System.TermInfo.ParameterizedStrings.FormatPrintF C# (CSharp) Method

            private static unsafe string FormatPrintF(string format, object arg)
            {
                Debug.Assert(arg is string || arg is Int32);

                // Determine how much space is needed to store the formatted string.
                string stringArg = arg as string;
                int neededLength = stringArg != null ?
                    Interop.Sys.SNPrintF(null, 0, format, stringArg) :
                    Interop.Sys.SNPrintF(null, 0, format, (int)arg);
                if (neededLength == 0)
                {
                    return string.Empty;
                }
                if (neededLength < 0)
                {
                    throw new InvalidOperationException(SR.InvalidOperation_PrintF);
                }

                // Allocate the needed space, format into it, and return the data as a string.
                byte[] bytes = new byte[neededLength + 1]; // extra byte for the null terminator
                fixed (byte* ptr = bytes)
                {
                    int length = stringArg != null ?
                        Interop.Sys.SNPrintF(ptr, bytes.Length, format, stringArg) :
                        Interop.Sys.SNPrintF(ptr, bytes.Length, format, (int)arg);
                    if (length != neededLength)
                    {
                        throw new InvalidOperationException(SR.InvalidOperation_PrintF);
                    }
                }
                return Encoding.ASCII.GetString(bytes, 0, neededLength);
            }