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Reading / writing strings of length 255
Hey Georg,
I am trying to read / write strings, that are 255 characters long from the PLC. I tried it like this, but this limits me to 32 bytes:
let handle = ads::Handle::new(device, "MyValue").unwrap();
let mut somevalue: [u8; 32];
somevalue = handle.read_value().unwrap();
What is the correct way to achieve my goal?
Thanks
Mebus
You have two options:
- since you read a byte array anyway, use
Handle::read
instead ofread_value
- create a type with the correct length with
ads::make_string_type!
and use that
This seems to work:
const LEN: usize = 255;
let mut msg: [u8; LEN] = [0; LEN];
handle.read(&mut msg).unwrap();
println!("MY_SYMBOL value is {:?}", msg);
let thestring = str::from_utf8(&msg).unwrap();
println!("{}", thestring);
:-)
Mebus
Yes, that's option 1. Option 2, to compare:
ads::make_string_type!(String255, 255); // on toplevel
let plc_str: String255 = handle.read_value().unwrap();
let rust_str: String = plc_str.try_into().unwrap();
You might have to use std::convert::TryInto
if you're using Rust edition 2015/18.