Remove Windows specific implementation

internal/symlinks/symlink.go

@@ -13,12 +13,11 @@
 // You should have received a copy of the GNU General Public License along
 // with this program. If not, see <http://www.gnu.org/licenses/>.
 
-// +build !windows
-
 package symlinks
 
 import (
 	"os"
+	"runtime"
 
 	"github.com/syncthing/syncthing/internal/osutil"
 	"github.com/syncthing/syncthing/internal/protocol"
@@ -54,5 +53,30 @@ func Create(source, target string, flags uint32) error {
 }
 
 func ChangeType(path string, flags uint32) error {
-	return nil
+	if runtime.GOOS != "windows" {
+		// This is a Windows-only concept.
+		return nil
+	}
+
+	target, cflags, err := Read(path)
+	if err != nil {
+		return err
+	}
+
+	// If it's the same type, nothing to do.
+	if cflags&protocol.SymlinkTypeMask == flags&protocol.SymlinkTypeMask {
+		return nil
+	}
+
+	// If the actual type is unknown, but the new type is file, nothing to do
+	if cflags&protocol.FlagSymlinkMissingTarget != 0 && flags&protocol.FlagDirectory == 0 {
+		return nil
+	}
+
+	return osutil.InWritableDir(func(path string) error {
+		// It should be a symlink as well hence no need to change permissions
+		// on the file.
+		os.Remove(path)
+		return Create(path, target, flags)
+	}, path)
 }

internal/symlinks/symlink_windows.go

@@ -1,212 +0,0 @@
-// Copyright (C) 2014 The Syncthing Authors.
-//
-// This program is free software: you can redistribute it and/or modify it
-// under the terms of the GNU General Public License as published by the Free
-// Software Foundation, either version 3 of the License, or (at your option)
-// any later version.
-//
-// This program is distributed in the hope that it will be useful, but WITHOUT
-// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
-// more details.
-//
-// You should have received a copy of the GNU General Public License along
-// with this program. If not, see <http://www.gnu.org/licenses/>.
-
-// +build windows
-
-package symlinks
-
-import (
-	"os"
-	"path/filepath"
-
-	"github.com/syncthing/syncthing/internal/osutil"
-	"github.com/syncthing/syncthing/internal/protocol"
-
-	"syscall"
-	"unicode/utf16"
-	"unsafe"
-)
-
-const (
-	FSCTL_GET_REPARSE_POINT      = 0x900a8
-	FILE_FLAG_OPEN_REPARSE_POINT = 0x00200000
-	FILE_ATTRIBUTE_REPARSE_POINT = 0x400
-	IO_REPARSE_TAG_SYMLINK       = 0xA000000C
-	SYMBOLIC_LINK_FLAG_DIRECTORY = 0x1
-)
-
-var (
-	modkernel32            = syscall.NewLazyDLL("kernel32.dll")
-	procDeviceIoControl    = modkernel32.NewProc("DeviceIoControl")
-	procCreateSymbolicLink = modkernel32.NewProc("CreateSymbolicLinkW")
-
-	Supported = false
-)
-
-func init() {
-	defer func() {
-		if err := recover(); err != nil {
-			// Ensure that the supported flag is disabled when we hit an
-			// error, even though it should already be. Also, silently swallow
-			// the error since it's fine for a system not to support symlinks.
-			Supported = false
-		}
-	}()
-
-	// Needs administrator priviledges.
-	// Let's check that everything works.
-	// This could be done more officially:
-	// http://stackoverflow.com/questions/2094663/determine-if-windows-process-has-privilege-to-create-symbolic-link
-	// But I don't want to define 10 more structs just to look this up.
-	base := os.TempDir()
-	path := filepath.Join(base, "symlinktest")
-	defer os.Remove(path)
-
-	err := Create(path, base, protocol.FlagDirectory)
-	if err != nil {
-		return
-	}
-
-	isLink, err := IsSymlink(path)
-	if err != nil || !isLink {
-		return
-	}
-
-	target, flags, err := Read(path)
-	if err != nil || osutil.NativeFilename(target) != base || flags&protocol.FlagDirectory == 0 {
-		return
-	}
-	Supported = true
-}
-
-type reparseData struct {
-	reparseTag          uint32
-	reparseDataLength   uint16
-	reserved            uint16
-	substitueNameOffset uint16
-	substitueNameLength uint16
-	printNameOffset     uint16
-	printNameLength     uint16
-	flags               uint32
-	// substituteName - 264 widechars max = 528 bytes
-	// printName      - 260 widechars max = 520 bytes
-	//                                    = 1048 bytes total
-	buffer [1048]uint16
-}
-
-func (r *reparseData) PrintName() string {
-	// No clue why the offset and length is doubled...
-	offset := r.printNameOffset / 2
-	length := r.printNameLength / 2
-	return string(utf16.Decode(r.buffer[offset : offset+length]))
-}
-
-func (r *reparseData) SubstituteName() string {
-	// No clue why the offset and length is doubled...
-	offset := r.substitueNameOffset / 2
-	length := r.substitueNameLength / 2
-	return string(utf16.Decode(r.buffer[offset : offset+length]))
-}
-
-func Read(path string) (string, uint32, error) {
-	ptr, err := syscall.UTF16PtrFromString(path)
-	if err != nil {
-		return "", protocol.FlagSymlinkMissingTarget, err
-	}
-	handle, err := syscall.CreateFile(ptr, 0, syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE|syscall.FILE_SHARE_DELETE, nil, syscall.OPEN_EXISTING, syscall.FILE_FLAG_BACKUP_SEMANTICS|FILE_FLAG_OPEN_REPARSE_POINT, 0)
-	if err != nil || handle == syscall.InvalidHandle {
-		return "", protocol.FlagSymlinkMissingTarget, err
-	}
-	defer syscall.Close(handle)
-	var ret uint16
-	var data reparseData
-
-	r1, _, err := syscall.Syscall9(procDeviceIoControl.Addr(), 8, uintptr(handle), FSCTL_GET_REPARSE_POINT, 0, 0, uintptr(unsafe.Pointer(&data)), unsafe.Sizeof(data), uintptr(unsafe.Pointer(&ret)), 0, 0)
-	if r1 == 0 {
-		return "", protocol.FlagSymlinkMissingTarget, err
-	}
-
-	var flags uint32 = 0
-	attr, err := syscall.GetFileAttributes(ptr)
-	if err != nil {
-		flags = protocol.FlagSymlinkMissingTarget
-	} else if attr&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
-		flags = protocol.FlagDirectory
-	}
-
-	return osutil.NormalizedFilename(data.PrintName()), flags, nil
-}
-
-func IsSymlink(path string) (bool, error) {
-	ptr, err := syscall.UTF16PtrFromString(path)
-	if err != nil {
-		return false, err
-	}
-
-	attr, err := syscall.GetFileAttributes(ptr)
-	if err != nil {
-		return false, err
-	}
-	return attr&FILE_ATTRIBUTE_REPARSE_POINT != 0, nil
-}
-
-func Create(source, target string, flags uint32) error {
-	srcp, err := syscall.UTF16PtrFromString(source)
-	if err != nil {
-		return err
-	}
-
-	trgp, err := syscall.UTF16PtrFromString(osutil.NativeFilename(target))
-	if err != nil {
-		return err
-	}
-
-	// Sadly for Windows we need to specify the type of the symlink,
-	// whether it's a directory symlink or a file symlink.
-	// If the flags doesn't reveal the target type, try to evaluate it
-	// ourselves, and worst case default to the symlink pointing to a file.
-	mode := 0
-	if flags&protocol.FlagSymlinkMissingTarget != 0 {
-		path := target
-		if !filepath.IsAbs(target) {
-			path = filepath.Join(filepath.Dir(source), target)
-		}
-
-		stat, err := os.Stat(path)
-		if err == nil && stat.IsDir() {
-			mode = SYMBOLIC_LINK_FLAG_DIRECTORY
-		}
-	} else if flags&protocol.FlagDirectory != 0 {
-		mode = SYMBOLIC_LINK_FLAG_DIRECTORY
-	}
-
-	r0, _, err := syscall.Syscall(procCreateSymbolicLink.Addr(), 3, uintptr(unsafe.Pointer(srcp)), uintptr(unsafe.Pointer(trgp)), uintptr(mode))
-	if r0 == 1 {
-		return nil
-	}
-	return err
-}
-
-func ChangeType(path string, flags uint32) error {
-	target, cflags, err := Read(path)
-	if err != nil {
-		return err
-	}
-	// If it's the same type, nothing to do.
-	if cflags&protocol.SymlinkTypeMask == flags&protocol.SymlinkTypeMask {
-		return nil
-	}
-
-	// If the actual type is unknown, but the new type is file, nothing to do
-	if cflags&protocol.FlagSymlinkMissingTarget != 0 && flags&protocol.FlagDirectory == 0 {
-		return nil
-	}
-	return osutil.InWritableDir(func(path string) error {
-		// It should be a symlink as well hence no need to change permissions on
-		// the file.
-		os.Remove(path)
-		return Create(path, target, flags)
-	}, path)
-}