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")]
51#[doc(search_unbox)]
52pub type Result<T> = result::Result<T, Error>;
53
54/// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and
55/// associated traits.
56///
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
59/// [`ErrorKind`].
60///
61/// [`Read`]: crate::io::Read
62/// [`Write`]: crate::io::Write
63/// [`Seek`]: crate::io::Seek
64#[stable(feature = "rust1", since = "1.0.0")]
65pub struct Error {
66 repr: Repr,
67}
68
69#[stable(feature = "rust1", since = "1.0.0")]
70impl fmt::Debug for Error {
71 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
72 fmt::Debug::fmt(&self.repr, f)
73 }
74}
75
76/// Common errors constants for use in std
77#[allow(dead_code)]
78impl Error {
79 pub(crate) const INVALID_UTF8: Self =
80 const_error!(ErrorKind::InvalidData, "stream did not contain valid UTF-8");
81
82 pub(crate) const READ_EXACT_EOF: Self =
83 const_error!(ErrorKind::UnexpectedEof, "failed to fill whole buffer");
84
85 pub(crate) const UNKNOWN_THREAD_COUNT: Self = const_error!(
86 ErrorKind::NotFound,
87 "the number of hardware threads is not known for the target platform",
88 );
89
90 pub(crate) const UNSUPPORTED_PLATFORM: Self =
91 const_error!(ErrorKind::Unsupported, "operation not supported on this platform");
92
93 pub(crate) const WRITE_ALL_EOF: Self =
94 const_error!(ErrorKind::WriteZero, "failed to write whole buffer");
95
96 pub(crate) const ZERO_TIMEOUT: Self =
97 const_error!(ErrorKind::InvalidInput, "cannot set a 0 duration timeout");
98}
99
100#[stable(feature = "rust1", since = "1.0.0")]
101impl From<alloc::ffi::NulError> for Error {
102 /// Converts a [`alloc::ffi::NulError`] into a [`Error`].
103 fn from(_: alloc::ffi::NulError) -> Error {
104 const_error!(ErrorKind::InvalidInput, "data provided contains a nul byte")
105 }
106}
107
108#[stable(feature = "io_error_from_try_reserve", since = "1.78.0")]
109impl From<alloc::collections::TryReserveError> for Error {
110 /// Converts `TryReserveError` to an error with [`ErrorKind::OutOfMemory`].
111 ///
112 /// `TryReserveError` won't be available as the error `source()`,
113 /// but this may change in the future.
114 fn from(_: alloc::collections::TryReserveError) -> Error {
115 // ErrorData::Custom allocates, which isn't great for handling OOM errors.
116 ErrorKind::OutOfMemory.into()
117 }
118}
119
120// Only derive debug in tests, to make sure it
121// doesn't accidentally get printed.
122#[cfg_attr(test, derive(Debug))]
123enum ErrorData<C> {
124 Os(RawOsError),
125 Simple(ErrorKind),
126 SimpleMessage(&'static SimpleMessage),
127 Custom(C),
128}
129
130/// The type of raw OS error codes returned by [`Error::raw_os_error`].
131///
132/// This is an [`i32`] on all currently supported platforms, but platforms
133/// added in the future (such as UEFI) may use a different primitive type like
134/// [`usize`]. Use `as`or [`into`] conversions where applicable to ensure maximum
135/// portability.
136///
137/// [`into`]: Into::into
138#[unstable(feature = "raw_os_error_ty", issue = "107792")]
139pub type RawOsError = sys::RawOsError;
140
141// `#[repr(align(4))]` is probably redundant, it should have that value or
142// higher already. We include it just because repr_bitpacked.rs's encoding
143// requires an alignment >= 4 (note that `#[repr(align)]` will not reduce the
144// alignment required by the struct, only increase it).
145//
146// If we add more variants to ErrorData, this can be increased to 8, but it
147// should probably be behind `#[cfg_attr(target_pointer_width = "64", ...)]` or
148// whatever cfg we're using to enable the `repr_bitpacked` code, since only the
149// that version needs the alignment, and 8 is higher than the alignment we'll
150// have on 32 bit platforms.
151//
152// (For the sake of being explicit: the alignment requirement here only matters
153// if `error/repr_bitpacked.rs` is in use — for the unpacked repr it doesn't
154// matter at all)
155#[doc(hidden)]
156#[unstable(feature = "io_const_error_internals", issue = "none")]
157#[repr(align(4))]
158#[derive(Debug)]
159pub struct SimpleMessage {
160 pub kind: ErrorKind,
161 pub message: &'static str,
162}
163
164/// Creates a new I/O error from a known kind of error and a string literal.
165///
166/// Contrary to [`Error::new`], this macro does not allocate and can be used in
167/// `const` contexts.
168///
169/// # Example
170/// ```
171/// #![feature(io_const_error)]
172/// use std::io::{const_error, Error, ErrorKind};
173///
174/// const FAIL: Error = const_error!(ErrorKind::Unsupported, "tried something that never works");
175///
176/// fn not_here() -> Result<(), Error> {
177/// Err(FAIL)
178/// }
179/// ```
180#[rustc_macro_transparency = "semitransparent"]
181#[unstable(feature = "io_const_error", issue = "133448")]
182#[allow_internal_unstable(hint_must_use, io_const_error_internals)]
183pub macro const_error($kind:expr, $message:expr $(,)?) {
184 $crate::hint::must_use($crate::io::Error::from_static_message(
185 const { &$crate::io::SimpleMessage { kind: $kind, message: $message } },
186 ))
187}
188
189// As with `SimpleMessage`: `#[repr(align(4))]` here is just because
190// repr_bitpacked's encoding requires it. In practice it almost certainly be
191// already be this high or higher.
192#[derive(Debug)]
193#[repr(align(4))]
194struct Custom {
195 kind: ErrorKind,
196 error: Box<dyn error::Error + Send + Sync>,
197}
198
199/// A list specifying general categories of I/O error.
200///
201/// This list is intended to grow over time and it is not recommended to
202/// exhaustively match against it.
203///
204/// It is used with the [`io::Error`] type.
205///
206/// [`io::Error`]: Error
207///
208/// # Handling errors and matching on `ErrorKind`
209///
210/// In application code, use `match` for the `ErrorKind` values you are
211/// expecting; use `_` to match "all other errors".
212///
213/// In comprehensive and thorough tests that want to verify that a test doesn't
214/// return any known incorrect error kind, you may want to cut-and-paste the
215/// current full list of errors from here into your test code, and then match
216/// `_` as the correct case. This seems counterintuitive, but it will make your
217/// tests more robust. In particular, if you want to verify that your code does
218/// produce an unrecognized error kind, the robust solution is to check for all
219/// the recognized error kinds and fail in those cases.
220#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
221#[stable(feature = "rust1", since = "1.0.0")]
222#[allow(deprecated)]
223#[non_exhaustive]
224pub enum ErrorKind {
225 /// An entity was not found, often a file.
226 #[stable(feature = "rust1", since = "1.0.0")]
227 NotFound,
228 /// The operation lacked the necessary privileges to complete.
229 #[stable(feature = "rust1", since = "1.0.0")]
230 PermissionDenied,
231 /// The connection was refused by the remote server.
232 #[stable(feature = "rust1", since = "1.0.0")]
233 ConnectionRefused,
234 /// The connection was reset by the remote server.
235 #[stable(feature = "rust1", since = "1.0.0")]
236 ConnectionReset,
237 /// The remote host is not reachable.
238 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
239 HostUnreachable,
240 /// The network containing the remote host is not reachable.
241 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
242 NetworkUnreachable,
243 /// The connection was aborted (terminated) by the remote server.
244 #[stable(feature = "rust1", since = "1.0.0")]
245 ConnectionAborted,
246 /// The network operation failed because it was not connected yet.
247 #[stable(feature = "rust1", since = "1.0.0")]
248 NotConnected,
249 /// A socket address could not be bound because the address is already in
250 /// use elsewhere.
251 #[stable(feature = "rust1", since = "1.0.0")]
252 AddrInUse,
253 /// A nonexistent interface was requested or the requested address was not
254 /// local.
255 #[stable(feature = "rust1", since = "1.0.0")]
256 AddrNotAvailable,
257 /// The system's networking is down.
258 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
259 NetworkDown,
260 /// The operation failed because a pipe was closed.
261 #[stable(feature = "rust1", since = "1.0.0")]
262 BrokenPipe,
263 /// An entity already exists, often a file.
264 #[stable(feature = "rust1", since = "1.0.0")]
265 AlreadyExists,
266 /// The operation needs to block to complete, but the blocking operation was
267 /// requested to not occur.
268 #[stable(feature = "rust1", since = "1.0.0")]
269 WouldBlock,
270 /// A filesystem object is, unexpectedly, not a directory.
271 ///
272 /// For example, a filesystem path was specified where one of the intermediate directory
273 /// components was, in fact, a plain file.
274 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
275 NotADirectory,
276 /// The filesystem object is, unexpectedly, a directory.
277 ///
278 /// A directory was specified when a non-directory was expected.
279 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
280 IsADirectory,
281 /// A non-empty directory was specified where an empty directory was expected.
282 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
283 DirectoryNotEmpty,
284 /// The filesystem or storage medium is read-only, but a write operation was attempted.
285 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
286 ReadOnlyFilesystem,
287 /// Loop in the filesystem or IO subsystem; often, too many levels of symbolic links.
288 ///
289 /// There was a loop (or excessively long chain) resolving a filesystem object
290 /// or file IO object.
291 ///
292 /// On Unix this is usually the result of a symbolic link loop; or, of exceeding the
293 /// system-specific limit on the depth of symlink traversal.
294 #[unstable(feature = "io_error_more", issue = "86442")]
295 FilesystemLoop,
296 /// Stale network file handle.
297 ///
298 /// With some network filesystems, notably NFS, an open file (or directory) can be invalidated
299 /// by problems with the network or server.
300 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
301 StaleNetworkFileHandle,
302 /// A parameter was incorrect.
303 #[stable(feature = "rust1", since = "1.0.0")]
304 InvalidInput,
305 /// Data not valid for the operation were encountered.
306 ///
307 /// Unlike [`InvalidInput`], this typically means that the operation
308 /// parameters were valid, however the error was caused by malformed
309 /// input data.
310 ///
311 /// For example, a function that reads a file into a string will error with
312 /// `InvalidData` if the file's contents are not valid UTF-8.
313 ///
314 /// [`InvalidInput`]: ErrorKind::InvalidInput
315 #[stable(feature = "io_invalid_data", since = "1.2.0")]
316 InvalidData,
317 /// The I/O operation's timeout expired, causing it to be canceled.
318 #[stable(feature = "rust1", since = "1.0.0")]
319 TimedOut,
320 /// An error returned when an operation could not be completed because a
321 /// call to [`write`] returned [`Ok(0)`].
322 ///
323 /// This typically means that an operation could only succeed if it wrote a
324 /// particular number of bytes but only a smaller number of bytes could be
325 /// written.
326 ///
327 /// [`write`]: crate::io::Write::write
328 /// [`Ok(0)`]: Ok
329 #[stable(feature = "rust1", since = "1.0.0")]
330 WriteZero,
331 /// The underlying storage (typically, a filesystem) is full.
332 ///
333 /// This does not include out of quota errors.
334 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
335 StorageFull,
336 /// Seek on unseekable file.
337 ///
338 /// Seeking was attempted on an open file handle which is not suitable for seeking - for
339 /// example, on Unix, a named pipe opened with `File::open`.
340 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
341 NotSeekable,
342 /// Filesystem quota or some other kind of quota was exceeded.
343 #[stable(feature = "io_error_quota_exceeded", since = "1.85.0")]
344 QuotaExceeded,
345 /// File larger than allowed or supported.
346 ///
347 /// This might arise from a hard limit of the underlying filesystem or file access API, or from
348 /// an administratively imposed resource limitation. Simple disk full, and out of quota, have
349 /// their own errors.
350 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
351 FileTooLarge,
352 /// Resource is busy.
353 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
354 ResourceBusy,
355 /// Executable file is busy.
356 ///
357 /// An attempt was made to write to a file which is also in use as a running program. (Not all
358 /// operating systems detect this situation.)
359 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
360 ExecutableFileBusy,
361 /// Deadlock (avoided).
362 ///
363 /// A file locking operation would result in deadlock. This situation is typically detected, if
364 /// at all, on a best-effort basis.
365 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
366 Deadlock,
367 /// Cross-device or cross-filesystem (hard) link or rename.
368 #[stable(feature = "io_error_crosses_devices", since = "1.85.0")]
369 CrossesDevices,
370 /// Too many (hard) links to the same filesystem object.
371 ///
372 /// The filesystem does not support making so many hardlinks to the same file.
373 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
374 TooManyLinks,
375 /// A filename was invalid.
376 ///
377 /// This error can also occur if a length limit for a name was exceeded.
378 #[stable(feature = "io_error_invalid_filename", since = "1.87.0")]
379 InvalidFilename,
380 /// Program argument list too long.
381 ///
382 /// When trying to run an external program, a system or process limit on the size of the
383 /// arguments would have been exceeded.
384 #[stable(feature = "io_error_a_bit_more", since = "1.83.0")]
385 ArgumentListTooLong,
386 /// This operation was interrupted.
387 ///
388 /// Interrupted operations can typically be retried.
389 #[stable(feature = "rust1", since = "1.0.0")]
390 Interrupted,
391
392 /// This operation is unsupported on this platform.
393 ///
394 /// This means that the operation can never succeed.
395 #[stable(feature = "unsupported_error", since = "1.53.0")]
396 Unsupported,
397
398 // ErrorKinds which are primarily categorisations for OS error
399 // codes should be added above.
400 //
401 /// An error returned when an operation could not be completed because an
402 /// "end of file" was reached prematurely.
403 ///
404 /// This typically means that an operation could only succeed if it read a
405 /// particular number of bytes but only a smaller number of bytes could be
406 /// read.
407 #[stable(feature = "read_exact", since = "1.6.0")]
408 UnexpectedEof,
409
410 /// An operation could not be completed, because it failed
411 /// to allocate enough memory.
412 #[stable(feature = "out_of_memory_error", since = "1.54.0")]
413 OutOfMemory,
414
415 /// The operation was partially successful and needs to be checked
416 /// later on due to not blocking.
417 #[unstable(feature = "io_error_inprogress", issue = "130840")]
418 InProgress,
419
420 // "Unusual" error kinds which do not correspond simply to (sets
421 // of) OS error codes, should be added just above this comment.
422 // `Other` and `Uncategorized` should remain at the end:
423 //
424 /// A custom error that does not fall under any other I/O error kind.
425 ///
426 /// This can be used to construct your own [`Error`]s that do not match any
427 /// [`ErrorKind`].
428 ///
429 /// This [`ErrorKind`] is not used by the standard library.
430 ///
431 /// Errors from the standard library that do not fall under any of the I/O
432 /// error kinds cannot be `match`ed on, and will only match a wildcard (`_`) pattern.
433 /// New [`ErrorKind`]s might be added in the future for some of those.
434 #[stable(feature = "rust1", since = "1.0.0")]
435 Other,
436
437 /// Any I/O error from the standard library that's not part of this list.
438 ///
439 /// Errors that are `Uncategorized` now may move to a different or a new
440 /// [`ErrorKind`] variant in the future. It is not recommended to match
441 /// an error against `Uncategorized`; use a wildcard match (`_`) instead.
442 #[unstable(feature = "io_error_uncategorized", issue = "none")]
443 #[doc(hidden)]
444 Uncategorized,
445}
446
447impl ErrorKind {
448 pub(crate) fn as_str(&self) -> &'static str {
449 use ErrorKind::*;
450 match *self {
451 // tidy-alphabetical-start
452 AddrInUse => "address in use",
453 AddrNotAvailable => "address not available",
454 AlreadyExists => "entity already exists",
455 ArgumentListTooLong => "argument list too long",
456 BrokenPipe => "broken pipe",
457 ConnectionAborted => "connection aborted",
458 ConnectionRefused => "connection refused",
459 ConnectionReset => "connection reset",
460 CrossesDevices => "cross-device link or rename",
461 Deadlock => "deadlock",
462 DirectoryNotEmpty => "directory not empty",
463 ExecutableFileBusy => "executable file busy",
464 FilesystemLoop => "filesystem loop or indirection limit (e.g. symlink loop)",
465 FileTooLarge => "file too large",
466 HostUnreachable => "host unreachable",
467 InProgress => "in progress",
468 Interrupted => "operation interrupted",
469 InvalidData => "invalid data",
470 InvalidFilename => "invalid filename",
471 InvalidInput => "invalid input parameter",
472 IsADirectory => "is a directory",
473 NetworkDown => "network down",
474 NetworkUnreachable => "network unreachable",
475 NotADirectory => "not a directory",
476 NotConnected => "not connected",
477 NotFound => "entity not found",
478 NotSeekable => "seek on unseekable file",
479 Other => "other error",
480 OutOfMemory => "out of memory",
481 PermissionDenied => "permission denied",
482 QuotaExceeded => "quota exceeded",
483 ReadOnlyFilesystem => "read-only filesystem or storage medium",
484 ResourceBusy => "resource busy",
485 StaleNetworkFileHandle => "stale network file handle",
486 StorageFull => "no storage space",
487 TimedOut => "timed out",
488 TooManyLinks => "too many links",
489 Uncategorized => "uncategorized error",
490 UnexpectedEof => "unexpected end of file",
491 Unsupported => "unsupported",
492 WouldBlock => "operation would block",
493 WriteZero => "write zero",
494 // tidy-alphabetical-end
495 }
496 }
497}
498
499#[stable(feature = "io_errorkind_display", since = "1.60.0")]
500impl fmt::Display for ErrorKind {
501 /// Shows a human-readable description of the `ErrorKind`.
502 ///
503 /// This is similar to `impl Display for Error`, but doesn't require first converting to Error.
504 ///
505 /// # Examples
506 /// ```
507 /// use std::io::ErrorKind;
508 /// assert_eq!("entity not found", ErrorKind::NotFound.to_string());
509 /// ```
510 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
511 fmt.write_str(self.as_str())
512 }
513}
514
515/// Intended for use for errors not exposed to the user, where allocating onto
516/// the heap (for normal construction via Error::new) is too costly.
517#[stable(feature = "io_error_from_errorkind", since = "1.14.0")]
518impl From<ErrorKind> for Error {
519 /// Converts an [`ErrorKind`] into an [`Error`].
520 ///
521 /// This conversion creates a new error with a simple representation of error kind.
522 ///
523 /// # Examples
524 ///
525 /// ```
526 /// use std::io::{Error, ErrorKind};
527 ///
528 /// let not_found = ErrorKind::NotFound;
529 /// let error = Error::from(not_found);
530 /// assert_eq!("entity not found", format!("{error}"));
531 /// ```
532 #[inline]
533 fn from(kind: ErrorKind) -> Error {
534 Error { repr: Repr::new_simple(kind) }
535 }
536}
537
538impl Error {
539 /// Creates a new I/O error from a known kind of error as well as an
540 /// arbitrary error payload.
541 ///
542 /// This function is used to generically create I/O errors which do not
543 /// originate from the OS itself. The `error` argument is an arbitrary
544 /// payload which will be contained in this [`Error`].
545 ///
546 /// Note that this function allocates memory on the heap.
547 /// If no extra payload is required, use the `From` conversion from
548 /// `ErrorKind`.
549 ///
550 /// # Examples
551 ///
552 /// ```
553 /// use std::io::{Error, ErrorKind};
554 ///
555 /// // errors can be created from strings
556 /// let custom_error = Error::new(ErrorKind::Other, "oh no!");
557 ///
558 /// // errors can also be created from other errors
559 /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
560 ///
561 /// // creating an error without payload (and without memory allocation)
562 /// let eof_error = Error::from(ErrorKind::UnexpectedEof);
563 /// ```
564 #[stable(feature = "rust1", since = "1.0.0")]
565 #[inline(never)]
566 pub fn new<E>(kind: ErrorKind, error: E) -> Error
567 where
568 E: Into<Box<dyn error::Error + Send + Sync>>,
569 {
570 Self::_new(kind, error.into())
571 }
572
573 /// Creates a new I/O error from an arbitrary error payload.
574 ///
575 /// This function is used to generically create I/O errors which do not
576 /// originate from the OS itself. It is a shortcut for [`Error::new`]
577 /// with [`ErrorKind::Other`].
578 ///
579 /// # Examples
580 ///
581 /// ```
582 /// use std::io::Error;
583 ///
584 /// // errors can be created from strings
585 /// let custom_error = Error::other("oh no!");
586 ///
587 /// // errors can also be created from other errors
588 /// let custom_error2 = Error::other(custom_error);
589 /// ```
590 #[stable(feature = "io_error_other", since = "1.74.0")]
591 pub fn other<E>(error: E) -> Error
592 where
593 E: Into<Box<dyn error::Error + Send + Sync>>,
594 {
595 Self::_new(ErrorKind::Other, error.into())
596 }
597
598 fn _new(kind: ErrorKind, error: Box<dyn error::Error + Send + Sync>) -> Error {
599 Error { repr: Repr::new_custom(Box::new(Custom { kind, error })) }
600 }
601
602 /// Creates a new I/O error from a known kind of error as well as a constant
603 /// message.
604 ///
605 /// This function does not allocate.
606 ///
607 /// You should not use this directly, and instead use the `const_error!`
608 /// macro: `io::const_error!(ErrorKind::Something, "some_message")`.
609 ///
610 /// This function should maybe change to `from_static_message<const MSG: &'static
611 /// str>(kind: ErrorKind)` in the future, when const generics allow that.
612 #[inline]
613 #[doc(hidden)]
614 #[unstable(feature = "io_const_error_internals", issue = "none")]
615 pub const fn from_static_message(msg: &'static SimpleMessage) -> Error {
616 Self { repr: Repr::new_simple_message(msg) }
617 }
618
619 /// Returns an error representing the last OS error which occurred.
620 ///
621 /// This function reads the value of `errno` for the target platform (e.g.
622 /// `GetLastError` on Windows) and will return a corresponding instance of
623 /// [`Error`] for the error code.
624 ///
625 /// This should be called immediately after a call to a platform function,
626 /// otherwise the state of the error value is indeterminate. In particular,
627 /// other standard library functions may call platform functions that may
628 /// (or may not) reset the error value even if they succeed.
629 ///
630 /// # Examples
631 ///
632 /// ```
633 /// use std::io::Error;
634 ///
635 /// let os_error = Error::last_os_error();
636 /// println!("last OS error: {os_error:?}");
637 /// ```
638 #[stable(feature = "rust1", since = "1.0.0")]
639 #[doc(alias = "GetLastError")]
640 #[doc(alias = "errno")]
641 #[must_use]
642 #[inline]
643 pub fn last_os_error() -> Error {
644 Error::from_raw_os_error(sys::os::errno())
645 }
646
647 /// Creates a new instance of an [`Error`] from a particular OS error code.
648 ///
649 /// # Examples
650 ///
651 /// On Linux:
652 ///
653 /// ```
654 /// # if cfg!(target_os = "linux") {
655 /// use std::io;
656 ///
657 /// let error = io::Error::from_raw_os_error(22);
658 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
659 /// # }
660 /// ```
661 ///
662 /// On Windows:
663 ///
664 /// ```
665 /// # if cfg!(windows) {
666 /// use std::io;
667 ///
668 /// let error = io::Error::from_raw_os_error(10022);
669 /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
670 /// # }
671 /// ```
672 #[stable(feature = "rust1", since = "1.0.0")]
673 #[must_use]
674 #[inline]
675 pub fn from_raw_os_error(code: RawOsError) -> Error {
676 Error { repr: Repr::new_os(code) }
677 }
678
679 /// Returns the OS error that this error represents (if any).
680 ///
681 /// If this [`Error`] was constructed via [`last_os_error`] or
682 /// [`from_raw_os_error`], then this function will return [`Some`], otherwise
683 /// it will return [`None`].
684 ///
685 /// [`last_os_error`]: Error::last_os_error
686 /// [`from_raw_os_error`]: Error::from_raw_os_error
687 ///
688 /// # Examples
689 ///
690 /// ```
691 /// use std::io::{Error, ErrorKind};
692 ///
693 /// fn print_os_error(err: &Error) {
694 /// if let Some(raw_os_err) = err.raw_os_error() {
695 /// println!("raw OS error: {raw_os_err:?}");
696 /// } else {
697 /// println!("Not an OS error");
698 /// }
699 /// }
700 ///
701 /// fn main() {
702 /// // Will print "raw OS error: ...".
703 /// print_os_error(&Error::last_os_error());
704 /// // Will print "Not an OS error".
705 /// print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
706 /// }
707 /// ```
708 #[stable(feature = "rust1", since = "1.0.0")]
709 #[must_use]
710 #[inline]
711 pub fn raw_os_error(&self) -> Option<RawOsError> {
712 match self.repr.data() {
713 ErrorData::Os(i) => Some(i),
714 ErrorData::Custom(..) => None,
715 ErrorData::Simple(..) => None,
716 ErrorData::SimpleMessage(..) => None,
717 }
718 }
719
720 /// Returns a reference to the inner error wrapped by this error (if any).
721 ///
722 /// If this [`Error`] was constructed via [`new`] then this function will
723 /// return [`Some`], otherwise it will return [`None`].
724 ///
725 /// [`new`]: Error::new
726 ///
727 /// # Examples
728 ///
729 /// ```
730 /// use std::io::{Error, ErrorKind};
731 ///
732 /// fn print_error(err: &Error) {
733 /// if let Some(inner_err) = err.get_ref() {
734 /// println!("Inner error: {inner_err:?}");
735 /// } else {
736 /// println!("No inner error");
737 /// }
738 /// }
739 ///
740 /// fn main() {
741 /// // Will print "No inner error".
742 /// print_error(&Error::last_os_error());
743 /// // Will print "Inner error: ...".
744 /// print_error(&Error::new(ErrorKind::Other, "oh no!"));
745 /// }
746 /// ```
747 #[stable(feature = "io_error_inner", since = "1.3.0")]
748 #[must_use]
749 #[inline]
750 pub fn get_ref(&self) -> Option<&(dyn error::Error + Send + Sync + 'static)> {
751 match self.repr.data() {
752 ErrorData::Os(..) => None,
753 ErrorData::Simple(..) => None,
754 ErrorData::SimpleMessage(..) => None,
755 ErrorData::Custom(c) => Some(&*c.error),
756 }
757 }
758
759 /// Returns a mutable reference to the inner error wrapped by this error
760 /// (if any).
761 ///
762 /// If this [`Error`] was constructed via [`new`] then this function will
763 /// return [`Some`], otherwise it will return [`None`].
764 ///
765 /// [`new`]: Error::new
766 ///
767 /// # Examples
768 ///
769 /// ```
770 /// use std::io::{Error, ErrorKind};
771 /// use std::{error, fmt};
772 /// use std::fmt::Display;
773 ///
774 /// #[derive(Debug)]
775 /// struct MyError {
776 /// v: String,
777 /// }
778 ///
779 /// impl MyError {
780 /// fn new() -> MyError {
781 /// MyError {
782 /// v: "oh no!".to_string()
783 /// }
784 /// }
785 ///
786 /// fn change_message(&mut self, new_message: &str) {
787 /// self.v = new_message.to_string();
788 /// }
789 /// }
790 ///
791 /// impl error::Error for MyError {}
792 ///
793 /// impl Display for MyError {
794 /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
795 /// write!(f, "MyError: {}", self.v)
796 /// }
797 /// }
798 ///
799 /// fn change_error(mut err: Error) -> Error {
800 /// if let Some(inner_err) = err.get_mut() {
801 /// inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
802 /// }
803 /// err
804 /// }
805 ///
806 /// fn print_error(err: &Error) {
807 /// if let Some(inner_err) = err.get_ref() {
808 /// println!("Inner error: {inner_err}");
809 /// } else {
810 /// println!("No inner error");
811 /// }
812 /// }
813 ///
814 /// fn main() {
815 /// // Will print "No inner error".
816 /// print_error(&change_error(Error::last_os_error()));
817 /// // Will print "Inner error: ...".
818 /// print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
819 /// }
820 /// ```
821 #[stable(feature = "io_error_inner", since = "1.3.0")]
822 #[must_use]
823 #[inline]
824 pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error + Send + Sync + 'static)> {
825 match self.repr.data_mut() {
826 ErrorData::Os(..) => None,
827 ErrorData::Simple(..) => None,
828 ErrorData::SimpleMessage(..) => None,
829 ErrorData::Custom(c) => Some(&mut *c.error),
830 }
831 }
832
833 /// Consumes the `Error`, returning its inner error (if any).
834 ///
835 /// If this [`Error`] was constructed via [`new`] or [`other`],
836 /// then this function will return [`Some`],
837 /// otherwise it will return [`None`].
838 ///
839 /// [`new`]: Error::new
840 /// [`other`]: Error::other
841 ///
842 /// # Examples
843 ///
844 /// ```
845 /// use std::io::{Error, ErrorKind};
846 ///
847 /// fn print_error(err: Error) {
848 /// if let Some(inner_err) = err.into_inner() {
849 /// println!("Inner error: {inner_err}");
850 /// } else {
851 /// println!("No inner error");
852 /// }
853 /// }
854 ///
855 /// fn main() {
856 /// // Will print "No inner error".
857 /// print_error(Error::last_os_error());
858 /// // Will print "Inner error: ...".
859 /// print_error(Error::new(ErrorKind::Other, "oh no!"));
860 /// }
861 /// ```
862 #[stable(feature = "io_error_inner", since = "1.3.0")]
863 #[must_use = "`self` will be dropped if the result is not used"]
864 #[inline]
865 pub fn into_inner(self) -> Option<Box<dyn error::Error + Send + Sync>> {
866 match self.repr.into_data() {
867 ErrorData::Os(..) => None,
868 ErrorData::Simple(..) => None,
869 ErrorData::SimpleMessage(..) => None,
870 ErrorData::Custom(c) => Some(c.error),
871 }
872 }
873
874 /// Attempts to downcast the custom boxed error to `E`.
875 ///
876 /// If this [`Error`] contains a custom boxed error,
877 /// then it would attempt downcasting on the boxed error,
878 /// otherwise it will return [`Err`].
879 ///
880 /// If the custom boxed error has the same type as `E`, it will return [`Ok`],
881 /// otherwise it will also return [`Err`].
882 ///
883 /// This method is meant to be a convenience routine for calling
884 /// `Box<dyn Error + Sync + Send>::downcast` on the custom boxed error, returned by
885 /// [`Error::into_inner`].
886 ///
887 ///
888 /// # Examples
889 ///
890 /// ```
891 /// use std::fmt;
892 /// use std::io;
893 /// use std::error::Error;
894 ///
895 /// #[derive(Debug)]
896 /// enum E {
897 /// Io(io::Error),
898 /// SomeOtherVariant,
899 /// }
900 ///
901 /// impl fmt::Display for E {
902 /// // ...
903 /// # fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
904 /// # todo!()
905 /// # }
906 /// }
907 /// impl Error for E {}
908 ///
909 /// impl From<io::Error> for E {
910 /// fn from(err: io::Error) -> E {
911 /// err.downcast::<E>()
912 /// .unwrap_or_else(E::Io)
913 /// }
914 /// }
915 ///
916 /// impl From<E> for io::Error {
917 /// fn from(err: E) -> io::Error {
918 /// match err {
919 /// E::Io(io_error) => io_error,
920 /// e => io::Error::new(io::ErrorKind::Other, e),
921 /// }
922 /// }
923 /// }
924 ///
925 /// # fn main() {
926 /// let e = E::SomeOtherVariant;
927 /// // Convert it to an io::Error
928 /// let io_error = io::Error::from(e);
929 /// // Cast it back to the original variant
930 /// let e = E::from(io_error);
931 /// assert!(matches!(e, E::SomeOtherVariant));
932 ///
933 /// let io_error = io::Error::from(io::ErrorKind::AlreadyExists);
934 /// // Convert it to E
935 /// let e = E::from(io_error);
936 /// // Cast it back to the original variant
937 /// let io_error = io::Error::from(e);
938 /// assert_eq!(io_error.kind(), io::ErrorKind::AlreadyExists);
939 /// assert!(io_error.get_ref().is_none());
940 /// assert!(io_error.raw_os_error().is_none());
941 /// # }
942 /// ```
943 #[stable(feature = "io_error_downcast", since = "1.79.0")]
944 pub fn downcast<E>(self) -> result::Result<E, Self>
945 where
946 E: error::Error + Send + Sync + 'static,
947 {
948 match self.repr.into_data() {
949 ErrorData::Custom(b) if b.error.is::<E>() => {
950 let res = (*b).error.downcast::<E>();
951
952 // downcast is a really trivial and is marked as inline, so
953 // it's likely be inlined here.
954 //
955 // And the compiler should be able to eliminate the branch
956 // that produces `Err` here since b.error.is::<E>()
957 // returns true.
958 Ok(*res.unwrap())
959 }
960 repr_data => Err(Self { repr: Repr::new(repr_data) }),
961 }
962 }
963
964 /// Returns the corresponding [`ErrorKind`] for this error.
965 ///
966 /// This may be a value set by Rust code constructing custom `io::Error`s,
967 /// or if this `io::Error` was sourced from the operating system,
968 /// it will be a value inferred from the system's error encoding.
969 /// See [`last_os_error`] for more details.
970 ///
971 /// [`last_os_error`]: Error::last_os_error
972 ///
973 /// # Examples
974 ///
975 /// ```
976 /// use std::io::{Error, ErrorKind};
977 ///
978 /// fn print_error(err: Error) {
979 /// println!("{:?}", err.kind());
980 /// }
981 ///
982 /// fn main() {
983 /// // As no error has (visibly) occurred, this may print anything!
984 /// // It likely prints a placeholder for unidentified (non-)errors.
985 /// print_error(Error::last_os_error());
986 /// // Will print "AddrInUse".
987 /// print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
988 /// }
989 /// ```
990 #[stable(feature = "rust1", since = "1.0.0")]
991 #[must_use]
992 #[inline]
993 pub fn kind(&self) -> ErrorKind {
994 match self.repr.data() {
995 ErrorData::Os(code) => sys::decode_error_kind(code),
996 ErrorData::Custom(c) => c.kind,
997 ErrorData::Simple(kind) => kind,
998 ErrorData::SimpleMessage(m) => m.kind,
999 }
1000 }
1001
1002 #[inline]
1003 pub(crate) fn is_interrupted(&self) -> bool {
1004 match self.repr.data() {
1005 ErrorData::Os(code) => sys::is_interrupted(code),
1006 ErrorData::Custom(c) => c.kind == ErrorKind::Interrupted,
1007 ErrorData::Simple(kind) => kind == ErrorKind::Interrupted,
1008 ErrorData::SimpleMessage(m) => m.kind == ErrorKind::Interrupted,
1009 }
1010 }
1011}
1012
1013impl fmt::Debug for Repr {
1014 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
1015 match self.data() {
1016 ErrorData::Os(code: i32) => fmt&mut DebugStruct<'_, '_>
1017 .debug_struct("Os")
1018 .field("code", &code)
1019 .field("kind", &sys::decode_error_kind(code))
1020 .field(name:"message", &sys::os::error_string(errno:code))
1021 .finish(),
1022 ErrorData::Custom(c: &Custom) => fmt::Debug::fmt(&c, f:fmt),
1023 ErrorData::Simple(kind: ErrorKind) => fmt.debug_tuple(name:"Kind").field(&kind).finish(),
1024 ErrorData::SimpleMessage(msg: &'static SimpleMessage) => fmt&mut DebugStruct<'_, '_>
1025 .debug_struct("Error")
1026 .field("kind", &msg.kind)
1027 .field(name:"message", &msg.message)
1028 .finish(),
1029 }
1030 }
1031}
1032
1033#[stable(feature = "rust1", since = "1.0.0")]
1034impl fmt::Display for Error {
1035 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
1036 match self.repr.data() {
1037 ErrorData::Os(code: i32) => {
1038 let detail: String = sys::os::error_string(errno:code);
1039 write!(fmt, "{detail} (os error {code})")
1040 }
1041 ErrorData::Custom(ref c: &&Custom) => c.error.fmt(fmt),
1042 ErrorData::Simple(kind: ErrorKind) => write!(fmt, "{}", kind.as_str()),
1043 ErrorData::SimpleMessage(msg: &'static SimpleMessage) => msg.message.fmt(fmt),
1044 }
1045 }
1046}
1047
1048#[stable(feature = "rust1", since = "1.0.0")]
1049impl error::Error for Error {
1050 #[allow(deprecated, deprecated_in_future)]
1051 fn description(&self) -> &str {
1052 match self.repr.data() {
1053 ErrorData::Os(..) | ErrorData::Simple(..) => self.kind().as_str(),
1054 ErrorData::SimpleMessage(msg) => msg.message,
1055 ErrorData::Custom(c) => c.error.description(),
1056 }
1057 }
1058
1059 #[allow(deprecated)]
1060 fn cause(&self) -> Option<&dyn error::Error> {
1061 match self.repr.data() {
1062 ErrorData::Os(..) => None,
1063 ErrorData::Simple(..) => None,
1064 ErrorData::SimpleMessage(..) => None,
1065 ErrorData::Custom(c) => c.error.cause(),
1066 }
1067 }
1068
1069 fn source(&self) -> Option<&(dyn error::Error + 'static)> {
1070 match self.repr.data() {
1071 ErrorData::Os(..) => None,
1072 ErrorData::Simple(..) => None,
1073 ErrorData::SimpleMessage(..) => None,
1074 ErrorData::Custom(c) => c.error.source(),
1075 }
1076 }
1077}
1078
1079fn _assert_error_is_sync_send() {
1080 fn _is_sync_send<T: Sync + Send>() {}
1081 _is_sync_send::<Error>();
1082}
1083

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