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//! General utility functions used internally throughout the crate, such as
//! writing to sysfs files.

use errors::*;
use std::fs::File;
use std::io::{Write, Read};

/// Writes data to a sysfs device file.
pub fn write_file(data: &str, attr: &str, pin_num: &u8) -> Result<()> {
  let path = format!("/sys/class/gpio/gpio{}/{}", pin_num, attr);

  // Open the file (write-only) and write data to it
  File::create(&path)
    .chain_err(|| format!("Failed to open file {} for writing", &path))?
    .write_all(data.as_bytes())
    .chain_err(|| format!("Failed to write to file {}", &path))?;
  Ok(())
}

/// Reads from a sysfs device file.
pub fn read_file(attr: &str, pin_num: &u8) -> Result<(bool)> {
  let path = format!("/sys/class/gpio/gpio{}/{}", pin_num, attr);
  let mut value_str = String::new();

  // Open the file (read-only) and read it's contents into the string
  let _ = File::open(&path)
    .chain_err(|| format!("Failed to open file {} for reading", &path))?
    .read_to_string(&mut value_str)
    .chain_err(|| format!("Failed to read from file {}", &path))?;

  // Convert the string into a bool
  Ok(match value_str.trim() {
       "0" => false,
       "1" => true,
       _ => bail!(format!("Invalid value read from file {}", &path)),
     })
}