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1 // endian/detail/intrinsic.hpp -------------------------------------------------------//
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2
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3 // Copyright (C) 2012 David Stone
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4 // Copyright Beman Dawes 2013
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5
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6 // Distributed under the Boost Software License, Version 1.0.
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7 // http://www.boost.org/LICENSE_1_0.txt
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8
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9 #ifndef BOOST_ENDIAN_INTRINSIC_HPP
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10 #define BOOST_ENDIAN_INTRINSIC_HPP
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11
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12 // Allow user to force BOOST_ENDIAN_NO_INTRINSICS in case they aren't available for a
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13 // particular platform/compiler combination. Please report such platform/compiler
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14 // combinations to the Boost mailing list.
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15 #ifndef BOOST_ENDIAN_NO_INTRINSICS
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16
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17 #ifndef __has_builtin // Optional of course
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18 #define __has_builtin(x) 0 // Compatibility with non-clang compilers
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19 #endif
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20
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21 // GCC and Clang recent versions provide intrinsic byte swaps via builtins
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22 #if (defined(__clang__) && __has_builtin(__builtin_bswap32) && __has_builtin(__builtin_bswap64)) \
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23 || (defined(__GNUC__ ) && \
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24 (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
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25 # define BOOST_ENDIAN_INTRINSIC_MSG "__builtin_bswap16, etc."
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26 // prior to 4.8, gcc did not provide __builtin_bswap16 on some platforms so we emulate it
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27 // see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624
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28 // Clang has a similar problem, but their feature test macros make it easier to detect
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29 # if (defined(__clang__) && __has_builtin(__builtin_bswap16)) \
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30 || (defined(__GNUC__) &&(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)))
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31 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) __builtin_bswap16(x)
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32 # else
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33 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) __builtin_bswap32((x) << 16)
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34 # endif
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35 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x) __builtin_bswap32(x)
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36 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x) __builtin_bswap64(x)
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37
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38 // Linux systems provide the byteswap.h header, with
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39 #elif defined(__linux__)
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40 // don't check for obsolete forms defined(linux) and defined(__linux) on the theory that
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41 // compilers that predefine only these are so old that byteswap.h probably isn't present.
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42 # define BOOST_ENDIAN_INTRINSIC_MSG "byteswap.h bswap_16, etc."
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43 # include <byteswap.h>
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44 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) bswap_16(x)
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45 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x) bswap_32(x)
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46 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x) bswap_64(x)
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47
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48 #elif defined(_MSC_VER)
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49 // Microsoft documents these as being compatible since Windows 95 and specificly
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50 // lists runtime library support since Visual Studio 2003 (aka 7.1).
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51 # define BOOST_ENDIAN_INTRINSIC_MSG "cstdlib _byteswap_ushort, etc."
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52 # include <cstdlib>
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53 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) _byteswap_ushort(x)
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54 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x) _byteswap_ulong(x)
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55 # define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x) _byteswap_uint64(x)
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56 #else
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57 # define BOOST_ENDIAN_NO_INTRINSICS
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58 # define BOOST_ENDIAN_INTRINSIC_MSG "no byte swap intrinsics"
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59 #endif
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60
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61 #elif !defined(BOOST_ENDIAN_INTRINSIC_MSG)
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62 # define BOOST_ENDIAN_INTRINSIC_MSG "no byte swap intrinsics"
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63 #endif // BOOST_ENDIAN_NO_INTRINSICS
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64 #endif // BOOST_ENDIAN_INTRINSIC_HPP
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