ServiceStack.HttpRequestExtensions.ResolvePathInfoFromMappedPath C# (CSharp) Method

        public static string ResolvePathInfoFromMappedPath(string fullPath, string mappedPathRoot)
        {
            if (mappedPathRoot == null) return null;

            var sbPathInfo = StringBuilderCache.Allocate();
            var fullPathParts = fullPath.Split('/');
            var mappedPathRootParts = mappedPathRoot.Split('/');
            var fullPathIndexOffset = mappedPathRootParts.Length - 1;
            var pathRootFound = false;

            for (var fullPathIndex = 0; fullPathIndex < fullPathParts.Length; fullPathIndex++)
            {
                if (pathRootFound)
                {
                    sbPathInfo.Append("/" + fullPathParts[fullPathIndex]);
                }
                else if (fullPathIndex - fullPathIndexOffset >= 0)
                {
                    pathRootFound = true;
                    for (var mappedPathRootIndex = 0; mappedPathRootIndex < mappedPathRootParts.Length; mappedPathRootIndex++)
                    {
                        if (!string.Equals(fullPathParts[fullPathIndex - fullPathIndexOffset + mappedPathRootIndex], mappedPathRootParts[mappedPathRootIndex], StringComparison.OrdinalIgnoreCase))
                        {
                            pathRootFound = false;
                            break;
                        }
                    }
                }
            }
            if (!pathRootFound) return null;

            var path = StringBuilderCache.ReturnAndFree(sbPathInfo);
            return path.Length > 1 ? path.TrimEnd('/') : "/";
        }