Changeset 1752

Timestamp:

07/12/10 14:18:21 (14 years ago)

Author:

andrei

Message:

Added emplace for class types

Files:

• trunk/phobos/std/conv.d (modified) (2 diffs)

trunk/phobos/std/conv.d

@@ -3627 +3627 @@
-
-// Bugzilla 3961
-unittest
-{
-    struct Int { int x; }
-    Int i = to!Int(1);
-}
-
-// emplace
-/**
-type 
-
-
-
+non-
+
+
+T) needs and 
-
-This function can be $(D @trusted) if the corresponding constructor of
-$(D T) is $(D @safe).
-
-Returns: A pointer to the newly constructed object.
- */
-T* emplace(T, Args...)(void[] chunk, Args args) if (!is(T == class))
-{
-    enforce(chunk.length >= T.sizeof);
-    auto a = cast(size_t) chunk.ptr;
@@ -3698 +3698 @@
-        double x = 5, y = 6;
-        this(int a, int b) { assert(x == 5 && y == 6); x = a; y = b; }
-    }
-
-    auto s1 = new void[S.sizeof];
-    auto s2 = S(42, 43);
-    assert(*emplace!S(s1, s2) == s2);
-    assert(*emplace!S(s1, 44, 45) == S(44, 45));
-}
-
+// emplace
+/**
+Given a raw memory area $(D chunk), constructs an object of $(D class)
+type $(D T) at that address. The constructor is passed the arguments
+$(D Args). The $(D chunk) must be as least as large as $(D T) needs
+and should have an alignment multiple of $(D T)'s alignment. (The size
+of a $(D class) instance is obtained by using $(D
+__traits(classInstanceSize, T))).
+
+This function can be $(D @trusted) if the corresponding constructor of
+$(D T) is $(D @safe).
+
+Returns: A pointer to the newly constructed object.
+ */
+T emplace(T, Args...)(void[] chunk, Args args) if (is(T == class))
+{
+    enforce(chunk.length >= __traits(classInstanceSize, T));
+    auto a = cast(size_t) chunk.ptr;
+    enforce(a % real.alignof == 0);
+    auto result = cast(typeof(return)) chunk.ptr;
+
+    // Initialize the object in its pre-ctor state
+    (cast(byte[]) chunk)[] = typeid(T).init[];
+
+    // Call the ctor if any
+    static if (is(typeof(result.__ctor(args))))
+    {
+        // T defines a genuine constructor accepting args
+        // Go the classic route: write .init first, then call ctor
+        result.__ctor(args);
+    }
+    else
+    {
+        static assert(args.length == 0 && !is(typeof(&T.__ctor)),
+                "Don't know how to initialize an object of type "
+                ~ T.stringof ~ " with arguments " ~ Args.stringof);
+    }
+    return result;
+}
+
+unittest
+{
+    class A
+    {
+        int x = 5;
+        int y = 42;
+        this(int z) { assert(x == 5 && y == 42); x = y = z;}
+    }
+    static byte[__traits(classInstanceSize,A)] buf;
+    auto a = emplace!A(cast(void[]) buf, 55);
+    assert(a.x == 55 && a.y == 55);
+    static assert(!is(typeof(emplace!A(cast(void[]) buf))));
+}
+
-unittest
-{
-    // Check fix for http://d.puremagic.com/issues/show_bug.cgi?id=2971
-    assert(equal(map!(to!int)(["42", "34", "345"]), [42, 34, 345]));
-}
-