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Reading a binary file in chunks...

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Join Date: Jul 2009

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bobjonson4 bobjonson4 is offline

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Reading a binary file in chunks...

Jul 7th, 2009

Hi All,

Got a bit of a problem.
I have a COM Component for an ASP project that reads a binary file from a location on the HDD (could be from 60MB-200MB) and, with the response object found in ASP.DLL, sends the file in chunks of 96kb.

The aim was for me to create code that doesn't load the entire file into memory and then send it. But looking at the memory usage in task manager, it seemingly is loading a lot of data in -- memory usage skyrockets to about the size of the file and gradually reduces until the file is sent.

My question to the experts out there -- could you guys help me or give me some pointers to make this code read the file in "as required"? Like not all at once, only read the chunks when needed and send. Hope that makes sense!

 Help with Code Tags 
 Visual Basic 4 / 5 / 6 Syntax (Toggle Plain Text) 
Dim objFSO As New FileSystemObject
Dim filePath As String
 
filePath = "C:\filename here"
 
If (objFSO.FileExists(filePath)) Then
	Set objFSO = Nothing
 
	Dim iFileNum As Integer
	Dim lBytesLeft As Long
	Dim B() As Byte
 
	iFileNum = FreeFile
	ReDim B(BUFF_SIZE - 1)
 
	Open filePath For Binary As iFileNum
 
	response.Buffer = True
	response.AddHeader "Content-Length", LOF(iFileNum)
 
	response.ContentType = "application/octet-stream"
 
	lBytesLeft = LOF(iFileNum)
 
	If (response.IsClientConnected) Then
		Do While (lBytesLeft > 0)
			If (lBytesLeft < BUFF_SIZE) Then
				ReDim B(lBytesLeft - 1)
			End If
 
			Get #iFileNum, , B()
 
			response.BinaryWrite B
			response.Flush
			Sleep 0.55
 
			lBytesLeft = lBytesLeft - BUFF_SIZE
		Loop
	Else
		response.End
	End If
 
	Close iFileNum
end if
Dim objFSO As New FileSystemObject
Dim filePath As String

filePath = "C:\filename here"

If (objFSO.FileExists(filePath)) Then
	Set objFSO = Nothing
	
	Dim iFileNum As Integer
	Dim lBytesLeft As Long
	Dim B() As Byte
	
	iFileNum = FreeFile
	ReDim B(BUFF_SIZE - 1)
	
	Open filePath For Binary As iFileNum
	
	response.Buffer = True
	response.AddHeader "Content-Length", LOF(iFileNum)
	
	response.ContentType = "application/octet-stream"
	
	lBytesLeft = LOF(iFileNum)
	
	If (response.IsClientConnected) Then
		Do While (lBytesLeft > 0)
			If (lBytesLeft < BUFF_SIZE) Then
				ReDim B(lBytesLeft - 1)
			End If
			
			Get #iFileNum, , B()
			
			response.BinaryWrite B
			response.Flush
			Sleep 0.55
			
			lBytesLeft = lBytesLeft - BUFF_SIZE
		Loop
	Else
		response.End
	End If
	
	Close iFileNum
end if