Xbase++

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.

Xbase++

LOCAL nSuccess
LOCAL oMime
LOCAL oPart1
LOCAL oPart2
LOCAL n
LOCAL oPart

nSuccess := 0

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

oMime := CreateObject("Chilkat.Mime")

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

oPart2 := CreateObject("Chilkat.Mime")
nSuccess := oPart2:SetBodyFromPlainText("This is part 2")
oPart2:Encoding := "base64"

nSuccess := oMime:NewMultipartMixed()
oMime:UseMmDescription := 0
nSuccess := oMime:AppendPart(oPart1)
nSuccess := oMime:AppendPart(oPart2)

//  Show the MIME message:
? oMime: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 := oMime:NumParts
? "Num Parts = " + Str(n)
? "Body = " + oMime:GetBodyDecoded()

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

//  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 := CreateObject("Chilkat.Mime")
oMime:PartAt(1, oPart)

? "Decoded Body:"
? oPart:GetBodyDecoded()
? "Encoded Body:"
? oPart:GetBodyEncoded()

oMime:destroy()
oPart1:destroy()
oPart2:destroy()
oPart:destroy()