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")]
102 /// An entity was not found, often a file.
103 #[stable(feature = "rust1", since = "1.0.0")]
105 /// The operation lacked the necessary privileges to complete.
106 #[stable(feature = "rust1", since = "1.0.0")]
108 /// The connection was refused by the remote server.
109 #[stable(feature = "rust1", since = "1.0.0")]
111 /// The connection was reset by the remote server.
112 #[stable(feature = "rust1", since = "1.0.0")]
114 /// The connection was aborted (terminated) by the remote server.
115 #[stable(feature = "rust1", since = "1.0.0")]
117 /// The network operation failed because it was not connected yet.
118 #[stable(feature = "rust1", since = "1.0.0")]
120 /// A socket address could not be bound because the address is already in
122 #[stable(feature = "rust1", since = "1.0.0")]
124 /// A nonexistent interface was requested or the requested address was not
126 #[stable(feature = "rust1", since = "1.0.0")]
128 /// The operation failed because a pipe was closed.
129 #[stable(feature = "rust1", since = "1.0.0")]
131 /// An entity already exists, often a file.
132 #[stable(feature = "rust1", since = "1.0.0")]
134 /// The operation needs to block to complete, but the blocking operation was
135 /// requested to not occur.
136 #[stable(feature = "rust1", since = "1.0.0")]
138 /// A parameter was incorrect.
139 #[stable(feature = "rust1", since = "1.0.0")]
141 /// Data not valid for the operation were encountered.
143 /// Unlike [`InvalidInput`], this typically means that the operation
144 /// parameters were valid, however the error was caused by malformed
147 /// For example, a function that reads a file into a string will error with
148 /// `InvalidData` if the file's contents are not valid UTF-8.
150 /// [`InvalidInput`]: #variant.InvalidInput
151 #[stable(feature = "io_invalid_data", since = "1.2.0")]
153 /// The I/O operation's timeout expired, causing it to be canceled.
154 #[stable(feature = "rust1", since = "1.0.0")]
156 /// An error returned when an operation could not be completed because a
157 /// call to [`write`] returned [`Ok(0)`].
159 /// This typically means that an operation could only succeed if it wrote a
160 /// particular number of bytes but only a smaller number of bytes could be
163 /// [`write`]: ../../std/io/trait.Write.html#tymethod.write
164 /// [`Ok(0)`]: ../../std/io/type.Result.html
165 #[stable(feature = "rust1", since = "1.0.0")]
167 /// This operation was interrupted.
169 /// Interrupted operations can typically be retried.
170 #[stable(feature = "rust1", since = "1.0.0")]
172 /// Any I/O error not part of this list.
173 #[stable(feature = "rust1", since = "1.0.0")]
176 /// An error returned when an operation could not be completed because an
177 /// "end of file" was reached prematurely.
179 /// This typically means that an operation could only succeed if it read a
180 /// particular number of bytes but only a smaller number of bytes could be
182 #[stable(feature = "read_exact", since = "1.6.0")]
187 fn as_str(&self) -> &'static str {
189 ErrorKind::NotFound => "entity not found",
190 ErrorKind::PermissionDenied => "permission denied",
191 ErrorKind::ConnectionRefused => "connection refused",
192 ErrorKind::ConnectionReset => "connection reset",
193 ErrorKind::ConnectionAborted => "connection aborted",
194 ErrorKind::NotConnected => "not connected",
195 ErrorKind::AddrInUse => "address in use",
196 ErrorKind::AddrNotAvailable => "address not available",
197 ErrorKind::BrokenPipe => "broken pipe",
198 ErrorKind::AlreadyExists => "entity already exists",
199 ErrorKind::WouldBlock => "operation would block",
200 ErrorKind::InvalidInput => "invalid input parameter",
201 ErrorKind::InvalidData => "invalid data",
202 ErrorKind::TimedOut => "timed out",
203 ErrorKind::WriteZero => "write zero",
204 ErrorKind::Interrupted => "operation interrupted",
205 ErrorKind::Other => "other os error",
206 ErrorKind::UnexpectedEof => "unexpected end of file",
211 /// Intended for use for errors not exposed to the user, where allocating onto
212 /// the heap (for normal construction via Error::new) is too costly.
213 #[stable(feature = "io_error_from_errorkind", since = "1.14.0")]
214 impl From<ErrorKind> for Error {
215 /// Converts a [`ErrorKind`] into a [`Error`].
217 /// This conversion allocates a new error with a simple representation of error kind.
222 /// use std::io::{Error, ErrorKind};
224 /// let not_found = ErrorKind::NotFound;
225 /// let error = Error::from(not_found);
226 /// assert_eq!("entity not found", format!("{}", error));
229 fn from(kind: ErrorKind) -> Error {
231 repr: Repr::Simple(kind)
237 /// Creates a new I/O error from a known kind of error as well as an
238 /// arbitrary error payload.
240 /// This function is used to generically create I/O errors which do not
241 /// originate from the OS itself. The `error` argument is an arbitrary
242 /// payload which will be contained in this `Error`.
247 /// use std::io::{Error, ErrorKind};
249 /// // errors can be created from strings
250 /// let custom_error = Error::new(ErrorKind::Other, "oh no!");
252 /// // errors can also be created from other errors
253 /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
255 #[stable(feature = "rust1", since = "1.0.0")]
256 pub fn new<E>(kind: ErrorKind, error: E) -> Error
257 where E: Into<Box<dyn error::Error+Send+Sync>>
259 Self::_new(kind, error.into())
262 fn _new(kind: ErrorKind, error: Box<dyn error::Error+Send+Sync>) -> Error {
264 repr: Repr::Custom(Box::new(Custom {
271 /// Returns an error representing the last OS error which occurred.
273 /// This function reads the value of `errno` for the target platform (e.g.
274 /// `GetLastError` on Windows) and will return a corresponding instance of
275 /// `Error` for the error code.
280 /// use std::io::Error;
282 /// println!("last OS error: {:?}", Error::last_os_error());
284 #[stable(feature = "rust1", since = "1.0.0")]
285 pub fn last_os_error() -> Error {
286 Error::from_raw_os_error(sys::os::errno() as i32)
289 /// Creates a new instance of an `Error` from a particular OS error code.
296 /// # if cfg!(target_os = "linux") {
299 /// let error = io::Error::from_raw_os_error(22);
300 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
307 /// # if cfg!(windows) {
310 /// let error = io::Error::from_raw_os_error(10022);
311 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
314 #[stable(feature = "rust1", since = "1.0.0")]
315 pub fn from_raw_os_error(code: i32) -> Error {
316 Error { repr: Repr::Os(code) }
319 /// Returns the OS error that this error represents (if any).
321 /// If this `Error` was constructed via `last_os_error` or
322 /// `from_raw_os_error`, then this function will return `Some`, otherwise
323 /// it will return `None`.
328 /// use std::io::{Error, ErrorKind};
330 /// fn print_os_error(err: &Error) {
331 /// if let Some(raw_os_err) = err.raw_os_error() {
332 /// println!("raw OS error: {:?}", raw_os_err);
334 /// println!("Not an OS error");
339 /// // Will print "raw OS error: ...".
340 /// print_os_error(&Error::last_os_error());
341 /// // Will print "Not an OS error".
342 /// print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
345 #[stable(feature = "rust1", since = "1.0.0")]
346 pub fn raw_os_error(&self) -> Option<i32> {
348 Repr::Os(i) => Some(i),
349 Repr::Custom(..) => None,
350 Repr::Simple(..) => None,
354 /// Returns a reference to the inner error wrapped by this error (if any).
356 /// If this `Error` was constructed via `new` then this function will
357 /// return `Some`, otherwise it will return `None`.
362 /// use std::io::{Error, ErrorKind};
364 /// fn print_error(err: &Error) {
365 /// if let Some(inner_err) = err.get_ref() {
366 /// println!("Inner error: {:?}", inner_err);
368 /// println!("No inner error");
373 /// // Will print "No inner error".
374 /// print_error(&Error::last_os_error());
375 /// // Will print "Inner error: ...".
376 /// print_error(&Error::new(ErrorKind::Other, "oh no!"));
379 #[stable(feature = "io_error_inner", since = "1.3.0")]
380 pub fn get_ref(&self) -> Option<&(dyn error::Error+Send+Sync+'static)> {
382 Repr::Os(..) => None,
383 Repr::Simple(..) => None,
384 Repr::Custom(ref c) => Some(&*c.error),
388 /// Returns a mutable reference to the inner error wrapped by this error
391 /// If this `Error` was constructed via `new` then this function will
392 /// return `Some`, otherwise it will return `None`.
397 /// use std::io::{Error, ErrorKind};
398 /// use std::{error, fmt};
399 /// use std::fmt::Display;
407 /// fn new() -> MyError {
409 /// v: "oh no!".to_string()
413 /// fn change_message(&mut self, new_message: &str) {
414 /// self.v = new_message.to_string();
418 /// impl error::Error for MyError {
419 /// fn description(&self) -> &str { &self.v }
422 /// impl Display for MyError {
423 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
424 /// write!(f, "MyError: {}", &self.v)
428 /// fn change_error(mut err: Error) -> Error {
429 /// if let Some(inner_err) = err.get_mut() {
430 /// inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
435 /// fn print_error(err: &Error) {
436 /// if let Some(inner_err) = err.get_ref() {
437 /// println!("Inner error: {}", inner_err);
439 /// println!("No inner error");
444 /// // Will print "No inner error".
445 /// print_error(&change_error(Error::last_os_error()));
446 /// // Will print "Inner error: ...".
447 /// print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
450 #[stable(feature = "io_error_inner", since = "1.3.0")]
451 pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error+Send+Sync+'static)> {
453 Repr::Os(..) => None,
454 Repr::Simple(..) => None,
455 Repr::Custom(ref mut c) => Some(&mut *c.error),
459 /// Consumes the `Error`, returning its inner error (if any).
461 /// If this `Error` was constructed via `new` then this function will
462 /// return `Some`, otherwise it will return `None`.
467 /// use std::io::{Error, ErrorKind};
469 /// fn print_error(err: Error) {
470 /// if let Some(inner_err) = err.into_inner() {
471 /// println!("Inner error: {}", inner_err);
473 /// println!("No inner error");
478 /// // Will print "No inner error".
479 /// print_error(Error::last_os_error());
480 /// // Will print "Inner error: ...".
481 /// print_error(Error::new(ErrorKind::Other, "oh no!"));
484 #[stable(feature = "io_error_inner", since = "1.3.0")]
485 pub fn into_inner(self) -> Option<Box<dyn error::Error+Send+Sync>> {
487 Repr::Os(..) => None,
488 Repr::Simple(..) => None,
489 Repr::Custom(c) => Some(c.error)
493 /// Returns the corresponding `ErrorKind` for this error.
498 /// use std::io::{Error, ErrorKind};
500 /// fn print_error(err: Error) {
501 /// println!("{:?}", err.kind());
505 /// // Will print "No inner error".
506 /// print_error(Error::last_os_error());
507 /// // Will print "Inner error: ...".
508 /// print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
511 #[stable(feature = "rust1", since = "1.0.0")]
512 pub fn kind(&self) -> ErrorKind {
514 Repr::Os(code) => sys::decode_error_kind(code),
515 Repr::Custom(ref c) => c.kind,
516 Repr::Simple(kind) => kind,
521 impl fmt::Debug for Repr {
522 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
525 fmt.debug_struct("Os")
526 .field("code", &code)
527 .field("kind", &sys::decode_error_kind(code))
528 .field("message", &sys::os::error_string(code)).finish(),
529 Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
530 Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
535 #[stable(feature = "rust1", since = "1.0.0")]
536 impl fmt::Display for Error {
537 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
540 let detail = sys::os::error_string(code);
541 write!(fmt, "{} (os error {})", detail, code)
543 Repr::Custom(ref c) => c.error.fmt(fmt),
544 Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
549 #[stable(feature = "rust1", since = "1.0.0")]
550 impl error::Error for Error {
551 fn description(&self) -> &str {
553 Repr::Os(..) | Repr::Simple(..) => self.kind().as_str(),
554 Repr::Custom(ref c) => c.error.description(),
558 fn cause(&self) -> Option<&dyn error::Error> {
560 Repr::Os(..) => None,
561 Repr::Simple(..) => None,
562 Repr::Custom(ref c) => c.error.cause(),
567 fn _assert_error_is_sync_send() {
568 fn _is_sync_send<T: Sync+Send>() {}
569 _is_sync_send::<Error>();
574 use super::{Error, ErrorKind, Repr, Custom};
577 use sys::os::error_string;
578 use sys::decode_error_kind;
581 fn test_debug_error() {
583 let msg = error_string(code);
584 let kind = decode_error_kind(code);
586 repr: Repr::Custom(box Custom {
587 kind: ErrorKind::InvalidInput,
589 repr: super::Repr::Os(code)
593 let expected = format!(
595 kind: InvalidInput, \
604 assert_eq!(format!("{:?}", err), expected);
608 fn test_downcasting() {
612 impl fmt::Display for TestError {
613 fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
618 impl error::Error for TestError {
619 fn description(&self) -> &str {
624 // we have to call all of these UFCS style right now since method
625 // resolution won't implicitly drop the Send+Sync bounds
626 let mut err = Error::new(ErrorKind::Other, TestError);
627 assert!(err.get_ref().unwrap().is::<TestError>());
628 assert_eq!("asdf", err.get_ref().unwrap().description());
629 assert!(err.get_mut().unwrap().is::<TestError>());
630 let extracted = err.into_inner().unwrap();
631 extracted.downcast::<TestError>().unwrap();