endian.h

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#ifndef DMLC_ENDIAN_H_
#define DMLC_ENDIAN_H_
 
#include "./base.h"
 
#ifdef DMLC_CMAKE_LITTLE_ENDIAN
  // If compiled with CMake, use CMake's endian detection logic
  #define DMLC_LITTLE_ENDIAN DMLC_CMAKE_LITTLE_ENDIAN
#else
  #if defined(__APPLE__) || defined(_WIN32)
    #define DMLC_LITTLE_ENDIAN 1
  #elif defined(__GLIBC__) || defined(__GNU_LIBRARY__) \
        || defined(__ANDROID__) || defined(__RISCV__)
    #include <endian.h>
    #define DMLC_LITTLE_ENDIAN (__BYTE_ORDER == __LITTLE_ENDIAN)
  #elif defined(__FreeBSD__) || defined(__OpenBSD__)
    #include <sys/endian.h>
    #define DMLC_LITTLE_ENDIAN (_BYTE_ORDER == _LITTLE_ENDIAN)
  #elif defined(__EMSCRIPTEN__) || defined(__hexagon__)
    #define DMLC_LITTLE_ENDIAN 1
  #elif defined(__sun) || defined(sun)
    #include <sys/isa_defs.h>
    #if defined(_LITTLE_ENDIAN)
      #define DMLC_LITTLE_ENDIAN 1
    #else
      #define DMLC_LITTLE_ENDIAN 0
    #endif
  #else
    #error "Unable to determine endianness of your machine; use CMake to compile"
  #endif
#endif
 
#define DMLC_IO_NO_ENDIAN_SWAP (DMLC_LITTLE_ENDIAN == DMLC_IO_USE_LITTLE_ENDIAN)
 
namespace dmlc {
 
inline void ByteSwap(void* data, size_t elem_bytes, size_t num_elems) {
  for (size_t i = 0; i < num_elems; ++i) {
    uint8_t* bptr = reinterpret_cast<uint8_t*>(data) + elem_bytes * i;
    for (size_t j = 0; j < elem_bytes / 2; ++j) {
      uint8_t v = bptr[elem_bytes - 1 - j];
      bptr[elem_bytes - 1 - j] = bptr[j];
      bptr[j] = v;
    }
  }
}
 
}  // namespace dmlc
#endif  // DMLC_ENDIAN_H_