Fastest way of reading a file

I've tried opening files using Open and Get but it takes around 2 minutes to open a 100 mb file. Is there any way using VB to open a file in binary mode that ranges from 100mbs to 200mbs within 5 seconds?

Show the code you are currently using to open the file and read in the data.

Show the code you are currently using to open the file and read in the data.


Public Function FileContents(filename As String)
Dim ff As Integer
Dim txt As String

On Error GoTo Failed
ff = OpenFile(filename, "BINARY")
txt = Space(LOF(ff))
Get ff, , txt
Close ff
FileContents = txt
Failed:
End Function

Public Function OpenFile(filename As String, mode As String) As Long
Dim ff As Long

On Error GoTo Failed
ff = FreeFile
OpenFile = ff
Select Case UCase(mode)
Case "INPUT"
Open filename For Input As ff
Case "OUTPUT"
Open filename For Output As ff
Case "APPEND"
Open filename For Append As ff
Case "RANDOM"
Open filename For Random As ff
Case "BINARY"
Open filename For Binary As ff
Case Else
Open filename For Binary As ff
End Select
Exit Function
Failed:
OpenFile = 0
End Function


It takes over 40 seconds to open a 100mb file using this method.

The reason its taking so long most likely has to do with the amount of memory you're using. Here is the code you posted:


Public Function FileContents(filename As String)
Dim ff As Integer
Dim txt As String

On Error Goto Failed
ff = OpenFile(filename, "BINARY" )
txt = Space(LOF(ff)) ' allocate 200 megs
Get ff, , txt ' read 100 megs from the HD and convert to unicode
Close ff
FileContents = txt ' allocate another 200 megs and copy original 200 megs into a variant
Failed:
End Function


You can see right off you're allocating 400 megs and deallocating 200. Plus converting to unicode. You could do this all in 100 megs by passing a byte array to the function and allocating memory in it, plus there would be no unicode conversion. This might eventually need to happen if you need it in a string for some reason.

A more efficient way to do this would be to read chunks (perhaps ~64K at a time) and process them one at a time.

Could you show me a example code of how to read a file by chunks of 2048 bytes a time?

http://www.visualbasicforum.com/showpost.php?postid=343278&postcount=6

wow thanks a lot :D