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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2023- OpenVPN Inc.
//
// SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
#pragma once
#include <cstdint>
#include <limits>
#include <type_traits>
#include <functional>
namespace openvpn::numeric_util {
// Evaluates true if both template args are integral.
template <typename OutT, typename InT>
constexpr bool is_int_conversion()
{
return std::is_integral_v<InT> && std::is_integral_v<OutT>;
}
// Returns true if the in param is an unsigned integral type and out param is a signed integral type.
template <typename OutT, typename InT>
constexpr bool is_int_u2s()
{
return is_int_conversion<OutT, InT>() && std::is_unsigned_v<InT> && std::is_signed_v<OutT>;
}
// Returns true if the in param is a signed integral type and out param is an unsigned integral type.
template <typename OutT, typename InT>
constexpr bool is_int_s2u()
{
return is_int_conversion<OutT, InT>() && std::is_signed_v<InT> && std::is_unsigned_v<OutT>;
}
// Returns true if both args are integral and the range of OutT can contain the range of InT
template <typename OutT, typename InT>
constexpr bool is_int_rangesafe()
{
constexpr auto out_digits = std::numeric_limits<OutT>::digits;
constexpr auto in_digits = std::numeric_limits<InT>::digits;
return is_int_conversion<OutT, InT>() && !is_int_s2u<OutT, InT>() && out_digits >= in_digits;
}
/* ============================================================================================================= */
// is_safe_conversion
/* ============================================================================================================= */
/**
* @brief Returns true if the given value can be contained by the out type
*
* @tparam OutT Output type
* @tparam InT Input type
* @param inVal Input value
* @return true | false
*/
template <typename OutT, typename InT>
bool is_safe_conversion(InT inVal)
{
if constexpr (!numeric_util::is_int_rangesafe<OutT, InT>())
{
if constexpr (numeric_util::is_int_u2s<OutT, InT>())
{
auto unsignedInVal = static_cast<uintmax_t>(inVal);
auto outMax = static_cast<uintmax_t>(std::numeric_limits<OutT>::max());
if (outMax < unsignedInVal)
return false;
}
else if constexpr (numeric_util::is_int_s2u<OutT, InT>())
{
auto lowerVal = static_cast<uintmax_t>(std::max(inVal, InT(0)));
auto upperLimit = static_cast<uintmax_t>(std::numeric_limits<OutT>::max());
if (inVal < 0 || lowerVal > upperLimit)
return false;
}
else
{
auto outMin = static_cast<InT>(std::numeric_limits<OutT>::min());
auto outMax = static_cast<InT>(std::numeric_limits<OutT>::max());
if (inVal < outMin || inVal > outMax)
return false;
}
}
return true;
}
} // namespace openvpn::numeric_util
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