Error Codes

[Seth-Harlaar]

Hello,
I was wondering if someone could provide me with further explanation of the error codes, the ones at the top of picojpeg.h.
Specifically, me and my classmates have run into error code 19 and 20 while using this library. What does this actually mean, and how does it relate to the code we've written?

We have another issue where sometimes the jpeg_decode_int() function will only call the need_more_bytes_callback() 3 times and retrieve 252 bytes each time and that's it, while there are roughly 20kB waiting to be processed.

If someone could provide me with any guidance that would be great, I can answer further questions but would be hesitant to provide large chunks of code for academic misconduct reasons.
Thanks.