libcruft-util/endian.hpp

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