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