5 use crate::convert::From;
7 /// A specialized [`Result`](../result/enum.Result.html) type for I/O
10 /// This type is broadly used across [`std::io`] for any operation which may
13 /// This typedef is generally used to avoid writing out [`io::Error`] directly and
14 /// is otherwise a direct mapping to [`Result`].
16 /// While usual Rust style is to import types directly, aliases of [`Result`]
17 /// often are not, to make it easier to distinguish between them. [`Result`] is
18 /// generally assumed to be [`std::result::Result`][`Result`], and so users of this alias
19 /// will generally use `io::Result` instead of shadowing the prelude's import
20 /// of [`std::result::Result`][`Result`].
22 /// [`std::io`]: ../io/index.html
23 /// [`io::Error`]: ../io/struct.Error.html
24 /// [`Result`]: ../result/enum.Result.html
28 /// A convenience function that bubbles an `io::Result` to its caller:
33 /// fn get_string() -> io::Result<String> {
34 /// let mut buffer = String::new();
36 /// io::stdin().read_line(&mut buffer)?;
41 #[stable(feature = "rust1", since = "1.0.0")]
42 pub type Result<T> = result::Result<T, Error>;
44 /// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and
45 /// associated traits.
47 /// Errors mostly originate from the underlying OS, but custom instances of
48 /// `Error` can be created with crafted error messages and a particular value of
51 /// [`Read`]: ../io/trait.Read.html
52 /// [`Write`]: ../io/trait.Write.html
53 /// [`Seek`]: ../io/trait.Seek.html
54 /// [`ErrorKind`]: enum.ErrorKind.html
55 #[stable(feature = "rust1", since = "1.0.0")]
60 #[stable(feature = "rust1", since = "1.0.0")]
61 impl fmt::Debug for Error {
62 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
63 fmt::Debug::fmt(&self.repr, f)
76 error: Box<dyn error::Error+Send+Sync>,
79 /// A list specifying general categories of I/O error.
81 /// This list is intended to grow over time and it is not recommended to
82 /// exhaustively match against it.
84 /// It is used with the [`io::Error`] type.
86 /// [`io::Error`]: struct.Error.html
87 #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
88 #[stable(feature = "rust1", since = "1.0.0")]
92 /// An entity was not found, often a file.
93 #[stable(feature = "rust1", since = "1.0.0")]
95 /// The operation lacked the necessary privileges to complete.
96 #[stable(feature = "rust1", since = "1.0.0")]
98 /// The connection was refused by the remote server.
99 #[stable(feature = "rust1", since = "1.0.0")]
101 /// The connection was reset by the remote server.
102 #[stable(feature = "rust1", since = "1.0.0")]
104 /// The connection was aborted (terminated) by the remote server.
105 #[stable(feature = "rust1", since = "1.0.0")]
107 /// The network operation failed because it was not connected yet.
108 #[stable(feature = "rust1", since = "1.0.0")]
110 /// A socket address could not be bound because the address is already in
112 #[stable(feature = "rust1", since = "1.0.0")]
114 /// A nonexistent interface was requested or the requested address was not
116 #[stable(feature = "rust1", since = "1.0.0")]
118 /// The operation failed because a pipe was closed.
119 #[stable(feature = "rust1", since = "1.0.0")]
121 /// An entity already exists, often a file.
122 #[stable(feature = "rust1", since = "1.0.0")]
124 /// The operation needs to block to complete, but the blocking operation was
125 /// requested to not occur.
126 #[stable(feature = "rust1", since = "1.0.0")]
128 /// A parameter was incorrect.
129 #[stable(feature = "rust1", since = "1.0.0")]
131 /// Data not valid for the operation were encountered.
133 /// Unlike [`InvalidInput`], this typically means that the operation
134 /// parameters were valid, however the error was caused by malformed
137 /// For example, a function that reads a file into a string will error with
138 /// `InvalidData` if the file's contents are not valid UTF-8.
140 /// [`InvalidInput`]: #variant.InvalidInput
141 #[stable(feature = "io_invalid_data", since = "1.2.0")]
143 /// The I/O operation's timeout expired, causing it to be canceled.
144 #[stable(feature = "rust1", since = "1.0.0")]
146 /// An error returned when an operation could not be completed because a
147 /// call to [`write`] returned [`Ok(0)`].
149 /// This typically means that an operation could only succeed if it wrote a
150 /// particular number of bytes but only a smaller number of bytes could be
153 /// [`write`]: ../../std/io/trait.Write.html#tymethod.write
154 /// [`Ok(0)`]: ../../std/io/type.Result.html
155 #[stable(feature = "rust1", since = "1.0.0")]
157 /// This operation was interrupted.
159 /// Interrupted operations can typically be retried.
160 #[stable(feature = "rust1", since = "1.0.0")]
162 /// Any I/O error not part of this list.
163 #[stable(feature = "rust1", since = "1.0.0")]
166 /// An error returned when an operation could not be completed because an
167 /// "end of file" was reached prematurely.
169 /// This typically means that an operation could only succeed if it read a
170 /// particular number of bytes but only a smaller number of bytes could be
172 #[stable(feature = "read_exact", since = "1.6.0")]
177 pub(crate) fn as_str(&self) -> &'static str {
179 ErrorKind::NotFound => "entity not found",
180 ErrorKind::PermissionDenied => "permission denied",
181 ErrorKind::ConnectionRefused => "connection refused",
182 ErrorKind::ConnectionReset => "connection reset",
183 ErrorKind::ConnectionAborted => "connection aborted",
184 ErrorKind::NotConnected => "not connected",
185 ErrorKind::AddrInUse => "address in use",
186 ErrorKind::AddrNotAvailable => "address not available",
187 ErrorKind::BrokenPipe => "broken pipe",
188 ErrorKind::AlreadyExists => "entity already exists",
189 ErrorKind::WouldBlock => "operation would block",
190 ErrorKind::InvalidInput => "invalid input parameter",
191 ErrorKind::InvalidData => "invalid data",
192 ErrorKind::TimedOut => "timed out",
193 ErrorKind::WriteZero => "write zero",
194 ErrorKind::Interrupted => "operation interrupted",
195 ErrorKind::Other => "other os error",
196 ErrorKind::UnexpectedEof => "unexpected end of file",
201 /// Intended for use for errors not exposed to the user, where allocating onto
202 /// the heap (for normal construction via Error::new) is too costly.
203 #[stable(feature = "io_error_from_errorkind", since = "1.14.0")]
204 impl From<ErrorKind> for Error {
205 /// Converts an [`ErrorKind`] into an [`Error`].
207 /// This conversion allocates a new error with a simple representation of error kind.
212 /// use std::io::{Error, ErrorKind};
214 /// let not_found = ErrorKind::NotFound;
215 /// let error = Error::from(not_found);
216 /// assert_eq!("entity not found", format!("{}", error));
219 /// [`ErrorKind`]: ../../std/io/enum.ErrorKind.html
220 /// [`Error`]: ../../std/io/struct.Error.html
222 fn from(kind: ErrorKind) -> Error {
224 repr: Repr::Simple(kind)
230 /// Creates a new I/O error from a known kind of error as well as an
231 /// arbitrary error payload.
233 /// This function is used to generically create I/O errors which do not
234 /// originate from the OS itself. The `error` argument is an arbitrary
235 /// payload which will be contained in this `Error`.
240 /// use std::io::{Error, ErrorKind};
242 /// // errors can be created from strings
243 /// let custom_error = Error::new(ErrorKind::Other, "oh no!");
245 /// // errors can also be created from other errors
246 /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
248 #[stable(feature = "rust1", since = "1.0.0")]
249 pub fn new<E>(kind: ErrorKind, error: E) -> Error
250 where E: Into<Box<dyn error::Error+Send+Sync>>
252 Self::_new(kind, error.into())
255 fn _new(kind: ErrorKind, error: Box<dyn error::Error+Send+Sync>) -> Error {
257 repr: Repr::Custom(Box::new(Custom {
264 /// Returns an error representing the last OS error which occurred.
266 /// This function reads the value of `errno` for the target platform (e.g.
267 /// `GetLastError` on Windows) and will return a corresponding instance of
268 /// `Error` for the error code.
273 /// use std::io::Error;
275 /// println!("last OS error: {:?}", Error::last_os_error());
277 #[stable(feature = "rust1", since = "1.0.0")]
278 pub fn last_os_error() -> Error {
279 Error::from_raw_os_error(sys::os::errno() as i32)
282 /// Creates a new instance of an `Error` from a particular OS error code.
289 /// # if cfg!(target_os = "linux") {
292 /// let error = io::Error::from_raw_os_error(22);
293 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
300 /// # if cfg!(windows) {
303 /// let error = io::Error::from_raw_os_error(10022);
304 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
307 #[stable(feature = "rust1", since = "1.0.0")]
308 pub fn from_raw_os_error(code: i32) -> Error {
309 Error { repr: Repr::Os(code) }
312 /// Returns the OS error that this error represents (if any).
314 /// If this `Error` was constructed via `last_os_error` or
315 /// `from_raw_os_error`, then this function will return `Some`, otherwise
316 /// it will return `None`.
321 /// use std::io::{Error, ErrorKind};
323 /// fn print_os_error(err: &Error) {
324 /// if let Some(raw_os_err) = err.raw_os_error() {
325 /// println!("raw OS error: {:?}", raw_os_err);
327 /// println!("Not an OS error");
332 /// // Will print "raw OS error: ...".
333 /// print_os_error(&Error::last_os_error());
334 /// // Will print "Not an OS error".
335 /// print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
338 #[stable(feature = "rust1", since = "1.0.0")]
339 pub fn raw_os_error(&self) -> Option<i32> {
341 Repr::Os(i) => Some(i),
342 Repr::Custom(..) => None,
343 Repr::Simple(..) => None,
347 /// Returns a reference to the inner error wrapped by this error (if any).
349 /// If this `Error` was constructed via `new` then this function will
350 /// return `Some`, otherwise it will return `None`.
355 /// use std::io::{Error, ErrorKind};
357 /// fn print_error(err: &Error) {
358 /// if let Some(inner_err) = err.get_ref() {
359 /// println!("Inner error: {:?}", inner_err);
361 /// println!("No inner error");
366 /// // Will print "No inner error".
367 /// print_error(&Error::last_os_error());
368 /// // Will print "Inner error: ...".
369 /// print_error(&Error::new(ErrorKind::Other, "oh no!"));
372 #[stable(feature = "io_error_inner", since = "1.3.0")]
373 pub fn get_ref(&self) -> Option<&(dyn error::Error+Send+Sync+'static)> {
375 Repr::Os(..) => None,
376 Repr::Simple(..) => None,
377 Repr::Custom(ref c) => Some(&*c.error),
381 /// Returns a mutable reference to the inner error wrapped by this error
384 /// If this `Error` was constructed via `new` then this function will
385 /// return `Some`, otherwise it will return `None`.
390 /// use std::io::{Error, ErrorKind};
391 /// use std::{error, fmt};
392 /// use std::fmt::Display;
400 /// fn new() -> MyError {
402 /// v: "oh no!".to_string()
406 /// fn change_message(&mut self, new_message: &str) {
407 /// self.v = new_message.to_string();
411 /// impl error::Error for MyError {
412 /// fn description(&self) -> &str { &self.v }
415 /// impl Display for MyError {
416 /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
417 /// write!(f, "MyError: {}", &self.v)
421 /// fn change_error(mut err: Error) -> Error {
422 /// if let Some(inner_err) = err.get_mut() {
423 /// inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
428 /// fn print_error(err: &Error) {
429 /// if let Some(inner_err) = err.get_ref() {
430 /// println!("Inner error: {}", inner_err);
432 /// println!("No inner error");
437 /// // Will print "No inner error".
438 /// print_error(&change_error(Error::last_os_error()));
439 /// // Will print "Inner error: ...".
440 /// print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
443 #[stable(feature = "io_error_inner", since = "1.3.0")]
444 pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error+Send+Sync+'static)> {
446 Repr::Os(..) => None,
447 Repr::Simple(..) => None,
448 Repr::Custom(ref mut c) => Some(&mut *c.error),
452 /// Consumes the `Error`, returning its inner error (if any).
454 /// If this `Error` was constructed via `new` then this function will
455 /// return `Some`, otherwise it will return `None`.
460 /// use std::io::{Error, ErrorKind};
462 /// fn print_error(err: Error) {
463 /// if let Some(inner_err) = err.into_inner() {
464 /// println!("Inner error: {}", inner_err);
466 /// println!("No inner error");
471 /// // Will print "No inner error".
472 /// print_error(Error::last_os_error());
473 /// // Will print "Inner error: ...".
474 /// print_error(Error::new(ErrorKind::Other, "oh no!"));
477 #[stable(feature = "io_error_inner", since = "1.3.0")]
478 pub fn into_inner(self) -> Option<Box<dyn error::Error+Send+Sync>> {
480 Repr::Os(..) => None,
481 Repr::Simple(..) => None,
482 Repr::Custom(c) => Some(c.error)
486 /// Returns the corresponding `ErrorKind` for this error.
491 /// use std::io::{Error, ErrorKind};
493 /// fn print_error(err: Error) {
494 /// println!("{:?}", err.kind());
498 /// // Will print "No inner error".
499 /// print_error(Error::last_os_error());
500 /// // Will print "Inner error: ...".
501 /// print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
504 #[stable(feature = "rust1", since = "1.0.0")]
505 pub fn kind(&self) -> ErrorKind {
507 Repr::Os(code) => sys::decode_error_kind(code),
508 Repr::Custom(ref c) => c.kind,
509 Repr::Simple(kind) => kind,
514 impl fmt::Debug for Repr {
515 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
518 fmt.debug_struct("Os")
519 .field("code", &code)
520 .field("kind", &sys::decode_error_kind(code))
521 .field("message", &sys::os::error_string(code)).finish(),
522 Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
523 Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
528 #[stable(feature = "rust1", since = "1.0.0")]
529 impl fmt::Display for Error {
530 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
533 let detail = sys::os::error_string(code);
534 write!(fmt, "{} (os error {})", detail, code)
536 Repr::Custom(ref c) => c.error.fmt(fmt),
537 Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
542 #[stable(feature = "rust1", since = "1.0.0")]
543 impl error::Error for Error {
544 fn description(&self) -> &str {
546 Repr::Os(..) | Repr::Simple(..) => self.kind().as_str(),
547 Repr::Custom(ref c) => c.error.description(),
552 fn cause(&self) -> Option<&dyn error::Error> {
554 Repr::Os(..) => None,
555 Repr::Simple(..) => None,
556 Repr::Custom(ref c) => c.error.cause(),
560 fn source(&self) -> Option<&(dyn error::Error + 'static)> {
562 Repr::Os(..) => None,
563 Repr::Simple(..) => None,
564 Repr::Custom(ref c) => c.error.source(),
569 fn _assert_error_is_sync_send() {
570 fn _is_sync_send<T: Sync+Send>() {}
571 _is_sync_send::<Error>();
576 use super::{Error, ErrorKind, Repr, Custom};
579 use crate::sys::os::error_string;
580 use crate::sys::decode_error_kind;
583 fn test_debug_error() {
585 let msg = error_string(code);
586 let kind = decode_error_kind(code);
588 repr: Repr::Custom(box Custom {
589 kind: ErrorKind::InvalidInput,
591 repr: super::Repr::Os(code)
595 let expected = format!(
597 kind: InvalidInput, \
606 assert_eq!(format!("{:?}", err), expected);
610 fn test_downcasting() {
614 impl fmt::Display for TestError {
615 fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result {
620 impl error::Error for TestError {
621 fn description(&self) -> &str {
626 // we have to call all of these UFCS style right now since method
627 // resolution won't implicitly drop the Send+Sync bounds
628 let mut err = Error::new(ErrorKind::Other, TestError);
629 assert!(err.get_ref().unwrap().is::<TestError>());
630 assert_eq!("asdf", err.get_ref().unwrap().description());
631 assert!(err.get_mut().unwrap().is::<TestError>());
632 let extracted = err.into_inner().unwrap();
633 extracted.downcast::<TestError>().unwrap();