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MIME Body vs. Sub-Parts

See more MIME Examples

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.

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Local $bSuccess = False

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

$oMime = ObjCreate("Chilkat.Mime")

; Create a multipart/mixed MIME message with two sub-parts.
; We'll use the Base64 encoding for the 2nd sub-part.
$oPart1 = ObjCreate("Chilkat.Mime")
$bSuccess = $oPart1.SetBodyFromPlainText("This is part 1")

$oPart2 = ObjCreate("Chilkat.Mime")
$bSuccess = $oPart2.SetBodyFromPlainText("This is part 2")
$oPart2.Encoding = "base64"

$bSuccess = $oMime.NewMultipartMixed()
$oMime.UseMmDescription = False
$bSuccess = $oMime.AppendPart($oPart1)
$bSuccess = $oMime.AppendPart($oPart2)

; Show the MIME message:
ConsoleWrite($oMime.GetMime() & @CRLF)

; 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)
Local $iN = $oMime.NumParts
ConsoleWrite("Num Parts = " & $iN & @CRLF)
ConsoleWrite("Body = " & $oMime.GetBodyDecoded() & @CRLF)

; The GetEntireBody retrieves the entire content after
; the header.  (Perhaps GetEntireBody should've been named
; GetEntireContent to make it less confusing...)
ConsoleWrite("---- EntireBody:" & @CRLF)
ConsoleWrite($oMime.GetEntireBody() & @CRLF)
ConsoleWrite("********" & @CRLF)

; 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.
$oPart = ObjCreate("Chilkat.Mime")
$oMime.PartAt(1,$oPart)

ConsoleWrite("Decoded Body:" & @CRLF)
ConsoleWrite($oPart.GetBodyDecoded() & @CRLF)
ConsoleWrite("Encoded Body:" & @CRLF)
ConsoleWrite($oPart.GetBodyEncoded() & @CRLF)