PowerBuilder

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?

PowerBuilder

integer li_rc
integer li_Success
oleobject loo_Bd
oleobject loo_Sb
integer li_CaseSensitive

li_Success = 0

// 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.

loo_Bd = create oleobject
li_rc = loo_Bd.ConnectToNewObject("Chilkat.BinData")
if li_rc < 0 then
    destroy loo_Bd
    MessageBox("Error","Connecting to COM object failed")
    return
end if

li_Success = loo_Bd.LoadFile("qa_data/p7m/a.p7m")
if li_Success = 0 then
    Write-Debug "Failed to load the file."
    destroy loo_Bd
    return
end if

loo_Sb = create oleobject
li_rc = loo_Sb.ConnectToNewObject("Chilkat.StringBuilder")

loo_Sb.Append(loo_Bd.GetEncodedChunk(0,2,"hex"))

li_CaseSensitive = 1
if loo_Sb.ContentsEqual("3080",li_CaseSensitive) OR loo_Sb.ContentsEqual("3081",li_CaseSensitive) OR loo_Sb.ContentsEqual("3082",li_CaseSensitive) OR loo_Sb.ContentsEqual("3083",li_CaseSensitive) then
    Write-Debug "This is a .p7m or .p7s file."
else
    Write-Debug "This is not a .p7m or .p7s file."
end if



destroy loo_Bd
destroy loo_Sb