update data.h

src/data.cpp

@@ -14,6 +14,12 @@
 
 namespace pvxs {
 
+NoField::NoField()
+    :std::runtime_error ("No such field")
+{}
+
+NoField::~NoField() {}
+
 NoConvert::NoConvert()
     :std::runtime_error ("No conversion defined")
 {}
@@ -154,6 +160,12 @@ const std::string& Value::id() const
     return desc->id;
 }
 
+bool Value::idStartsWith(const std::string& prefix) const
+{
+    auto ID = this->id();
+    return ID.size()>=prefix.size() && prefix==ID.substr(0u, prefix.size());
+}
+
 namespace {
 // C-style cast between scalar storage types, and print to string (base 10)
 template<typename Src>
@@ -176,7 +188,7 @@ bool copyOutScalar(const Src& src, void *ptr, StoreType type)
 void Value::copyOut(void *ptr, StoreType type) const
 {
     if(!desc)
-        throw NoConvert();
+        throw NoField();
 
     switch(store->code) {
     case StoreType::Real:     if(copyOutScalar(store->as<double>(), ptr, type)) return; else break;
@@ -251,7 +263,7 @@ bool copyInScalar(Dest& dest, const void *ptr, StoreType type)
 void Value::copyIn(const void *ptr, StoreType type)
 {
     if(!desc)
-        throw NoConvert();
+        throw NoField();
 
     switch(store->code) {
     case StoreType::Real:     if(!copyInScalar(store->as<double>(), ptr, type)) throw NoConvert(); break;
@@ -316,8 +328,14 @@ void Value::copyIn(const void *ptr, StoreType type)
                 break;
             }
         }
-        // fall through
+        throw NoConvert();
     case StoreType::Null:
+        if(desc->code==TypeCode::Struct && type==StoreType::Compound) {
+            auto& val = *reinterpret_cast<const Value*>(ptr);
+            if(val.desc && val.desc->code==TypeCode::Struct) {
+                // Struct to Struct assignment.
+            }
+        }
         throw NoConvert();
     }
 

src/nt.cpp

@@ -9,8 +9,7 @@
 namespace pvxs {
 namespace nt {
 
-
-TypeDef NTScalar::build()
+TypeDef NTScalar::build() const
 {
     return TypeDef(TypeCode::Struct,
                    value.isarray() ? "epics:nt/NTScalarArray:1.0" : "epics:nt/NTScalar:1.0", {
@@ -72,7 +71,7 @@ TypeDef NTScalar::build()
 //    return def;
 }
 
-TypeDef NTNDArray::build()
+TypeDef NTNDArray::build() const
 {
     TypeDef def(TypeCode::Struct, "epics:nt/NTNDArray:1.0");
 

src/pvxs/data.h

@@ -37,7 +37,7 @@ struct FieldDesc;
 
 //! maps T to one of the types which can be stored in the FieldStorage::store union
 //! typename StorageMap<T>::store_t is, if existant, is one such type.
-//! Can store_t shall be cast-able to/from T.
+//! store_t shall be cast-able to/from T.
 //! StorageMap<T>::code is the associated StoreType.
 template<typename T, typename Enable=void>
 struct StorageMap;
@@ -65,6 +65,10 @@ template<>
 struct StorageMap<char*>
 { typedef std::string store_t;   static constexpr StoreType code{StoreType::String}; };
 
+template<>
+struct StorageMap<const char*>
+{ typedef std::string store_t;   static constexpr StoreType code{StoreType::String}; };
+
 template<>
 struct StorageMap<shared_array<const void>>
 { typedef shared_array<const void> store_t;   static constexpr StoreType code{StoreType::Array}; };
@@ -214,11 +218,16 @@ public:
 PVXS_API
 std::ostream& operator<<(std::ostream& strm, const TypeDef&);
 
+struct PVXS_API NoField : public std::runtime_error
+{
+    explicit NoField();
+    virtual ~NoField();
+};
+
 struct PVXS_API NoConvert : public std::runtime_error
 {
     explicit NoConvert();
     virtual ~NoConvert();
-    TypeCode source;
 };
 
 //! pointer-like reference to a single data field
@@ -265,6 +274,7 @@ public:
     TypeCode type() const;
     StoreType storageType() const;
     const std::string& id() const;
+    bool idStartsWith(const std::string& prefix) const;
 
     //! test for instance equality.
     inline bool compareInst(const Value& o) { return store==o.store; }

src/pvxs/nt.h

@@ -9,6 +9,8 @@
 #include <pvxs/version.h>
 #include <pvxs/data.h>
 
+struct epicsTimeStamp; // epicsTime.h
+
 namespace pvxs {
 namespace nt {
 
@@ -19,12 +21,18 @@ struct NTScalar {
     bool valueAlarm;
 
     PVXS_API
-    TypeDef build();
+    TypeDef build() const;
+    inline Value create() const {
+        return build().create();
+    }
 };
 
 struct NTNDArray {
     PVXS_API
-    TypeDef build();
+    TypeDef build() const;
+    inline Value create() const {
+        return build().create();
+    }
 };
 
 }} // namespace pvxs::nt

test/testtype.cpp

@@ -43,7 +43,7 @@ void testBasic()
         testOk1(!val.valid());
         testOk1(!val.isMarked());
 
-        testThrows<NoConvert>([&val]() {
+        testThrows<NoField>([&val]() {
             val.from(4.2);
         });
     }