/*

* Safe(r) Integer Handling

* (C) 2016 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#ifndef BOTAN_UTILS_SAFE_INT_H_

#define BOTAN_UTILS_SAFE_INT_H_

#include <botan/exceptn.h>

#include <botan/internal/fmt.h>

#include <optional>

#include <string_view>

#if defined(_MSC_VER)

   #include <intsafe.h>

#endif

namespace Botan {

class Integer_Overflow_Detected final : public Exception {

   public:

      Integer_Overflow_Detected(std::string_view file, int line) :

            Exception(fmt("Integer overflow detected at {}:{}", file, line)) {}

      ErrorType error_type() const noexcept override { return ErrorType::InternalError; }

};

inline size_t checked_add(size_t x, size_t y, const char* file, int line) {

#if BOTAN_COMPILER_HAS_BUILTIN(__builtin_add_overflow)

   size_t z;

   if(__builtin_add_overflow(x, y, &z)) [[unlikely]]

#elif defined(_MSC_VER)

   size_t z;

   if(SizeTAdd(x, y, &z) != S_OK) [[unlikely]]

#else

   size_t z = x + y;

   if(z < x) [[unlikely]]

#endif

   {

      throw Integer_Overflow_Detected(file, line);

   }

   return z;

}

inline std::optional<size_t> checked_mul(size_t x, size_t y) {

#if BOTAN_COMPILER_HAS_BUILTIN(__builtin_add_overflow)

   size_t z;

   if(__builtin_mul_overflow(x, y, &z)) [[unlikely]]

#elif defined(_MSC_VER)

   size_t z;

   if(SizeTMult(x, y, &z) != S_OK) [[unlikely]]

#else

   size_t z = x * y;

   if(y && z / y != x) [[unlikely]]

#endif

   {

      return std::nullopt;

   }

   return z;

}

template <typename RT, typename AT>

RT checked_cast_to(AT i) {

   RT c = static_cast<RT>(i);

   if(i != static_cast<AT>(c))

      throw Internal_Error("Error during integer conversion");

   return c;

}

#define BOTAN_CHECKED_ADD(x, y) checked_add(x, y, __FILE__, __LINE__)

#define BOTAN_CHECKED_MUL(x, y) checked_mul(x, y)

}  // namespace Botan

#endif