UnrealEngineUWP/Engine/Source/Programs/UnrealHeaderTool/Private/StringUtils.cpp

// Copyright 1998-2019 Epic Games, Inc. All Rights Reserved.

#include "StringUtils.h"
#include "UnrealHeaderTool.h"
#include "Containers/UnrealString.h"
#include "Hash/CityHash.h"

FString GetClassNameWithPrefixRemoved(const FString InClassName)
{
	const FString ClassPrefix = GetClassPrefix( InClassName );
	if( !ClassPrefix.IsEmpty() )
	{	
		return InClassName.Right(InClassName.Len() - ClassPrefix.Len());
	}
	return FString();
}

FString GetClassNameWithoutPrefix( const FString& InClassNameOrFilename )
{
	// Check for header names (they don't come with a full path so we only search for the first dot)
	const int32 DotIndex = InClassNameOrFilename.Find(TEXT("."), ESearchCase::CaseSensitive);
	if (DotIndex == INDEX_NONE)
	{
		const FString ClassPrefix = GetClassPrefix( InClassNameOrFilename );
		return InClassNameOrFilename.Right(InClassNameOrFilename.Len() - ClassPrefix.Len());
	}
	else
	{
		return InClassNameOrFilename.Mid(0, DotIndex);
	}
}

FString GetClassPrefix( const FString InClassName )
{
	bool bIsLabledDeprecated;
	return GetClassPrefix(InClassName, /*out*/ bIsLabledDeprecated);
}

FString GetClassPrefix( const FString InClassName, bool& bIsLabeledDeprecated )
{
	FString ClassPrefix = InClassName.Left(1);

	bIsLabeledDeprecated = false;

	if (!ClassPrefix.IsEmpty())
	{
		const TCHAR ClassPrefixChar = ClassPrefix[0];
		switch (ClassPrefixChar)
		{
		case TEXT('I'):
		case TEXT('A'):
		case TEXT('U'):
			// If it is a class prefix, check for deprecated class prefix also
			if (InClassName.Mid(1, 11).Compare(TEXT("DEPRECATED_"), ESearchCase::CaseSensitive) == 0)
			{
				bIsLabeledDeprecated = true;
				ClassPrefix = InClassName.Left(12);
			}
			break;

		case TEXT('F'):
		case TEXT('T'):
			// Struct prefixes are also fine.
			break;

		default:
			// If it's not a class or struct prefix, it's invalid
			ClassPrefix.Empty();
			break;
		}
	}
	return ClassPrefix;
}

// Returns zero only for '\r' and '\0' 
FORCEINLINE uint64 FindCrOrNulHelper(TCHAR C)
{
	uint64 LoPassMask = ~((uint64(1) << '\0') | (uint64(1) << '\r'));
	uint64 LoBit = uint64(1) << (C & 63);
	uint64 LoPass = LoBit & LoPassMask;
	uint64 HiPass = C & ~63;

	return LoPass | HiPass;
}

// Finds next CR or null term with a single branch 
// to help treat CR-LF and LF line endings identically
FORCEINLINE const TCHAR* FindCrOrNul(const TCHAR* Str)
{
	while (FindCrOrNulHelper(*Str))
	{
		++Str;
	}

	return Str;
}

FORCEINLINE uint64 GenerateTextHash64(const TCHAR* Str)
{
	uint64 Hash = 0;

	while (true)
	{
		const TCHAR* End = FindCrOrNul(Str);
		
		if (int32 Len = End - Str)
		{
			Hash = CityHash64WithSeed(reinterpret_cast<const char*>(Str), Len * sizeof(TCHAR), Hash);
		}

		if (*End == '\0')
		{
			return Hash;
		}

		Str = End + 1;
	}
}

uint32 GenerateTextHash(const TCHAR* Data)
{
	uint64 Hash = GenerateTextHash64(Data);
	return static_cast<uint32>(Hash) + static_cast<uint32>(Hash >> 32);
}