Danny Robson
0ea3d5b9ac
specifics of signed byteswap are unclear so we should remove it, but it's not known exactly which projects rely on this functionality.
108 lines
3.6 KiB
C++
108 lines
3.6 KiB
C++
/*
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* This file is part of libgim.
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*
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* libgim is free software: you can redistribute it and/or modify it under the
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* terms of the GNU General Public License as published by the Free Software
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* Foundation, either version 3 of the License, or (at your option) any later
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* version.
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*
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* libgim is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License
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* along with libgim. If not, see <http://www.gnu.org/licenses/>.
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*
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* Copyright 2010-2014 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef __UTIL_ENDIAN_HPP
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#define __UTIL_ENDIAN_HPP
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#include "types/bits.hpp"
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#include <cstdint>
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#include <type_traits>
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//-----------------------------------------------------------------------------
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// Uses the TIFF header values. Just because. Don't rely on this.
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enum class endian : uint16_t {
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BIG = 0x4D4D,
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LITTLE = 0x4949,
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};
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//-----------------------------------------------------------------------------
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template <typename T>
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constexpr T
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bswap (T);
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//template <> constexpr int8_t bswap ( int8_t v) { return v; }
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//template <> constexpr int16_t bswap (int16_t v) { return __builtin_bswap16 (v); }
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//template <> constexpr int32_t bswap (int32_t v) { return __builtin_bswap32 (v); }
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//template <> constexpr int64_t bswap (int64_t v) { return __builtin_bswap64 (v); }
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template <> constexpr uint8_t bswap ( uint8_t v) { return v; }
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template <> constexpr uint16_t bswap (uint16_t v) { return __builtin_bswap16 (v); }
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template <> constexpr uint32_t bswap (uint32_t v) { return __builtin_bswap32 (v); }
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template <> constexpr uint64_t bswap (uint64_t v) { return __builtin_bswap64 (v); }
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//-----------------------------------------------------------------------------
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template <typename T>
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constexpr T
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identity (T &&v) {
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return v;
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}
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//-----------------------------------------------------------------------------
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#if defined(WORDS_BIGENDIAN)
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template <typename T> constexpr T hton (T v) { return v; }
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template <typename T> constexpr T ntoh (T v) { return v; }
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template <typename T> constexpr T htob (T v) { return v; }
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template <typename T> constexpr T htol (T v) { return bswap (v); }
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template <typename T> constexpr T btoh (T v) { return v; }
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template <typename T> constexpr T ltoh (T v) { return bswap (v); }
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#else
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template <typename T> constexpr T hton (T v) { return bswap (v); }
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template <typename T> constexpr T ntoh (T v) { return bswap (v); }
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template <typename T> constexpr T htob (T v) { return bswap (v); }
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template <typename T> constexpr T htol (T v) { return v; }
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template <typename T> constexpr T btoh (T v) { return bswap (v); }
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template <typename T> constexpr T ltoh (T v) { return v; }
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#endif
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//-----------------------------------------------------------------------------
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struct from_endian {
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from_endian (endian _endian):
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src (_endian)
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{ ; }
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template <typename T>
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T operator() (const T v) const {
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static_assert (std::is_integral<T>::value || std::is_enum<T>::value,
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"endian conversion is only defined for integrals currently");
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auto u = static_cast<
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typename std::conditional<
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std::is_signed<T>::value,
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typename sized_type<T>::sint,
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typename sized_type<T>::uint
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>::type
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> (v);
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return static_cast<T> (
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(src == endian::LITTLE) ? ltoh (u) : btoh (u)
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);
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}
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endian src;
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};
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#endif
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