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From "Stefano Bagnara (JIRA)" <mime4j-...@james.apache.org>
Subject [jira] Commented: (MIME4J-58) Lenient dealing with headless messages or malformed header/body separation
Date Thu, 31 Dec 2009 14:23:29 GMT

    [ https://issues.apache.org/jira/browse/MIME4J-58?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12795602#action_12795602
] 

Stefano Bagnara commented on MIME4J-58:
---------------------------------------

I don't think that copying the buffer instead of switching it will have any impact in the
API. It is mainly an implementation issue hidden in the linereader class. THe only API change
is about the unread(ByteArrayBuffer) method contract: currently it will read the bytes directly
from the provided bytearray so the caller can't reuse the same byte[] array, instead if we
copy then the user can reuse the buffer (currently the only client code creates a field buffer
for each field, so this wouldn't change the client code, anyway).

IMHO as it is "hidden" in the class and that the cycleclean solution is both performant and
memory efficient I wouldn't spare time to change it further, but if you think it worth it
just join the branch.

Please review also the other changes, as the goal of the branch is to be merged back to trunk
as soon as other committers will have the time to review.

> Lenient dealing with headless messages or malformed header/body separation
> --------------------------------------------------------------------------
>
>                 Key: MIME4J-58
>                 URL: https://issues.apache.org/jira/browse/MIME4J-58
>             Project: JAMES Mime4j
>          Issue Type: Task
>    Affects Versions: 0.3
>            Reporter: Stefano Bagnara
>            Assignee: Stefano Bagnara
>             Fix For: 0.8
>
>         Attachments: headerbody-nocrlfcrlf.msg, headerbody-noheader.msg
>
>
> Define how to deal with non canonical messages like this one:
> -----------------------
> This is a simple message not having headers.
> The whole text should be recognized as body.
> -----------------------
> or this one:
> -----------------------
> Subject: this is a subject
> This is an invalid header
> AnotherHeader: is this an header or the first part of the body?
> Body text
> -----------------------
> In the first case mime4j output twice an  "invalid header" error and a roundtrip write
result in an empty message.
> In the SMTP case this is unfortunate because sometimes it happens messages are sent without
header.
> In the second case mime4j currenlty take Subject and AnotherHeader as headers and "This
is an invalid header" raise a monitor for "invalid header" and "Body text" is considered the
body.
> A compromise we evaluated in past between compliance, leniency and performace was to
"alter" the requirement for CRLFCRLF between headers and body with a different rule: if during
parsing of the headers we find a line (not multiline) and not including an "HeaderName: something"
then we virtually add a CRLF *before* that line and consider that line the first line of the
body. This allow us to only buffer a single line (as opposite to parsing the whole message
in search of a CRLFCRLF and consider the full message a body if no CRLFCRLF is found) and
to be very lenient with input. The "side effect" (maybe not bad) is that a wrong header in
the middle of headers will result in some headers moved to the body.
> With this algorythm the above would be "virtually" parsed as it was:
> -----------------------
> This is a simple message not having headers.
> The whole text should be recognized as body.
> -----------------------
> or this one:
> -----------------------
> Subject: this is a subject
> This is an invalid header
> AnotherHeader: is this an header or the first part of the body?
> Body text
> -----------------------
> If we think about strict and lenient approaches I think that current mime4j result is
ok when using a strict parsing, while the one I propose is a good lenient alternative.
> Opinions? Alternatives?

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