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//! A wrapper to a attribute file commonly in the `/sys/class/` directory.
use std::error::Error;
use std::fs::{self, File, OpenOptions};
use std::io::{Read, Seek, SeekFrom, Write};
use std::os::unix::fs::PermissionsExt;
use std::os::unix::io::{AsRawFd, RawFd};
use std::path::{Path, PathBuf};
use std::string::String;
use std::sync::{Arc, Mutex};
use crate::driver::DRIVER_PATH;
use crate::utils::OrErr;
use crate::{Ev3Error, Ev3Result};
/// A wrapper to a attribute file in the `/sys/class/` directory.
#[derive(Debug, Clone)]
pub struct Attribute {
file_path: PathBuf,
file: Arc<Mutex<File>>,
}
impl Attribute {
/// Create a new `Attribute` instance for the given path.
pub fn from_path(path: &Path) -> Ev3Result<Attribute> {
let stat = fs::metadata(path)?;
let mode = stat.permissions().mode();
// Read permission for group (`ev3dev`)
let readable = mode & 0o040 == 0o040;
let writeable = mode & 0o020 == 0o020;
let file = OpenOptions::new()
.read(readable)
.write(writeable)
.open(path)?;
Ok(Attribute {
file_path: PathBuf::from(path),
file: Arc::new(Mutex::new(file)),
})
}
/// Create a new `Attribute` instance that wrap's
/// the file `/sys/class/{class_name}/{name}{attribute_name}`.
pub fn from_sys_class(
class_name: &str,
name: &str,
attribute_name: &str,
) -> Ev3Result<Attribute> {
let path = Path::new(DRIVER_PATH)
.join(class_name)
.join(name)
.join(attribute_name);
Attribute::from_path(path.as_ref())
}
/// Create a new `Attribute` instance by a discriminator attribute.
/// This can be used to manually access driver files or advances features like raw encoder values.
/// To find the correct file, this function iterates over all directories `$d` in `driver_path` and
/// checks if the content of `driver_path/$d/discriminator_path` equals `discriminator_value`. When a
/// match is found it returns an Attribute for file `driver_path/$d/attribute_path`.
///
/// # Example
/// ```no_run
/// use ev3dev_lang_rust::Attribute;
///
/// # fn main() -> ev3dev_lang_rust::Ev3Result<()> {
/// // Get value0 of first connected color sensor.
/// let color_sensor_value = Attribute::from_path_with_discriminator(
/// "/sys/class/lego-sensor",
/// "value0",
/// "driver_name",
/// "lego-ev3-color"
/// )?;
/// println!("value0 of color sensor: {}", color_sensor_value.get::<i32>()?);
///
/// // Get raw rotation count of motor in port `A`.
/// // See https://github.com/ev3dev/ev3dev/wiki/Internals:-ev3dev-stretch for more information.
/// let rotation_count = Attribute::from_path_with_discriminator(
/// "/sys/bus/iio/devices",
/// "in_count0_raw",
/// "name",
/// "ev3-tacho"
/// )?;
/// println!("Raw rotation count: {}", rotation_count.get::<i32>()?);
///
/// # Ok(())
/// # }
/// ```
pub fn from_path_with_discriminator(
driver_path: &str,
attribute_path: &str,
discriminator_path: &str,
discriminator_value: &str,
) -> Ev3Result<Attribute> {
let paths = fs::read_dir(driver_path)?;
for path_result in paths {
let path_buf = path_result?.path();
let current_path = path_buf.to_str().or_err()?;
let discriminator_attribute = Attribute::from_path(&PathBuf::from(format!(
"{current_path}/{discriminator_path}"
)))?;
if discriminator_attribute.get::<String>()? == discriminator_value {
return Attribute::from_path(&PathBuf::from(format!(
"{current_path}/{attribute_path}"
)));
}
}
Err(Ev3Error::InternalError {
msg: format!(
"Attribute `{attribute_path}` at driver path `{driver_path}` could not be found!"
),
})
}
/// Returns the current content of the wrapped file.
pub fn get_bytes(&self) -> Ev3Result<Vec<u8>> {
let mut value: Vec<u8> = Vec::new();
let mut file = self.file.lock().unwrap();
file.seek(SeekFrom::Start(0))?;
file.read_to_end(&mut value)?;
Ok(value)
}
/// Returns the current value of the wrapped file.
fn get_str(&self) -> Ev3Result<String> {
let mut value = String::new();
let mut file = self.file.lock().unwrap();
file.seek(SeekFrom::Start(0))?;
file.read_to_string(&mut value)?;
Ok(value.trim_end().to_owned())
}
/// Sets the value of the wrapped file.
/// Returns a `Ev3Result::InternalError` if the file is not writable.
fn set_str(&self, value: &str) -> Ev3Result<()> {
let mut file = self.file.lock().unwrap();
file.seek(SeekFrom::Start(0))?;
file.write_all(value.as_bytes())?;
Ok(())
}
/// Returns the current value of the wrapped file.
/// The value is parsed to the type `T`.
/// Returns a `Ev3Result::InternalError` if the current value is not parsable to type `T`.
pub fn get<T>(&self) -> Ev3Result<T>
where
T: std::str::FromStr,
<T as std::str::FromStr>::Err: Error,
{
let value = self.get_str()?;
match value.parse::<T>() {
Ok(value) => Ok(value),
Err(err) => Err(Ev3Error::InternalError {
msg: format!("{err}"),
}),
}
}
/// Sets the value of the wrapped file.
/// The value is parsed from the type `T`.
/// Returns a `Ev3Result::InternalError` if the file is not writable.
pub fn set<T>(&self, value: T) -> Ev3Result<()>
where
T: std::string::ToString,
{
self.set_str(&value.to_string())
}
#[inline]
/// Sets the value of the wrapped file.
/// This function skips the string parsing of the `self.set<T>()` function.
/// Returns a `Ev3Result::InternalError` if the file is not writable.
pub fn set_str_slice(&self, value: &str) -> Ev3Result<()> {
self.set_str(value)
}
/// Returns a string vector representation of the wrapped file.
/// The file value is splitted at whitespace's.
pub fn get_vec(&self) -> Ev3Result<Vec<String>> {
let value = self.get_str()?;
let vec = value
.split_whitespace()
.map(|word| word.to_owned())
.collect();
Ok(vec)
}
/// Returns a C pointer to the wrapped file.
pub fn get_raw_fd(&self) -> RawFd {
self.file.lock().unwrap().as_raw_fd()
}
/// Returns the path to the wrapped file.
pub fn get_file_path(&self) -> PathBuf {
self.file_path.clone()
}
}