Refactor registers to initialize all of them at startup and add null register

Fixes #497

1 files changed, 63 insertions, 3 deletions

diff --git a/src/register_manager.hh b/src/register_manager.hh
index df829763..355bec1f 100644
--- a/src/register_manager.hh
+++ b/src/register_manager.hh
@@ -2,6 +2,7 @@
 #define register_manager_hh_INCLUDED
 
 #include "array_view.hh"
+#include "exception.hh"
 #include "utils.hh"
 #include "unordered_map.hh"
 #include "string.hh"
@@ -23,14 +24,73 @@ public:
     virtual ConstArrayView<String> values(const Context& context) = 0;
 };
 
+// static value register, which can be modified
+// using operator=, so should be user modifiable
+class StaticRegister : public Register
+{
+public:
+    Register& operator=(ConstArrayView<String> values) override
+    {
+        m_content = Vector<String, MemoryDomain::Registers>(values.begin(), values.end());
+        return *this;
+    }
+
+    ConstArrayView<String> values(const Context&) override
+    {
+        if (m_content.empty())
+            return ConstArrayView<String>(String::ms_empty);
+        else
+            return ConstArrayView<String>(m_content);
+    }
+protected:
+    Vector<String, MemoryDomain::Registers> m_content;
+};
+
 using RegisterRetriever = std::function<Vector<String, MemoryDomain::Registers> (const Context&)>;
 
+// Dynamic value register, use it's RegisterRetriever
+// to get it's value when needed.
+class DynamicRegister : public StaticRegister
+{
+public:
+    DynamicRegister(RegisterRetriever function)
+        : m_function(std::move(function)) {}
+
+    Register& operator=(ConstArrayView<String> values) override
+    {
+        throw runtime_error("this register is not assignable");
+    }
+
+    ConstArrayView<String> values(const Context& context) override
+    {
+        m_content = m_function(context);
+        return StaticRegister::values(context);
+    }
+
+private:
+    RegisterRetriever m_function;
+};
+
+class NullRegister : public Register
+{
+public:
+    Register& operator=(ConstArrayView<String> values) override
+    {
+        return *this;
+    }
+
+    ConstArrayView<String> values(const Context& context) override
+    {
+        return ConstArrayView<String>(String::ms_empty);
+    }
+};
+
 class RegisterManager : public Singleton<RegisterManager>
 {
 public:
-    Register& operator[](StringView reg);
-    Register& operator[](Codepoint c);
-    void register_dynamic_register(char reg, RegisterRetriever function);
+    Register& operator[](StringView reg) const;
+    Register& operator[](Codepoint c) const;
+    void add_register(char c, std::unique_ptr<Register> reg);
 
 protected:
     UnorderedMap<char, std::unique_ptr<Register>, MemoryDomain::Registers> m_registers;