-mime.txt
-by Luke Ehresman
-June 22, 2000 - Last updated: June 22, 2000
+SquirrelMail MIME Support Introduction
+======================================
-Who should read this?
----------------------
- The intended audience for this document are people who want to understand how
- the MIME code works. This is a technical documentation of how mime.php
- works and how it parses a MIME encoded message.
+The intended audience for this document are people who want to understand how
+the MIME code works. This is a technical documentation of how mime.php
+works and how it parses a MIME encoded message.
Object Structure
----------------
- There are two objects that are used: "message" and "msg_header". here is a
- brief overview of what each object contains.
+There are two objects that are used: "message" and "msg_header". here is a
+brief overview of what each object contains.
- msg_header
- Contains variables for all the necessary parts of the header of a
- message. This includes (but is not limited to) the following: to, from,
- subject, type (type0), subtype (type1), filename ...
+msg_header
+ Contains variables for all the necessary parts of the header of a
+ message. This includes (but is not limited to) the following: to, from,
+ subject, type (type0), subtype (type1), filename ...
- message
- This contains the structure for the message. It contains two parts:
- $header and $entities[]. $header is of type msg_header, and $entities[]
- is an array of type $message. The $entities[] array is optional. If
- it does not exist, then we are at a leaf node, and have an actual
- attachment (entity) that can be displayed. Here is a tree view of how
- this object functions.
-
- header
- entities
- |
- +--- header
- |
- +--- header
- | entities
- | |
- | +--- header
- | |
- | +--- header
- |
- +--- header
+message
+ This contains the structure for the message. It contains two parts:
+ $header and $entities[]. $header is of type msg_header, and $entities[]
+ is an array of type $message. The $entities[] array is optional. If
+ it does not exist, then we are at a leaf node, and have an actual
+ attachment (entity) that can be displayed. Here is a tree view of how
+ this object functions.
+
+ header
+ entities
+ |
+ +--- header
+ |
+ +--- header
+ | entities
+ | |
+ | +--- header
+ | |
+ | +--- header
+ |
+ +--- header
Getting the Structure
---------------------
- Previously (version 0.4 and below), SquirrelMail handled all the parsing of
- the email message. It would read the entire message in, search for
- boundaries, and created an array similar to the $message object discribed
- above. This was very inefficient.
+Previously (version 0.4 and below), SquirrelMail handled all the parsing of
+the email message. It would read the entire message in, search for
+boundaries, and created an array similar to the $message object discribed
+above. This was very inefficient.
- Currently, all the parsing of the body of the message takes place on the
- IMAP server itself. According to RFC 2060 section 7.4.2, we can use the
- BODYSTRUCTURE function which will return the structure of the body (imagine
- that). It goes into detail of how the bodystructure should be formatted,
- and we have based our new MIME support on this specification.
+Currently, all the parsing of the body of the message takes place on the
+IMAP server itself. According to RFC 2060 section 7.4.2, we can use the
+BODYSTRUCTURE function which will return the structure of the body (imagine
+that). It goes into detail of how the bodystructure should be formatted,
+and we have based our new MIME support on this specification.
- A simple text/plain message would have a BODYSTRUCTURE similar to the
- following:
+A simple text/plain message would have a BODYSTRUCTURE similar to the
+following:
- ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 23)
+ ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 23)
- A more complicated multipart message with an attachment would look like:
+A more complicated multipart message with an attachment would look like:
- (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 23)("TEXT"
- "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
- "<960723163407.20117h@cac.washington.edu>" "Compiler diff" "BASE64"
- 4554 73) "MIXED"))
+ (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 23)("TEXT"
+ "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
+ "<960723163407.20117h@cac.washington.edu>" "Compiler diff" "BASE64"
+ 4554 73) "MIXED"))
- Our MIME functionality implements different functions that recursively
- run through this text and parses out the structure of the message. If you
- want to learn more about how the structure of a message is returned with
- the BODYSTRUCTURE function, please see RFC 2060 section 7.4.2.
+Our MIME functionality implements different functions that recursively
+run through this text and parses out the structure of the message. If you
+want to learn more about how the structure of a message is returned with
+the BODYSTRUCTURE function, please see RFC 2060 section 7.4.2.
- NOTE: SquirrelMail passes the MIME Torture Test written by Mark
- Crispin (author of the IMAP protocol). This message is crazy! It
- has about 30 parts nested inside each other. A very good test,
- and SquirrelMail passed it. It can be found here:
+NOTE: SquirrelMail passes the MIME Torture Test written by Mark
+ Crispin (author of the IMAP protocol). This message is crazy! It
+ has about 30 parts nested inside each other. A very good test,
+ and SquirrelMail passed it. It can be found here:
- ftp://ftp.lysator.liu.se/mirror/unix/imapd/mime/torture-test.mbox
+ ftp://ftp.lysator.liu.se/mirror/unix/imapd/mime/torture-test.mbox
Getting the Body
----------------
- Once all of the structure of the message has been read into the $message
- object, we then need to display the body of one entity. There are a number
- of ways we decide which entity to display at a certain time, and I won't go
- into that here.
+Once all of the structure of the message has been read into the $message
+object, we then need to display the body of one entity. There are a number
+of ways we decide which entity to display at a certain time, and I won't go
+into that here.
- Each entity has its own ID. Entity IDs look something like "1.2.1", or
- "4.1", or just "2". You can find a detailed description of how entities
- should be identified by reading RFC 2060 section 6.4.5. To fetch the body
- of a particular entity, we use the function "BODY[<section>]". For
- instance, if we were wanting to return entity 1.2.1, we would send the
- IMAP server the command: "a001 FETCH <msg_id> BODY[1.2.1]".
+Each entity has its own ID. Entity IDs look something like "1.2.1", or
+"4.1", or just "2". You can find a detailed description of how entities
+should be identified by reading RFC 2060 section 6.4.5. To fetch the body
+of a particular entity, we use the function "BODY[<section>]". For
+instance, if we were wanting to return entity 1.2.1, we would send the
+IMAP server the command: "a001 FETCH <msg_id> BODY[1.2.1]".
- This returns a string of the entire body. Based upon what is in the header,
- we may need to decode it or do other things to it.
+This returns a string of the entire body. Based upon what is in the header,
+we may need to decode it or do other things to it.
Closing Notes
-------------
- That is basically how it works. There is a variable in mime.php called
- $debug_mime that is defined at the top of that file. If you set it to true,
- it will output all kinds of valuable information while it tries to decode
- the MIME message.
+That is basically how it works. There is a variable in mime.php called
+$debug_mime that is defined at the top of that file. If you set it to true,
+it will output all kinds of valuable information while it tries to decode
+the MIME message.
- The code in mime.php is pretty well documented, so you might want to poke
- around there as well to find out more details of how this works.
-
- If you have questions about this, please direct them to our mailing list:
- squirrelmail-list@sourceforge.net
+The code in mime.php is pretty well documented, so you might want to poke
+around there as well to find out more details of how this works.
+
+If you have questions about this, please direct them to our mailing list:
+squirrelmail-list@sourceforge.net