util/error: add error handling

src/lib.rs

@@ -5,3 +5,4 @@ extern crate ffmpeg_sys as ffi;
 #[macro_use] extern crate bitflags;
 
 pub mod util;
+pub use util::error::Error;

src/util/error.rs

@@ -0,0 +1,50 @@
+use ffi::*;
+use std::error;
+use std::fmt;
+use std::cell::RefCell;
+use libc::c_int;
+use std::ffi::CStr;
+use std::str::from_utf8_unchecked;
+
+pub struct Error {
+	code: c_int,
+	desc: RefCell<Option<[i8; AV_ERROR_MAX_STRING_SIZE as usize]>>,
+}
+
+impl Error {
+	pub fn new(code: c_int) -> Self {
+		Error { code: code, desc: RefCell::new(None) }
+	}
+}
+
+impl fmt::Display for Error {
+	fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+		f.write_str(error::Error::description(self))
+	}
+}
+
+impl fmt::Debug for Error {
+	fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+		try!(f.write_str("ffmpeg::Error("));
+		try!(f.write_str(&format!("{}: ", AVUNERROR(self.code))));
+		try!(fmt::Display::fmt(self, f));
+		f.write_str(")")
+	}
+}
+
+impl error::Error for Error {
+	fn description(&self) -> &str {
+		unsafe {
+			let mut desc = self.desc.borrow_mut();
+
+			if let None = *desc {
+				let mut buf = [0i8; AV_ERROR_MAX_STRING_SIZE as usize];
+				av_strerror(self.code, buf.as_mut_ptr(), AV_ERROR_MAX_STRING_SIZE);
+
+				*desc = Some(buf);
+			}
+
+			from_utf8_unchecked(CStr::from_ptr(desc.unwrap().as_ptr()).to_bytes())
+		}
+	}
+}

src/util/mod.rs

@@ -1,3 +1,5 @@
+pub mod error;
+
 use std::ffi::CStr;
 use std::str::from_utf8_unchecked;