LazyPrintf.h

Go to the documentation of this file.

// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Misc/AssertionMacros.h"
#include "Containers/UnrealString.h"
 
// to avoid limits with the Printf parameter count, for more readability and type safety
class FLazyPrintf
{
public:
    // constructor
    FLazyPrintf(const TCHAR* InputWithPercentS)
        : CurrentInputPos(InputWithPercentS)
    {
        // to avoid reallocations
        CurrentState.Empty(50 * 1024);
    }
 
    [[nodiscard]] FString GetResultString()
    {
        // internal error more %s than %s in MaterialTemplate.usf
        check(!ProcessUntilPercentS());
 
        // copy all remaining input data
        CurrentState += CurrentInputPos;
 
        return CurrentState;
    }
 
    // %s
    void PushParam(const TCHAR* Data)
    {
        if(ProcessUntilPercentS())
        {
            CurrentState += Data;
        }
        else
        {
            // internal error, more ReplacePercentS() calls than %s in MaterialTemplate.ush
            check(0);
        }
    }
 
private:
 
    // @param Pattern e.g. TEXT("%s")
    bool ProcessUntilPercentS()
    {
        const TCHAR* Found = FCString::Strstr(CurrentInputPos, TEXT("%s"));
 
        if(Found == 0)
        {
            return false;
        }
 
        // copy from input until %s
        while(CurrentInputPos < Found)
        {
            // can cause reallocations we could avoid
            CurrentState += *CurrentInputPos++;
        }
 
        // jump over %s
        CurrentInputPos += 2;
 
        return true;
    }
 
    const TCHAR* CurrentInputPos;
    FString CurrentState;
};