syncthing/lib/osutil/osutil.go
2015-09-30 12:41:29 +02:00

332 lines
9.0 KiB
Go

// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
// Package osutil implements utilities for native OS support.
package osutil
import (
"errors"
"fmt"
"io"
"net"
"os"
"path/filepath"
"runtime"
"sort"
"strings"
"time"
"github.com/calmh/du"
"github.com/syncthing/syncthing/lib/sync"
)
var ErrNoHome = errors.New("No home directory found - set $HOME (or the platform equivalent).")
// Try to keep this entire operation atomic-like. We shouldn't be doing this
// often enough that there is any contention on this lock.
var renameLock = sync.NewMutex()
// TryRename renames a file, leaving source file intact in case of failure.
// Tries hard to succeed on various systems by temporarily tweaking directory
// permissions and removing the destination file when necessary.
func TryRename(from, to string) error {
renameLock.Lock()
defer renameLock.Unlock()
return withPreparedTarget(from, to, func() error {
return os.Rename(from, to)
})
}
// Rename moves a temporary file to it's final place.
// Will make sure to delete the from file if the operation fails, so use only
// for situations like committing a temp file to it's final location.
// Tries hard to succeed on various systems by temporarily tweaking directory
// permissions and removing the destination file when necessary.
func Rename(from, to string) error {
// Don't leave a dangling temp file in case of rename error
if !(runtime.GOOS == "windows" && strings.EqualFold(from, to)) {
defer os.Remove(from)
}
return TryRename(from, to)
}
// Copy copies the file content from source to destination.
// Tries hard to succeed on various systems by temporarily tweaking directory
// permissions and removing the destination file when necessary.
func Copy(from, to string) (err error) {
return withPreparedTarget(from, to, func() error {
return copyFileContents(from, to)
})
}
// InWritableDir calls fn(path), while making sure that the directory
// containing `path` is writable for the duration of the call.
func InWritableDir(fn func(string) error, path string) error {
dir := filepath.Dir(path)
info, err := os.Stat(dir)
if err != nil {
return err
}
if !info.IsDir() {
return errors.New("Not a directory: " + path)
}
if info.Mode()&0200 == 0 {
// A non-writeable directory (for this user; we assume that's the
// relevant part). Temporarily change the mode so we can delete the
// file or directory inside it.
err = os.Chmod(dir, 0755)
if err == nil {
defer func() {
err = os.Chmod(dir, info.Mode())
if err != nil {
// We managed to change the permission bits like a
// millisecond ago, so it'd be bizarre if we couldn't
// change it back.
panic(err)
}
}()
}
}
return fn(path)
}
// Remove removes the given path. On Windows, removes the read-only attribute
// from the target prior to deletion.
func Remove(path string) error {
if runtime.GOOS == "windows" {
info, err := os.Stat(path)
if err != nil {
return err
}
if info.Mode()&0200 == 0 {
os.Chmod(path, 0700)
}
}
return os.Remove(path)
}
func ExpandTilde(path string) (string, error) {
if path == "~" {
return getHomeDir()
}
path = filepath.FromSlash(path)
if !strings.HasPrefix(path, fmt.Sprintf("~%c", os.PathSeparator)) {
return path, nil
}
home, err := getHomeDir()
if err != nil {
return "", err
}
return filepath.Join(home, path[2:]), nil
}
func getHomeDir() (string, error) {
var home string
switch runtime.GOOS {
case "windows":
home = filepath.Join(os.Getenv("HomeDrive"), os.Getenv("HomePath"))
if home == "" {
home = os.Getenv("UserProfile")
}
default:
home = os.Getenv("HOME")
}
if home == "" {
return "", ErrNoHome
}
return home, nil
}
// Tries hard to succeed on various systems by temporarily tweaking directory
// permissions and removing the destination file when necessary.
func withPreparedTarget(from, to string, f func() error) error {
// Make sure the destination directory is writeable
toDir := filepath.Dir(to)
if info, err := os.Stat(toDir); err == nil && info.IsDir() && info.Mode()&0200 == 0 {
os.Chmod(toDir, 0755)
defer os.Chmod(toDir, info.Mode())
}
// On Windows, make sure the destination file is writeable (or we can't delete it)
if runtime.GOOS == "windows" {
os.Chmod(to, 0666)
if !strings.EqualFold(from, to) {
err := os.Remove(to)
if err != nil && !os.IsNotExist(err) {
return err
}
}
}
return f()
}
// copyFileContents copies the contents of the file named src to the file named
// by dst. The file will be created if it does not already exist. If the
// destination file exists, all it's contents will be replaced by the contents
// of the source file.
func copyFileContents(src, dst string) (err error) {
in, err := os.Open(src)
if err != nil {
return
}
defer in.Close()
out, err := os.Create(dst)
if err != nil {
return
}
defer func() {
cerr := out.Close()
if err == nil {
err = cerr
}
}()
if _, err = io.Copy(out, in); err != nil {
return
}
err = out.Sync()
return
}
var execExts map[string]bool
func init() {
// PATHEXT contains a list of executable file extensions, on Windows
pathext := filepath.SplitList(os.Getenv("PATHEXT"))
// We want the extensions in execExts to be lower case
execExts = make(map[string]bool, len(pathext))
for _, ext := range pathext {
execExts[strings.ToLower(ext)] = true
}
}
// IsWindowsExecutable returns true if the given path has an extension that is
// in the list of executable extensions.
func IsWindowsExecutable(path string) bool {
return execExts[strings.ToLower(filepath.Ext(path))]
}
func DiskFreeBytes(path string) (free int64, err error) {
u, err := du.Get(path)
return u.FreeBytes, err
}
func DiskFreePercentage(path string) (freePct float64, err error) {
u, err := du.Get(path)
return (float64(u.FreeBytes) / float64(u.TotalBytes)) * 100, err
}
// SetTCPOptions sets syncthings default TCP options on a TCP connection
func SetTCPOptions(conn *net.TCPConn) error {
var err error
if err = conn.SetLinger(0); err != nil {
return err
}
if err = conn.SetNoDelay(false); err != nil {
return err
}
if err = conn.SetKeepAlivePeriod(60 * time.Second); err != nil {
return err
}
if err = conn.SetKeepAlive(true); err != nil {
return err
}
return nil
}
// The CachedCaseSensitiveStat provides an Lstat() method similar to
// os.Lstat(), but that is always case sensitive regardless of underlying file
// system semantics. The "Cached" part refers to the fact that it lists the
// contents of a directory the first time it's needed and then retains this
// information for the duration. It's expected that instances of this type are
// fairly short lived.
//
// There's some song and dance to check directories that are parents to the
// checked path as well, that is we want to catch the situation that someone
// calls Lstat("foo/BAR/baz") when the actual path is "foo/bar/baz" and return
// NotExist appropriately. But we don't want to do this check too high up, as
// the user may have told us the folder path is ~/Sync while it is actually
// ~/sync and this *should* work properly... Sigh. Hence the "base" parameter.
type CachedCaseSensitiveStat struct {
base string // base directory, we should not check stuff above this
results map[string][]os.FileInfo // directory path => list of children
}
func NewCachedCaseSensitiveStat(base string) *CachedCaseSensitiveStat {
return &CachedCaseSensitiveStat{
base: strings.ToLower(base),
results: make(map[string][]os.FileInfo),
}
}
func (c *CachedCaseSensitiveStat) Lstat(name string) (os.FileInfo, error) {
dir := filepath.Dir(name)
base := filepath.Base(name)
if !strings.HasPrefix(strings.ToLower(dir), c.base) {
// We only validate things within the base directory, which we need to
// compare case insensitively against.
return nil, os.ErrInvalid
}
// If we don't already have a list of directory entries for this
// directory, try to list it. Return error if this fails.
l, ok := c.results[dir]
if !ok {
if len(dir) > len(c.base) {
// We are checking in a subdirectory of base. Must make sure *it*
// exists with the specified casing, up to the base directory.
if _, err := c.Lstat(dir); err != nil {
return nil, err
}
}
fd, err := os.Open(dir)
if err != nil {
return nil, err
}
defer fd.Close()
l, err = fd.Readdir(-1)
if err != nil {
return nil, err
}
sort.Sort(fileInfoList(l))
c.results[dir] = l
}
// Get the index of the first entry with name >= base using binary search.
idx := sort.Search(len(l), func(i int) bool {
return l[i].Name() >= base
})
if idx >= len(l) || l[idx].Name() != base {
// The search didn't find any such entry
return nil, os.ErrNotExist
}
return l[idx], nil
}
type fileInfoList []os.FileInfo
func (l fileInfoList) Len() int {
return len(l)
}
func (l fileInfoList) Swap(a, b int) {
l[a], l[b] = l[b], l[a]
}
func (l fileInfoList) Less(a, b int) bool {
return l[a].Name() < l[b].Name()
}