Christopher Haster
Flexible templated function class and related utilities that avoid dynamic memory allocation without limiting functionality
FuncPtr provides a flexible templated function class and related utilities while avoiding dynamic memory allocation and avoiding limited functionality.
FuncPtr provides an intuitive template interface:
FuncPtr<void(const char *)> func(puts);
func("hello!\n"); // prints hello!
Several function types are supported by FuncPtr:
// Simple C functions
void func();
FuncPtr<void()> fp(func);
// C++ Methods
struct Thing { void func(); };
Thing thing;
FuncPtr<void()> fp(&thing, &Thing::func);
// C functions with context
void func(Thing *);
FuncPtr<void()> fp(&thing, func);
// Function objects
struct Thing { void operator()(); };
Thing thing;
FuncPtr<void()> fp(&thing);
There is no dynamic memory allocation, managing memory is placed entirely on the user. More advanced function manipulation can be accomplished with statically allocated classes:
// Function binding
Binder<void(const char *), const char *> bind(putc, "hi!");
bind(); // prints hi!
// Function composition
Composer<int(const char *), const char *(int)> comp(puts, itoa);
comp(10); // prints 10
// Function chaining
Chainer<void(const char *), 2> chain;
chain.attach(puts);
chain.attach(puts);
chain("hi!\n"); // prints hi! twice
FuncPtr allows easy support of a large range of function types in C++ APIs with very few lines of code:
class Thing {
public:
// The following two methods are sufficient for supporting
// every supported function type
void attach(FuncPtr<void()> func) {
_func.attach(func);
}
template<typename T, typename M>
void attach(T *obj, M method) {
attach(FuncPtr<void()>(obj, method));
}
private:
FuncPtr<void()> _func;
}
Additionally, FuncPtrs have several utilities for easy integration with C APIs:
// C style callbacks void register_callback(void (*callback)(void *), void *data); register_callback(&FuncPtr<void()>::thunk, &func); // C style functions without context void register_callback(void (*callback)()); Thunker thunk(func); register_callback(thunk); // mbed style callbacks void register_callback(T *obj, void (T::*M)()); register_callback(&func, &FuncPtr<void()>::call);
Diff: FuncPtr.h
- Revision:
- 18:a0fde14b6c39
- Parent:
- 14:79be4e700cc9
--- a/FuncPtr.h Wed Apr 20 02:43:14 2016 -0500
+++ b/FuncPtr.h Sun Apr 17 23:38:04 2016 -0500
@@ -17,6 +17,160 @@
/** Flexible templated function class
*/
+template <typename R, typename A0, typename A1, typename A2, typename A3, typename A4>
+class FuncPtr<R(A0, A1, A2, A3, A4)> {
+public:
+ /** Create a FuncPtr with a static function
+ * @param func Static function to attach
+ */
+ FuncPtr(R (*func)(A0, A1, A2, A3, A4) = 0) {
+ attach(func);
+ }
+
+ /** Create a FuncPtr with a static function and bound pointer
+ * @param obj Pointer to object to bind to function
+ * @param func Static function to attach
+ */
+ template<typename T>
+ FuncPtr(T *obj, R (*func)(T*, A0, A1, A2, A3, A4)) {
+ attach(obj, func);
+ }
+
+ /** Create a FuncPtr with a method
+ * @param obj Pointer to object to invoke method on
+ * @param func Method to attach
+ */
+ template<typename T>
+ FuncPtr(T *obj, R (T::*func)(A0, A1, A2, A3, A4)) {
+ attach(obj, func);
+ }
+
+ /** Create a FuncPtr with a function object
+ * @param func Function object to attach
+ */
+ template<typename T>
+ FuncPtr(T *obj) {
+ attach(obj, &T::operator());
+ }
+
+ /** Create a FuncPtr with another FuncPtr
+ * @param func FuncPtr to attach
+ */
+ FuncPtr(const FuncPtr<R(A0, A1, A2, A3, A4)> &func) {
+ attach(func);
+ }
+
+ /** Attach a static function
+ * @param func Static function to attach
+ */
+ void attach(R (*func)(A0, A1, A2, A3, A4)) {
+ memcpy(&_func, &func, sizeof func);
+ _thunk = func ? &FuncPtr::_staticthunk : 0;
+ }
+
+ /** Attach a static function with a bound pointer
+ * @param obj Pointer to object to bind to function
+ * @param func Static function to attach
+ */
+ template <typename T>
+ void attach(T *obj, R (*func)(T*, A0, A1, A2, A3, A4)) {
+ _obj = static_cast<void*>(obj);
+ memcpy(&_func, &func, sizeof func);
+ _thunk = &FuncPtr::_boundthunk<T>;
+ }
+
+ /** Attach a method
+ * @param obj Pointer to object to invoke method on
+ * @param func Method to attach
+ */
+ template<typename T>
+ void attach(T *obj, R (T::*func)(A0, A1, A2, A3, A4)) {
+ _obj = static_cast<void*>(obj);
+ memcpy(&_func, &func, sizeof func);
+ _thunk = &FuncPtr::_methodthunk<T>;
+ }
+
+ /** Attach a function object
+ * @param func Function object to attach
+ */
+ template<typename T>
+ void attach(T *func) {
+ attach(func, &T::operator());
+ }
+
+ /** Attach a FuncPtr
+ * @param func The FuncPtr to attach
+ */
+ void attach(const FuncPtr<R(A0, A1, A2, A3, A4)> &func) {
+ _obj = func._obj;
+ memcpy(&_func, &func._func, sizeof _func);
+ _thunk = func._thunk;
+ }
+
+ /** Call the attached function
+ */
+ R call(A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+ return _thunk(_obj, &_func, a0, a1, a2, a3, a4);
+ }
+
+ /** Call the attached function
+ */
+ R operator()(A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+ return call(a0, a1, a2, a3, a4);
+ }
+
+ /** Test if function has been attached
+ */
+ operator bool() const {
+ return _thunk;
+ }
+
+ /** Static thunk for passing as C-style function
+ * @param func FuncPtr to call passed as void pointer
+ */
+ static R thunk(void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+ return static_cast<FuncPtr<R(A0, A1, A2, A3, A4)>*>(func)
+ ->call(a0, a1, a2, a3, a4);
+ }
+
+private:
+ // Internal thunks for various function types
+ static R _staticthunk(void*, void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+ return (*reinterpret_cast<R (**)(A0, A1, A2, A3, A4)>(func))
+ (a0, a1, a2, a3, a4);
+ }
+
+ template<typename T>
+ static R _boundthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+ return (*reinterpret_cast<R (**)(T*, A0, A1, A2, A3, A4)>(func))
+ (static_cast<T*>(obj), a0, a1, a2, a3, a4);
+ }
+
+ template<typename T>
+ static R _methodthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+ return (static_cast<T*>(obj)->*
+ (*reinterpret_cast<R (T::**)(A0, A1, A2, A3, A4)>(func)))
+ (a0, a1, a2, a3, a4);
+ }
+
+ // Stored as pointer to function and pointer to optional object
+ // Function pointer is stored as union of possible function types
+ // to garuntee proper size and alignment
+ struct _class;
+ union {
+ void (*_staticfunc)();
+ void (*_boundfunc)(_class *);
+ void (_class::*_methodfunc)();
+ } _func;
+
+ void *_obj;
+
+ // Thunk registered on attach to dispatch calls
+ R (*_thunk)(void*, void*, A0, A1, A2, A3, A4);
+};
+
+/** Flexible templated function class
+ */
template <typename R, typename A0, typename A1, typename A2, typename A3>
class FuncPtr<R(A0, A1, A2, A3)> {
public: