[UE4]File & Directory Operation Notes

FString Str;
FFileHelper::LoadFileToString(Str, FilePath);

TArray<FString> StrList;
FFileHelper::LoadFileToStringArray(StrList, FilePath);

TArray<uint8> Stream;
FFileHelper::LoadFileToArray(Stream, *FilePath);

TArray<uint8> Stream;
Stream.Add(1);
FFileHelper::SaveStringToFile(FBase64::Encode(Stream), *FilePath, FFileHelper::EEncodingOptions::ForceUTF8);

TArray<uint8> Stream;
Stream.Add(1);
FFileHelper::SaveArrayToFile(Stream, *FilePath);

FString SavePath = FPaths::ProjectSavedDir() + TEXT("/TestDir/");
IPlatformFile& PlatformFile = FPlatformFileManager::Get().GetPlatformFile();
if (!PlatformFile.DirectoryExists(*SavePath))
{
    PlatformFile.CreateDirectory(*SavePath);
}

FString AbsDir = UKismetSystemLibrary::GetProjectDirectory();

FString RelativePath = FPaths::ProjectDir();
FString AbsDir = UKismetSystemLibrary::ConvertToAbsolutePath(RelativePath);

/* Convert all / and \ to TEXT("/") */
UFUNCTION(BlueprintPure, Category="Utilities|Paths", meta=(BlueprintThreadSafe))
static FString UKismetSystemLibrary::NormalizeFilename(const FString& InFilename);

FDateTime Time = FDateTime::Now();
int Year = Time.GetYear();
int Month = Time.GetMonth();
int Day = Time.GetDay();
int Hour = Time.GetHour();
int Minute = Time.GetMinute();
int Second = Time.GetSecond();
FString SavePath = FPaths::ProjectSavedDir() + TEXT("/TestDir/");
FString Filename = FString::Printf(TEXT("TestFile_%d-%.2d-%.2d-%.2d%.2d%.2d.txt"), Year, Month, Day, Hour, Minute, Second);
FString FilePath = SavePath + Filename;
FFileHelper::SaveStringToFile(Content, *FilePath, FFileHelper::EEncodingOptions::ForceUTF8);

TMap<int32, FString> FileMap;
TArray<int32> TimeArray;
TArray<FString> FoundFiles;
FString Directory = GetDefault<UEngine>()->GameScreenshotSaveDirectory.Path;
FString fileExt = TEXT("png");
IFileManager::Get().FindFiles(FoundFiles, *Directory, *fileExt);

for(FString FileName : FoundFiles)
{
    FDateTime Data = IFileManager::Get().GetTimeStamp(*FileName);
    int32 UnixTimestamp = Data.GetSecond();
    FileMap.Add(UnixTimestamp, FileName);
    TimeArray.Add(UnixTimestamp);
}
TimeArray.Sort();
if(TimeArray.Num() > 0)
{
    FString* LatestFile = FileMap.Find(TimeArray[0]);
    UE_LOG(LogTemp, Log, TEXT("latestfile: %s"), *LatestFile);
}

//FullDir: D:/MyGame/Content/foo/bar/baz/
void AMyFunctionLibrary::CreateSubDirectory(const FString& FullDir)
{
    FString FullDirNew = FullDir.Replace(TEXT("/"), TEXT("\\"));
    int32 Index = FullDirNew.Find(TEXT("\\"));
    FString RootDir = FullDirNew.Left(Index);
    FString RelativeDir = FullDirNew.Replace(*RootDir, TEXT(""));

    //remove the first slash in beginning
    if (RelativeDir.Left(1) == TEXT("\\"))
    {
        RelativeDir = RelativeDir.Right(RelativeDir.Len() - 1);
    }

    FString LastRelativeDir = RootDir;
    while (RelativeDir.Len() > 0)
    {
        FString SubDir;
        int32 SlashIndex = RelativeDir.Find("\\");
        if (SlashIndex >= 0)
        {
            SubDir = RelativeDir.Mid(0, SlashIndex);
            RelativeDir = RelativeDir.Mid(SlashIndex + 1, RelativeDir.Len() - SlashIndex);
        }
        else
        {
            SubDir = RelativeDir;
            RelativeDir = TEXT("");
        }

        FString NewDir = FPaths::Combine(LastRelativeDir, SubDir);
        IPlatformFile& PlatformFile = FPlatformFileManager::Get().GetPlatformFile();
        if (!PlatformFile.DirectoryExists(*NewDir))
        {
            PlatformFile.CreateDirectory(*NewDir);
        }
        LastRelativeDir = NewDir;
    }
}

FPlatformMisc::GamePersistentDownloadDir()

FString SaveDirectory;

#if PLATFORM_WINDOWS
    SaveDirectory = FWindowsPlatformMisc::GamePersistentDownloadDir();
#endif

#if PLATFORM_ANDROID
    SaveDirectory = FAndroidMisc::GamePersistentDownloadDir();
#endif

#if PLATFORM_IOS
    SaveDirectory = FIOSPlatformMisc::GamePersistentDownloadDir();
#endif

FString ExePath = TEXT("C:/Program Files/WinRAR/Rar.exe");
FString Args = TEXT("a -df -k -r -s D:/mysqldump/%filename%-%data_time_str%.rar  %filename%-%date_str%*.sql");
FProcHandle Handle = FPlatformProcess::CreateProc(*ExePath, *Args, false, true, false, nullptr, 0, nullptr, nullptr);

//wait process while running native command
FPlatformProcess::WaitForProc(Handle);

//check if process was finished
FPlatformProcess::IsProcRunning(Handle);

//e.g. [Project]/Content/
FString ContentDir = FPaths::ProjectContentDir();

//[Project]/Config/WindowsNoEditor/
FPaths::ProjectConfigDir()
FPaths::SourceConfigDir()

//[Project]/Saved/Config/WindowsNoEditor/
FPaths::GeneratedConfigDir()

[MyGameSettings]
+AssetList=/Script/Engine.Blueprint'/Game/Test/MyActor01.MyActor01'
+AssetList=/Script/Engine.Blueprint'/Game/Test/MyActor02.MyActor02'
+AssetList=/Script/Engine.Blueprint'/Game/Test/MyActor03.MyActor03'

TArray<FString> AssetList;
FString Path = FPaths::GeneratedConfigDir() + TEXT("DefaultMyGameSettings.ini");
GConfig->GetArray(TEXT("/Script/MyGame.MyGameSettings"), TEXT("+AssetList"), AssetList, Path);

FApp::GetProjectName()

//e.g. [Project]/Saved/Screenshots/WindowsNoEditor/
GetDefault<UEngine>()->GameScreenshotSaveDirectory.Path

IPlatformFile& Handle = FPlatformFileManager::Get().GetPlatformFile();
int64 Size = Handle.FileSize(TEXT("C:/test.png"));

FMD5Hash Hash = FMD5Hash::HashFile(Filename);
const FString HasAsString = LexToString(Hash);

FString MD5Str = FMD5::HashAnsiString(TEXT("Wang Aiguo"));

static FString HashBytes(const uint8* input, uint64 inputLen)