mirror of
https://github.com/autc04/Retro68.git
synced 2024-08-31 09:29:37 +00:00
724 lines
22 KiB
Go
724 lines
22 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 provides a platform-independent interface to operating system
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// functionality. The design is Unix-like, although the error handling is
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// Go-like; failing calls return values of type error rather than error numbers.
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// Often, more information is available within the error. For example,
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// if a call that takes a file name fails, such as Open or Stat, the error
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// will include the failing file name when printed and will be of type
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// *PathError, which may be unpacked for more information.
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//
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// The os interface is intended to be uniform across all operating systems.
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// Features not generally available appear in the system-specific package syscall.
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//
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// Here is a simple example, opening a file and reading some of it.
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//
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// file, err := os.Open("file.go") // For read access.
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// if err != nil {
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// log.Fatal(err)
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// }
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//
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// If the open fails, the error string will be self-explanatory, like
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//
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// open file.go: no such file or directory
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//
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// The file's data can then be read into a slice of bytes. Read and
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// Write take their byte counts from the length of the argument slice.
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//
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// data := make([]byte, 100)
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// count, err := file.Read(data)
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// if err != nil {
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// log.Fatal(err)
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// }
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// fmt.Printf("read %d bytes: %q\n", count, data[:count])
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//
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// Note: The maximum number of concurrent operations on a File may be limited by
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// the OS or the system. The number should be high, but exceeding it may degrade
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// performance or cause other issues.
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//
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package os
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import (
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"errors"
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"internal/poll"
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"internal/testlog"
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"internal/unsafeheader"
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"io"
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"io/fs"
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"runtime"
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"syscall"
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"time"
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"unsafe"
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)
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// Name returns the name of the file as presented to Open.
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func (f *File) Name() string { return f.name }
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// Stdin, Stdout, and Stderr are open Files pointing to the standard input,
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// standard output, and standard error file descriptors.
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//
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// Note that the Go runtime writes to standard error for panics and crashes;
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// closing Stderr may cause those messages to go elsewhere, perhaps
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// to a file opened later.
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var (
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Stdin = NewFile(uintptr(syscall.Stdin), "/dev/stdin")
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Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")
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Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr")
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)
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// Flags to OpenFile wrapping those of the underlying system. Not all
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// flags may be implemented on a given system.
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const (
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// Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
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O_RDONLY int = syscall.O_RDONLY // open the file read-only.
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O_WRONLY int = syscall.O_WRONLY // open the file write-only.
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O_RDWR int = syscall.O_RDWR // open the file read-write.
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// The remaining values may be or'ed in to control behavior.
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O_APPEND int = syscall.O_APPEND // append data to the file when writing.
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O_CREATE int = syscall.O_CREAT // create a new file if none exists.
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O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist.
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O_SYNC int = syscall.O_SYNC // open for synchronous I/O.
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O_TRUNC int = syscall.O_TRUNC // truncate regular writable file when opened.
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)
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// Seek whence values.
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//
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// Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd.
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const (
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SEEK_SET int = 0 // seek relative to the origin of the file
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SEEK_CUR int = 1 // seek relative to the current offset
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SEEK_END int = 2 // seek relative to the end
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)
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// LinkError records an error during a link or symlink or rename
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// system call and the paths that caused it.
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type LinkError struct {
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Op string
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Old string
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New string
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Err error
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}
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func (e *LinkError) Error() string {
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return e.Op + " " + e.Old + " " + e.New + ": " + e.Err.Error()
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}
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func (e *LinkError) Unwrap() error {
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return e.Err
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}
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// Read reads up to len(b) bytes from the File and stores them in b.
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// It returns the number of bytes read and any error encountered.
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// At end of file, Read returns 0, io.EOF.
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func (f *File) Read(b []byte) (n int, err error) {
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if err := f.checkValid("read"); err != nil {
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return 0, err
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}
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n, e := f.read(b)
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return n, f.wrapErr("read", e)
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}
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// ReadAt reads len(b) bytes from the File starting at byte offset off.
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// It returns the number of bytes read and the error, if any.
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// ReadAt always returns a non-nil error when n < len(b).
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// At end of file, that error is io.EOF.
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func (f *File) ReadAt(b []byte, off int64) (n int, err error) {
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if err := f.checkValid("read"); err != nil {
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return 0, err
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}
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if off < 0 {
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return 0, &PathError{Op: "readat", Path: f.name, Err: errors.New("negative offset")}
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}
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for len(b) > 0 {
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m, e := f.pread(b, off)
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if e != nil {
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err = f.wrapErr("read", e)
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break
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}
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n += m
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b = b[m:]
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off += int64(m)
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}
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return
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}
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// ReadFrom implements io.ReaderFrom.
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func (f *File) ReadFrom(r io.Reader) (n int64, err error) {
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if err := f.checkValid("write"); err != nil {
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return 0, err
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}
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n, handled, e := f.readFrom(r)
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if !handled {
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return genericReadFrom(f, r) // without wrapping
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}
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return n, f.wrapErr("write", e)
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}
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func genericReadFrom(f *File, r io.Reader) (int64, error) {
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return io.Copy(onlyWriter{f}, r)
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}
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type onlyWriter struct {
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io.Writer
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}
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// Write writes len(b) bytes from b to the File.
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// It returns the number of bytes written and an error, if any.
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// Write returns a non-nil error when n != len(b).
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func (f *File) Write(b []byte) (n int, err error) {
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if err := f.checkValid("write"); err != nil {
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return 0, err
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}
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n, e := f.write(b)
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if n < 0 {
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n = 0
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}
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if n != len(b) {
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err = io.ErrShortWrite
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}
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epipecheck(f, e)
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if e != nil {
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err = f.wrapErr("write", e)
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}
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return n, err
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}
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var errWriteAtInAppendMode = errors.New("os: invalid use of WriteAt on file opened with O_APPEND")
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// WriteAt writes len(b) bytes to the File starting at byte offset off.
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// It returns the number of bytes written and an error, if any.
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// WriteAt returns a non-nil error when n != len(b).
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//
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// If file was opened with the O_APPEND flag, WriteAt returns an error.
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func (f *File) WriteAt(b []byte, off int64) (n int, err error) {
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if err := f.checkValid("write"); err != nil {
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return 0, err
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}
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if f.appendMode {
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return 0, errWriteAtInAppendMode
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}
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if off < 0 {
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return 0, &PathError{Op: "writeat", Path: f.name, Err: errors.New("negative offset")}
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}
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for len(b) > 0 {
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m, e := f.pwrite(b, off)
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if e != nil {
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err = f.wrapErr("write", e)
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break
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}
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n += m
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b = b[m:]
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off += int64(m)
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}
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return
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}
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// Seek sets the offset for the next Read or Write on file to offset, interpreted
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// according to whence: 0 means relative to the origin of the file, 1 means
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// relative to the current offset, and 2 means relative to the end.
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// It returns the new offset and an error, if any.
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// The behavior of Seek on a file opened with O_APPEND is not specified.
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//
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// If f is a directory, the behavior of Seek varies by operating
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// system; you can seek to the beginning of the directory on Unix-like
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// operating systems, but not on Windows.
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func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
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if err := f.checkValid("seek"); err != nil {
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return 0, err
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}
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r, e := f.seek(offset, whence)
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if e == nil && f.dirinfo != nil && r != 0 {
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e = syscall.EISDIR
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}
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if e != nil {
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return 0, f.wrapErr("seek", e)
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}
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return r, nil
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}
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// WriteString is like Write, but writes the contents of string s rather than
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// a slice of bytes.
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func (f *File) WriteString(s string) (n int, err error) {
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var b []byte
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hdr := (*unsafeheader.Slice)(unsafe.Pointer(&b))
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hdr.Data = (*unsafeheader.String)(unsafe.Pointer(&s)).Data
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hdr.Cap = len(s)
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hdr.Len = len(s)
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return f.Write(b)
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}
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// Mkdir creates a new directory with the specified name and permission
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// bits (before umask).
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// If there is an error, it will be of type *PathError.
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func Mkdir(name string, perm FileMode) error {
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if runtime.GOOS == "windows" && isWindowsNulName(name) {
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return &PathError{Op: "mkdir", Path: name, Err: syscall.ENOTDIR}
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}
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longName := fixLongPath(name)
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e := ignoringEINTR(func() error {
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return syscall.Mkdir(longName, syscallMode(perm))
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})
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if e != nil {
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return &PathError{Op: "mkdir", Path: name, Err: e}
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}
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// mkdir(2) itself won't handle the sticky bit on *BSD and Solaris
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if !supportsCreateWithStickyBit && perm&ModeSticky != 0 {
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e = setStickyBit(name)
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if e != nil {
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Remove(name)
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return e
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}
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}
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return nil
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}
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// setStickyBit adds ModeSticky to the permission bits of path, non atomic.
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func setStickyBit(name string) error {
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fi, err := Stat(name)
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if err != nil {
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return err
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}
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return Chmod(name, fi.Mode()|ModeSticky)
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}
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// Chdir changes the current working directory to the named directory.
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// If there is an error, it will be of type *PathError.
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func Chdir(dir string) error {
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if e := syscall.Chdir(dir); e != nil {
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testlog.Open(dir) // observe likely non-existent directory
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return &PathError{Op: "chdir", Path: dir, Err: e}
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}
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if log := testlog.Logger(); log != nil {
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wd, err := Getwd()
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if err == nil {
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log.Chdir(wd)
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}
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}
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return nil
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}
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// Open opens the named file for reading. If successful, methods on
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// the returned file can be used for reading; the associated file
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// descriptor has mode O_RDONLY.
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// If there is an error, it will be of type *PathError.
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func Open(name string) (*File, error) {
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return OpenFile(name, O_RDONLY, 0)
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}
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// Create creates or truncates the named file. If the file already exists,
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// it is truncated. If the file does not exist, it is created with mode 0666
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// (before umask). If successful, methods on the returned File can
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// be used for I/O; the associated file descriptor has mode O_RDWR.
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// If there is an error, it will be of type *PathError.
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func Create(name string) (*File, error) {
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return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
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}
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// OpenFile is the generalized open call; most users will use Open
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// or Create instead. It opens the named file with specified flag
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// (O_RDONLY etc.). If the file does not exist, and the O_CREATE flag
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// is passed, it is created with mode perm (before umask). If successful,
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// methods on the returned File can be used for I/O.
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// If there is an error, it will be of type *PathError.
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func OpenFile(name string, flag int, perm FileMode) (*File, error) {
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testlog.Open(name)
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f, err := openFileNolog(name, flag, perm)
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if err != nil {
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return nil, err
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}
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f.appendMode = flag&O_APPEND != 0
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return f, nil
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}
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// lstat is overridden in tests.
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var lstat = Lstat
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// Rename renames (moves) oldpath to newpath.
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// If newpath already exists and is not a directory, Rename replaces it.
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// OS-specific restrictions may apply when oldpath and newpath are in different directories.
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// If there is an error, it will be of type *LinkError.
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func Rename(oldpath, newpath string) error {
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return rename(oldpath, newpath)
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}
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// Many functions in package syscall return a count of -1 instead of 0.
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// Using fixCount(call()) instead of call() corrects the count.
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func fixCount(n int, err error) (int, error) {
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if n < 0 {
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n = 0
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}
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return n, err
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}
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// wrapErr wraps an error that occurred during an operation on an open file.
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// It passes io.EOF through unchanged, otherwise converts
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// poll.ErrFileClosing to ErrClosed and wraps the error in a PathError.
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func (f *File) wrapErr(op string, err error) error {
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if err == nil || err == io.EOF {
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return err
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}
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if err == poll.ErrFileClosing {
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err = ErrClosed
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}
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return &PathError{Op: op, Path: f.name, Err: err}
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}
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// TempDir returns the default directory to use for temporary files.
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//
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// On Unix systems, it returns $TMPDIR if non-empty, else /tmp.
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// On Windows, it uses GetTempPath, returning the first non-empty
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// value from %TMP%, %TEMP%, %USERPROFILE%, or the Windows directory.
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// On Plan 9, it returns /tmp.
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//
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// The directory is neither guaranteed to exist nor have accessible
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// permissions.
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func TempDir() string {
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return tempDir()
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}
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// UserCacheDir returns the default root directory to use for user-specific
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// cached data. Users should create their own application-specific subdirectory
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// within this one and use that.
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//
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// On Unix systems, it returns $XDG_CACHE_HOME as specified by
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// https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if
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// non-empty, else $HOME/.cache.
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// On Darwin, it returns $HOME/Library/Caches.
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// On Windows, it returns %LocalAppData%.
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// On Plan 9, it returns $home/lib/cache.
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//
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// If the location cannot be determined (for example, $HOME is not defined),
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// then it will return an error.
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func UserCacheDir() (string, error) {
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var dir string
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switch runtime.GOOS {
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case "windows":
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dir = Getenv("LocalAppData")
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if dir == "" {
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return "", errors.New("%LocalAppData% is not defined")
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}
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case "darwin", "ios":
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dir = Getenv("HOME")
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if dir == "" {
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return "", errors.New("$HOME is not defined")
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}
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dir += "/Library/Caches"
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case "plan9":
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dir = Getenv("home")
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if dir == "" {
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return "", errors.New("$home is not defined")
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}
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dir += "/lib/cache"
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default: // Unix
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dir = Getenv("XDG_CACHE_HOME")
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if dir == "" {
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dir = Getenv("HOME")
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if dir == "" {
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return "", errors.New("neither $XDG_CACHE_HOME nor $HOME are defined")
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}
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dir += "/.cache"
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}
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}
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return dir, nil
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}
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// UserConfigDir returns the default root directory to use for user-specific
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// configuration data. Users should create their own application-specific
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// subdirectory within this one and use that.
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//
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// On Unix systems, it returns $XDG_CONFIG_HOME as specified by
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// https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if
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// non-empty, else $HOME/.config.
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// On Darwin, it returns $HOME/Library/Application Support.
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// On Windows, it returns %AppData%.
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// On Plan 9, it returns $home/lib.
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//
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// If the location cannot be determined (for example, $HOME is not defined),
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// then it will return an error.
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func UserConfigDir() (string, error) {
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var dir string
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switch runtime.GOOS {
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case "windows":
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dir = Getenv("AppData")
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if dir == "" {
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return "", errors.New("%AppData% is not defined")
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}
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case "darwin", "ios":
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dir = Getenv("HOME")
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if dir == "" {
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return "", errors.New("$HOME is not defined")
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}
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dir += "/Library/Application Support"
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case "plan9":
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dir = Getenv("home")
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if dir == "" {
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return "", errors.New("$home is not defined")
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}
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dir += "/lib"
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default: // Unix
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dir = Getenv("XDG_CONFIG_HOME")
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if dir == "" {
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dir = Getenv("HOME")
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if dir == "" {
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return "", errors.New("neither $XDG_CONFIG_HOME nor $HOME are defined")
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}
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dir += "/.config"
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}
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}
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return dir, nil
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}
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// UserHomeDir returns the current user's home directory.
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//
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// On Unix, including macOS, it returns the $HOME environment variable.
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|
// On Windows, it returns %USERPROFILE%.
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// On Plan 9, it returns the $home environment variable.
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func UserHomeDir() (string, error) {
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env, enverr := "HOME", "$HOME"
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switch runtime.GOOS {
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case "windows":
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env, enverr = "USERPROFILE", "%userprofile%"
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case "plan9":
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env, enverr = "home", "$home"
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}
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if v := Getenv(env); v != "" {
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return v, nil
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}
|
|
// On some geese the home directory is not always defined.
|
|
switch runtime.GOOS {
|
|
case "android":
|
|
return "/sdcard", nil
|
|
case "ios":
|
|
return "/", nil
|
|
}
|
|
return "", errors.New(enverr + " is not defined")
|
|
}
|
|
|
|
// Chmod changes the mode of the named file to mode.
|
|
// If the file is a symbolic link, it changes the mode of the link's target.
|
|
// If there is an error, it will be of type *PathError.
|
|
//
|
|
// A different subset of the mode bits are used, depending on the
|
|
// operating system.
|
|
//
|
|
// On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and
|
|
// ModeSticky are used.
|
|
//
|
|
// On Windows, only the 0200 bit (owner writable) of mode is used; it
|
|
// controls whether the file's read-only attribute is set or cleared.
|
|
// The other bits are currently unused. For compatibility with Go 1.12
|
|
// and earlier, use a non-zero mode. Use mode 0400 for a read-only
|
|
// file and 0600 for a readable+writable file.
|
|
//
|
|
// On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive,
|
|
// and ModeTemporary are used.
|
|
func Chmod(name string, mode FileMode) error { return chmod(name, mode) }
|
|
|
|
// Chmod changes the mode of the file to mode.
|
|
// If there is an error, it will be of type *PathError.
|
|
func (f *File) Chmod(mode FileMode) error { return f.chmod(mode) }
|
|
|
|
// SetDeadline sets the read and write deadlines for a File.
|
|
// It is equivalent to calling both SetReadDeadline and SetWriteDeadline.
|
|
//
|
|
// Only some kinds of files support setting a deadline. Calls to SetDeadline
|
|
// for files that do not support deadlines will return ErrNoDeadline.
|
|
// On most systems ordinary files do not support deadlines, but pipes do.
|
|
//
|
|
// A deadline is an absolute time after which I/O operations fail with an
|
|
// error instead of blocking. The deadline applies to all future and pending
|
|
// I/O, not just the immediately following call to Read or Write.
|
|
// After a deadline has been exceeded, the connection can be refreshed
|
|
// by setting a deadline in the future.
|
|
//
|
|
// If the deadline is exceeded a call to Read or Write or to other I/O
|
|
// methods will return an error that wraps ErrDeadlineExceeded.
|
|
// This can be tested using errors.Is(err, os.ErrDeadlineExceeded).
|
|
// That error implements the Timeout method, and calling the Timeout
|
|
// method will return true, but there are other possible errors for which
|
|
// the Timeout will return true even if the deadline has not been exceeded.
|
|
//
|
|
// An idle timeout can be implemented by repeatedly extending
|
|
// the deadline after successful Read or Write calls.
|
|
//
|
|
// A zero value for t means I/O operations will not time out.
|
|
func (f *File) SetDeadline(t time.Time) error {
|
|
return f.setDeadline(t)
|
|
}
|
|
|
|
// SetReadDeadline sets the deadline for future Read calls and any
|
|
// currently-blocked Read call.
|
|
// A zero value for t means Read will not time out.
|
|
// Not all files support setting deadlines; see SetDeadline.
|
|
func (f *File) SetReadDeadline(t time.Time) error {
|
|
return f.setReadDeadline(t)
|
|
}
|
|
|
|
// SetWriteDeadline sets the deadline for any future Write calls and any
|
|
// currently-blocked Write call.
|
|
// Even if Write times out, it may return n > 0, indicating that
|
|
// some of the data was successfully written.
|
|
// A zero value for t means Write will not time out.
|
|
// Not all files support setting deadlines; see SetDeadline.
|
|
func (f *File) SetWriteDeadline(t time.Time) error {
|
|
return f.setWriteDeadline(t)
|
|
}
|
|
|
|
// SyscallConn returns a raw file.
|
|
// This implements the syscall.Conn interface.
|
|
func (f *File) SyscallConn() (syscall.RawConn, error) {
|
|
if err := f.checkValid("SyscallConn"); err != nil {
|
|
return nil, err
|
|
}
|
|
return newRawConn(f)
|
|
}
|
|
|
|
// isWindowsNulName reports whether name is os.DevNull ('NUL') on Windows.
|
|
// True is returned if name is 'NUL' whatever the case.
|
|
func isWindowsNulName(name string) bool {
|
|
if len(name) != 3 {
|
|
return false
|
|
}
|
|
if name[0] != 'n' && name[0] != 'N' {
|
|
return false
|
|
}
|
|
if name[1] != 'u' && name[1] != 'U' {
|
|
return false
|
|
}
|
|
if name[2] != 'l' && name[2] != 'L' {
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
|
|
// DirFS returns a file system (an fs.FS) for the tree of files rooted at the directory dir.
|
|
//
|
|
// Note that DirFS("/prefix") only guarantees that the Open calls it makes to the
|
|
// operating system will begin with "/prefix": DirFS("/prefix").Open("file") is the
|
|
// same as os.Open("/prefix/file"). So if /prefix/file is a symbolic link pointing outside
|
|
// the /prefix tree, then using DirFS does not stop the access any more than using
|
|
// os.Open does. DirFS is therefore not a general substitute for a chroot-style security
|
|
// mechanism when the directory tree contains arbitrary content.
|
|
func DirFS(dir string) fs.FS {
|
|
return dirFS(dir)
|
|
}
|
|
|
|
func containsAny(s, chars string) bool {
|
|
for i := 0; i < len(s); i++ {
|
|
for j := 0; j < len(chars); j++ {
|
|
if s[i] == chars[j] {
|
|
return true
|
|
}
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
type dirFS string
|
|
|
|
func (dir dirFS) Open(name string) (fs.File, error) {
|
|
if !fs.ValidPath(name) || runtime.GOOS == "windows" && containsAny(name, `\:`) {
|
|
return nil, &PathError{Op: "open", Path: name, Err: ErrInvalid}
|
|
}
|
|
f, err := Open(string(dir) + "/" + name)
|
|
if err != nil {
|
|
return nil, err // nil fs.File
|
|
}
|
|
return f, nil
|
|
}
|
|
|
|
func (dir dirFS) Stat(name string) (fs.FileInfo, error) {
|
|
if !fs.ValidPath(name) || runtime.GOOS == "windows" && containsAny(name, `\:`) {
|
|
return nil, &PathError{Op: "stat", Path: name, Err: ErrInvalid}
|
|
}
|
|
f, err := Stat(string(dir) + "/" + name)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return f, nil
|
|
}
|
|
|
|
// ReadFile reads the named file and returns the contents.
|
|
// A successful call returns err == nil, not err == EOF.
|
|
// Because ReadFile reads the whole file, it does not treat an EOF from Read
|
|
// as an error to be reported.
|
|
func ReadFile(name string) ([]byte, error) {
|
|
f, err := Open(name)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
defer f.Close()
|
|
|
|
var size int
|
|
if info, err := f.Stat(); err == nil {
|
|
size64 := info.Size()
|
|
if int64(int(size64)) == size64 {
|
|
size = int(size64)
|
|
}
|
|
}
|
|
size++ // one byte for final read at EOF
|
|
|
|
// If a file claims a small size, read at least 512 bytes.
|
|
// In particular, files in Linux's /proc claim size 0 but
|
|
// then do not work right if read in small pieces,
|
|
// so an initial read of 1 byte would not work correctly.
|
|
if size < 512 {
|
|
size = 512
|
|
}
|
|
|
|
data := make([]byte, 0, size)
|
|
for {
|
|
if len(data) >= cap(data) {
|
|
d := append(data[:cap(data)], 0)
|
|
data = d[:len(data)]
|
|
}
|
|
n, err := f.Read(data[len(data):cap(data)])
|
|
data = data[:len(data)+n]
|
|
if err != nil {
|
|
if err == io.EOF {
|
|
err = nil
|
|
}
|
|
return data, err
|
|
}
|
|
}
|
|
}
|
|
|
|
// WriteFile writes data to the named file, creating it if necessary.
|
|
// If the file does not exist, WriteFile creates it with permissions perm (before umask);
|
|
// otherwise WriteFile truncates it before writing, without changing permissions.
|
|
func WriteFile(name string, data []byte, perm FileMode) error {
|
|
f, err := OpenFile(name, O_WRONLY|O_CREATE|O_TRUNC, perm)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
_, err = f.Write(data)
|
|
if err1 := f.Close(); err1 != nil && err == nil {
|
|
err = err1
|
|
}
|
|
return err
|
|
}
|