4 use crate::convert::From;
10 /// A specialized [`Result`] type for I/O operations.
12 /// This type is broadly used across [`std::io`] for any operation which may
15 /// This typedef is generally used to avoid writing out [`io::Error`] directly and
16 /// is otherwise a direct mapping to [`Result`].
18 /// While usual Rust style is to import types directly, aliases of [`Result`]
19 /// often are not, to make it easier to distinguish between them. [`Result`] is
20 /// generally assumed to be [`std::result::Result`][`Result`], and so users of this alias
21 /// will generally use `io::Result` instead of shadowing the [prelude]'s import
22 /// of [`std::result::Result`][`Result`].
24 /// [`std::io`]: crate::io
25 /// [`io::Error`]: Error
26 /// [`Result`]: crate::result::Result
27 /// [prelude]: crate::prelude
31 /// A convenience function that bubbles an `io::Result` to its caller:
36 /// fn get_string() -> io::Result<String> {
37 /// let mut buffer = String::new();
39 /// io::stdin().read_line(&mut buffer)?;
44 #[stable(feature = "rust1", since = "1.0.0")]
45 pub type Result<T> = result::Result<T, Error>;
47 /// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and
48 /// associated traits.
50 /// Errors mostly originate from the underlying OS, but custom instances of
51 /// `Error` can be created with crafted error messages and a particular value of
54 /// [`Read`]: crate::io::Read
55 /// [`Write`]: crate::io::Write
56 /// [`Seek`]: crate::io::Seek
57 #[stable(feature = "rust1", since = "1.0.0")]
62 #[stable(feature = "rust1", since = "1.0.0")]
63 impl fmt::Debug for Error {
64 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
65 fmt::Debug::fmt(&self.repr, f)
72 // &str is a fat pointer, but &&str is a thin pointer.
73 SimpleMessage(ErrorKind, &'static &'static str),
80 error: Box<dyn error::Error + Send + Sync>,
83 /// A list specifying general categories of I/O error.
85 /// This list is intended to grow over time and it is not recommended to
86 /// exhaustively match against it.
88 /// It is used with the [`io::Error`] type.
90 /// [`io::Error`]: Error
91 #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
92 #[stable(feature = "rust1", since = "1.0.0")]
96 /// An entity was not found, often a file.
97 #[stable(feature = "rust1", since = "1.0.0")]
99 /// The operation lacked the necessary privileges to complete.
100 #[stable(feature = "rust1", since = "1.0.0")]
102 /// The connection was refused by the remote server.
103 #[stable(feature = "rust1", since = "1.0.0")]
105 /// The connection was reset by the remote server.
106 #[stable(feature = "rust1", since = "1.0.0")]
108 /// The connection was aborted (terminated) by the remote server.
109 #[stable(feature = "rust1", since = "1.0.0")]
111 /// The network operation failed because it was not connected yet.
112 #[stable(feature = "rust1", since = "1.0.0")]
114 /// A socket address could not be bound because the address is already in
116 #[stable(feature = "rust1", since = "1.0.0")]
118 /// A nonexistent interface was requested or the requested address was not
120 #[stable(feature = "rust1", since = "1.0.0")]
122 /// The operation failed because a pipe was closed.
123 #[stable(feature = "rust1", since = "1.0.0")]
125 /// An entity already exists, often a file.
126 #[stable(feature = "rust1", since = "1.0.0")]
128 /// The operation needs to block to complete, but the blocking operation was
129 /// requested to not occur.
130 #[stable(feature = "rust1", since = "1.0.0")]
132 /// A parameter was incorrect.
133 #[stable(feature = "rust1", since = "1.0.0")]
135 /// Data not valid for the operation were encountered.
137 /// Unlike [`InvalidInput`], this typically means that the operation
138 /// parameters were valid, however the error was caused by malformed
141 /// For example, a function that reads a file into a string will error with
142 /// `InvalidData` if the file's contents are not valid UTF-8.
144 /// [`InvalidInput`]: ErrorKind::InvalidInput
145 #[stable(feature = "io_invalid_data", since = "1.2.0")]
147 /// The I/O operation's timeout expired, causing it to be canceled.
148 #[stable(feature = "rust1", since = "1.0.0")]
150 /// An error returned when an operation could not be completed because a
151 /// call to [`write`] returned [`Ok(0)`].
153 /// This typically means that an operation could only succeed if it wrote a
154 /// particular number of bytes but only a smaller number of bytes could be
157 /// [`write`]: crate::io::Write::write
159 #[stable(feature = "rust1", since = "1.0.0")]
161 /// This operation was interrupted.
163 /// Interrupted operations can typically be retried.
164 #[stable(feature = "rust1", since = "1.0.0")]
166 /// Any I/O error not part of this list.
168 /// Errors that are `Other` now may move to a different or a new
169 /// [`ErrorKind`] variant in the future. It is not recommended to match
170 /// an error against `Other` and to expect any additional characteristics,
171 /// e.g., a specific [`Error::raw_os_error`] return value.
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 /// This operation is unsupported on this platform.
186 /// This means that the operation can never succeed.
187 #[stable(feature = "unsupported_error", since = "1.53.0")]
192 pub(crate) fn as_str(&self) -> &'static str {
194 ErrorKind::NotFound => "entity not found",
195 ErrorKind::PermissionDenied => "permission denied",
196 ErrorKind::ConnectionRefused => "connection refused",
197 ErrorKind::ConnectionReset => "connection reset",
198 ErrorKind::ConnectionAborted => "connection aborted",
199 ErrorKind::NotConnected => "not connected",
200 ErrorKind::AddrInUse => "address in use",
201 ErrorKind::AddrNotAvailable => "address not available",
202 ErrorKind::BrokenPipe => "broken pipe",
203 ErrorKind::AlreadyExists => "entity already exists",
204 ErrorKind::WouldBlock => "operation would block",
205 ErrorKind::InvalidInput => "invalid input parameter",
206 ErrorKind::InvalidData => "invalid data",
207 ErrorKind::TimedOut => "timed out",
208 ErrorKind::WriteZero => "write zero",
209 ErrorKind::Interrupted => "operation interrupted",
210 ErrorKind::Other => "other os error",
211 ErrorKind::UnexpectedEof => "unexpected end of file",
212 ErrorKind::Unsupported => "unsupported",
217 /// Intended for use for errors not exposed to the user, where allocating onto
218 /// the heap (for normal construction via Error::new) is too costly.
219 #[stable(feature = "io_error_from_errorkind", since = "1.14.0")]
220 impl From<ErrorKind> for Error {
221 /// Converts an [`ErrorKind`] into an [`Error`].
223 /// This conversion allocates a new error with a simple representation of error kind.
228 /// use std::io::{Error, ErrorKind};
230 /// let not_found = ErrorKind::NotFound;
231 /// let error = Error::from(not_found);
232 /// assert_eq!("entity not found", format!("{}", error));
235 fn from(kind: ErrorKind) -> Error {
236 Error { repr: Repr::Simple(kind) }
241 /// Creates a new I/O error from a known kind of error as well as an
242 /// arbitrary error payload.
244 /// This function is used to generically create I/O errors which do not
245 /// originate from the OS itself. The `error` argument is an arbitrary
246 /// payload which will be contained in this [`Error`].
251 /// use std::io::{Error, ErrorKind};
253 /// // errors can be created from strings
254 /// let custom_error = Error::new(ErrorKind::Other, "oh no!");
256 /// // errors can also be created from other errors
257 /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
259 #[stable(feature = "rust1", since = "1.0.0")]
260 pub fn new<E>(kind: ErrorKind, error: E) -> Error
262 E: Into<Box<dyn error::Error + Send + Sync>>,
264 Self::_new(kind, error.into())
267 fn _new(kind: ErrorKind, error: Box<dyn error::Error + Send + Sync>) -> Error {
268 Error { repr: Repr::Custom(Box::new(Custom { kind, error })) }
271 /// Creates a new I/O error from a known kind of error as well as a
272 /// constant message.
274 /// This function does not allocate.
276 /// This function should maybe change to
277 /// `new_const<const MSG: &'static str>(kind: ErrorKind)`
278 /// in the future, when const generics allow that.
280 pub(crate) const fn new_const(kind: ErrorKind, message: &'static &'static str) -> Error {
281 Self { repr: Repr::SimpleMessage(kind, message) }
284 /// Returns an error representing the last OS error which occurred.
286 /// This function reads the value of `errno` for the target platform (e.g.
287 /// `GetLastError` on Windows) and will return a corresponding instance of
288 /// [`Error`] for the error code.
293 /// use std::io::Error;
295 /// println!("last OS error: {:?}", Error::last_os_error());
297 #[stable(feature = "rust1", since = "1.0.0")]
299 pub fn last_os_error() -> Error {
300 Error::from_raw_os_error(sys::os::errno() as i32)
303 /// Creates a new instance of an [`Error`] from a particular OS error code.
310 /// # if cfg!(target_os = "linux") {
313 /// let error = io::Error::from_raw_os_error(22);
314 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
321 /// # if cfg!(windows) {
324 /// let error = io::Error::from_raw_os_error(10022);
325 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
328 #[stable(feature = "rust1", since = "1.0.0")]
330 pub fn from_raw_os_error(code: i32) -> Error {
331 Error { repr: Repr::Os(code) }
334 /// Returns the OS error that this error represents (if any).
336 /// If this [`Error`] was constructed via [`last_os_error`] or
337 /// [`from_raw_os_error`], then this function will return [`Some`], otherwise
338 /// it will return [`None`].
340 /// [`last_os_error`]: Error::last_os_error
341 /// [`from_raw_os_error`]: Error::from_raw_os_error
346 /// use std::io::{Error, ErrorKind};
348 /// fn print_os_error(err: &Error) {
349 /// if let Some(raw_os_err) = err.raw_os_error() {
350 /// println!("raw OS error: {:?}", raw_os_err);
352 /// println!("Not an OS error");
357 /// // Will print "raw OS error: ...".
358 /// print_os_error(&Error::last_os_error());
359 /// // Will print "Not an OS error".
360 /// print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
363 #[stable(feature = "rust1", since = "1.0.0")]
365 pub fn raw_os_error(&self) -> Option<i32> {
367 Repr::Os(i) => Some(i),
368 Repr::Custom(..) => None,
369 Repr::Simple(..) => None,
370 Repr::SimpleMessage(..) => None,
374 /// Returns a reference to the inner error wrapped by this error (if any).
376 /// If this [`Error`] was constructed via [`new`] then this function will
377 /// return [`Some`], otherwise it will return [`None`].
379 /// [`new`]: Error::new
384 /// use std::io::{Error, ErrorKind};
386 /// fn print_error(err: &Error) {
387 /// if let Some(inner_err) = err.get_ref() {
388 /// println!("Inner error: {:?}", inner_err);
390 /// println!("No inner error");
395 /// // Will print "No inner error".
396 /// print_error(&Error::last_os_error());
397 /// // Will print "Inner error: ...".
398 /// print_error(&Error::new(ErrorKind::Other, "oh no!"));
401 #[stable(feature = "io_error_inner", since = "1.3.0")]
403 pub fn get_ref(&self) -> Option<&(dyn error::Error + Send + Sync + 'static)> {
405 Repr::Os(..) => None,
406 Repr::Simple(..) => None,
407 Repr::SimpleMessage(..) => None,
408 Repr::Custom(ref c) => Some(&*c.error),
412 /// Returns a mutable reference to the inner error wrapped by this error
415 /// If this [`Error`] was constructed via [`new`] then this function will
416 /// return [`Some`], otherwise it will return [`None`].
418 /// [`new`]: Error::new
423 /// use std::io::{Error, ErrorKind};
424 /// use std::{error, fmt};
425 /// use std::fmt::Display;
433 /// fn new() -> MyError {
435 /// v: "oh no!".to_string()
439 /// fn change_message(&mut self, new_message: &str) {
440 /// self.v = new_message.to_string();
444 /// impl error::Error for MyError {}
446 /// impl Display for MyError {
447 /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
448 /// write!(f, "MyError: {}", &self.v)
452 /// fn change_error(mut err: Error) -> Error {
453 /// if let Some(inner_err) = err.get_mut() {
454 /// inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
459 /// fn print_error(err: &Error) {
460 /// if let Some(inner_err) = err.get_ref() {
461 /// println!("Inner error: {}", inner_err);
463 /// println!("No inner error");
468 /// // Will print "No inner error".
469 /// print_error(&change_error(Error::last_os_error()));
470 /// // Will print "Inner error: ...".
471 /// print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
474 #[stable(feature = "io_error_inner", since = "1.3.0")]
476 pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error + Send + Sync + 'static)> {
478 Repr::Os(..) => None,
479 Repr::Simple(..) => None,
480 Repr::SimpleMessage(..) => None,
481 Repr::Custom(ref mut c) => Some(&mut *c.error),
485 /// Consumes the `Error`, returning its inner error (if any).
487 /// If this [`Error`] was constructed via [`new`] then this function will
488 /// return [`Some`], otherwise it will return [`None`].
490 /// [`new`]: Error::new
495 /// use std::io::{Error, ErrorKind};
497 /// fn print_error(err: Error) {
498 /// if let Some(inner_err) = err.into_inner() {
499 /// println!("Inner error: {}", inner_err);
501 /// println!("No inner error");
506 /// // Will print "No inner error".
507 /// print_error(Error::last_os_error());
508 /// // Will print "Inner error: ...".
509 /// print_error(Error::new(ErrorKind::Other, "oh no!"));
512 #[stable(feature = "io_error_inner", since = "1.3.0")]
514 pub fn into_inner(self) -> Option<Box<dyn error::Error + Send + Sync>> {
516 Repr::Os(..) => None,
517 Repr::Simple(..) => None,
518 Repr::SimpleMessage(..) => None,
519 Repr::Custom(c) => Some(c.error),
523 /// Returns the corresponding [`ErrorKind`] for this error.
528 /// use std::io::{Error, ErrorKind};
530 /// fn print_error(err: Error) {
531 /// println!("{:?}", err.kind());
535 /// // Will print "Other".
536 /// print_error(Error::last_os_error());
537 /// // Will print "AddrInUse".
538 /// print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
541 #[stable(feature = "rust1", since = "1.0.0")]
543 pub fn kind(&self) -> ErrorKind {
545 Repr::Os(code) => sys::decode_error_kind(code),
546 Repr::Custom(ref c) => c.kind,
547 Repr::Simple(kind) => kind,
548 Repr::SimpleMessage(kind, _) => kind,
553 impl fmt::Debug for Repr {
554 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
556 Repr::Os(code) => fmt
558 .field("code", &code)
559 .field("kind", &sys::decode_error_kind(code))
560 .field("message", &sys::os::error_string(code))
562 Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
563 Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
564 Repr::SimpleMessage(kind, &message) => {
565 fmt.debug_struct("Error").field("kind", &kind).field("message", &message).finish()
571 #[stable(feature = "rust1", since = "1.0.0")]
572 impl fmt::Display for Error {
573 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
576 let detail = sys::os::error_string(code);
577 write!(fmt, "{} (os error {})", detail, code)
579 Repr::Custom(ref c) => c.error.fmt(fmt),
580 Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
581 Repr::SimpleMessage(_, &msg) => msg.fmt(fmt),
586 #[stable(feature = "rust1", since = "1.0.0")]
587 impl error::Error for Error {
588 #[allow(deprecated, deprecated_in_future)]
589 fn description(&self) -> &str {
591 Repr::Os(..) | Repr::Simple(..) => self.kind().as_str(),
592 Repr::SimpleMessage(_, &msg) => msg,
593 Repr::Custom(ref c) => c.error.description(),
598 fn cause(&self) -> Option<&dyn error::Error> {
600 Repr::Os(..) => None,
601 Repr::Simple(..) => None,
602 Repr::SimpleMessage(..) => None,
603 Repr::Custom(ref c) => c.error.cause(),
607 fn source(&self) -> Option<&(dyn error::Error + 'static)> {
609 Repr::Os(..) => None,
610 Repr::Simple(..) => None,
611 Repr::SimpleMessage(..) => None,
612 Repr::Custom(ref c) => c.error.source(),
617 fn _assert_error_is_sync_send() {
618 fn _is_sync_send<T: Sync + Send>() {}
619 _is_sync_send::<Error>();