwing an exception.
+	*/
+
+	throw new java.lang.RuntimeException(
+			""deep copy not yet fully implemented"");
+}
+").
+
 %-----------------------------------------------------------------------------%
 
 % unsafe_promise_unique is a compiler builtin.
@@ -650,6 +721,20 @@
 ").
 
 :- pragma foreign_proc("C#",
+	copy(X::in, Y::uo),
+	[may_call_mercury, thread_safe, promise_pure],
+"
+        Y = deep_copy(X);
+").
+
+:- pragma foreign_proc("Java",
+	copy(X::ui, Y::uo),
+	[may_call_mercury, thread_safe, promise_pure],
+"
+        Y = deep_copy(X);
+").
+
+:- pragma foreign_proc("Java",
 	copy(X::in, Y::uo),
 	[may_call_mercury, thread_safe, promise_pure],
 "
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