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69 lines
1.9 KiB
C++
69 lines
1.9 KiB
C++
#ifndef _C4_SZCONV_HPP_
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#define _C4_SZCONV_HPP_
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/** @file szconv.hpp utilities to deal safely with narrowing conversions */
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#include "c4/config.hpp"
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#include "c4/error.hpp"
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#include <limits>
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namespace c4 {
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C4_SUPPRESS_WARNING_GCC_CLANG_WITH_PUSH("-Wold-style-cast")
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/** @todo this would be so much easier with calls to numeric_limits::max()... */
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template<class SizeOut, class SizeIn>
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struct is_narrower_size : std::conditional
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<
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(std::is_signed<SizeOut>::value == std::is_signed<SizeIn>::value)
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?
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(sizeof(SizeOut) < sizeof(SizeIn))
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:
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(
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(sizeof(SizeOut) < sizeof(SizeIn))
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||
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(
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(sizeof(SizeOut) == sizeof(SizeIn))
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&&
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(std::is_signed<SizeOut>::value && std::is_unsigned<SizeIn>::value)
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)
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),
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std::true_type,
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std::false_type
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>::type
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{
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static_assert(std::is_integral<SizeIn >::value, "must be integral type");
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static_assert(std::is_integral<SizeOut>::value, "must be integral type");
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};
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/** when SizeOut is wider than SizeIn, assignment can occur without reservations */
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template<class SizeOut, class SizeIn>
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C4_ALWAYS_INLINE
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typename std::enable_if< ! is_narrower_size<SizeOut, SizeIn>::value, SizeOut>::type
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szconv(SizeIn sz) noexcept
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{
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return static_cast<SizeOut>(sz);
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}
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/** when SizeOut is narrower than SizeIn, narrowing will occur, so we check
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* for overflow. Note that this check is done only if C4_XASSERT is enabled.
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* @see C4_XASSERT */
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template<class SizeOut, class SizeIn>
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C4_ALWAYS_INLINE
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typename std::enable_if<is_narrower_size<SizeOut, SizeIn>::value, SizeOut>::type
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szconv(SizeIn sz) C4_NOEXCEPT_X
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{
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C4_XASSERT(sz >= 0);
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C4_XASSERT_MSG((SizeIn)sz <= (SizeIn)std::numeric_limits<SizeOut>::max(), "size conversion overflow: in=%zu", (size_t)sz);
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SizeOut szo = static_cast<SizeOut>(sz);
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return szo;
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}
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C4_SUPPRESS_WARNING_GCC_CLANG_POP
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} // namespace c4
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#endif /* _C4_SZCONV_HPP_ */
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