1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
17 /// A specialized [`Result`](../result/enum.Result.html) type for I/O
20 /// This type is broadly used across [`std::io`] for any operation which may
23 /// This typedef is generally used to avoid writing out [`io::Error`] directly and
24 /// is otherwise a direct mapping to [`Result`].
26 /// While usual Rust style is to import types directly, aliases of [`Result`]
27 /// often are not, to make it easier to distinguish between them. [`Result`] is
28 /// generally assumed to be [`std::result::Result`][`Result`], and so users of this alias
29 /// will generally use `io::Result` instead of shadowing the prelude's import
30 /// of [`std::result::Result`][`Result`].
32 /// [`std::io`]: ../io/index.html
33 /// [`io::Error`]: ../io/struct.Error.html
34 /// [`Result`]: ../result/enum.Result.html
38 /// A convenience function that bubbles an `io::Result` to its caller:
43 /// fn get_string() -> io::Result<String> {
44 /// let mut buffer = String::new();
46 /// io::stdin().read_line(&mut buffer)?;
51 #[stable(feature = "rust1", since = "1.0.0")]
52 pub type Result<T> = result::Result<T, Error>;
54 /// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and
55 /// associated traits.
57 /// Errors mostly originate from the underlying OS, but custom instances of
58 /// `Error` can be created with crafted error messages and a particular value of
61 /// [`Read`]: ../io/trait.Read.html
62 /// [`Write`]: ../io/trait.Write.html
63 /// [`Seek`]: ../io/trait.Seek.html
64 /// [`ErrorKind`]: enum.ErrorKind.html
65 #[stable(feature = "rust1", since = "1.0.0")]
70 #[stable(feature = "rust1", since = "1.0.0")]
71 impl fmt::Debug for Error {
72 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
73 fmt::Debug::fmt(&self.repr, f)
86 error: Box<dyn error::Error+Send+Sync>,
89 /// A list specifying general categories of I/O error.
91 /// This list is intended to grow over time and it is not recommended to
92 /// exhaustively match against it.
94 /// It is used with the [`io::Error`] type.
96 /// [`io::Error`]: struct.Error.html
97 #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
98 #[stable(feature = "rust1", since = "1.0.0")]
101 /// An entity was not found, often a file.
102 #[stable(feature = "rust1", since = "1.0.0")]
104 /// The operation lacked the necessary privileges to complete.
105 #[stable(feature = "rust1", since = "1.0.0")]
107 /// The connection was refused by the remote server.
108 #[stable(feature = "rust1", since = "1.0.0")]
110 /// The connection was reset by the remote server.
111 #[stable(feature = "rust1", since = "1.0.0")]
113 /// The connection was aborted (terminated) by the remote server.
114 #[stable(feature = "rust1", since = "1.0.0")]
116 /// The network operation failed because it was not connected yet.
117 #[stable(feature = "rust1", since = "1.0.0")]
119 /// A socket address could not be bound because the address is already in
121 #[stable(feature = "rust1", since = "1.0.0")]
123 /// A nonexistent interface was requested or the requested address was not
125 #[stable(feature = "rust1", since = "1.0.0")]
127 /// The operation failed because a pipe was closed.
128 #[stable(feature = "rust1", since = "1.0.0")]
130 /// An entity already exists, often a file.
131 #[stable(feature = "rust1", since = "1.0.0")]
133 /// The operation needs to block to complete, but the blocking operation was
134 /// requested to not occur.
135 #[stable(feature = "rust1", since = "1.0.0")]
137 /// A parameter was incorrect.
138 #[stable(feature = "rust1", since = "1.0.0")]
140 /// Data not valid for the operation were encountered.
142 /// Unlike [`InvalidInput`], this typically means that the operation
143 /// parameters were valid, however the error was caused by malformed
146 /// For example, a function that reads a file into a string will error with
147 /// `InvalidData` if the file's contents are not valid UTF-8.
149 /// [`InvalidInput`]: #variant.InvalidInput
150 #[stable(feature = "io_invalid_data", since = "1.2.0")]
152 /// The I/O operation's timeout expired, causing it to be canceled.
153 #[stable(feature = "rust1", since = "1.0.0")]
155 /// An error returned when an operation could not be completed because a
156 /// call to [`write`] returned [`Ok(0)`].
158 /// This typically means that an operation could only succeed if it wrote a
159 /// particular number of bytes but only a smaller number of bytes could be
162 /// [`write`]: ../../std/io/trait.Write.html#tymethod.write
163 /// [`Ok(0)`]: ../../std/io/type.Result.html
164 #[stable(feature = "rust1", since = "1.0.0")]
166 /// This operation was interrupted.
168 /// Interrupted operations can typically be retried.
169 #[stable(feature = "rust1", since = "1.0.0")]
171 /// Any I/O error not part of this list.
172 #[stable(feature = "rust1", since = "1.0.0")]
175 /// An error returned when an operation could not be completed because an
176 /// "end of file" was reached prematurely.
178 /// This typically means that an operation could only succeed if it read a
179 /// particular number of bytes but only a smaller number of bytes could be
181 #[stable(feature = "read_exact", since = "1.6.0")]
184 /// A marker variant that tells the compiler that users of this enum cannot
185 /// match it exhaustively.
186 #[unstable(feature = "io_error_internals",
187 reason = "better expressed through extensible enums that this \
188 enum cannot be exhaustively matched against",
195 fn as_str(&self) -> &'static str {
197 ErrorKind::NotFound => "entity not found",
198 ErrorKind::PermissionDenied => "permission denied",
199 ErrorKind::ConnectionRefused => "connection refused",
200 ErrorKind::ConnectionReset => "connection reset",
201 ErrorKind::ConnectionAborted => "connection aborted",
202 ErrorKind::NotConnected => "not connected",
203 ErrorKind::AddrInUse => "address in use",
204 ErrorKind::AddrNotAvailable => "address not available",
205 ErrorKind::BrokenPipe => "broken pipe",
206 ErrorKind::AlreadyExists => "entity already exists",
207 ErrorKind::WouldBlock => "operation would block",
208 ErrorKind::InvalidInput => "invalid input parameter",
209 ErrorKind::InvalidData => "invalid data",
210 ErrorKind::TimedOut => "timed out",
211 ErrorKind::WriteZero => "write zero",
212 ErrorKind::Interrupted => "operation interrupted",
213 ErrorKind::Other => "other os error",
214 ErrorKind::UnexpectedEof => "unexpected end of file",
215 ErrorKind::__Nonexhaustive => unreachable!()
220 /// Intended for use for errors not exposed to the user, where allocating onto
221 /// the heap (for normal construction via Error::new) is too costly.
222 #[stable(feature = "io_error_from_errorkind", since = "1.14.0")]
223 impl From<ErrorKind> for Error {
225 fn from(kind: ErrorKind) -> Error {
227 repr: Repr::Simple(kind)
233 /// Creates a new I/O error from a known kind of error as well as an
234 /// arbitrary error payload.
236 /// This function is used to generically create I/O errors which do not
237 /// originate from the OS itself. The `error` argument is an arbitrary
238 /// payload which will be contained in this `Error`.
243 /// use std::io::{Error, ErrorKind};
245 /// // errors can be created from strings
246 /// let custom_error = Error::new(ErrorKind::Other, "oh no!");
248 /// // errors can also be created from other errors
249 /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
251 #[stable(feature = "rust1", since = "1.0.0")]
252 pub fn new<E>(kind: ErrorKind, error: E) -> Error
253 where E: Into<Box<dyn error::Error+Send+Sync>>
255 Self::_new(kind, error.into())
258 fn _new(kind: ErrorKind, error: Box<dyn error::Error+Send+Sync>) -> Error {
260 repr: Repr::Custom(Box::new(Custom {
267 /// Returns an error representing the last OS error which occurred.
269 /// This function reads the value of `errno` for the target platform (e.g.
270 /// `GetLastError` on Windows) and will return a corresponding instance of
271 /// `Error` for the error code.
276 /// use std::io::Error;
278 /// println!("last OS error: {:?}", Error::last_os_error());
280 #[stable(feature = "rust1", since = "1.0.0")]
281 pub fn last_os_error() -> Error {
282 Error::from_raw_os_error(sys::os::errno() as i32)
285 /// Creates a new instance of an `Error` from a particular OS error code.
292 /// # if cfg!(target_os = "linux") {
295 /// let error = io::Error::from_raw_os_error(22);
296 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
303 /// # if cfg!(windows) {
306 /// let error = io::Error::from_raw_os_error(10022);
307 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
310 #[stable(feature = "rust1", since = "1.0.0")]
311 pub fn from_raw_os_error(code: i32) -> Error {
312 Error { repr: Repr::Os(code) }
315 /// Returns the OS error that this error represents (if any).
317 /// If this `Error` was constructed via `last_os_error` or
318 /// `from_raw_os_error`, then this function will return `Some`, otherwise
319 /// it will return `None`.
324 /// use std::io::{Error, ErrorKind};
326 /// fn print_os_error(err: &Error) {
327 /// if let Some(raw_os_err) = err.raw_os_error() {
328 /// println!("raw OS error: {:?}", raw_os_err);
330 /// println!("Not an OS error");
335 /// // Will print "raw OS error: ...".
336 /// print_os_error(&Error::last_os_error());
337 /// // Will print "Not an OS error".
338 /// print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
341 #[stable(feature = "rust1", since = "1.0.0")]
342 pub fn raw_os_error(&self) -> Option<i32> {
344 Repr::Os(i) => Some(i),
345 Repr::Custom(..) => None,
346 Repr::Simple(..) => None,
350 /// Returns a reference to the inner error wrapped by this error (if any).
352 /// If this `Error` was constructed via `new` then this function will
353 /// return `Some`, otherwise it will return `None`.
358 /// use std::io::{Error, ErrorKind};
360 /// fn print_error(err: &Error) {
361 /// if let Some(inner_err) = err.get_ref() {
362 /// println!("Inner error: {:?}", inner_err);
364 /// println!("No inner error");
369 /// // Will print "No inner error".
370 /// print_error(&Error::last_os_error());
371 /// // Will print "Inner error: ...".
372 /// print_error(&Error::new(ErrorKind::Other, "oh no!"));
375 #[stable(feature = "io_error_inner", since = "1.3.0")]
376 pub fn get_ref(&self) -> Option<&(dyn error::Error+Send+Sync+'static)> {
378 Repr::Os(..) => None,
379 Repr::Simple(..) => None,
380 Repr::Custom(ref c) => Some(&*c.error),
384 /// Returns a mutable reference to the inner error wrapped by this error
387 /// If this `Error` was constructed via `new` then this function will
388 /// return `Some`, otherwise it will return `None`.
393 /// use std::io::{Error, ErrorKind};
394 /// use std::{error, fmt};
395 /// use std::fmt::Display;
403 /// fn new() -> MyError {
405 /// v: "oh no!".to_string()
409 /// fn change_message(&mut self, new_message: &str) {
410 /// self.v = new_message.to_string();
414 /// impl error::Error for MyError {
415 /// fn description(&self) -> &str { &self.v }
418 /// impl Display for MyError {
419 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
420 /// write!(f, "MyError: {}", &self.v)
424 /// fn change_error(mut err: Error) -> Error {
425 /// if let Some(inner_err) = err.get_mut() {
426 /// inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
431 /// fn print_error(err: &Error) {
432 /// if let Some(inner_err) = err.get_ref() {
433 /// println!("Inner error: {}", inner_err);
435 /// println!("No inner error");
440 /// // Will print "No inner error".
441 /// print_error(&change_error(Error::last_os_error()));
442 /// // Will print "Inner error: ...".
443 /// print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
446 #[stable(feature = "io_error_inner", since = "1.3.0")]
447 pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error+Send+Sync+'static)> {
449 Repr::Os(..) => None,
450 Repr::Simple(..) => None,
451 Repr::Custom(ref mut c) => Some(&mut *c.error),
455 /// Consumes the `Error`, returning its inner error (if any).
457 /// If this `Error` was constructed via `new` then this function will
458 /// return `Some`, otherwise it will return `None`.
463 /// use std::io::{Error, ErrorKind};
465 /// fn print_error(err: Error) {
466 /// if let Some(inner_err) = err.into_inner() {
467 /// println!("Inner error: {}", inner_err);
469 /// println!("No inner error");
474 /// // Will print "No inner error".
475 /// print_error(Error::last_os_error());
476 /// // Will print "Inner error: ...".
477 /// print_error(Error::new(ErrorKind::Other, "oh no!"));
480 #[stable(feature = "io_error_inner", since = "1.3.0")]
481 pub fn into_inner(self) -> Option<Box<dyn error::Error+Send+Sync>> {
483 Repr::Os(..) => None,
484 Repr::Simple(..) => None,
485 Repr::Custom(c) => Some(c.error)
489 /// Returns the corresponding `ErrorKind` for this error.
494 /// use std::io::{Error, ErrorKind};
496 /// fn print_error(err: Error) {
497 /// println!("{:?}", err.kind());
501 /// // Will print "No inner error".
502 /// print_error(Error::last_os_error());
503 /// // Will print "Inner error: ...".
504 /// print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
507 #[stable(feature = "rust1", since = "1.0.0")]
508 pub fn kind(&self) -> ErrorKind {
510 Repr::Os(code) => sys::decode_error_kind(code),
511 Repr::Custom(ref c) => c.kind,
512 Repr::Simple(kind) => kind,
517 impl fmt::Debug for Repr {
518 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
521 fmt.debug_struct("Os")
522 .field("code", &code)
523 .field("kind", &sys::decode_error_kind(code))
524 .field("message", &sys::os::error_string(code)).finish(),
525 Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
526 Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
531 #[stable(feature = "rust1", since = "1.0.0")]
532 impl fmt::Display for Error {
533 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
536 let detail = sys::os::error_string(code);
537 write!(fmt, "{} (os error {})", detail, code)
539 Repr::Custom(ref c) => c.error.fmt(fmt),
540 Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
545 #[stable(feature = "rust1", since = "1.0.0")]
546 impl error::Error for Error {
547 fn description(&self) -> &str {
549 Repr::Os(..) | Repr::Simple(..) => self.kind().as_str(),
550 Repr::Custom(ref c) => c.error.description(),
554 fn cause(&self) -> Option<&dyn error::Error> {
556 Repr::Os(..) => None,
557 Repr::Simple(..) => None,
558 Repr::Custom(ref c) => c.error.cause(),
563 fn _assert_error_is_sync_send() {
564 fn _is_sync_send<T: Sync+Send>() {}
565 _is_sync_send::<Error>();
570 use super::{Error, ErrorKind, Repr, Custom};
573 use sys::os::error_string;
574 use sys::decode_error_kind;
577 fn test_debug_error() {
579 let msg = error_string(code);
580 let kind = decode_error_kind(code);
582 repr: Repr::Custom(box Custom {
583 kind: ErrorKind::InvalidInput,
585 repr: super::Repr::Os(code)
589 let expected = format!(
591 kind: InvalidInput, \
600 assert_eq!(format!("{:?}", err), expected);
604 fn test_downcasting() {
608 impl fmt::Display for TestError {
609 fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
614 impl error::Error for TestError {
615 fn description(&self) -> &str {
620 // we have to call all of these UFCS style right now since method
621 // resolution won't implicitly drop the Send+Sync bounds
622 let mut err = Error::new(ErrorKind::Other, TestError);
623 assert!(err.get_ref().unwrap().is::<TestError>());
624 assert_eq!("asdf", err.get_ref().unwrap().description());
625 assert!(err.get_mut().unwrap().is::<TestError>());
626 let extracted = err.into_inner().unwrap();
627 extracted.downcast::<TestError>().unwrap();