如果 Unreal Engine 5 c++ 中的整数值超过 127，Protoc 无法解析输入

Question

环境：

• Unreal Engine 5
• Windows 10
• 协议缓冲区 v3.18.0

我正在尝试使用 protoc 解码 Unreal Engine 5 (c++) 中的序列化数据。如果消息包含小于 127 的 int var 值，则一切正常。但如果值超过 127，我会发现错误：Failed to parse input.

player.proto:

syntax = "proto3";
package com.game;

message Player {
    string username = 1;
    int64 experience = 2;
}

成功案例

C++序列化并保存到文件：

com::game::Player MyPlayer;
MyPlayer.set_username("test user name");
MyPlayer.set_experience(127); // <-- PAY ATTENTION

// serialization
std::string MyPlayerString;
if(!MyPlayer.SerializeToString(&MyPlayerString))
{
    UE_LOG(LogGameInstance, Error, TEXT("Can't serialize MyPlayer to String"));
    return;
}
const FString MyPlayerFString(MyPlayerString.c_str());

// save to file
const FString File = *FPaths::Combine(FPaths::GameSourceDir(), FApp::GetProjectName(), TEXT("temp.dat"));
FFileHelper::SaveStringToFile(
    MyPlayerFString,
    *File,
    FFileHelper::EEncodingOptions::AutoDetect,
    &IFileManager::Get()
);

协议 --decode_raw < temp.dat

1: "test user name"
2: 127

失败案例

C++序列化并保存到文件：

...
MyPlayer.set_experience(128); // <-- PAY ATTENTION
...

协议 --decode_raw < temp.dat

Failed to parse input.

我想我尝试转换 std::string -> FString 时出现了问题。有什么想法吗？

Answer 1

我找到了解决方法。

我会把它留在这里，也许它会对某人有所帮助。 我更改了实现以避免字符串转换。

之前:

...

// serialization
std::string MyPlayerString;
if(!MyPlayer.SerializeToString(&MyPlayerString))
{
    UE_LOG(LogGameInstance, Error, TEXT("Can't serialize MyPlayer to String"));
    return;
}
const FString MyPlayerFString(MyPlayerString.c_str());

// save to file
const FString File = *FPaths::Combine(FPaths::GameSourceDir(), FApp::GetProjectName(), TEXT("temp.dat"));
FFileHelper::SaveStringToFile(
    MyPlayerFString,
    *File,
    FFileHelper::EEncodingOptions::AutoDetect,
    &IFileManager::Get()
);

之后：

// serialization
const auto MyPlayerSize = MyPlayer.ByteSizeLong();
const auto MyPlayerBytes = new uint8[MyPlayerSize]();
if(!MyPlayer.SerializeToArray(MyPlayerBytes, MyPlayerSize))
{
    UE_LOG(LogGameInstance, Error, TEXT("Can't serialize MyPlayer to Array"));
    return;
}
TArray64<uint8>* MyPlayerArray = new TArray<uint8, FDefaultAllocator64>(MyPlayerBytes, MyPlayerSize);

// save to file
const FString File = *FPaths::Combine(FPaths::GameSourceDir(), FApp::GetProjectName(), TEXT("temp.dat"));
FFileHelper::SaveArrayToFile(
    *MyPlayerArray,
    *File,
    &IFileManager::Get()
);