Rust

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.

Rust

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

let mime = chilkat::Mime::new();

// Create a multipart/mixed MIME message with two sub-parts.
// We'll use the Base64 encoding for the 2nd sub-part.
let part1 = chilkat::Mime::new();
let _ = part1.set_body_from_plain_text("This is part 1").is_ok();

let part2 = chilkat::Mime::new();
let _ = part2.set_body_from_plain_text("This is part 2").is_ok();
part2.set_encoding("base64");

let _ = mime.new_multipart_mixed().is_ok();
mime.set_use_mm_description(false);
let _ = mime.append_part(&part1).is_ok();
let _ = mime.append_part(&part2).is_ok();

// Show the MIME message:
println!("{}", mime.get_mime().unwrap_or_default());

// 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)
let n = mime.num_parts();
println!("Num Parts = {}", n);
println!("Body = {}", mime.get_body_decoded().unwrap_or_default());

// The GetEntireBody retrieves the entire content after
// the header.  (Perhaps GetEntireBody should've been named
// GetEntireContent to make it less confusing...)
println!("---- EntireBody:");
println!("{}", mime.get_entire_body().unwrap_or_default());
println!("********");

// 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.
let part = chilkat::Mime::new();
let _ = mime.part_at(1, &part);

println!("Decoded Body:");
println!("{}", part.get_body_decoded().unwrap_or_default());
println!("Encoded Body:");
println!("{}", part.get_body_encoded().unwrap_or_default());