truncate already parsed bytes instead of unparsed bytes.

[AviRaboah]

I found in the code the change of the truncate method in order to improve performance.
but the change cause an issue in case the rest field is greater than 0.

if rest greater than 0 the truncate method will truncate from self.bytes the first remaining bytes number which included some of the parsed bytes.

that scenario cause the next iteration to parse the same packet instead of the remaining packet it should be read from the beginning.

https://github.com/datafuselabs/opensrv/blob/b44c9d1360da297b305abf33aecfa94888e1554c/mysql/src/packet_reader.rs#L140-L152

one optional fix - maybe instead of truncate the bytes vector you can set the start value to be the correct one to start from for next iteration.

but I want to consult with you guys before I change some low level code like that.

thanks.

[AviRaboah]

any updates?

[sunng87]

We had same issue with packet_reader and this should have been fixed in #39

[AviRaboah]

thanks a lot guys.