When working with structs containing multiple members of different sizes, we need to handle each member's endianness individually. Here's a structured approach to handling this common scenario:
Basic Approach
First, let's look at a simple struct and how to properly serialize it:
#include <iostream>
#include "SDL.h"
struct PlayerData {
Uint16 Level;
Uint32 Experience;
float Health;
};
void WritePlayerData(SDL_RWops* Handle,
const PlayerData& Data) {
SDL_WriteLE16(Handle, Data.Level);
SDL_WriteLE32(Handle, Data.Experience);
SDL_WriteLE32(Handle, Data.Health);
}
PlayerData ReadPlayerData(SDL_RWops* Handle) {
PlayerData Data;
Data.Level = SDL_ReadLE16(Handle);
Data.Experience = SDL_ReadLE32(Handle);
Data.Health = SDL_ReadLE32(Handle);
return Data;
}
int main() {
// Create test data
PlayerData TestData{
.Level = 42,
.Experience = 1000000,
.Health = 98.5f
};
// Write to file
SDL_RWops* WriteHandle{
SDL_RWFromFile("player.dat", "wb")};
if (WriteHandle) {
WritePlayerData(WriteHandle, TestData);
SDL_RWclose(WriteHandle);
}
// Read and verify
SDL_RWops* ReadHandle{
SDL_RWFromFile("player.dat", "rb")};
if (ReadHandle) {
PlayerData LoadedData{
ReadPlayerData(ReadHandle)};
SDL_RWclose(ReadHandle);
std::cout << "Level: " << LoadedData.Level
<< "\nExp: " << LoadedData.Experience
<< "\nHealth: " << LoadedData.Health
<< '\n';
}
}Level: 42
Exp: 1000000
Health: 98.5Advanced Techniques
For more complex structs, you might want to create a serialization helper class:
#include <iostream>
#include "SDL.h"
class BinaryWriter {
SDL_RWops* Handle;
public:
explicit
BinaryWriter(SDL_RWops* Handle)
: Handle{Handle} {}
void Write(Uint16 Value) {
SDL_WriteLE16(Handle, Value);
}
void Write(Uint32 Value) {
SDL_WriteLE32(Handle, Value);
}
void Write(float Value) {
SDL_WriteLE32(Handle, Value);
}
};
struct PlayerData {
Uint16 Level;
Uint32 Experience;
float Health;
void Serialize(BinaryWriter& Writer) {
Writer.Write(Level);
Writer.Write(Experience);
Writer.Write(Health);
}
};
int main() {
PlayerData Data{
.Level = 42,
.Experience = 1000000,
.Health = 98.5f
};
SDL_RWops* Handle{
SDL_RWFromFile("player.dat", "wb")};
if (Handle) {
BinaryWriter Writer{Handle};
Data.Serialize(Writer);
SDL_RWclose(Handle);
}
}Key points to remember:
- Always handle each member individually with the appropriate endianness function
- Keep track of the order of serialization to match when deserializing
- Consider padding and alignment in your structs
- Use helper classes to make the code more maintainable
- Document your serialization format for future maintenance
Answers to questions are automatically generated and may not have been reviewed.
This Question is from the Lesson:
Byte Order and Endianness
Learn how to handle byte order in using SDL's endianness functions
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