(PowerBuilder) MIME Body vs. Sub-Parts

Explains the difference between sub-parts and body.

MIME documents (i.e. messages) can have a nested structure. The simplest MIME message contains a header followed by content (possibly encoded). The header is delimited from the content by two consecutive CRLF's.

A MIME message may be multipart. If so, then the Content-Type header field indicates "multipart" and the content the follows the header is itself a MIME message, which may also be multipart, etc. You can see how MIME messages effectively have a tree structure. The non-leaf nodes have Content-Types that are "multipart/" and the leaf nodes have non-multipart Content-Types.

The Chilkat MIME component/library uses two terms that need to be understood in order to effectively use the API. These are "body" and "sub-part". A multipart node has 1 or more sub-parts, but its body is empty. A leaf node (i.e. non-multipart node) has no sub-parts, but the body is (usually) non-empty.

This example creates a multipart MIME message and shows the results of getting the sub-parts and body of each node.

Note: This example requires Chilkat v11.0.0 or greater.

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integer li_rc
integer li_Success
oleobject loo_Mime
oleobject loo_Part1
oleobject loo_Part2
integer n
oleobject loo_Part

li_Success = 0

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

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

// Create a multipart/mixed MIME message with two sub-parts.
// We'll use the Base64 encoding for the 2nd sub-part.
loo_Part1 = create oleobject
li_rc = loo_Part1.ConnectToNewObject("Chilkat.Mime")

li_Success = loo_Part1.SetBodyFromPlainText("This is part 1")

loo_Part2 = create oleobject
li_rc = loo_Part2.ConnectToNewObject("Chilkat.Mime")

li_Success = loo_Part2.SetBodyFromPlainText("This is part 2")
loo_Part2.Encoding = "base64"

li_Success = loo_Mime.NewMultipartMixed()
loo_Mime.UseMmDescription = 0
li_Success = loo_Mime.AppendPart(loo_Part1)
li_Success = loo_Mime.AppendPart(loo_Part2)

// Show the MIME message:
Write-Debug loo_Mime.GetMime()

// Here's the MIME:
// Content-Type: multipart/mixed;
// 	boundary="------------040605030407000302060008"
// 
// --------------040605030407000302060008
// Content-Type: text/plain;
// 	 charset="us-ascii"
// Content-Transfer-Encoding: 7bit
// 
// This is part 1
// --------------040605030407000302060008
// Content-Type: text/plain;
// 	 charset="us-ascii"
// Content-Transfer-Encoding: base64
// 
// VGhpcyBpcyBwYXJ0IDI=
// 
// --------------040605030407000302060008--

// If we examine the root node of the MIME message, 
// we see that it has 2 sub-parts and the body is empty (as expected)
n = loo_Mime.NumParts
Write-Debug "Num Parts = " + string(n)
Write-Debug "Body = " + loo_Mime.GetBodyDecoded()

// The GetEntireBody retrieves the entire content after
// the header.  (Perhaps GetEntireBody should've been named
// GetEntireContent to make it less confusing...)
Write-Debug "---- EntireBody:"
Write-Debug loo_Mime.GetEntireBody()
Write-Debug "********"

// Now examine the 2nd sub-part.  It has a body encoded
// using base64.  Get the contents of the body in both
// decoded and encoded forms:

// index 0 is the 1st part, index 1 is the 2nd part.
loo_Part = create oleobject
li_rc = loo_Part.ConnectToNewObject("Chilkat.Mime")

loo_Mime.PartAt(1,loo_Part)

Write-Debug "Decoded Body:"
Write-Debug loo_Part.GetBodyDecoded()
Write-Debug "Encoded Body:"
Write-Debug loo_Part.GetBodyEncoded()


destroy loo_Mime
destroy loo_Part1
destroy loo_Part2
destroy loo_Part