What is the fastest way to tell if one file is equal to another?

Anyone know?
Id assume the first check would be to just see if the filesizes are the same, and if they are.. then what? Should I do a CRC32 checksum? Or just load the data of the files into 2 strings and see if they are the same? What is the fastest way to do so?

If you load in a string, since a string is unicode, you take twice the memory of the file, and since you open 2 files, you take quite a lot of memory....

You should load in a byte array, like this:

Code:

---

Option Explicit

Private Sub Form_Load()
    Dim File1() As Byte
    Dim File2() As Byte
    Dim K As Long
   
    Open "C:\File1.txt" For Binary Access Read As #1
    Open "C:\File2.txt" For Binary Access Read As #2
        ReDim File1(LOF(1) - 1)
        ReDim File2(LOF(2) - 1)
       
        Get #1, , File1
        Get #2, , File2
    Close #1, #2
   
    For K = 0 To UBound(File1)
        If File1(K) <> File2(K) Then Exit For
    Next K
   
    If K = UBound(File1) + 1 Then
        MsgBox "Files contain the same data", vbInformation
    Else
        MsgBox "Files are not the same at position: " & K, vbInformation
    End If
End Sub

---

And if the files are very big, then it would be better to load chunks at a time instead of the whole file (if you don't know how to do that I can write a short example for you)

CVMichael aid, "And if the files are very big, then it would be better to load chunks at a time instead of the whole file (if you don't know how to do that I can write a short example for you)."
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I tried your code using a matched pair of 3.3 Mb Rtf files. I'm not sure what your definition of "very big" is, but the code ran with these two files in about a millisecond or so on my 1.7 GHz machine. I didn't use a timer control to check it, but my eyes don't blink much faster. :thumb: