DataFlex

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

See more Misc Examples

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?

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoBd
    Handle hoSb
    Boolean iCaseSensitive
    String sTemp1
    Boolean bTemp1
    Boolean bTemp2
    Boolean bTemp3
    Boolean bTemp4

    Move False To iSuccess

    // 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.

    Get Create (RefClass(cComChilkatBinData)) To hoBd
    If (Not(IsComObjectCreated(hoBd))) Begin
        Send CreateComObject of hoBd
    End

    Get ComLoadFile Of hoBd "qa_data/p7m/a.p7m" To iSuccess
    If (iSuccess = False) Begin
        Showln "Failed to load the file."
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatStringBuilder)) To hoSb
    If (Not(IsComObjectCreated(hoSb))) Begin
        Send CreateComObject of hoSb
    End
    Get ComGetEncodedChunk Of hoBd 0 2 "hex" To sTemp1
    Get ComAppend Of hoSb sTemp1 To iSuccess

    Move True To iCaseSensitive
    Get ComContentsEqual Of hoSb "3080" iCaseSensitive To bTemp1
    Get ComContentsEqual Of hoSb "3081" iCaseSensitive To bTemp2
    Get ComContentsEqual Of hoSb "3082" iCaseSensitive To bTemp3
    Get ComContentsEqual Of hoSb "3083" iCaseSensitive To bTemp4
    If (bTemp1 Or bTemp2 Or bTemp3 Or bTemp4) Begin
        Showln "This is a .p7m or .p7s file."
    End
    Else Begin
        Showln "This is not a .p7m or .p7s file."
    End



End_Procedure