Update read_int

[BmdOnline]

The offset is missing in the calculation.
For example, the MySQL error code returned is false.

[ChuckBell]

Please specify what version of MySQL you used to test this change.

[BmdOnline]

Hi,
I used this version :

mysql Ver 15.1 Distrib 10.5.9-MariaDB, for Linux (x86_64) using readline 5.1

But it's not related to MySQL version.
It's a typo in your code,
You forget to apply offset in buffer.

[BmdOnline]

To be more specific, I'm trying to catch MySQL errors.

For example, try this query when the table arduino doesn't exists:
char INSERT_SQL[] = "INSERT INTO test_arduino.hello_arduino (message) VALUES ('Hello, Arduino!')";
You will get this error :
Error: 57 = Table 'test_arduino.hello_arduino' doesn't exist.

According to MySQL reference, it should be:
Error: 1146 = Table 'test_arduino.hello_arduino' doesn't exist.

Buffer, in this case, is :
39:00:00:01:FF:7A:04:23:....

Error code is at and 5th position.
57 is decimal conversion of buffer starting at position 0 : 39:00
1146 is decimal conversion of buffer starting at position 5 : 7A:04

In parse_error_packet from MySQL_Packet.cpp, you're right when writing:

  Bytes                       Name
  -----                       ----
  1                           field_count, always = 0xff
  2                           errno
  1                           (sqlstate marker), always '#'
  5                           sqlstate (5 characters)
  n                           message

And when you're doing :
Serial.print(read_int(5, 2));

Everything seems good, but read_int always return first bytes, not Nth ones (5th in this case).

I haven't checked other usages of read_int.

References
About error codes, from MySQL and MariaDB :
https://dev.mysql.com/doc/mysql-errors/8.0/en/server-error-reference.html
https://mariadb.com/docs/reference/cs10.5/error-codes/
https://mariadb.com/kb/en/mariadb-error-codes/
https://docs.oracle.com/cd/E19078-01/mysql/mysql-refman-5.0/error-handling.html

About decoding error packet, from MySQL and MariaDB :
https://dev.mysql.com/doc/dev/mysql-server/8.0.11/page_protocol_basic_err_packet.html
https://mariadb.com/kb/en/err_packet/

[ChuckBell]

Yes, I am well aware of the error packet and I will review your suggestions to ensure it is compatible with Oracle MySQL. I do (can) not make changes to support anything else, hence my guarded questions. I will reply back later this week. Thanks!