anyscalar.h: add ctor from type code and void*

also helper bufferUnsafe() to get storage pointer
or c_str().

src/misc/pv/anyscalar.h

@@ -112,6 +112,18 @@ public:
         _stype = (ScalarType)ScalarTypeID<TT>::value;
     }
 
+    AnyScalar(ScalarType type, const void *buf)
+    {
+        if(type==pvString) {
+            new (_wrap.blob) std::string(*static_cast<const std::string*>(buf));
+
+        } else {
+            memcpy(_wrap.blob, buf, ScalarTypeFunc::elementSize(type));
+        }
+
+        _stype = type;
+    }
+
     AnyScalar(const AnyScalar& o)
         :_stype(o._stype)
     {
@@ -269,6 +281,16 @@ public:
     operator bool_type() const { return !empty() ? &AnyScalar::swap : 0; }
 #endif
 
+    //! Provide read-only access to underlying buffer.
+    //! For a string this is std::string::c_str().
+    const void* bufferUnsafe() const {
+        if(_stype==pvString) {
+            return as<std::string>().c_str();
+        } else {
+            return _wrap.blob;
+        }
+    }
+
     /** Return reference to wrapped value */
     template<typename T>
     // T -> strip_const -> map to storage type -> add reference

testApp/misc/testanyscalar.cpp

@@ -42,6 +42,23 @@ void test_ctor()
     testEqual(D.ref<std::string>(), "bar");
 }
 
+void test_ctor_void()
+{
+    testDiag("test_ctor_void()");
+
+    pvd::int32 i = 42;
+    pvd::AnyScalar A(pvd::pvInt, (void*)&i);
+
+    testEqual(A.type(), pvd::pvInt);
+    testEqual(A.ref<pvd::int32>(), 42);
+
+    std::string s("hello");
+    pvd::AnyScalar B(pvd::pvString, (void*)&s);
+
+    testEqual(B.type(), pvd::pvString);
+    testEqual(B.ref<std::string>(), "hello");
+}
+
 void test_basic()
 {
     testDiag("test_basic()");
@@ -213,10 +230,11 @@ void test_move()
 
 MAIN(testanyscalar)
 {
-    testPlan(66);
+    testPlan(70);
     try {
         test_empty();
         test_ctor();
+        test_ctor_void();
         test_basic();
         test_swap();
         test_move();