将二进制文件转换为Base64字符串

I need to convert uploaded binary files to base64 string format on the fly. I'm using ASP, Vbscript. Using Midori's component for base64 conversion. For small size files (<20K) the performance is okay. But when it exceeds 75 or 100K, its totally lost. Is there any efficient way to convert big binary files (2MB) to base64 string format?I need to convert uploaded binary files to base