reverse_bytes.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2018, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */
 
#include "core-precomp.h"  // Precompiled headers
 
#include <mrpt/core/reverse_bytes.h>
#include <cstring>
#include <cstdlib>
 
// These #defines from:
// https://github.com/boostorg/endian/blob/master/include/boost/endian/detail/intrinsic.hpp
#ifndef __has_builtin
#define __has_builtin(x) 0  // Compatibility with non-clang compilers
#endif
#if (                                                         \
        defined(__clang__) && __has_builtin(__builtin_bswap32) && \
        __has_builtin(__builtin_bswap64)) ||                      \
        (defined(__GNUC__) &&                                     \
         (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
#define HAVE_BSWAP_INTRINSICS
#endif
 
template <typename T>
void reverseBytesInPlace_2b(T& v_in_out)
{
        uint16_t org;
        ::memcpy(
                &org, &v_in_out,
                sizeof(T));  // Was: = *reinterpret_cast<uint16_t*>(&v_in_out); but
        // caused SIGBUS in some archs
        const uint16_t val_rev = ((org & 0xff00) >> 8) | ((org & 0x00ff) << 8);
        ::memcpy(&v_in_out, &val_rev, sizeof(T));  // This avoid deref. puned
        // pointer warning with:
        // *reinterpret_cast<const
        // T*>(&val_rev);
}
 
template <typename T>
void reverseBytesInPlace_4b(T& v_in_out)
{
        uint32_t org;
        ::memcpy(
                &org, &v_in_out,
                sizeof(T));  // Was: = = *reinterpret_cast<uint32_t*>(&v_in_out); but
        // caused SIGBUS in some archs
        const uint32_t val_rev =
#if defined(_MSC_VER)
                _byteswap_ulong(org);
#elif defined(HAVE_BSWAP_INTRINSICS)
                __builtin_bswap32(org);
#else
                ((org & 0xff000000) >> (3 * 8)) | ((org & 0x00ff0000) >> (1 * 8)) |
                ((org & 0x0000ff00) << (1 * 8)) | ((org & 0x000000ff) << (3 * 8));
#endif
        ::memcpy(&v_in_out, &val_rev, sizeof(T));  // This avoid deref. puned
        // pointer warning with:
        // *reinterpret_cast<const
        // T*>(&val_rev);
}
 
template <typename T>
void reverseBytesInPlace_8b(T& v_in_out)
{
        uint64_t org;
        ::memcpy(
                &org, &v_in_out,
                sizeof(T));  // Was: = *reinterpret_cast<uint64_t*>(&v_in_out); but
// caused SIGBUS in some archs
#if defined(_MSC_VER)
        uint64_t val_rev = _byteswap_uint64(org);
#elif defined(HAVE_BSWAP_INTRINSICS)
        uint64_t val_rev = __builtin_bswap64(org);
#else
        uint64_t val_rev = 0;
        int i, j;
        for (i = 7, j = 7; i >= 4; i--, j -= 2)
                val_rev |= ((org & (UINT64_C(0xff) << (i * 8))) >> (j * 8));
        for (i = 3, j = 1; i >= 0; i--, j += 2)
                val_rev |= ((org & (UINT64_C(0xff) << (i * 8))) << (j * 8));
#endif
        ::memcpy(&v_in_out, &val_rev, sizeof(T));  // This avoid deref. puned
        // pointer warning with:
        // *reinterpret_cast<const
        // T*>(&val_rev);
}
 
void mrpt::reverseBytesInPlace(bool&)
{
        // Nothing to do.
}
 
void mrpt::reverseBytesInPlace(uint8_t& /*v_in_out*/)
{
        // Nothing to do.
}
void mrpt::reverseBytesInPlace(int8_t& /*v_in_out*/)
{
        // Nothing to do.
}
 
void mrpt::reverseBytesInPlace(uint16_t& v_in_out)
{
        reverseBytesInPlace_2b(v_in_out);
}
 
void mrpt::reverseBytesInPlace(int16_t& v_in_out)
{
        reverseBytesInPlace_2b(v_in_out);
}
 
void mrpt::reverseBytesInPlace(uint32_t& v_in_out)
{
        reverseBytesInPlace_4b(v_in_out);
}
 
void mrpt::reverseBytesInPlace(int32_t& v_in_out)
{
        reverseBytesInPlace_4b(v_in_out);
}
 
void mrpt::reverseBytesInPlace(uint64_t& v_in_out)
{
        reverseBytesInPlace_8b(v_in_out);
}
 
void mrpt::reverseBytesInPlace(int64_t& v_in_out)
{
        reverseBytesInPlace_8b(v_in_out);
}
 
void mrpt::reverseBytesInPlace(float& v_in_out)
{
        reverseBytesInPlace_4b(v_in_out);
}
 
void mrpt::reverseBytesInPlace(double& v_in_out)
{
        reverseBytesInPlace_8b(v_in_out);
}
 
#ifdef HAVE_LONG_DOUBLE
void mrpt::reverseBytesInPlace(long double& v_in_out)
{
        uint64_t dat[2];
        ::memcpy(
                &dat[0], &v_in_out, sizeof(long double));  // This avoid deref. puned
        // pointer warning with:
        // *reinterpret_cast<const
        // T*>(&val_rev);
        std::swap(dat[0], dat[1]);
        reverseBytesInPlace(dat[0]);
        reverseBytesInPlace(dat[1]);
        ::memcpy(&v_in_out, &dat[0], sizeof(long double));
}
#endif