Add support for parsing of incomplete base64 and QP MIME parts

[disaykin]

It useful when MIME part is requested and loaded to memory by small chunks.

[dinhvh]

Could you post some example about how to use it?

I feel like we might want to return some different error code when more data are required, only in the case of parsing partial data.
IMAP has MAILIMAP_ERROR_NEEDS_MORE_DATA.
What do you think?

Thanks!

[disaykin]

My use case is loading big attachment by imap_fetch_range. In pseudocode:

uint32_t received = 0;
uint32_t partLength = bodystructure[partId]->length;
for (;;) {
  struct imap_range_t range = { received, 1024*1024 };
  char *result;
  size_t result_len;
  imap_fetch_part_range(uid, partId, range, &result, &result_len);

  if (result_len == 0) {
    // requested range is empty. part is completely fetched
    break;
  }

  bool isThisRangeLast = (received + result_len >= partLength); // determine that the received data is the last, may be more difficult (in case of invalid metadata on the server).

  char *decoded;
  size_t decoded_len;
  if (isThisRangeLast) {
    uint32_t index = 0;
    mailmime_part_parse(result, result_len, encoding, &index, &decoded, &decoded_len);
    break;
  }
  else {
    uint32_t index = 0;
    mailmime_part_parse_partial(result, result_len, encoding, &index, &decoded, &decoded_len);
    // we may have some non-decoded bytes at the end of chunk.
    // in this case we just request it in the next chunk 
    received += index;
  }
}

[disaykin]

I think that return the MAILIMAP_ERROR_NEEDS_MORE_DATA in this case is not needed. It is not an error, it is normal scenario in handling of data stream.

But I can add this, if need.

[dinhvh]

No need to add the return code. Your example is helpful. I have some comments though.

[dinhvh]

could change partial == FALSE to !partial ?

[dinhvh]

ping?

[disaykin]

I'm a little busy right now. In the near future I will proceed.

[disaykin]

Done.

[dinhvh]

did you mean if (partial) here?
or you did you change a behavior?
or did you fix an issue?

[dinhvh]

I just have a question.
Thanks!

[disaykin]

it was a missed change of behavior. I deleted those lines.

[dinhvh]

Thanks a lot for that contribution!