(C) 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.

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#include <C_CkMime.h>

void ChilkatSample(void)
    {
    HCkMime mime;
    HCkMime part1;
    BOOL success;
    HCkMime part2;
    int n;
    HCkMime part;

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

    mime = CkMime_Create();

    // Create a multipart/mixed MIME message with two sub-parts.
    // We'll use the Base64 encoding for the 2nd sub-part.
    part1 = CkMime_Create();
    success = CkMime_SetBodyFromPlainText(part1,"This is part 1");

    part2 = CkMime_Create();
    success = CkMime_SetBodyFromPlainText(part2,"This is part 2");
    CkMime_putEncoding(part2,"base64");

    success = CkMime_NewMultipartMixed(mime);
    CkMime_putUseMmDescription(mime,FALSE);
    success = CkMime_AppendPart(mime,part1);
    success = CkMime_AppendPart(mime,part2);

    // Show the MIME message:
    printf("%s\n",CkMime_getMime(mime));

    // 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 = CkMime_getNumParts(mime);
    printf("Num Parts = %d\n",n);
    printf("Body = %s\n",CkMime_getBodyDecoded(mime));

    // The GetEntireBody retrieves the entire content after
    // the header.  (Perhaps GetEntireBody should've been named
    // GetEntireContent to make it less confusing...)
    printf("---- EntireBody:\n");
    printf("%s\n",CkMime_getEntireBody(mime));
    printf("********\n");

    // 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.
    part = CkMime_GetPart(mime,1);
    printf("Decoded Body:\n");
    printf("%s\n",CkMime_getBodyDecoded(part));
    printf("Encoded Body:\n");
    printf("%s\n",CkMime_getBodyEncoded(part));

    CkMime_Dispose(part);


    CkMime_Dispose(mime);
    CkMime_Dispose(part1);
    CkMime_Dispose(part2);

    }