AP_Scripting: added readstring for uarts

[tridge]

this is much more efficient than reading a byte at a time

broken out from #25678

[IamPete1]

I suspect there is a way to directly read into a lua string/buffer to remove the need for the extra allocation and copy. But I can't work it out, this method should work fine.

The lua docs say strings should be OK with trailing 0's but it might be a good idea to double check.

[IamPete1]

Looks good, Thanks

[tpwrules]

I suspect there is a way to directly read into a lua string/buffer to remove the need for the extra allocation and copy. But I can't work it out, this method should work fine.

See luaL_Buffer, in particular luaL_buffinitsize (returns a pointer where a string of at most a given length can be copied into) and luaL_pushresultsize (pushes the string with the length actually copied into that space).

[tridge]

See luaL_Buffer, in particular luaL_buffinitsize (returns a pointer where a string of at most a given length can be copied into) and luaL_pushresultsize (pushes the string with the length actually copied into that space).

thanks! I will try that as part of a rework I'm doing for speed in the web server