bswap.h

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/*
* Byte Swapping Operations
* (C) 1999-2011,2018 Jack Lloyd
* (C) 2007 Yves Jerschow
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_BYTE_SWAP_H_
#define BOTAN_BYTE_SWAP_H_

#include <botan/types.h>

#if defined(BOTAN_BUILD_COMPILER_IS_MSVC)
  #include <stdlib.h>
#endif

namespace Botan {

/**
* Swap a 16 bit integer
*/
inline uint16_t reverse_bytes(uint16_t val)
   {
#if defined(BOTAN_BUILD_COMPILER_IS_GCC) || defined(BOTAN_BUILD_COMPILER_IS_CLANG) || defined(BOTAN_BUILD_COMPILER_IS_XLC)
   return __builtin_bswap16(val);
#else
   return static_cast<uint16_t>((val << 8) | (val >> 8));
#endif
   }

/**
* Swap a 32 bit integer
*/
inline uint32_t reverse_bytes(uint32_t val)
   {
#if defined(BOTAN_BUILD_COMPILER_IS_GCC) || defined(BOTAN_BUILD_COMPILER_IS_CLANG) || defined(BOTAN_BUILD_COMPILER_IS_XLC)
   return __builtin_bswap32(val);

#elif defined(BOTAN_BUILD_COMPILER_IS_MSVC)
   return _byteswap_ulong(val);

#elif defined(BOTAN_USE_GCC_INLINE_ASM) && defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)

   // GCC-style inline assembly for x86 or x86-64
   asm("bswapl %0" : "=r" (val) : "0" (val));
   return val;

#else
   // Generic implementation
   uint16_t hi = static_cast<uint16_t>(val >> 16);
   uint16_t lo = static_cast<uint16_t>(val);

   hi = reverse_bytes(hi);
   lo = reverse_bytes(lo);

   return (static_cast<uint32_t>(lo) << 16) | hi;
#endif
   }

/**
* Swap a 64 bit integer
*/
inline uint64_t reverse_bytes(uint64_t val)
   {
#if defined(BOTAN_BUILD_COMPILER_IS_GCC) || defined(BOTAN_BUILD_COMPILER_IS_CLANG) || defined(BOTAN_BUILD_COMPILER_IS_XLC)
   return __builtin_bswap64(val);

#elif defined(BOTAN_BUILD_COMPILER_IS_MSVC)
   return _byteswap_uint64(val);

#elif defined(BOTAN_USE_GCC_INLINE_ASM) && defined(BOTAN_TARGET_ARCH_IS_X86_64)
   // GCC-style inline assembly for x86-64
   asm("bswapq %0" : "=r" (val) : "0" (val));
   return val;

#else
   /* Generic implementation. Defined in terms of 32-bit bswap so any
    * optimizations in that version can help.
    */

   uint32_t hi = static_cast<uint32_t>(val >> 32);
   uint32_t lo = static_cast<uint32_t>(val);

   hi = reverse_bytes(hi);
   lo = reverse_bytes(lo);

   return (static_cast<uint64_t>(lo) << 32) | hi;
#endif
   }

/**
* Swap 4 Ts in an array
*/
template<typename T>
inline void bswap_4(T x[4])
   {
   x[0] = reverse_bytes(x[0]);
   x[1] = reverse_bytes(x[1]);
   x[2] = reverse_bytes(x[2]);
   x[3] = reverse_bytes(x[3]);
   }

}

#endif