Linux device checks for a folder existance during refresh (closes #29)

battery-ffi/Cargo.toml

@@ -31,7 +31,7 @@ path = "../battery"
 libc = "^0.2"
 
 [build-dependencies]
-cbindgen = { version = "0.8.0", optional = true }
+cbindgen = { version = "0.8.7", optional = true }
 
 [package.metadata.docs.rs]
 no-default-features = true

battery-ffi/src/battery.rs

@@ -155,13 +155,13 @@ pub unsafe extern "C" fn battery_get_temperature(ptr: *const Battery) -> libc::c
 ///
 /// # Returns
 ///
-/// If value is not available, function returns max possible value for `uint32` type (`4294967295`).
+/// If value is not available, function returns max possible value for the `u32` type (`4294967295`).
 ///
 /// # Panics
 ///
 /// This function will panic if passed pointer is `NULL`
 #[no_mangle]
-pub unsafe extern "C" fn battery_get_cycle_count(ptr: *const Battery) -> libc::uint32_t {
+pub unsafe extern "C" fn battery_get_cycle_count(ptr: *const Battery) -> u32 {
     assert!(!ptr.is_null());
     let battery = &*ptr;
 

battery/Cargo.toml

@@ -36,5 +36,5 @@ core-foundation = "0.6.4"
 winapi = { version ="0.3.7", features = ["impl-default", "devguid", "winbase", "ioapiset", "ntdef", "setupapi", "handleapi", "errhandlingapi", "winerror"] }
 
 [target.'cfg(any(target_os = "dragonfly", target_os = "freebsd"))'.dependencies]
-nix = "0.13.0"
-libc = "0.2.51"
+nix = "^0.14"
+libc = "^0.2"

battery/src/errors.rs

@@ -1,5 +1,6 @@
 //! Errors handling
-//!
+
+use std::borrow::Cow;
 use std::error::Error as StdError;
 use std::fmt;
 use std::io;
@@ -15,21 +16,31 @@ pub type Result<T> = result::Result<T, Error>;
 #[derive(Debug)]
 pub struct Error {
     source: io::Error,
-    description: Option<&'static str>,
+    description: Option<Cow<'static, str>>,
 }
 
 impl Error {
-    pub fn not_found(description: &'static str) -> Error {
+    #[allow(unused)]
+    pub(crate) fn new<T>(e: io::Error, description: T) -> Error where T: Into<Cow<'static, str>> {
+        Error {
+            source: e,
+            description: Some(description.into()),
+        }
+    }
+
+    #[allow(unused)]
+    pub(crate) fn not_found<T>(description: T) -> Error where T: Into<Cow<'static, str>> {
         Error {
             source: io::Error::from(io::ErrorKind::NotFound),
-            description: Some(description),
+            description: Some(description.into()),
         }
     }
 
-    pub fn invalid_data(description: &'static str) -> Error {
+    #[allow(unused)]
+    pub(crate) fn invalid_data<T>(description: T) -> Error where T: Into<Cow<'static, str>> {
         Error {
             source: io::Error::from(io::ErrorKind::InvalidData),
-            description: Some(description),
+            description: Some(description.into()),
         }
     }
 }
@@ -42,7 +53,7 @@ impl StdError for Error {
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self.description {
+        match &self.description {
             Some(desc) => write!(f, "{}", desc),
             None => self.source.fmt(f),
         }
@@ -69,19 +80,19 @@ mod nix_impl {
             match e {
                 nix::Error::Sys(errno) => Error {
                     source: io::Error::from_raw_os_error(errno as i32),
-                    description: Some(errno.desc()),
+                    description: Some(errno.desc().into()),
                 },
                 nix::Error::InvalidPath => Error {
                     source: io::Error::new(io::ErrorKind::InvalidInput, e),
-                    description: Some("Invalid path"),
+                    description: Some("Invalid path".into()),
                 },
                 nix::Error::InvalidUtf8 => Error {
                     source: io::Error::new(io::ErrorKind::InvalidData, e),
-                    description: Some("Invalid UTF-8 string"),
+                    description: Some("Invalid UTF-8 string".into()),
                 },
                 nix::Error::UnsupportedOperation => Error {
                     source: io::Error::new(io::ErrorKind::Other, e),
-                    description: Some("Unsupported operation"),
+                    description: Some("Unsupported operation".into()),
                 },
             }
         }

battery/src/platform/linux/device.rs

@@ -1,9 +1,10 @@
+use std::io;
 use std::fmt;
 use std::path::{Path, PathBuf};
 
 use crate::platform::traits::*;
 use crate::units::{ElectricPotential, Energy, Power, Ratio, ThermodynamicTemperature};
-use crate::{Result, State, Technology};
+use crate::{Result, Error, State, Technology};
 
 use super::sysfs::{fs, DataBuilder, InstantData, Scope, Type};
 
@@ -50,9 +51,23 @@ impl SysFsDevice {
     }
 
     pub fn refresh(&mut self) -> Result<()> {
-        let builder = DataBuilder::new(&self.root);
-        self.source = builder.collect()?;
-        Ok(())
+        // It is necessary to ensure that `self.root`
+        // still exists and accessible.
+        // See https://github.com/svartalf/rust-battery/issues/29
+        if self.root.is_dir() {
+            let builder = DataBuilder::new(&self.root);
+            self.source = builder.collect()?;
+
+            Ok(())
+        } else {
+            let inner = io::Error::from(io::ErrorKind::NotFound);
+            let e = Error::new(
+                inner,
+                format!("Device directory `{:?}` is missing", self.root),
+            );
+
+            Err(e)
+        }
     }
 }