Floating-Point Endianness

1#include <iomanip>
2#include <iostream>
3#include "SDL.h"
4
5void PrintBytes(
6  const char* Label, float Value
7) {
8  auto* Bytes = reinterpret_cast<Uint8*>(
9    &Value);
10  std::cout << Label << ": ";
11
12  for (int i = 0; i < sizeof(float); ++i) {
13    std::cout << std::hex << std::setw(2)
14      << std::setfill('0')
15      << static_cast<int>(Bytes[i]) << " ";
16  }
17  std::cout << "(" << std::dec << Value
18    << ")\n";
19}
20
21int main() {
22  float Original{3.14f};
23  PrintBytes("Original ", Original);
24
25  // Swap endianness
26  float Swapped{SDL_SwapFloat(Original)}; 
27  PrintBytes("Swapped  ", Swapped);
28
29  // Swap back
30  float Restored{SDL_SwapFloat(Swapped)}; 
31  PrintBytes("Restored ", Restored);
32}

1#include <SDL.h>
2#include <iostream>
3
4// Write a float to an SDL_RWops stream in
5// little-endian order
6bool WriteFloat(SDL_RWops* rw, float value) {
7  Uint32 data = *reinterpret_cast<Uint32*>(&
8    value);
9  return SDL_WriteLE32(rw, data) > 0;
10}
11
12// Read a float from an SDL_RWops stream in
13// little-endian order
14bool ReadFloat(SDL_RWops* rw, float& value) {
15  Uint32 data = SDL_ReadLE32(rw);
16  if (data == 0 && SDL_RWtell(rw) == 0) {
17    // Check for read error
18    return false;
19  }
20  value = *reinterpret_cast<float*>(&data);
21  return true;
22}
23
24int main(int argc, char** argv) {
25  SDL_RWops* rw = SDL_RWFromFile(
26    "example.bin", "wb+");
27  if (!rw) {
28    std::cerr << "Failed to open file: "
29      << SDL_GetError() << std::endl;
30    return 1;
31  }
32
33  float valueToWrite = 3.14159f;
34  if (!WriteFloat(rw, valueToWrite)) {
35    std::cerr << "Failed to write float."
36      << std::endl;
37  }
38
39  SDL_RWseek(rw, 0, RW_SEEK_SET);
40  // Reset file pointer
41
42  float valueRead;
43  if (!ReadFloat(rw, valueRead)) {
44    std::cerr << "Failed to read float."
45      << std::endl;
46  } else {
47    std::cout << "Read value: " << valueRead
48      << std::endl;
49  }
50
51  SDL_RWclose(rw);
52  return 0;
53}