85 lines
3.5 KiB
C++
85 lines
3.5 KiB
C++
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///////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
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//
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// This code is licensed under the MIT License (MIT).
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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///////////////////////////////////////////////////////////////////////////////
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#ifndef GSL_NARROW_H
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#define GSL_NARROW_H
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#include "assert" // for GSL_SUPPRESS
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#include "util" // for narrow_cast
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#include <exception> // for std::exception
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namespace gsl
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{
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struct narrowing_error : public std::exception
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{
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const char* what() const noexcept override { return "narrowing_error"; }
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};
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// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
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template <class T, class U, typename std::enable_if<std::is_arithmetic<T>::value>::type* = nullptr>
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// clang-format off
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GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
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GSL_SUPPRESS(f.6) // NO-FORMAT: attribute // TODO: MSVC /analyze does not recognise noexcept(false)
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GSL_SUPPRESS(es.46) // NO-FORMAT: attribute // The warning suggests that a floating->unsigned conversion can occur
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// in the static_cast below, and that gsl::narrow should be used instead.
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// Suppress this warning, since gsl::narrow is defined in terms of
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// static_cast
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// clang-format on
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constexpr T narrow(U u) noexcept(false)
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{
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constexpr const bool is_different_signedness =
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(std::is_signed<T>::value != std::is_signed<U>::value);
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GSL_SUPPRESS(es.103) // NO-FORMAT: attribute // don't overflow
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GSL_SUPPRESS(es.104) // NO-FORMAT: attribute // don't underflow
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GSL_SUPPRESS(p.2) // NO-FORMAT: attribute // don't rely on undefined behavior
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const T t = narrow_cast<T>(u); // While this is technically undefined behavior in some cases (i.e., if the source value is of floating-point type
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// and cannot fit into the destination integral type), the resultant behavior is benign on the platforms
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// that we target (i.e., no hardware trap representations are hit).
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#if defined(__clang__) || defined(__GNUC__)
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wfloat-equal"
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#endif
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// Note: NaN will always throw, since NaN != NaN
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if (static_cast<U>(t) != u || (is_different_signedness && ((t < T{}) != (u < U{}))))
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{
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throw narrowing_error{};
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}
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#if defined(__clang__) || defined(__GNUC__)
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#pragma GCC diagnostic pop
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#endif
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return t;
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}
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template <class T, class U, typename std::enable_if<!std::is_arithmetic<T>::value>::type* = nullptr>
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// clang-format off
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GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
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GSL_SUPPRESS(f.6) // NO-FORMAT: attribute // TODO: MSVC /analyze does not recognise noexcept(false)
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// clang-format on
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constexpr T narrow(U u) noexcept(false)
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{
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const T t = narrow_cast<T>(u);
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if (static_cast<U>(t) != u)
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{
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throw narrowing_error{};
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}
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return t;
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}
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} // namespace gsl
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#endif // GSL_NARROW_H
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