Hi,

I am not sure if there is any uploader product that would work for you. You can perform such checking either on the server side or client side. If you would like to perform such checking on the client side, you would need to implement the logic with signed code such Java or ActiveX because for security reasons, no browser will allow you to "peek" into client side files.

If you choose to check on the server, obviously the easiest way is to get the whole file first. This of course missed the whole point. In theory, an uploader can implement a “filter” interface that would allow you to examine the data and rejects the request if necessary. However in order to filter the data, you still have to have the data transferred to the server first. So this will only work if your special bytes are located in the very beginning of the file. If those bytes are in the middle of the file, or is maintained with a more complicated structure so that you will actually need to seek the file in order to decide whether it’s valid or not, then such filtering interface would have no use to you.

As such your best solution might be performing the checking on the client side with signed code. If that passes, you can then start upload by calling our client side JavaScript interface.

Thanks!