Initial data commit

Task/Queue-Usage/D/queue-usage-2.d

@@ -0,0 +1,75 @@
+module queue_usage2;
+
+import std.traits: hasIndirections;
+
+struct GrowableCircularQueue(T) {
+    public size_t length;
+    private size_t first, last;
+    private T[] A = [T.init];
+
+    this(T[] items...) pure nothrow @safe {
+        foreach (x; items)
+            push(x);
+    }
+
+    @property bool empty() const pure nothrow @safe @nogc {
+        return length == 0;
+    }
+
+    @property T front() pure nothrow @safe @nogc {
+        assert(length != 0);
+        return A[first];
+    }
+
+    T opIndex(in size_t i) pure nothrow @safe @nogc {
+        assert(i < length);
+        return A[(first + i) & (A.length - 1)];
+    }
+
+    void push(T item) pure nothrow @safe {
+        if (length >= A.length) { // Double the queue.
+            immutable oldALen = A.length;
+            A.length *= 2;
+            if (last < first) {
+                A[oldALen .. oldALen + last + 1] = A[0 .. last + 1];
+                static if (hasIndirections!T)
+                    A[0 .. last + 1] = T.init; // Help for the GC.
+                last += oldALen;
+            }
+        }
+        last = (last + 1) & (A.length - 1);
+        A[last] = item;
+        length++;
+    }
+
+    @property T pop() pure nothrow @safe @nogc {
+        assert(length != 0);
+        auto saved = A[first];
+        static if (hasIndirections!T)
+            A[first] = T.init; // Help for the GC.
+        first = (first + 1) & (A.length - 1);
+        length--;
+        return saved;
+    }
+}
+
+version (queue_usage2_main) {
+    void main() {
+        GrowableCircularQueue!int q;
+        q.push(10);
+        q.push(20);
+        q.push(30);
+        assert(q.pop == 10);
+        assert(q.pop == 20);
+        assert(q.pop == 30);
+        assert(q.empty);
+
+        uint count = 0;
+        foreach (immutable i; 1 .. 1_000) {
+            foreach (immutable j; 0 .. i)
+                q.push(count++);
+            foreach (immutable j; 0 .. i)
+                q.pop;
+        }
+    }
+}