Method GetRelativePath

Engine/source/EtCore/FileSystem/FileUtil.cpp:429–488

--------------------------------- FileUtil::GetRelativePath Converts inPath to a path relative to rootPath - assumes both arguments paths are relative to the executable directory

// Converts inPath to a path relative to rootPath - assumes both arguments paths are relative to the executable directory
//
std::string FileUtil::GetRelativePath(std::string const& inPath, std::string const& rootPath)
{
	// Make sure both paths have the same format
	std::string absIn = GetAbsolutePath(inPath);
	std::string absRoot = GetAbsolutePath(rootPath);

	// Find the first letter that is different
	size_t idx = 0u;
	for (;idx < std::min(absIn.size(), absRoot.size()); ++idx)
	{
		if (absIn[idx] != absRoot[idx])
		{
			break;
		}
	}

	// trace backwards to the last path delimiter - delimiters should be all the same character (s_PathDelimiter) now due to GetAbsolutePath()
	while (idx > 0u)
	{
		--idx;
		if (absIn[idx] == s_PathDelimiter)
		{
			break;
		}
	}

	// figure out how many times we need to go to the parent directory
	size_t searchStart = idx; 
	size_t numParentDirs = 0u;
	for (;;)
	{
		searchStart = absRoot.find(s_PathDelimiter, ++searchStart); // idx is on a path delimiter right now, so we start from the next character
		if (searchStart != std::string::npos) // if we found another delimiter we have more parent directories
		{
			++numParentDirs;
		}
		else
		{
			break; // if we can't find any more we have reached the end of the string
		}
	}

	// build our output path

	// first escape the root directory into the first common directory
	std::string retVal;
	while (numParentDirs > 0u)
	{
		retVal += "../";
		--numParentDirs;
	}
	
	// append the rest of our input path
	// if the current common index is a delimiter we skip that
	if (absIn[idx] == s_PathDelimiter)
	{
		++idx;
	}