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How to Tell if a File is .p7m or .p7s

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This example explains how to detect if a file is a .p7m or .p7s. It provides as solution to the following problem:

Sometimes people submit P7S/P7M with wrong extensions. Can I check if file is P7S or P7M with Chilkat?

Also see What is a P7M or P7S File?

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Local $bSuccess = False

; A .p7m or .p7s file is binary and contains PKCS7.
; PKCS7 is ASN.1, and always begins with a SEQUENCE tag (a byte equal to 0x30)
; followed by an encoded length.
; If the file is larger than 128 bytes (and it SHOULD be), the encoded length will begin with either 0x80, 0x81, 0x82, or 0x83.
; It can also begin with 0x84, but only for very large files (where the length is too large for 3 bytes).
; See How ASN.1 Encodes Lengths

; Therefore, if we have a file that might be .p7m or .p7s, we can check by
; examining the 1st 2 bytes of the file.

$oBd = ObjCreate("Chilkat.BinData")

$bSuccess = $oBd.LoadFile("qa_data/p7m/a.p7m")
If ($bSuccess = False) Then
    ConsoleWrite("Failed to load the file." & @CRLF)
    Exit
EndIf

$oSb = ObjCreate("Chilkat.StringBuilder")
$oSb.Append($oBd.GetEncodedChunk(0,2,"hex"))

Local $bCaseSensitive = True
If ($oSb.ContentsEqual("3080",$bCaseSensitive) Or $oSb.ContentsEqual("3081",$bCaseSensitive) Or $oSb.ContentsEqual("3082",$bCaseSensitive) Or $oSb.ContentsEqual("3083",$bCaseSensitive)) Then
    ConsoleWrite("This is a .p7m or .p7s file." & @CRLF)
Else
    ConsoleWrite("This is not a .p7m or .p7s file." & @CRLF)
EndIf