Source file src/os/error.go

Documentation: os

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package os
     6  
     7  import (
     8  	"internal/oserror"
     9  	"internal/poll"
    10  )
    11  
    12  // Portable analogs of some common system call errors.
    13  //
    14  // Errors returned from this package may be tested against these errors
    15  // with errors.Is.
    16  var (
    17  	// ErrInvalid indicates an invalid argument.
    18  	// Methods on File will return this error when the receiver is nil.
    19  	ErrInvalid = errInvalid() // "invalid argument"
    20  
    21  	ErrPermission = errPermission() // "permission denied"
    22  	ErrExist      = errExist()      // "file already exists"
    23  	ErrNotExist   = errNotExist()   // "file does not exist"
    24  	ErrClosed     = errClosed()     // "file already closed"
    25  	ErrNoDeadline = errNoDeadline() // "file type does not support deadline"
    26  )
    27  
    28  func errInvalid() error    { return oserror.ErrInvalid }
    29  func errPermission() error { return oserror.ErrPermission }
    30  func errExist() error      { return oserror.ErrExist }
    31  func errNotExist() error   { return oserror.ErrNotExist }
    32  func errClosed() error     { return oserror.ErrClosed }
    33  func errNoDeadline() error { return poll.ErrNoDeadline }
    34  
    35  type timeout interface {
    36  	Timeout() bool
    37  }
    38  
    39  // PathError records an error and the operation and file path that caused it.
    40  type PathError struct {
    41  	Op   string
    42  	Path string
    43  	Err  error
    44  }
    45  
    46  func (e *PathError) Error() string { return e.Op + " " + e.Path + ": " + e.Err.Error() }
    47  
    48  func (e *PathError) Unwrap() error { return e.Err }
    49  
    50  // Timeout reports whether this error represents a timeout.
    51  func (e *PathError) Timeout() bool {
    52  	t, ok := e.Err.(timeout)
    53  	return ok && t.Timeout()
    54  }
    55  
    56  // SyscallError records an error from a specific system call.
    57  type SyscallError struct {
    58  	Syscall string
    59  	Err     error
    60  }
    61  
    62  func (e *SyscallError) Error() string { return e.Syscall + ": " + e.Err.Error() }
    63  
    64  func (e *SyscallError) Unwrap() error { return e.Err }
    65  
    66  // Timeout reports whether this error represents a timeout.
    67  func (e *SyscallError) Timeout() bool {
    68  	t, ok := e.Err.(timeout)
    69  	return ok && t.Timeout()
    70  }
    71  
    72  // NewSyscallError returns, as an error, a new SyscallError
    73  // with the given system call name and error details.
    74  // As a convenience, if err is nil, NewSyscallError returns nil.
    75  func NewSyscallError(syscall string, err error) error {
    76  	if err == nil {
    77  		return nil
    78  	}
    79  	return &SyscallError{syscall, err}
    80  }
    81  
    82  // IsExist returns a boolean indicating whether the error is known to report
    83  // that a file or directory already exists. It is satisfied by ErrExist as
    84  // well as some syscall errors.
    85  func IsExist(err error) bool {
    86  	return underlyingErrorIs(err, ErrExist)
    87  }
    88  
    89  // IsNotExist returns a boolean indicating whether the error is known to
    90  // report that a file or directory does not exist. It is satisfied by
    91  // ErrNotExist as well as some syscall errors.
    92  func IsNotExist(err error) bool {
    93  	return underlyingErrorIs(err, ErrNotExist)
    94  }
    95  
    96  // IsPermission returns a boolean indicating whether the error is known to
    97  // report that permission is denied. It is satisfied by ErrPermission as well
    98  // as some syscall errors.
    99  func IsPermission(err error) bool {
   100  	return underlyingErrorIs(err, ErrPermission)
   101  }
   102  
   103  // IsTimeout returns a boolean indicating whether the error is known
   104  // to report that a timeout occurred.
   105  func IsTimeout(err error) bool {
   106  	terr, ok := underlyingError(err).(timeout)
   107  	return ok && terr.Timeout()
   108  }
   109  
   110  func underlyingErrorIs(err, target error) bool {
   111  	// Note that this function is not errors.Is:
   112  	// underlyingError only unwraps the specific error-wrapping types
   113  	// that it historically did, not all errors.Wrapper implementations.
   114  	err = underlyingError(err)
   115  	if err == target {
   116  		return true
   117  	}
   118  	// To preserve prior behavior, only examine syscall errors.
   119  	e, ok := err.(syscallErrorType)
   120  	return ok && e.Is(target)
   121  }
   122  
   123  // underlyingError returns the underlying error for known os error types.
   124  func underlyingError(err error) error {
   125  	switch err := err.(type) {
   126  	case *PathError:
   127  		return err.Err
   128  	case *LinkError:
   129  		return err.Err
   130  	case *SyscallError:
   131  		return err.Err
   132  	}
   133  	return err
   134  }
   135  

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