when the text in the description field is larger than 500 kB, DAVx5 stops the synchronization process

[SergeyPetrov98]

When the text in the description field is larger than 500 kB, DAVx5 stops the synchronization process.

Older versions of DAVx5 threw an exception (see logcat_davx.txt), but the new version (4.4.3.2) silently stops the synchronization on the current event, and consequently all the events past the current doesn't get to the device. The synchronization stop was noticed, when DAVx5 processed letters containing a mix of simple and base64 text in the description field.

I have made a patch (davx.patch), which does the following:

1. it substitutes all the base64 text with the message: "--- the message was cut by DAVx5 ---";
2. if the message is anyway larger than 500 kB, it substitutes the text past 500 kB with the message: "--- the message was cut by DAVx5 ---".

May I propose this to be pushed into the master?

[ArnyminerZ]

May I propose this to be pushed into the master?

Of course, feel free to open a PR if desired, however, some things to consider:

1. Why 500kB? Is it related to a limitation imposed by Android? This should be investigated, hard-coding things like this may and will have unexpected consequences.
   According to the exception given, the limit is set by Android's parcel size top (https://developer.android.com/guide/components/activities/parcelables-and-bundles)

   The Binder transaction buffer has a limited fixed size, currently 1MB

   But then, why 500kB?

2. Regex, even though I agree is really useful, causes a lot of issues if not well-written (I'm not saying it's not correct what you propose). So if there are other solutions, it's preferred to use them.
   I guess that if the message is base64, substitutes it entirely with the text, or otherwise substitutes only the 500kB+ characters.

3. Following the point 2, it's important sticking to specification, so even though some people may use the description with binary data, it's not intended to be used that way (See).
   Specification says that it should be used for "textual" data, which binary data is not. Maybe that's why the problem is caused, because I can't think of any reason why anyone should have more than 500kB in plain text in a calendar event/note.
   So if that's the case, DAVx⁵ should be ready to handle those kinds of cases, in the sense that it should not break, but I don't think it's should be handled in any way, simply ignore the events/calendars that do not follow the specification. If we were to support every individual use case the app would get unmanageable pretty quickly.

In any case, feel free to discuss any of the points above.

[rfc2822]

For reference: see also #1126