version up

Remove failure

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "xdrfile"
-version = "0.1.0"
+version = "0.2.0"
 authors = ["Daniel Bauer <bauer@cbs.tu-darmstadt.de>"]
 license = "LGPL-3.0-only"
 edition = "2018"
@@ -8,7 +8,6 @@ description = "Wrapper around the gromacs libxdrfile library. Can be used to rea
 build = "build.rs"
 
 [dependencies]
-failure = "0.1"
 lazy-init = "0.3"
 
 [dev-dependencies]

src/c_abi/mod.rs

@@ -1,5 +1,6 @@
-#[allow(non_upper_case_globals)]
+#![allow(non_upper_case_globals, non_camel_case_types)]
+
+pub mod xdr_seek;
 pub mod xdrfile;
 pub mod xdrfile_trr;
 pub mod xdrfile_xtc;
-pub mod xdr_seek;

src/c_abi/xdr_seek.rs

@@ -103,12 +103,11 @@ extern "C" {
     pub fn xdr_flush(xd: *mut XDRFILE) -> ::std::os::raw::c_int;
 }
 
-
 #[cfg(test)]
 mod tests {
 
-    use super::*;
     use super::super::xdrfile_xtc::*;
+    use super::*;
     use std::ffi::CString;
 
     #[test]
@@ -129,10 +128,15 @@ mod tests {
             let tell = xdr_tell(xdr);
             assert!(tell == 0, "{}", tell);
 
-            read_xtc(xdr, num_atoms, &mut step, &mut time,
+            read_xtc(
+                xdr,
+                num_atoms,
+                &mut step,
+                &mut time,
                 box_vec.as_ptr() as *mut Matrix,
                 x_p,
-                &mut prec);
+                &mut prec,
+            );
 
             let tell = xdr_tell(xdr);
             assert!(tell > 0, "{}", tell);

src/c_abi/xdrfile.rs

@@ -1,4 +1,3 @@
-
 pub const DIM: u32 = 3;
 
 #[repr(C)]
@@ -7,7 +6,6 @@ pub struct XDRFILE {
     _unused: [u8; 0],
 }
 
-
 pub type BindgenTy1 = u32;
 pub const exdrOK: BindgenTy1 = 0;
 pub const exdrHEADER: BindgenTy1 = 1;

src/c_abi/xdrfile_trr.rs

@@ -1,6 +1,5 @@
 use super::xdrfile::*;
 
-
 extern "C" {
     pub fn read_trr_natoms(
         fn_: *const ::std::os::raw::c_char,
@@ -89,11 +88,17 @@ mod tests {
         unsafe {
             let mode = CString::new("w").unwrap();
             let xdr = xdrfile_open(tmp_path.as_ptr(), mode.as_ptr());
-            let write_code = write_trr(xdr, natoms, step, time, lambda,
+            let write_code = write_trr(
+                xdr,
+                natoms,
+                step,
+                time,
+                lambda,
                 box_vec.as_ptr() as *mut Matrix,
                 x.as_ptr() as *mut Rvec,
                 v.as_ptr() as *mut Rvec,
-                f.as_ptr() as *mut Rvec);
+                f.as_ptr() as *mut Rvec,
+            );
             assert!(write_code as u32 == exdrOK);
             xdrfile_close(xdr);
         }
@@ -111,11 +116,17 @@ mod tests {
         unsafe {
             let mode = CString::new("r").unwrap();
             let xdr = xdrfile_open(tmp_path.as_ptr(), mode.as_ptr());
-            let read_code = read_trr(xdr, natoms, &mut step2, &mut time2,
+            let read_code = read_trr(
-                &mut lambda2, box_vec2.as_ptr() as *mut Matrix,
+                xdr,
+                natoms,
+                &mut step2,
+                &mut time2,
+                &mut lambda2,
+                box_vec2.as_ptr() as *mut Matrix,
                 x2.as_ptr() as *mut Rvec,
                 v2.as_ptr() as *mut Rvec,
-                f2.as_ptr() as *mut Rvec);
+                f2.as_ptr() as *mut Rvec,
+            );
             assert!(read_code as u32 == exdrOK);
             xdrfile_close(xdr);
         }
@@ -129,5 +140,4 @@ mod tests {
         assert!(v2 == v);
         assert!(f2 == f);
     }
-
 }

src/c_abi/xdrfile_xtc.rs

@@ -1,6 +1,5 @@
 use super::xdrfile::*;
 
-
 extern "C" {
     pub fn read_xtc_natoms(
         fn_: *const ::std::os::raw::c_char,
@@ -81,9 +80,15 @@ mod tests {
         unsafe {
             let mode = CString::new("w").unwrap();
             let xdr = xdrfile_open(tmp_path.as_ptr(), mode.as_ptr());
-            let write_code = write_xtc(xdr, natoms, step, time,
+            let write_code = write_xtc(
-                box_vec.as_ptr() as *mut Matrix, x.as_ptr() as *mut Rvec,
+                xdr,
-                1000.0);
+                natoms,
+                step,
+                time,
+                box_vec.as_ptr() as *mut Matrix,
+                x.as_ptr() as *mut Rvec,
+                1000.0,
+            );
             assert!(write_code as u32 == exdrOK);
             xdrfile_close(xdr);
         }
@@ -98,9 +103,15 @@ mod tests {
         unsafe {
             let mode = CString::new("r").unwrap();
             let xdr = xdrfile_open(tmp_path.as_ptr(), mode.as_ptr());
-            let read_code = read_xtc(xdr, natoms, &mut step2, &mut time2,
+            let read_code = read_xtc(
-                box_vec2.as_ptr() as *mut Matrix, x2.as_ptr() as *mut Rvec,
+                xdr,
-                &mut prec);
+                natoms,
+                &mut step2,
+                &mut time2,
+                box_vec2.as_ptr() as *mut Matrix,
+                x2.as_ptr() as *mut Rvec,
+                &mut prec,
+            );
             assert!(read_code as u32 == exdrOK);
             xdrfile_close(xdr);
         }

src/frame.rs

@@ -26,38 +26,44 @@ impl Default for Frame {
             step: 0,
             time: 0.0,
             box_vector: [[0.0; 3]; 3],
-            coords: Vec::with_capacity(0)
+            coords: Vec::with_capacity(0),
         }
     }
 }
 
 impl fmt::Debug for Frame {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "Frame {{ atoms: {}, step: {}, time: {}, \
+        write!(
-            box: {:?}, coords: {:?} }}", self.num_atoms, self.step, self.time,
+            f,
-            self.box_vector, self.coords)
+            "Frame {{ atoms: {}, step: {}, time: {}, \
+            box: {:?}, coords: {:?} }}",
+            self.num_atoms, self.step, self.time, self.box_vector, self.coords
+        )
     }
 }
 
 impl Frame {
     /// Creates an empty frame with a capacity of 0
     pub fn new() -> Frame {
-        Frame{ ..Default::default() }
+        Frame {
+            ..Default::default()
+        }
     }
 
     /// Creates a frame with the given capacity
     pub fn with_capacity(num_atoms: u32) -> Frame {
         Frame {
-            num_atoms: num_atoms,
+            num_atoms,
             coords: vec![[0.0, 0.0, 0.0]; num_atoms as usize],
             ..Default::default()
         }
-
     }
 
     /// Filters the frame by removing all atoms not matching the given indeces.
     pub fn filter_coords(self: &mut Frame, indeces: &[usize]) {
-        self.coords = self.coords.iter() 
+        self.coords = self
+            .coords
+            .iter()
             .map(|elem| elem.clone())
             .enumerate()
             .filter(|&(i, _)| indeces.contains(&i))
@@ -72,8 +78,6 @@ impl Frame {
     }
 }
 
-
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -91,7 +95,7 @@ mod tests {
         frame.coords[0] = [1.0, 2.0, 3.0];
         frame.coords[1] = [4.0, 5.0, 6.0];
         frame.coords[2] = [7.0, 8.0, 9.0];
-        let filter: Vec<usize> = vec![1,2];
+        let filter: Vec<usize> = vec![1, 2];
         let mut frame_new = frame.clone();
         frame_new.filter_coords(&filter);
         assert!(frame_new.num_atoms as usize == filter.len());

src/iterator.rs

@@ -1,10 +1,9 @@
-use crate::*;
 use crate::c_abi::xdrfile::exdrENDOFFILE;
-use failure::Error;
+use crate::*;
 use std::rc::Rc;
 
 impl IntoIterator for XTCTrajectory {
-    type Item = Result<Rc<Frame>, Error>;
+    type Item = Result<Rc<Frame>>;
     type IntoIter = XTCTrajectoryIterator;
 
     fn into_iter(mut self) -> Self::IntoIter {
@@ -13,7 +12,7 @@ impl IntoIterator for XTCTrajectory {
         XTCTrajectoryIterator {
             trajectory: self,
             item: Rc::new(Frame::with_capacity(num_atoms)),
-            has_error: false
+            has_error: false,
         }
     }
 }
@@ -30,20 +29,21 @@ pub struct XTCTrajectoryIterator {
 }
 
 impl Iterator for XTCTrajectoryIterator {
-    type Item = Result<Rc<Frame>, Error>;
+    type Item = Result<Rc<Frame>>;
 
-    fn next(&mut self) -> Option<Self::Item> { // Reuse old frame
+    fn next(&mut self) -> Option<Self::Item> {
+        // Reuse old frame
         if self.has_error {
             return None;
         }
 
         let item: &mut Frame = match Rc::get_mut(&mut self.item) {
             Some(item) => item,
-            None => {  // caller kept frame. Create new one
+            None => {
+                // caller kept frame. Create new one
                 self.item = Rc::new(Frame::with_capacity(self.item.num_atoms));
                 Rc::get_mut(&mut self.item).unwrap()
             }
-
         };
         match self.trajectory.read(item) {
             Ok(()) => Some(Ok(Rc::clone(&self.item))),
@@ -60,7 +60,7 @@ impl Iterator for XTCTrajectoryIterator {
 }
 
 impl IntoIterator for TRRTrajectory {
-    type Item = Result<Rc<Frame>, Error>;
+    type Item = Result<Rc<Frame>>;
     type IntoIter = TRRTrajectoryIterator;
 
     fn into_iter(mut self) -> Self::IntoIter {
@@ -69,7 +69,7 @@ impl IntoIterator for TRRTrajectory {
         TRRTrajectoryIterator {
             trajectory: self,
             item: Rc::new(Frame::with_capacity(num_atoms)),
-            has_error: false
+            has_error: false,
         }
     }
 }
@@ -86,20 +86,21 @@ pub struct TRRTrajectoryIterator {
 }
 
 impl Iterator for TRRTrajectoryIterator {
-    type Item = Result<Rc<Frame>, Error>;
+    type Item = Result<Rc<Frame>>;
 
-    fn next(&mut self) -> Option<Self::Item> { // Reuse old frame
+    fn next(&mut self) -> Option<Self::Item> {
+        // Reuse old frame
         if self.has_error {
             return None;
         }
 
         let item: &mut Frame = match Rc::get_mut(&mut self.item) {
             Some(item) => item,
-            None => {  // caller kept frame. Create new one
+            None => {
+                // caller kept frame. Create new one
                 self.item = Rc::new(Frame::with_capacity(self.item.num_atoms));
                 Rc::get_mut(&mut self.item).unwrap()
             }
-
         };
         match self.trajectory.read(item) {
             Ok(()) => Some(Ok(Rc::clone(&self.item))),

src/lib.rs

@@ -58,33 +58,80 @@
 //! }
 //! ```
 
-
 #[cfg(test)]
-#[macro_use] extern crate assert_approx_eq;
+#[macro_use]
+extern crate assert_approx_eq;
 extern crate lazy_init;
 
+pub mod c_abi;
 mod frame;
 mod iterator;
-pub mod c_abi; 
 pub use frame::Frame;
 pub use iterator::*;
 
+use c_abi::xdr_seek;
 use c_abi::xdrfile;
 use c_abi::xdrfile::XDRFILE;
-use c_abi::xdr_seek;
-use c_abi::xdrfile_xtc;
 use c_abi::xdrfile_trr;
+use c_abi::xdrfile_xtc;
 
+use lazy_init::Lazy;
+use std::cell::Cell;
 use std::ffi::CString;
 use std::path::Path;
-use failure::{Error,err_msg};
-use std::cell::Cell;
-use lazy_init::Lazy;
 
+#[derive(Debug, Clone)]
+pub enum Error {
+    CouldNotOpenFile(std::path::PathBuf, FileMode),
+    CouldNotReadAtomNumber(u32),
+    CouldNotRead(u32),
+    CouldNotWrite(u32),
+    CouldNotFlush(u32),
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        use Error::*;
+        match self {
+            CouldNotOpenFile(path, mode) => write!(
+                f,
+                "Failed to open file at {path:?} with mode {mode:?}",
+                path = path,
+                mode = mode
+            ),
+            CouldNotReadAtomNumber(code) => write!(
+                f,
+                "Failed to read atom number from trajectory: C API returned error code {}",
+                code
+            ),
+            CouldNotRead(code) => write!(
+                f,
+                "Failed to read trajectory: C API returned error code {}",
+                code
+            ),
+            CouldNotWrite(code) => write!(
+                f,
+                "Failed to write trajectory: C API returned error code {}",
+                code
+            ),
+            CouldNotFlush(code) => write!(
+                f,
+                "Failed to flush trajectory: C API returned error code {}",
+                code
+            ),
+        }
+    }
+}
+
+impl std::error::Error for Error {}
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug, Clone, PartialEq)]
 pub enum FileMode {
     Write,
     Append,
-    Read    
+    Read,
 }
 
 impl FileMode {
@@ -99,29 +146,34 @@ impl FileMode {
 
 fn path_to_cstring(path: &Path) -> CString {
     CString::new(path.to_str().unwrap()).unwrap()
-    }
+}
 
 /// A safe wrapper around the c implementation of an XDRFile
 struct XDRFile {
     xdrfile: *mut XDRFILE,
+    #[allow(dead_code)]
     filemode: FileMode,
     path: String,
 }
 
 impl XDRFile {
-
+    pub fn open(path: &Path, filemode: FileMode) -> Result<XDRFile> {
-    pub fn open(path: &Path, filemode: FileMode) -> Result<XDRFile, Error> {
         let path_p = path_to_cstring(path).into_raw();
         let mode_p = CString::new(filemode.value()).unwrap().into_raw();
 
         unsafe {
             let xdrfile = xdrfile::xdrfile_open(path_p, mode_p);
 
-            if ! xdrfile.is_null() {
+            if !xdrfile.is_null() {
                 let path = String::from(path.to_str().unwrap());
-                Ok(XDRFile { xdrfile, filemode, path })
+                Ok(XDRFile {
-            } else {  // Something went wrong. But the C api does not tell us what
+                    xdrfile,
-                Err(err_msg("Failed to open trajectory file"))
+                    filemode,
+                    path,
+                })
+            } else {
+                // Something went wrong. But the C api does not tell us what
+                Err(Error::CouldNotOpenFile(path.into(), filemode))
             }
         }
     }
@@ -138,43 +190,46 @@ impl Drop for XDRFile {
 
 /// The trajectory trait defines shared methods for xtc and trr trajectories
 pub trait Trajectory {
-
     /// Read the next step of the trajectory into the frame object
-    fn read(&mut self, frame: &mut Frame) -> Result<(), Error>;
+    fn read(&mut self, frame: &mut Frame) -> Result<()>;
 
     /// Write the frame to the trajectory file
-    fn write(&mut self, frame: &Frame) -> Result<(), Error>;
+    fn write(&mut self, frame: &Frame) -> Result<()>;
 
     /// Flush the trajectory file
-    fn flush(&mut self) -> Result<(), Error>;
+    fn flush(&mut self) -> Result<()>;
 
     /// Get the number of atoms from the give trajectory
-    fn get_num_atoms(&mut self) -> Result<u32, Error>; 
+    fn get_num_atoms(&mut self) -> Result<u32>;
 }
 
 /// Read/Write XTC Trajectories
 pub struct XTCTrajectory {
     handle: XDRFile,
     precision: Cell<f32>, // internal mutability required for read method
-    num_atoms: Lazy<Result<u32, Error>>
+    num_atoms: Lazy<Result<u32>>,
 }
 
 impl XTCTrajectory {
-    pub fn open(path: &Path, filemode: FileMode) -> Result<XTCTrajectory, Error> {
+    pub fn open(path: &Path, filemode: FileMode) -> Result<XTCTrajectory> {
         let xdr = XDRFile::open(path, filemode)?;
-        Ok(XTCTrajectory { handle: xdr, precision: Cell::new(1000.0), num_atoms: Lazy::new() })
+        Ok(XTCTrajectory {
+            handle: xdr,
+            precision: Cell::new(1000.0),
+            num_atoms: Lazy::new(),
+        })
     }
 }
 
 impl Trajectory for XTCTrajectory {
-
+    fn read(&mut self, frame: &mut Frame) -> Result<()> {
-    fn read(&mut self, frame: &mut Frame) -> Result<(), Error> {
         unsafe {
             // C lib requires an i32 to be passed, but step is exposed it as u32
             // (A step cannot be negative, can it?). So we need to create a step
             // variable to pass to read_xtc and cast it afterwards to u32
             let mut step: i32 = 0;
-            let code = xdrfile_xtc::read_xtc(self.handle.xdrfile,
+            let code = xdrfile_xtc::read_xtc(
+                self.handle.xdrfile,
                 frame.num_atoms as i32,
                 &mut step,
                 &mut frame.time,
@@ -185,75 +240,76 @@ impl Trajectory for XTCTrajectory {
             frame.step = step as u32;
             match code {
                 xdrfile::exdrOK => Ok(()),
-                _ => Err(err_msg(format!("Failed to read trajectory. Error code: {}", code))), 
+                _ => Err(Error::CouldNotRead(code)),
             }
         }
     }
 
-    fn write(&mut self, frame: &Frame) -> Result<(), Error> {
+    fn write(&mut self, frame: &Frame) -> Result<()> {
         unsafe {
-            let code = xdrfile_xtc::write_xtc(self.handle.xdrfile,
+            let code = xdrfile_xtc::write_xtc(
+                self.handle.xdrfile,
                 frame.num_atoms as i32,
                 frame.step as i32,
                 frame.time,
                 frame.box_vector.as_ptr() as *mut [[f32; 3]; 3],
                 frame.coords[..].as_ptr() as *mut [f32; 3],
-                1000.0) as u32;
+                1000.0,
+            ) as u32;
             match code {
                 xdrfile::exdrOK => Ok(()),
-                _ => Err(err_msg(format!("Failed to write trajectory. Error code: {}", code)))
+                _ => Err(Error::CouldNotWrite(code)),
             }
         }
     }
 
-    fn flush(&mut self) -> Result<(), Error> {
+    fn flush(&mut self) -> Result<()> {
         unsafe {
             let code = xdr_seek::xdr_flush(self.handle.xdrfile) as u32;
             match code {
                 xdrfile::exdrOK => Ok(()),
-                _ => Err(err_msg(format!("Failed to flush trajectory. Error code: {}", code)))
+                _ => Err(Error::CouldNotFlush(code)),
             }
         }
     }
 
-    fn get_num_atoms(&mut self) -> Result<u32, Error> {
+    fn get_num_atoms(&mut self) -> Result<u32> {
-        let result = self.num_atoms.get_or_create(|| {
+        self.num_atoms
+            .get_or_create(|| {
                 let mut num_atoms: i32 = 0;
                 unsafe {
                     let path = CString::new(self.handle.path.as_str()).unwrap();
                     let path_p = path.into_raw();
-                let code = xdrfile_xtc::read_xtc_natoms(path_p, &mut num_atoms as *const i32) as u32;
+                    let code =
+                        xdrfile_xtc::read_xtc_natoms(path_p, &mut num_atoms as *const i32) as u32;
                     match code {
                         xdrfile::exdrOK => Ok(num_atoms as u32),
-                    _ => Err(err_msg(format!("Failed to read atom number from trajectory. Error code: {}", code)))
+                        _ => Err(Error::CouldNotReadAtomNumber(code)),
                     }
                 }
-        });
+            })
-        match result {
+            .clone()
-            Ok(val) => Ok(*val),
-            // ugly hack because failure::Error is not "Clone"
-            Err(err) => Err(err_msg(format!("{}", err)))
-        }
     }
 }
 
-
 /// Read/Write TRR Trajectories
 pub struct TRRTrajectory {
     handle: XDRFile,
-    num_atoms: Lazy<Result<u32, Error>>
+    num_atoms: Lazy<Result<u32>>,
 }
 
 impl TRRTrajectory {
-    pub fn open(path: &Path, filemode: FileMode) -> Result<TRRTrajectory, Error> {
+    pub fn open(path: &Path, filemode: FileMode) -> Result<TRRTrajectory> {
         let xdr = XDRFile::open(path, filemode)?;
-        Ok(TRRTrajectory { handle: xdr, num_atoms: Lazy::new() })
+        Ok(TRRTrajectory {
+            handle: xdr,
+            num_atoms: Lazy::new(),
+        })
     }
 }
 
 impl Trajectory for TRRTrajectory {
-
+    fn read(&mut self, frame: &mut Frame) -> Result<()> {
-    fn read(&mut self, frame: &mut Frame) -> Result<(), Error> {
         unsafe {
             // C lib requires an i32 to be passed, but step is exposed it as u32
             // (A step cannot be negative, can it?). So we need to create a step
@@ -261,7 +317,8 @@ impl Trajectory for TRRTrajectory {
             // Similar for lambda.
             let mut step: i32 = 0;
             let mut lambda: f32 = 0.0;
-            let code = xdrfile_trr::read_trr(self.handle.xdrfile,
+            let code = xdrfile_trr::read_trr(
+                self.handle.xdrfile,
                 frame.num_atoms as i32,
                 &mut step,
                 &mut frame.time,
@@ -269,19 +326,20 @@ impl Trajectory for TRRTrajectory {
                 &mut frame.box_vector,
                 frame.coords.as_ptr() as *mut [f32; 3],
                 std::ptr::null_mut(),
-                std::ptr::null_mut()
+                std::ptr::null_mut(),
             ) as u32;
             frame.step = step as u32;
             match code {
                 xdrfile::exdrOK => Ok(()),
-                _ => Err(err_msg(format!("Failed to read trajectory. Error code: {}", code)))
+                _ => Err(Error::CouldNotRead(code)),
             }
         }
     }
 
-    fn write(&mut self, frame: &Frame) -> Result<(), Error> {
+    fn write(&mut self, frame: &Frame) -> Result<()> {
         unsafe {
-            let code = xdrfile_trr::write_trr(self.handle.xdrfile,
+            let code = xdrfile_trr::write_trr(
+                self.handle.xdrfile,
                 frame.num_atoms as i32,
                 frame.step as i32,
                 frame.time,
@@ -289,46 +347,44 @@ impl Trajectory for TRRTrajectory {
                 frame.box_vector.as_ptr() as *mut [[f32; 3]; 3],
                 frame.coords[..].as_ptr() as *mut [f32; 3],
                 std::ptr::null_mut(),
-                std::ptr::null_mut()) as u32;
+                std::ptr::null_mut(),
+            ) as u32;
             match code {
                 xdrfile::exdrOK => Ok(()),
-                _ => Err(err_msg(format!("Failed to write trajectory. Error code: {}", code)))
+                _ => Err(Error::CouldNotWrite(code)),
             }
         }
     }
 
-    fn flush(&mut self) -> Result<(), Error> {
+    fn flush(&mut self) -> Result<()> {
         unsafe {
             let code = xdr_seek::xdr_flush(self.handle.xdrfile) as u32;
             match code {
                 xdrfile::exdrOK => Ok(()),
-                _ => Err(err_msg(format!("Failed to flush trajectory. Error code: {}", code))) 
+                _ => Err(Error::CouldNotFlush(code)),
             }
         }
     }
 
-    fn get_num_atoms(&mut self) -> Result<u32, Error> {
+    fn get_num_atoms(&mut self) -> Result<u32> {
-        let result = self.num_atoms.get_or_create(|| {
+        self.num_atoms
+            .get_or_create(|| {
                 let mut num_atoms: i32 = 0;
                 unsafe {
                     let path = CString::new(self.handle.path.as_str()).unwrap();
                     let path_p = path.into_raw();
-                let code = xdrfile_trr::read_trr_natoms(path_p, &mut num_atoms as *const i32) as u32;
+                    let code =
+                        xdrfile_trr::read_trr_natoms(path_p, &mut num_atoms as *const i32) as u32;
                     match code {
                         xdrfile::exdrOK => Ok(num_atoms as u32),
-                    _ => Err(err_msg(format!("Failed to read atom number from trajectory. Error code: {}", code)))
+                        _ => Err(Error::CouldNotReadAtomNumber(code)),
                     }
                 }
-        });
+            })
-        match result {
+            .clone()
-            Ok(val) => Ok(*val),
-            // ugly hack because failure::Error is not "Clone"
-            Err(err) => Err(err_msg(format!("{}", err)))
-        }
     }
 }
 
-
 #[cfg(test)]
 mod tests {
 
@@ -412,5 +468,50 @@ mod tests {
         assert_eq!(new_frame.box_vector, frame.box_vector);
         assert_eq!(new_frame.coords, frame.coords);
     }
-}
 
+    #[test]
+    fn test_err_could_not_open() {
+        let file_name = "non-existent.xtc";
+        let path = Path::new(&file_name);
+        if let Err(e) = XDRFile::open(path, FileMode::Read) {
+            match e {
+                Error::CouldNotOpenFile(err_path, err_mode) => {
+                    assert_eq!(path, err_path);
+                    assert!(FileMode::Read == err_mode)
+                }
+                _ => panic!("Wrong Error type"),
+            }
+        }
+    }
+
+    #[test]
+    fn test_err_could_not_read_atom_nr() {
+        let file_name = "README.md"; // not a trajectory
+        let path = Path::new(&file_name);
+        let mut trr = TRRTrajectory::open(path, FileMode::Read).unwrap();
+        if let Err(e) = trr.get_num_atoms() {
+            match e {
+                Error::CouldNotReadAtomNumber(code) => {
+                    assert_eq!(xdrfile::exdrMAGIC, code);
+                }
+                _ => panic!("Wrong Error type"),
+            }
+        }
+    }
+
+    #[test]
+    fn test_err_could_not_read() {
+        let file_name = "README.md"; // not a trajectory
+        let path = Path::new(&file_name);
+        let mut frame = Frame::with_capacity(1);
+        let mut trr = TRRTrajectory::open(path, FileMode::Read).unwrap();
+        if let Err(e) = trr.read(&mut frame) {
+            match e {
+                Error::CouldNotRead(code) => {
+                    assert_eq!(xdrfile::exdrMAGIC, code);
+                }
+                _ => panic!("Wrong Error type"),
+            }
+        }
+    }
+}

tests/integration.rs

@@ -1,9 +1,9 @@
 #[cfg(test)]
 mod integration {
 
+    use std::path::Path;
     use std::rc::Rc;
     use xdrfile::*;
-    use std::path::Path;
 
     #[test]
     fn test_use_library() {
@@ -25,8 +25,7 @@ mod integration {
         let trj = XTCTrajectory::open(path, FileMode::Read).unwrap();
         let frames: Vec<Rc<Frame>> = trj.into_iter().filter_map(Result::ok).collect();
         for (idx, frame) in frames.iter().enumerate() {
-            assert_eq!(frame.step as usize, idx+1);
+            assert_eq!(frame.step as usize, idx + 1);
         }
     }
-
 }