File uploading with COM and ASP

Introduction

This article is about file uploading through a COM component (IUploader interface). It uses the IRequest interface to retrieve the information needed.

There are a bunch of free and comercial solutions, but I wanted to make mine with an easy approach.

Since you cannot use the request object when you are uploading a file, I created the method GetFormValue to retrieve any variables from a form. You pass the variable name (case sensitive) and it returns the value found.

To accomplish the file upload and to retrieve any form variable is needed to get the whole buffer from the request object and interpret it. This a basic sample of this buffer:

-----------------------------7d034c2160334
Content-Disposition: form-data; name="UploadFile"; filename="C:\SampleFile.txt"
Content-Type: text/plain

Test file...

-----------------------------7d034c2160334
Content-Disposition: form-data; name="submit1"

Submit
-----------------------------7d034c2160334
Content-Disposition: form-data; name="userName"

me
-----------------------------7d034c2160334-- 

How to use it

These are the methods for the IUploader interface:

The following VBScript code uploads a file using my component:

const UploadOK               = 0
const FilesizeInvalid        = 1
const ExtensionNotAllowed    = 2
const DestinationPathInvalid = 3
const UnknownError           = 4
const UnableToCreateFile     = 5
const FileDoesntExist        = 6

 
Set objUploader = Server.CreateObject("InetUtil.Uploader") 
objUploader.StartUpload(Request)    'passing the IRequest interface for the component
 	
strUserName = objUploader.GetFormValue("userName")
objUploader.SetDestinationPath "c:\temp"
objUploader.SetAllowedExtensions "*"  ' all extensions
objUploader.SetForbiddenExtensions "exe", "com"
 	

nUploadResult = objUploader.UploadFile("uploadFile")

I could have used an ASP component so I would have the IRequest interface. But I had some problems with this in the past, that's why I don't use this approach. :o)

WARNING: There's two known memory leaks that I don't know from where they come. I think it's something about the bad use of COleSafeArray. If you find it please submit.

In order to use the demo you must have an Win 2K or NT Machine (IIS) because the COM server is an out-of-process. To use it in a Win95/98 machine (PWS) you should create a new in-proc component and then copy the implementation.