s0-meter/src/cfg_reader.rs

#[cfg(test)]
#[path = "./cfg_reader_test.rs"]
mod cfg_reader_test;

use serde_derive::Deserialize;
use std::fs::File;
use std::{error::Error, io::Read};

extern crate toml;

#[derive(Deserialize)]
pub struct S0Channel {
    pub id: u8,
    pub gpio: u8,
}

#[derive(Deserialize)]
pub struct Config {
    channel: Vec<S0Channel>,
}

impl Config {
    pub fn channels(&self) -> &Vec<S0Channel> {
        &self.channel
    }
}

// use std::any::type_name;
// fn type_of<T>(_: T) -> &'static str {
//     type_name::<T>()
// }

const MAX_CONFIG_FILE_SIZE: u64 = 1_000_000u64;

pub fn parse_file(config_file_name: &str) -> Result<Config, Box<dyn Error>> {
    let mut cfg_file = File::open(String::from(config_file_name))?;
    let cfg_file_meta = &cfg_file.metadata()?;
    let cfg_file_len = &cfg_file_meta.len();
    if cfg_file_len > &MAX_CONFIG_FILE_SIZE {
        return Err(From::from(format!(
            "Size of config file is {} exceeds the limit of {}",
            &cfg_file_len, MAX_CONFIG_FILE_SIZE
        )));
    }
    let mut cfg_file_content = String::new();
    cfg_file.read_to_string(&mut cfg_file_content).unwrap();
    parse_string(&cfg_file_content)
}

fn parse_string(cfg_str: &String) -> Result<Config, Box<dyn Error>> {
    match toml::from_str(cfg_str) {
        Ok(cfg) => Ok(cfg),
        Err(err) => Err(From::from(err)),
    }
}