cUpload: A closer look
Lets take a closer look at this cUpload class first. After a few public variables
for the class, you'll notice the
Public Sub OnStartPage(PassedScriptingContext As ScriptingContext)
line, which doesn't appear to be called by anything. In fact, this procedure
is called by the Active Server Pages engine when the object is initialized in
our ASP script, and passes us a ScriptingContext object. This object contains
all the objects available to your ASP script; Response, Request,
Server etc. In this instance, we are only interested in the Request
object (what has been sent to the ASP script), so we save it to our MyRequest
object using
Set MyRequest = PassedScriptingContext.Request
We then proceed to call the BuildForm procedure, which parses the data sent
to us via the form on upload.asp. This is where the bulk of our code lies.
As the form was posted using the encoding method, we cannot access the posted
objects using the standard Request.Form object. Instead, we read the entire
HTTP header into a variable. First, we get the length of the header:
varByteCount = MyRequest.TotalBytes
and then we read the header into varHTTPHeader using
varHTTPHeader = StrConv(MyRequest.BinaryRead(varByteCount), vbUnicode)
You will notice that we have also converted the header into Unicode. This is
to make it easier for us to parse the posted data; instead of receiving binary
data, we receive at least some readable characters. Below is a sample of what
might now be present in varHTTPHeader.
-----------------------------7d130d3810678
Content-Disposition: form-data; name="thefile"; filename="C:\devpad_description.txt"
Content-Type: text/plain
Developers Pad - the ultimate programming editor. Fully configurable, with syntax
highlighting, auto-indent, code library, powerful project view, quick-tag, find
& replace, find in files, add-ins and more!
-----------------------------7d130d3810678
Content-Disposition: form-data; name="filedescription"
-----------------------------7d130d3810678
Content-Disposition: form-data; name="folder"
0
-----------------------------7d130d3810678--
As you can see, each field is seperated by -----------------------------7d130d3810678.
Next, we are told the we are type of content, and the field name. In the case
of the file, we are also given the filename and content type. Finally, we are
given the value of that field. The BuildForm procedure now parses this data,
and creates the correct number of form objects. As the delimiter may vary, we
check it by taking the first 76 bytes:
varDelimeter = LeftB(varHTTPHeader, 76)
Next, we find where the first field is by searching for ; name="
lngFormFieldNameStart = InStrB(lngFormFieldNameStart + 1, varHTTPHeader,
"; name=" & Chr(34))
Note we use the InStrB function so that we are returned the byte position rather
than character position. Now, we start a Do...Loop which continues until lngFormFieldNameStart
= 0. For each field, we first initialize the FormField object:
Set clsFormField = New cFormItem
Next, we find out where the name property is going to end. We
do this by searching for a " character (Chr(34)), from the
fields starting position, plus the length of ; name=". Now
that we have the start and end positions, we can retreive the name of the field:
lngFormFieldNameEnd = InStrB(lngFormFieldNameStart + Len(StrConv(";
name=" _
& Chr(34), vbUnicode)), varHTTPHeader, Chr(34))
+ Len(StrConv(Chr(34), vbUnicode))
strFormFieldName = MidB(varHTTPHeader, lngFormFieldNameStart + _
Len(StrConv("; name=" & Chr(34),
vbUnicode)), (lngFormFieldNameEnd - _
Len(StrConv(Chr(34), vbUnicode))) - (lngFormFieldNameStart
+ _
Len(StrConv("; name=" & Chr(34),
vbUnicode))))
Now we check to see if there is a ; after the name field... If
there is, we know it is a file, otherwise, it isn't.
If it is a file, we proceed to get the filename: and ContentType properties.
After the ContentType property, we search for two vbCrLf (new lines), after
which is the file data. We now save all this extra file data (filename, file
size, content type etc) to the clsFormField object.
'add form field data
clsFormField.Add "FileName", strFileName
clsFormField.Add "FileLen", lngFileLength
clsFormField.Add "ContentType", strContentType
'save the files data to the collection...
clsFormField.FileData = MidB(varHTTPHeader, lngFileDataStart, lngFileLength)
If the form field isn't a file, we perform a similar operation, except we skip
searching for the filename, and just get the form fields value instead. Finally,
we save the fields name, and add the clsFormField object to our varFields collection:
clsFormField.Add "Name", strFormFieldName
'Assign formfieldnames and formfieldvalues to collection
varFields.Add clsFormField, strFormFieldName
We then reset the clsFormField, and search for another field to process....
and this continues until we have parsed all the fields. We then return the varFields
collection for use by our ASP script.