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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package os
import (
"internal/poll"
"io/fs"
)
// Portable analogs of some common system call errors.
//
// Errors returned from this package may be tested against these errors
// with errors.Is.
var (
// ErrInvalid indicates an invalid argument.
// Methods on File will return this error when the receiver is nil.
ErrInvalid = fs.ErrInvalid // "invalid argument"
ErrPermission = fs.ErrPermission // "permission denied"
ErrExist = fs.ErrExist // "file already exists"
ErrNotExist = fs.ErrNotExist // "file does not exist"
ErrClosed = fs.ErrClosed // "file already closed"
ErrNoDeadline = errNoDeadline() // "file type does not support deadline"
ErrDeadlineExceeded = errDeadlineExceeded() // "i/o timeout"
)
func errNoDeadline() error { return poll.ErrNoDeadline }
// errDeadlineExceeded returns the value for os.ErrDeadlineExceeded.
// This error comes from the internal/poll package, which is also
// used by package net. Doing it this way ensures that the net
// package will return os.ErrDeadlineExceeded for an exceeded deadline,
// as documented by net.Conn.SetDeadline, without requiring any extra
// work in the net package and without requiring the internal/poll
// package to import os (which it can't, because that would be circular).
func errDeadlineExceeded() error { return poll.ErrDeadlineExceeded }
type timeout interface {
Timeout() bool
}
// PathError records an error and the operation and file path that caused it.
type PathError = fs.PathError
// SyscallError records an error from a specific system call.
type SyscallError struct {
Syscall string
Err error
}
func (e *SyscallError) Error() string { return e.Syscall + ": " + e.Err.Error() }
func (e *SyscallError) Unwrap() error { return e.Err }
// Timeout reports whether this error represents a timeout.
func (e *SyscallError) Timeout() bool {
t, ok := e.Err.(timeout)
return ok && t.Timeout()
}
// NewSyscallError returns, as an error, a new SyscallError
// with the given system call name and error details.
// As a convenience, if err is nil, NewSyscallError returns nil.
func NewSyscallError(syscall string, err error) error {
if err == nil {
return nil
}
return &SyscallError{syscall, err}
}
// IsExist returns a boolean indicating whether the error is known to report
// that a file or directory already exists. It is satisfied by ErrExist as
// well as some syscall errors.
//
// This function predates errors.Is. It only supports errors returned by
// the os package. New code should use errors.Is(err, fs.ErrExist).
func IsExist(err error) bool {
return underlyingErrorIs(err, ErrExist)
}
// IsNotExist returns a boolean indicating whether the error is known to
// report that a file or directory does not exist. It is satisfied by
// ErrNotExist as well as some syscall errors.
//
// This function predates errors.Is. It only supports errors returned by
// the os package. New code should use errors.Is(err, fs.ErrNotExist).
func IsNotExist(err error) bool {
return underlyingErrorIs(err, ErrNotExist)
}
// IsPermission returns a boolean indicating whether the error is known to
// report that permission is denied. It is satisfied by ErrPermission as well
// as some syscall errors.
//
// This function predates errors.Is. It only supports errors returned by
// the os package. New code should use errors.Is(err, fs.ErrPermission).
func IsPermission(err error) bool {
return underlyingErrorIs(err, ErrPermission)
}
// IsTimeout returns a boolean indicating whether the error is known
// to report that a timeout occurred.
//
// This function predates errors.Is, and the notion of whether an
// error indicates a timeout can be ambiguous. For example, the Unix
// error EWOULDBLOCK sometimes indicates a timeout and sometimes does not.
// New code should use errors.Is with a value appropriate to the call
// returning the error, such as os.ErrDeadlineExceeded.
func IsTimeout(err error) bool {
terr, ok := underlyingError(err).(timeout)
return ok && terr.Timeout()
}
func underlyingErrorIs(err, target error) bool {
// Note that this function is not errors.Is:
// underlyingError only unwraps the specific error-wrapping types
// that it historically did, not all errors implementing Unwrap().
err = underlyingError(err)
if err == target {
return true
}
// To preserve prior behavior, only examine syscall errors.
e, ok := err.(syscallErrorType)
return ok && e.Is(target)
}
// underlyingError returns the underlying error for known os error types.
func underlyingError(err error) error {
switch err := err.(type) {
case *PathError:
return err.Err
case *LinkError:
return err.Err
case *SyscallError:
return err.Err
}
return err
}
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