1#[cfg(test)]
2mod tests;
3
4#[cfg(all(target_pointer_width = "64", not(target_os = "uefi")))]
5mod repr_bitpacked;
6#[cfg(all(target_pointer_width = "64", not(target_os = "uefi")))]
7use repr_bitpacked::Repr;
8
9#[cfg(any(not(target_pointer_width = "64"), target_os = "uefi"))]
10mod repr_unpacked;
11#[cfg(any(not(target_pointer_width = "64"), target_os = "uefi"))]
12use repr_unpacked::Repr;
13
14use crate::{error, fmt, result, sys};
15
16/// A specialized [`Result`] type for I/O operations.
17///
18/// This type is broadly used across [`std::io`] for any operation which may
19/// produce an error.
20///
21/// This typedef is generally used to avoid writing out [`io::Error`] directly and
22/// is otherwise a direct mapping to [`Result`].
23///
24/// While usual Rust style is to import types directly, aliases of [`Result`]
25/// often are not, to make it easier to distinguish between them. [`Result`] is
26/// generally assumed to be [`std::result::Result`][`Result`], and so users of this alias
27/// will generally use `io::Result` instead of shadowing the [prelude]'s import
28/// of [`std::result::Result`][`Result`].
29///
30/// [`std::io`]: crate::io
31/// [`io::Error`]: Error
32/// [`Result`]: crate::result::Result
33/// [prelude]: crate::prelude
34///
35/// # Examples
36///
37/// A convenience function that bubbles an `io::Result` to its caller:
38///
39/// ```
40/// use std::io;
41///
42/// fn get_string() -> io::Result<String> {
43/// let mut buffer = String::new();
44///
45/// io::stdin().read_line(&mut buffer)?;
46///
47/// Ok(buffer)
48/// }
49/// ```
50#[stable(feature = "rust1", since = "1.0.0")]
51pub type Result<T> = result::Result<T, Error>;
52
53/// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and
54/// associated traits.
55///
56/// Errors mostly originate from the underlying OS, but custom instances of
57/// `Error` can be created with crafted error messages and a particular value of
58/// [`ErrorKind`].
59///
60/// [`Read`]: crate::io::Read
61/// [`Write`]: crate::io::Write
62/// [`Seek`]: crate::io::Seek
63#[stable(feature = "rust1", since = "1.0.0")]
64pub struct Error {
65 repr: Repr,
66}
67
68#[stable(feature = "rust1", since = "1.0.0")]
69impl fmt::Debug for Error {
70 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
71 fmt::Debug::fmt(&self.repr, f)
72 }
73}
74
75/// Common errors constants for use in std
76#[allow(dead_code)]
77impl Error {
78 pub(crate) const INVALID_UTF8: Self =
79 const_error!(ErrorKind::InvalidData, "stream did not contain valid UTF-8");
80
81 pub(crate) const READ_EXACT_EOF: Self =
82 const_error!(ErrorKind::UnexpectedEof, "failed to fill whole buffer");
83
84 pub(crate) const UNKNOWN_THREAD_COUNT: Self = const_error!(
85 ErrorKind::NotFound,
86 "the number of hardware threads is not known for the target platform",
87 );
88
89 pub(crate) const UNSUPPORTED_PLATFORM: Self =
90 const_error!(ErrorKind::Unsupported, "operation not supported on this platform");
91
92 pub(crate) const WRITE_ALL_EOF: Self =
93 const_error!(ErrorKind::WriteZero, "failed to write whole buffer");
94
95 pub(crate) const ZERO_TIMEOUT: Self =
96 const_error!(ErrorKind::InvalidInput, "cannot set a 0 duration timeout");
97}
98
99#[stable(feature = "rust1", since = "1.0.0")]
100impl From<alloc::ffi::NulError> for Error {
101 /// Converts a [`alloc::ffi::NulError`] into a [`Error`].
102 fn from(_: alloc::ffi::NulError) -> Error {
103 const_error!(ErrorKind::InvalidInput, "data provided contains a nul byte")
104 }
105}
106
107#[stable(feature = "io_error_from_try_reserve", since = "1.78.0")]
108impl From<alloc::collections::TryReserveError> for Error {
109 /// Converts `TryReserveError` to an error with [`ErrorKind::OutOfMemory`].
110 ///
111 /// `TryReserveError` won't be available as the error `source()`,
112 /// but this may change in the future.
113 fn from(_: alloc::collections::TryReserveError) -> Error {
114 // ErrorData::Custom allocates, which isn't great for handling OOM errors.
115 ErrorKind::OutOfMemory.into()
116 }
117}
118
119// Only derive debug in tests, to make sure it
120// doesn't accidentally get printed.
121#[cfg_attr(test, derive(Debug))]
122enum ErrorData<C> {
123 Os(RawOsError),
124 Simple(ErrorKind),
125 SimpleMessage(&'static SimpleMessage),
126 Custom(C),
127}
128
129/// The type of raw OS error codes returned by [`Error::raw_os_error`].
130///
131/// This is an [`i32`] on all currently supported platforms, but platforms
132/// added in the future (such as UEFI) may use a different primitive type like
133/// [`usize`]. Use `as`or [`into`] conversions where applicable to ensure maximum
134/// portability.
135///
136/// [`into`]: Into::into
137#[unstable(feature = "raw_os_error_ty", issue = "107792")]
138pub type RawOsError = sys::RawOsError;
139
140// `#[repr(align(4))]` is probably redundant, it should have that value or
141// higher already. We include it just because repr_bitpacked.rs's encoding
142// requires an alignment >= 4 (note that `#[repr(align)]` will not reduce the
143// alignment required by the struct, only increase it).
144//
145// If we add more variants to ErrorData, this can be increased to 8, but it
146// should probably be behind `#[cfg_attr(target_pointer_width = "64", ...)]` or
147// whatever cfg we're using to enable the `repr_bitpacked` code, since only the
148// that version needs the alignment, and 8 is higher than the alignment we'll
149// have on 32 bit platforms.
150//
151// (For the sake of being explicit: the alignment requirement here only matters
152// if `error/repr_bitpacked.rs` is in use — for the unpacked repr it doesn't
153// matter at all)
154#[doc(hidden)]
155#[unstable(feature = "io_const_error_internals", issue = "none")]
156#[repr(align(4))]
157#[derive(Debug)]
158pub struct SimpleMessage {
159 pub kind: ErrorKind,
160 pub message: &'static str,
161}
162
163/// Creates a new I/O error from a known kind of error and a string literal.
164///
165/// Contrary to [`Error::new`], this macro does not allocate and can be used in
166/// `const` contexts.
167///
168/// # Example
169/// ```
170/// #![feature(io_const_error)]
171/// use std::io::{const_error, Error, ErrorKind};
172///
173/// const FAIL: Error = const_error!(ErrorKind::Unsupported, "tried something that never works");
174///
175/// fn not_here() -> Result<(), Error> {
176/// Err(FAIL)
177/// }
178/// ```
179#[rustc_macro_transparency = "semitransparent"]
180#[unstable(feature = "io_const_error", issue = "133448")]
181#[allow_internal_unstable(hint_must_use, io_const_error_internals)]
182pub macro const_error($kind:expr, $message:expr $(,)?) {
183 $crate::hint::must_use($crate::io::Error::from_static_message(
184 const { &$crate::io::SimpleMessage { kind: $kind, message: $message } },
185 ))
186}
187
188// As with `SimpleMessage`: `#[repr(align(4))]` here is just because
189// repr_bitpacked's encoding requires it. In practice it almost certainly be
190// already be this high or higher.
191#[derive(Debug)]
192#[repr(align(4))]
193struct Custom {
194 kind: ErrorKind,
195 error: Box<dyn error::Error + Send + Sync>,
196}
197
198/// A list specifying general categories of I/O error.
199///
200/// This list is intended to grow over time and it is not recommended to
201/// exhaustively match against it.
202///
203/// It is used with the [`io::Error`] type.
204///
205/// [`io::Error`]: Error
206///
207/// # Handling errors and matching on `ErrorKind`
208///
209/// In application code, use `match` for the `ErrorKind` values you are
210/// expecting; use `_` to match "all other errors".
211///
212/// In comprehensive and thorough tests that want to verify that a test doesn't
213/// return any known incorrect error kind, you may want to cut-and-paste the
214/// current full list of errors from here into your test code, and then match
215/// `_` as the correct case. This seems counterintuitive, but it will make your
216/// tests more robust. In particular, if you want to verify that your code does
217/// produce an unrecognized error kind, the robust solution is to check for all
218/// the recognized error kinds and fail in those cases.
219#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
220#[stable(feature = "rust1", since = "1.0.0")]
221#[allow(deprecated)]
222#[non_exhaustive]
223pub enum ErrorKind {
224 /// An entity was not found, often a file.
225 #[stable(feature = "rust1", since = "1.0.0")]
226 NotFound,
227 /// The operation lacked the necessary privileges to complete.
228 #[stable(feature = "rust1", since = "1.0.0")]
229 PermissionDenied,
230 /// The connection was refused by the remote server.
231 #[stable(feature = "rust1", since = "1.0.0")]
232 ConnectionRefused,
233 /// The connection was reset by the remote server.
234 #[stable(feature = "rust1", since = "1.0.0")]
235 ConnectionReset,
236 /// The remote host is not reachable.
237 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
238 HostUnreachable,
239 /// The network containing the remote host is not reachable.
240 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
241 NetworkUnreachable,
242 /// The connection was aborted (terminated) by the remote server.
243 #[stable(feature = "rust1", since = "1.0.0")]
244 ConnectionAborted,
245 /// The network operation failed because it was not connected yet.
246 #[stable(feature = "rust1", since = "1.0.0")]
247 NotConnected,
248 /// A socket address could not be bound because the address is already in
249 /// use elsewhere.
250 #[stable(feature = "rust1", since = "1.0.0")]
251 AddrInUse,
252 /// A nonexistent interface was requested or the requested address was not
253 /// local.
254 #[stable(feature = "rust1", since = "1.0.0")]
255 AddrNotAvailable,
256 /// The system's networking is down.
257 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
258 NetworkDown,
259 /// The operation failed because a pipe was closed.
260 #[stable(feature = "rust1", since = "1.0.0")]
261 BrokenPipe,
262 /// An entity already exists, often a file.
263 #[stable(feature = "rust1", since = "1.0.0")]
264 AlreadyExists,
265 /// The operation needs to block to complete, but the blocking operation was
266 /// requested to not occur.
267 #[stable(feature = "rust1", since = "1.0.0")]
268 WouldBlock,
269 /// A filesystem object is, unexpectedly, not a directory.
270 ///
271 /// For example, a filesystem path was specified where one of the intermediate directory
272 /// components was, in fact, a plain file.
273 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
274 NotADirectory,
275 /// The filesystem object is, unexpectedly, a directory.
276 ///
277 /// A directory was specified when a non-directory was expected.
278 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
279 IsADirectory,
280 /// A non-empty directory was specified where an empty directory was expected.
281 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
282 DirectoryNotEmpty,
283 /// The filesystem or storage medium is read-only, but a write operation was attempted.
284 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
285 ReadOnlyFilesystem,
286 /// Loop in the filesystem or IO subsystem; often, too many levels of symbolic links.
287 ///
288 /// There was a loop (or excessively long chain) resolving a filesystem object
289 /// or file IO object.
290 ///
291 /// On Unix this is usually the result of a symbolic link loop; or, of exceeding the
292 /// system-specific limit on the depth of symlink traversal.
293 #[unstable(feature = "io_error_more", issue = "86442")]
294 FilesystemLoop,
295 /// Stale network file handle.
296 ///
297 /// With some network filesystems, notably NFS, an open file (or directory) can be invalidated
298 /// by problems with the network or server.
299 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
300 StaleNetworkFileHandle,
301 /// A parameter was incorrect.
302 #[stable(feature = "rust1", since = "1.0.0")]
303 InvalidInput,
304 /// Data not valid for the operation were encountered.
305 ///
306 /// Unlike [`InvalidInput`], this typically means that the operation
307 /// parameters were valid, however the error was caused by malformed
308 /// input data.
309 ///
310 /// For example, a function that reads a file into a string will error with
311 /// `InvalidData` if the file's contents are not valid UTF-8.
312 ///
313 /// [`InvalidInput`]: ErrorKind::InvalidInput
314 #[stable(feature = "io_invalid_data", since = "1.2.0")]
315 InvalidData,
316 /// The I/O operation's timeout expired, causing it to be canceled.
317 #[stable(feature = "rust1", since = "1.0.0")]
318 TimedOut,
319 /// An error returned when an operation could not be completed because a
320 /// call to [`write`] returned [`Ok(0)`].
321 ///
322 /// This typically means that an operation could only succeed if it wrote a
323 /// particular number of bytes but only a smaller number of bytes could be
324 /// written.
325 ///
326 /// [`write`]: crate::io::Write::write
327 /// [`Ok(0)`]: Ok
328 #[stable(feature = "rust1", since = "1.0.0")]
329 WriteZero,
330 /// The underlying storage (typically, a filesystem) is full.
331 ///
332 /// This does not include out of quota errors.
333 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
334 StorageFull,
335 /// Seek on unseekable file.
336 ///
337 /// Seeking was attempted on an open file handle which is not suitable for seeking - for
338 /// example, on Unix, a named pipe opened with `File::open`.
339 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
340 NotSeekable,
341 /// Filesystem quota or some other kind of quota was exceeded.
342 #[stable(feature = "io_error_quota_exceeded", since = "1.85.0")]
343 QuotaExceeded,
344 /// File larger than allowed or supported.
345 ///
346 /// This might arise from a hard limit of the underlying filesystem or file access API, or from
347 /// an administratively imposed resource limitation. Simple disk full, and out of quota, have
348 /// their own errors.
349 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
350 FileTooLarge,
351 /// Resource is busy.
352 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
353 ResourceBusy,
354 /// Executable file is busy.
355 ///
356 /// An attempt was made to write to a file which is also in use as a running program. (Not all
357 /// operating systems detect this situation.)
358 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
359 ExecutableFileBusy,
360 /// Deadlock (avoided).
361 ///
362 /// A file locking operation would result in deadlock. This situation is typically detected, if
363 /// at all, on a best-effort basis.
364 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
365 Deadlock,
366 /// Cross-device or cross-filesystem (hard) link or rename.
367 #[stable(feature = "io_error_crosses_devices", since = "1.85.0")]
368 CrossesDevices,
369 /// Too many (hard) links to the same filesystem object.
370 ///
371 /// The filesystem does not support making so many hardlinks to the same file.
372 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
373 TooManyLinks,
374 /// A filename was invalid.
375 ///
376 /// This error can also occur if a length limit for a name was exceeded.
377 #[stable(feature = "io_error_invalid_filename", since = "1.87.0")]
378 InvalidFilename,
379 /// Program argument list too long.
380 ///
381 /// When trying to run an external program, a system or process limit on the size of the
382 /// arguments would have been exceeded.
383 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
384 ArgumentListTooLong,
385 /// This operation was interrupted.
386 ///
387 /// Interrupted operations can typically be retried.
388 #[stable(feature = "rust1", since = "1.0.0")]
389 Interrupted,
390
391 /// This operation is unsupported on this platform.
392 ///
393 /// This means that the operation can never succeed.
394 #[stable(feature = "unsupported_error", since = "1.53.0")]
395 Unsupported,
396
397 // ErrorKinds which are primarily categorisations for OS error
398 // codes should be added above.
399 //
400 /// An error returned when an operation could not be completed because an
401 /// "end of file" was reached prematurely.
402 ///
403 /// This typically means that an operation could only succeed if it read a
404 /// particular number of bytes but only a smaller number of bytes could be
405 /// read.
406 #[stable(feature = "read_exact", since = "1.6.0")]
407 UnexpectedEof,
408
409 /// An operation could not be completed, because it failed
410 /// to allocate enough memory.
411 #[stable(feature = "out_of_memory_error", since = "1.54.0")]
412 OutOfMemory,
413
414 /// The operation was partially successful and needs to be checked
415 /// later on due to not blocking.
416 #[unstable(feature = "io_error_inprogress", issue = "130840")]
417 InProgress,
418
419 // "Unusual" error kinds which do not correspond simply to (sets
420 // of) OS error codes, should be added just above this comment.
421 // `Other` and `Uncategorized` should remain at the end:
422 //
423 /// A custom error that does not fall under any other I/O error kind.
424 ///
425 /// This can be used to construct your own [`Error`]s that do not match any
426 /// [`ErrorKind`].
427 ///
428 /// This [`ErrorKind`] is not used by the standard library.
429 ///
430 /// Errors from the standard library that do not fall under any of the I/O
431 /// error kinds cannot be `match`ed on, and will only match a wildcard (`_`) pattern.
432 /// New [`ErrorKind`]s might be added in the future for some of those.
433 #[stable(feature = "rust1", since = "1.0.0")]
434 Other,
435
436 /// Any I/O error from the standard library that's not part of this list.
437 ///
438 /// Errors that are `Uncategorized` now may move to a different or a new
439 /// [`ErrorKind`] variant in the future. It is not recommended to match
440 /// an error against `Uncategorized`; use a wildcard match (`_`) instead.
441 #[unstable(feature = "io_error_uncategorized", issue = "none")]
442 #[doc(hidden)]
443 Uncategorized,
444}
445
446impl ErrorKind {
447 pub(crate) fn as_str(&self) -> &'static str {
448 use ErrorKind::*;
449 match *self {
450 // tidy-alphabetical-start
451 AddrInUse => "address in use",
452 AddrNotAvailable => "address not available",
453 AlreadyExists => "entity already exists",
454 ArgumentListTooLong => "argument list too long",
455 BrokenPipe => "broken pipe",
456 ConnectionAborted => "connection aborted",
457 ConnectionRefused => "connection refused",
458 ConnectionReset => "connection reset",
459 CrossesDevices => "cross-device link or rename",
460 Deadlock => "deadlock",
461 DirectoryNotEmpty => "directory not empty",
462 ExecutableFileBusy => "executable file busy",
463 FilesystemLoop => "filesystem loop or indirection limit (e.g. symlink loop)",
464 FileTooLarge => "file too large",
465 HostUnreachable => "host unreachable",
466 InProgress => "in progress",
467 Interrupted => "operation interrupted",
468 InvalidData => "invalid data",
469 InvalidFilename => "invalid filename",
470 InvalidInput => "invalid input parameter",
471 IsADirectory => "is a directory",
472 NetworkDown => "network down",
473 NetworkUnreachable => "network unreachable",
474 NotADirectory => "not a directory",
475 NotConnected => "not connected",
476 NotFound => "entity not found",
477 NotSeekable => "seek on unseekable file",
478 Other => "other error",
479 OutOfMemory => "out of memory",
480 PermissionDenied => "permission denied",
481 QuotaExceeded => "quota exceeded",
482 ReadOnlyFilesystem => "read-only filesystem or storage medium",
483 ResourceBusy => "resource busy",
484 StaleNetworkFileHandle => "stale network file handle",
485 StorageFull => "no storage space",
486 TimedOut => "timed out",
487 TooManyLinks => "too many links",
488 Uncategorized => "uncategorized error",
489 UnexpectedEof => "unexpected end of file",
490 Unsupported => "unsupported",
491 WouldBlock => "operation would block",
492 WriteZero => "write zero",
493 // tidy-alphabetical-end
494 }
495 }
496}
497
498#[stable(feature = "io_errorkind_display", since = "1.60.0")]
499impl fmt::Display for ErrorKind {
500 /// Shows a human-readable description of the `ErrorKind`.
501 ///
502 /// This is similar to `impl Display for Error`, but doesn't require first converting to Error.
503 ///
504 /// # Examples
505 /// ```
506 /// use std::io::ErrorKind;
507 /// assert_eq!("entity not found", ErrorKind::NotFound.to_string());
508 /// ```
509 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
510 fmt.write_str(self.as_str())
511 }
512}
513
514/// Intended for use for errors not exposed to the user, where allocating onto
515/// the heap (for normal construction via Error::new) is too costly.
516#[stable(feature = "io_error_from_errorkind", since = "1.14.0")]
517impl From<ErrorKind> for Error {
518 /// Converts an [`ErrorKind`] into an [`Error`].
519 ///
520 /// This conversion creates a new error with a simple representation of error kind.
521 ///
522 /// # Examples
523 ///
524 /// ```
525 /// use std::io::{Error, ErrorKind};
526 ///
527 /// let not_found = ErrorKind::NotFound;
528 /// let error = Error::from(not_found);
529 /// assert_eq!("entity not found", format!("{error}"));
530 /// ```
531 #[inline]
532 fn from(kind: ErrorKind) -> Error {
533 Error { repr: Repr::new_simple(kind) }
534 }
535}
536
537impl Error {
538 /// Creates a new I/O error from a known kind of error as well as an
539 /// arbitrary error payload.
540 ///
541 /// This function is used to generically create I/O errors which do not
542 /// originate from the OS itself. The `error` argument is an arbitrary
543 /// payload which will be contained in this [`Error`].
544 ///
545 /// Note that this function allocates memory on the heap.
546 /// If no extra payload is required, use the `From` conversion from
547 /// `ErrorKind`.
548 ///
549 /// # Examples
550 ///
551 /// ```
552 /// use std::io::{Error, ErrorKind};
553 ///
554 /// // errors can be created from strings
555 /// let custom_error = Error::new(ErrorKind::Other, "oh no!");
556 ///
557 /// // errors can also be created from other errors
558 /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
559 ///
560 /// // creating an error without payload (and without memory allocation)
561 /// let eof_error = Error::from(ErrorKind::UnexpectedEof);
562 /// ```
563 #[stable(feature = "rust1", since = "1.0.0")]
564 #[inline(never)]
565 pub fn new<E>(kind: ErrorKind, error: E) -> Error
566 where
567 E: Into<Box<dyn error::Error + Send + Sync>>,
568 {
569 Self::_new(kind, error.into())
570 }
571
572 /// Creates a new I/O error from an arbitrary error payload.
573 ///
574 /// This function is used to generically create I/O errors which do not
575 /// originate from the OS itself. It is a shortcut for [`Error::new`]
576 /// with [`ErrorKind::Other`].
577 ///
578 /// # Examples
579 ///
580 /// ```
581 /// use std::io::Error;
582 ///
583 /// // errors can be created from strings
584 /// let custom_error = Error::other("oh no!");
585 ///
586 /// // errors can also be created from other errors
587 /// let custom_error2 = Error::other(custom_error);
588 /// ```
589 #[stable(feature = "io_error_other", since = "1.74.0")]
590 pub fn other<E>(error: E) -> Error
591 where
592 E: Into<Box<dyn error::Error + Send + Sync>>,
593 {
594 Self::_new(ErrorKind::Other, error.into())
595 }
596
597 fn _new(kind: ErrorKind, error: Box<dyn error::Error + Send + Sync>) -> Error {
598 Error { repr: Repr::new_custom(Box::new(Custom { kind, error })) }
599 }
600
601 /// Creates a new I/O error from a known kind of error as well as a constant
602 /// message.
603 ///
604 /// This function does not allocate.
605 ///
606 /// You should not use this directly, and instead use the `const_error!`
607 /// macro: `io::const_error!(ErrorKind::Something, "some_message")`.
608 ///
609 /// This function should maybe change to `from_static_message<const MSG: &'static
610 /// str>(kind: ErrorKind)` in the future, when const generics allow that.
611 #[inline]
612 #[doc(hidden)]
613 #[unstable(feature = "io_const_error_internals", issue = "none")]
614 pub const fn from_static_message(msg: &'static SimpleMessage) -> Error {
615 Self { repr: Repr::new_simple_message(msg) }
616 }
617
618 /// Returns an error representing the last OS error which occurred.
619 ///
620 /// This function reads the value of `errno` for the target platform (e.g.
621 /// `GetLastError` on Windows) and will return a corresponding instance of
622 /// [`Error`] for the error code.
623 ///
624 /// This should be called immediately after a call to a platform function,
625 /// otherwise the state of the error value is indeterminate. In particular,
626 /// other standard library functions may call platform functions that may
627 /// (or may not) reset the error value even if they succeed.
628 ///
629 /// # Examples
630 ///
631 /// ```
632 /// use std::io::Error;
633 ///
634 /// let os_error = Error::last_os_error();
635 /// println!("last OS error: {os_error:?}");
636 /// ```
637 #[stable(feature = "rust1", since = "1.0.0")]
638 #[doc(alias = "GetLastError")]
639 #[doc(alias = "errno")]
640 #[must_use]
641 #[inline]
642 pub fn last_os_error() -> Error {
643 Error::from_raw_os_error(sys::os::errno())
644 }
645
646 /// Creates a new instance of an [`Error`] from a particular OS error code.
647 ///
648 /// # Examples
649 ///
650 /// On Linux:
651 ///
652 /// ```
653 /// # if cfg!(target_os = "linux") {
654 /// use std::io;
655 ///
656 /// let error = io::Error::from_raw_os_error(22);
657 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
658 /// # }
659 /// ```
660 ///
661 /// On Windows:
662 ///
663 /// ```
664 /// # if cfg!(windows) {
665 /// use std::io;
666 ///
667 /// let error = io::Error::from_raw_os_error(10022);
668 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
669 /// # }
670 /// ```
671 #[stable(feature = "rust1", since = "1.0.0")]
672 #[must_use]
673 #[inline]
674 pub fn from_raw_os_error(code: RawOsError) -> Error {
675 Error { repr: Repr::new_os(code) }
676 }
677
678 /// Returns the OS error that this error represents (if any).
679 ///
680 /// If this [`Error`] was constructed via [`last_os_error`] or
681 /// [`from_raw_os_error`], then this function will return [`Some`], otherwise
682 /// it will return [`None`].
683 ///
684 /// [`last_os_error`]: Error::last_os_error
685 /// [`from_raw_os_error`]: Error::from_raw_os_error
686 ///
687 /// # Examples
688 ///
689 /// ```
690 /// use std::io::{Error, ErrorKind};
691 ///
692 /// fn print_os_error(err: &Error) {
693 /// if let Some(raw_os_err) = err.raw_os_error() {
694 /// println!("raw OS error: {raw_os_err:?}");
695 /// } else {
696 /// println!("Not an OS error");
697 /// }
698 /// }
699 ///
700 /// fn main() {
701 /// // Will print "raw OS error: ...".
702 /// print_os_error(&Error::last_os_error());
703 /// // Will print "Not an OS error".
704 /// print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
705 /// }
706 /// ```
707 #[stable(feature = "rust1", since = "1.0.0")]
708 #[must_use]
709 #[inline]
710 pub fn raw_os_error(&self) -> Option<RawOsError> {
711 match self.repr.data() {
712 ErrorData::Os(i) => Some(i),
713 ErrorData::Custom(..) => None,
714 ErrorData::Simple(..) => None,
715 ErrorData::SimpleMessage(..) => None,
716 }
717 }
718
719 /// Returns a reference to the inner error wrapped by this error (if any).
720 ///
721 /// If this [`Error`] was constructed via [`new`] then this function will
722 /// return [`Some`], otherwise it will return [`None`].
723 ///
724 /// [`new`]: Error::new
725 ///
726 /// # Examples
727 ///
728 /// ```
729 /// use std::io::{Error, ErrorKind};
730 ///
731 /// fn print_error(err: &Error) {
732 /// if let Some(inner_err) = err.get_ref() {
733 /// println!("Inner error: {inner_err:?}");
734 /// } else {
735 /// println!("No inner error");
736 /// }
737 /// }
738 ///
739 /// fn main() {
740 /// // Will print "No inner error".
741 /// print_error(&Error::last_os_error());
742 /// // Will print "Inner error: ...".
743 /// print_error(&Error::new(ErrorKind::Other, "oh no!"));
744 /// }
745 /// ```
746 #[stable(feature = "io_error_inner", since = "1.3.0")]
747 #[must_use]
748 #[inline]
749 pub fn get_ref(&self) -> Option<&(dyn error::Error + Send + Sync + 'static)> {
750 match self.repr.data() {
751 ErrorData::Os(..) => None,
752 ErrorData::Simple(..) => None,
753 ErrorData::SimpleMessage(..) => None,
754 ErrorData::Custom(c) => Some(&*c.error),
755 }
756 }
757
758 /// Returns a mutable reference to the inner error wrapped by this error
759 /// (if any).
760 ///
761 /// If this [`Error`] was constructed via [`new`] then this function will
762 /// return [`Some`], otherwise it will return [`None`].
763 ///
764 /// [`new`]: Error::new
765 ///
766 /// # Examples
767 ///
768 /// ```
769 /// use std::io::{Error, ErrorKind};
770 /// use std::{error, fmt};
771 /// use std::fmt::Display;
772 ///
773 /// #[derive(Debug)]
774 /// struct MyError {
775 /// v: String,
776 /// }
777 ///
778 /// impl MyError {
779 /// fn new() -> MyError {
780 /// MyError {
781 /// v: "oh no!".to_string()
782 /// }
783 /// }
784 ///
785 /// fn change_message(&mut self, new_message: &str) {
786 /// self.v = new_message.to_string();
787 /// }
788 /// }
789 ///
790 /// impl error::Error for MyError {}
791 ///
792 /// impl Display for MyError {
793 /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
794 /// write!(f, "MyError: {}", self.v)
795 /// }
796 /// }
797 ///
798 /// fn change_error(mut err: Error) -> Error {
799 /// if let Some(inner_err) = err.get_mut() {
800 /// inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
801 /// }
802 /// err
803 /// }
804 ///
805 /// fn print_error(err: &Error) {
806 /// if let Some(inner_err) = err.get_ref() {
807 /// println!("Inner error: {inner_err}");
808 /// } else {
809 /// println!("No inner error");
810 /// }
811 /// }
812 ///
813 /// fn main() {
814 /// // Will print "No inner error".
815 /// print_error(&change_error(Error::last_os_error()));
816 /// // Will print "Inner error: ...".
817 /// print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
818 /// }
819 /// ```
820 #[stable(feature = "io_error_inner", since = "1.3.0")]
821 #[must_use]
822 #[inline]
823 pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error + Send + Sync + 'static)> {
824 match self.repr.data_mut() {
825 ErrorData::Os(..) => None,
826 ErrorData::Simple(..) => None,
827 ErrorData::SimpleMessage(..) => None,
828 ErrorData::Custom(c) => Some(&mut *c.error),
829 }
830 }
831
832 /// Consumes the `Error`, returning its inner error (if any).
833 ///
834 /// If this [`Error`] was constructed via [`new`] or [`other`],
835 /// then this function will return [`Some`],
836 /// otherwise it will return [`None`].
837 ///
838 /// [`new`]: Error::new
839 /// [`other`]: Error::other
840 ///
841 /// # Examples
842 ///
843 /// ```
844 /// use std::io::{Error, ErrorKind};
845 ///
846 /// fn print_error(err: Error) {
847 /// if let Some(inner_err) = err.into_inner() {
848 /// println!("Inner error: {inner_err}");
849 /// } else {
850 /// println!("No inner error");
851 /// }
852 /// }
853 ///
854 /// fn main() {
855 /// // Will print "No inner error".
856 /// print_error(Error::last_os_error());
857 /// // Will print "Inner error: ...".
858 /// print_error(Error::new(ErrorKind::Other, "oh no!"));
859 /// }
860 /// ```
861 #[stable(feature = "io_error_inner", since = "1.3.0")]
862 #[must_use = "`self` will be dropped if the result is not used"]
863 #[inline]
864 pub fn into_inner(self) -> Option<Box<dyn error::Error + Send + Sync>> {
865 match self.repr.into_data() {
866 ErrorData::Os(..) => None,
867 ErrorData::Simple(..) => None,
868 ErrorData::SimpleMessage(..) => None,
869 ErrorData::Custom(c) => Some(c.error),
870 }
871 }
872
873 /// Attempts to downcast the custom boxed error to `E`.
874 ///
875 /// If this [`Error`] contains a custom boxed error,
876 /// then it would attempt downcasting on the boxed error,
877 /// otherwise it will return [`Err`].
878 ///
879 /// If the custom boxed error has the same type as `E`, it will return [`Ok`],
880 /// otherwise it will also return [`Err`].
881 ///
882 /// This method is meant to be a convenience routine for calling
883 /// `Box<dyn Error + Sync + Send>::downcast` on the custom boxed error, returned by
884 /// [`Error::into_inner`].
885 ///
886 ///
887 /// # Examples
888 ///
889 /// ```
890 /// use std::fmt;
891 /// use std::io;
892 /// use std::error::Error;
893 ///
894 /// #[derive(Debug)]
895 /// enum E {
896 /// Io(io::Error),
897 /// SomeOtherVariant,
898 /// }
899 ///
900 /// impl fmt::Display for E {
901 /// // ...
902 /// # fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
903 /// # todo!()
904 /// # }
905 /// }
906 /// impl Error for E {}
907 ///
908 /// impl From<io::Error> for E {
909 /// fn from(err: io::Error) -> E {
910 /// err.downcast::<E>()
911 /// .unwrap_or_else(E::Io)
912 /// }
913 /// }
914 ///
915 /// impl From<E> for io::Error {
916 /// fn from(err: E) -> io::Error {
917 /// match err {
918 /// E::Io(io_error) => io_error,
919 /// e => io::Error::new(io::ErrorKind::Other, e),
920 /// }
921 /// }
922 /// }
923 ///
924 /// # fn main() {
925 /// let e = E::SomeOtherVariant;
926 /// // Convert it to an io::Error
927 /// let io_error = io::Error::from(e);
928 /// // Cast it back to the original variant
929 /// let e = E::from(io_error);
930 /// assert!(matches!(e, E::SomeOtherVariant));
931 ///
932 /// let io_error = io::Error::from(io::ErrorKind::AlreadyExists);
933 /// // Convert it to E
934 /// let e = E::from(io_error);
935 /// // Cast it back to the original variant
936 /// let io_error = io::Error::from(e);
937 /// assert_eq!(io_error.kind(), io::ErrorKind::AlreadyExists);
938 /// assert!(io_error.get_ref().is_none());
939 /// assert!(io_error.raw_os_error().is_none());
940 /// # }
941 /// ```
942 #[stable(feature = "io_error_downcast", since = "1.79.0")]
943 pub fn downcast<E>(self) -> result::Result<E, Self>
944 where
945 E: error::Error + Send + Sync + 'static,
946 {
947 match self.repr.into_data() {
948 ErrorData::Custom(b) if b.error.is::<E>() => {
949 let res = (*b).error.downcast::<E>();
950
951 // downcast is a really trivial and is marked as inline, so
952 // it's likely be inlined here.
953 //
954 // And the compiler should be able to eliminate the branch
955 // that produces `Err` here since b.error.is::<E>()
956 // returns true.
957 Ok(*res.unwrap())
958 }
959 repr_data => Err(Self { repr: Repr::new(repr_data) }),
960 }
961 }
962
963 /// Returns the corresponding [`ErrorKind`] for this error.
964 ///
965 /// This may be a value set by Rust code constructing custom `io::Error`s,
966 /// or if this `io::Error` was sourced from the operating system,
967 /// it will be a value inferred from the system's error encoding.
968 /// See [`last_os_error`] for more details.
969 ///
970 /// [`last_os_error`]: Error::last_os_error
971 ///
972 /// # Examples
973 ///
974 /// ```
975 /// use std::io::{Error, ErrorKind};
976 ///
977 /// fn print_error(err: Error) {
978 /// println!("{:?}", err.kind());
979 /// }
980 ///
981 /// fn main() {
982 /// // As no error has (visibly) occurred, this may print anything!
983 /// // It likely prints a placeholder for unidentified (non-)errors.
984 /// print_error(Error::last_os_error());
985 /// // Will print "AddrInUse".
986 /// print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
987 /// }
988 /// ```
989 #[stable(feature = "rust1", since = "1.0.0")]
990 #[must_use]
991 #[inline]
992 pub fn kind(&self) -> ErrorKind {
993 match self.repr.data() {
994 ErrorData::Os(code) => sys::decode_error_kind(code),
995 ErrorData::Custom(c) => c.kind,
996 ErrorData::Simple(kind) => kind,
997 ErrorData::SimpleMessage(m) => m.kind,
998 }
999 }
1000
1001 #[inline]
1002 pub(crate) fn is_interrupted(&self) -> bool {
1003 match self.repr.data() {
1004 ErrorData::Os(code) => sys::is_interrupted(code),
1005 ErrorData::Custom(c) => c.kind == ErrorKind::Interrupted,
1006 ErrorData::Simple(kind) => kind == ErrorKind::Interrupted,
1007 ErrorData::SimpleMessage(m) => m.kind == ErrorKind::Interrupted,
1008 }
1009 }
1010}
1011
1012impl fmt::Debug for Repr {
1013 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
1014 match self.data() {
1015 ErrorData::Os(code: i32) => fmt&mut DebugStruct<'_, '_>
1016 .debug_struct("Os")
1017 .field("code", &code)
1018 .field("kind", &sys::decode_error_kind(code))
1019 .field(name:"message", &sys::os::error_string(errno:code))
1020 .finish(),
1021 ErrorData::Custom(c: &Custom) => fmt::Debug::fmt(&c, f:fmt),
1022 ErrorData::Simple(kind: ErrorKind) => fmt.debug_tuple(name:"Kind").field(&kind).finish(),
1023 ErrorData::SimpleMessage(msg: &'static SimpleMessage) => fmt&mut DebugStruct<'_, '_>
1024 .debug_struct("Error")
1025 .field("kind", &msg.kind)
1026 .field(name:"message", &msg.message)
1027 .finish(),
1028 }
1029 }
1030}
1031
1032#[stable(feature = "rust1", since = "1.0.0")]
1033impl fmt::Display for Error {
1034 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
1035 match self.repr.data() {
1036 ErrorData::Os(code: i32) => {
1037 let detail: String = sys::os::error_string(errno:code);
1038 write!(fmt, "{detail} (os error {code})")
1039 }
1040 ErrorData::Custom(ref c: &&Custom) => c.error.fmt(fmt),
1041 ErrorData::Simple(kind: ErrorKind) => write!(fmt, "{}", kind.as_str()),
1042 ErrorData::SimpleMessage(msg: &'static SimpleMessage) => msg.message.fmt(fmt),
1043 }
1044 }
1045}
1046
1047#[stable(feature = "rust1", since = "1.0.0")]
1048impl error::Error for Error {
1049 #[allow(deprecated, deprecated_in_future)]
1050 fn description(&self) -> &str {
1051 match self.repr.data() {
1052 ErrorData::Os(..) | ErrorData::Simple(..) => self.kind().as_str(),
1053 ErrorData::SimpleMessage(msg) => msg.message,
1054 ErrorData::Custom(c) => c.error.description(),
1055 }
1056 }
1057
1058 #[allow(deprecated)]
1059 fn cause(&self) -> Option<&dyn error::Error> {
1060 match self.repr.data() {
1061 ErrorData::Os(..) => None,
1062 ErrorData::Simple(..) => None,
1063 ErrorData::SimpleMessage(..) => None,
1064 ErrorData::Custom(c) => c.error.cause(),
1065 }
1066 }
1067
1068 fn source(&self) -> Option<&(dyn error::Error + 'static)> {
1069 match self.repr.data() {
1070 ErrorData::Os(..) => None,
1071 ErrorData::Simple(..) => None,
1072 ErrorData::SimpleMessage(..) => None,
1073 ErrorData::Custom(c) => c.error.source(),
1074 }
1075 }
1076}
1077
1078fn _assert_error_is_sync_send() {
1079 fn _is_sync_send<T: Sync + Send>() {}
1080 _is_sync_send::<Error>();
1081}
1082