Merge pull request #1279 from NathanJPhillips/feature/expr_dynamic_cast

Implementation of expr_dynamic_cast

Author: smowton

src/util/expr_cast.h

@@ -0,0 +1,172 @@
+/*******************************************************************\
+
+Module:
+
+Author: Nathan Phillips <[email protected]>
+
+\*******************************************************************/
+
+#ifndef CPROVER_UTIL_EXPR_CAST_H
+#define CPROVER_UTIL_EXPR_CAST_H
+
+/// \file util/expr_cast.h
+/// \brief Templated functions to cast to specific exprt-derived classes
+
+#include <typeinfo>
+#include <type_traits>
+#include <functional>
+
+#include "invariant.h"
+#include "expr.h"
+#include "optional.h"
+
+/// \brief Check whether a reference to a generic \ref exprt is of a specific
+///   derived class.
+///
+///   Implement template specializations of this function to enable casting
+///
+/// \tparam T The exprt-derived class to check for
+/// \param base Reference to a generic \ref exprt
+/// \return true if \a base is of type \a T
+template<typename T> bool can_cast_expr(const exprt &base);
+
+
+/// \brief Try to cast a constant reference to a generic exprt to a specific
+///   derived class
+/// \tparam T The exprt-derived class to cast to
+/// \param base Reference to a generic \ref exprt
+/// \return Reference to object of type \a T or valueless optional if \a base
+///   is not an instance of \a T
+template<typename T>
+optionalt<std::reference_wrapper<typename std::remove_reference<T>::type>>
+expr_try_dynamic_cast(const exprt &base)
+{
+  return expr_try_dynamic_cast<
+    T,
+    typename std::remove_reference<T>::type,
+    typename std::remove_const<typename std::remove_reference<T>::type>::type,
+    const exprt>(base);
+}
+
+/// \brief Try to cast a reference to a generic exprt to a specific derived
+///   class
+/// \tparam T The exprt-derived class to cast to
+/// \param base Reference to a generic \ref exprt
+/// \return Reference to object of type \a T or valueless optional if \a base is
+///   not an instance of \a T
+template<typename T>
+optionalt<std::reference_wrapper<typename std::remove_reference<T>::type>>
+expr_try_dynamic_cast(exprt &base)
+{
+  return expr_try_dynamic_cast<
+    T,
+    typename std::remove_reference<T>::type,
+    typename std::remove_const<typename std::remove_reference<T>::type>::type,
+    exprt>(base);
+}
+
+/// \brief Try to cast a reference to a generic exprt to a specific derived
+///    class
+/// \tparam T The reference or const reference type to \a TUnderlying to cast
+///    to
+/// \tparam TUnderlying An exprt-derived class type
+/// \tparam TExpr The original type to cast from, either exprt or const exprt
+/// \param base Reference to a generic \ref exprt
+/// \return Reference to object of type \a TUnderlying
+///   or valueless optional if \a base is not an instance of \a TUnderlying
+template<typename T, typename TConst, typename TUnderlying, typename TExpr>
+optionalt<std::reference_wrapper<TConst>> expr_try_dynamic_cast(TExpr &base)
+{
+  static_assert(
+    std::is_same<typename std::remove_const<TExpr>::type, exprt>::value,
+    "Tried to expr_try_dynamic_cast from something that wasn't an exprt");
+  static_assert(
+    std::is_reference<T>::value,
+    "Tried to convert exprt & to non-reference type");
+  static_assert(
+    std::is_base_of<exprt, TUnderlying>::value,
+    "The template argument T must be derived from exprt.");
+  if(!can_cast_expr<TUnderlying>(base))
+    return optionalt<std::reference_wrapper<TConst>>();
+  T value=static_cast<T>(base);
+  validate_expr(value);
+  return optionalt<std::reference_wrapper<TConst>>(value);
+}
+
+/// \brief Cast a constant reference to a generic exprt to a specific derived
+///   class
+/// \tparam T The exprt-derived class to cast to
+/// \param base Reference to a generic \ref exprt
+/// \return Reference to object of type \a T
+/// \throw std::bad_cast If \a base is not an instance of \a T
+/// \remark If CBMC assertions (PRECONDITION) are set to abort then this will
+///   abort rather than throw if \a base is not an instance of \a T
+template<typename T>
+T expr_dynamic_cast(const exprt &base)
+{
+  return expr_dynamic_cast<
+    T,
+    typename std::remove_const<typename std::remove_reference<T>::type>::type,
+    const exprt>(base);
+}
+
+/// \brief Cast a reference to a generic exprt to a specific derived class
+/// \tparam T The exprt-derived class to cast to
+/// \param base Reference to a generic \ref exprt
+/// \return Reference to object of type \a T
+/// \throw std::bad_cast If \a base is not an instance of \a T
+/// \remark If CBMC assertions (PRECONDITION) are set to abort then this will
+///   abort rather than throw if \a base is not an instance of \a T
+template<typename T>
+T expr_dynamic_cast(exprt &base)
+{
+  return expr_dynamic_cast<
+    T,
+    typename std::remove_const<typename std::remove_reference<T>::type>::type,
+    exprt>(base);
+}
+
+/// \brief Cast a reference to a generic exprt to a specific derived class
+/// \tparam T The reference or const reference type to \a TUnderlying to cast to
+/// \tparam TUnderlying An exprt-derived class type
+/// \tparam TExpr The original type to cast from, either exprt or const exprt
+/// \param base Reference to a generic \ref exprt
+/// \return Reference to object of type \a T
+/// \throw std::bad_cast If \a base is not an instance of \a TUnderlying
+/// \remark If CBMC assertions (PRECONDITION) are set to abort then this will
+///   abort rather than throw if \a base is not an instance of \a TUnderlying
+template<typename T, typename TUnderlying, typename TExpr>
+T expr_dynamic_cast(TExpr &base)
+{
+  static_assert(
+    std::is_same<typename std::remove_const<TExpr>::type, exprt>::value,
+    "Tried to expr_dynamic_cast from something that wasn't an exprt");
+  static_assert(
+    std::is_reference<T>::value,
+    "Tried to convert exprt & to non-reference type");
+  static_assert(
+    std::is_base_of<exprt, TUnderlying>::value,
+    "The template argument T must be derived from exprt.");
+  PRECONDITION(can_cast_expr<TUnderlying>(base));
+  if(!can_cast_expr<TUnderlying>(base))
+    throw std::bad_cast();
+  T value=static_cast<T>(base);
+  validate_expr(value);
+  return value;
+}
+
+
+inline void validate_operands(
+  const exprt &value,
+  exprt::operandst::size_type number,
+  const char *message,
+  bool allow_more=false)
+{
+  DATA_INVARIANT(
+    allow_more
+      ? value.operands().size()==number
+      : value.operands().size()>=number,
+    message);
+}
+
+#endif  // CPROVER_UTIL_EXPR_CAST_H