Add atomic rename functions for Windows and Plan 9.

This code is based off leveldb (https://github.com/syndtr/goleveldb),
and the leveldb copyright notice (a 2-clause BSD license) has been
included where used.

disksync.go

@@ -149,7 +149,7 @@ func (a *Account) writeDirtyToDisk() error {
 
 		// TODO(jrick): this should be atomic on *nix, but is not on
 		// Windows.  Use _windows.go to provide atomic renames.
-		if err = os.Rename(tmpfilepath, utxofilepath); err != nil {
+		if err = Rename(tmpfilepath, utxofilepath); err != nil {
 			return err
 		}
 
@@ -175,7 +175,7 @@ func (a *Account) writeDirtyToDisk() error {
 
 		// TODO(jrick): this should be atomic on *nix, but is not on
 		// Windows.  Use _windows.go to provide atomic renames.
-		if err = os.Rename(tmpfilepath, txfilepath); err != nil {
+		if err = Rename(tmpfilepath, txfilepath); err != nil {
 			return err
 		}
 
@@ -201,7 +201,7 @@ func (a *Account) writeDirtyToDisk() error {
 
 		// TODO(jrick): this should be atomic on *nix, but is not on
 		// Windows.  Use _windows.go to provide atomic renames.
-		if err = os.Rename(tmpfilepath, wfilepath); err != nil {
+		if err = Rename(tmpfilepath, wfilepath); err != nil {
 			return err
 		}
 

rename_plan9.go

@@ -0,0 +1,47 @@
+// The following is adapted from goleveldb
+// (https://github.com/syndtr/goleveldb) under the following license:
+//
+// Copyright 2012 Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above copyright
+// notice, this list of conditions and the following disclaimer in the
+// documentation and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package main
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// Rename provides an atomic file rename.  newpath is replaced if it
+// already exists.
+func Rename(oldpath, newpath string) error {
+	if _, err := os.Stat(newpath); err == nil {
+		if err := os.Remove(newpath); err != nil {
+			return err
+		}
+	}
+
+	_, fname := filepath.Split(newpath)
+	return os.Rename(oldpath, fname)
+}

rename_unix.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2013 Conformal Systems LLC <info@conformal.com>
+//
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+// +build !windows,!plan9
+
+package main
+
+import (
+	"os"
+)
+
+// Rename provides an atomic file rename.  newpath is replaced if it
+// already exists. 
+func Rename(oldpath, newpath string) error {
+	return os.Rename(oldpath, newpath)
+}

rename_windows.go

@@ -0,0 +1,71 @@
+// The following is adapted from goleveldb
+// (https://github.com/syndtr/goleveldb) under the following license:
+//
+// Copyright 2012 Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above copyright
+// notice, this list of conditions and the following disclaimer in the
+// documentation and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package main
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var (
+	modkernel32     = syscall.NewLazyDLL("kernel32.dll")
+	procMoveFileExW = modkernel32.NewProc("MoveFileExW")
+)
+
+const (
+	_MOVEFILE_REPLACE_EXISTING = 1
+)
+
+func moveFileEx(from *uint16, to *uint16, flags uint32) error {
+	r1, _, e1 := syscall.Syscall(procMoveFileExW.Addr(), 3,
+		uintptr(unsafe.Pointer(from)), uintptr(unsafe.Pointer(to)),
+		uintptr(flags))
+	if r1 == 0 {
+		if e1 != 0 {
+			return error(e1)
+		} else {
+			return syscall.EINVAL
+		}
+	}
+	return nil
+}
+
+// Rename provides an atomic file rename.  newpath is replaced if it
+// already exists.
+func Rename(oldpath, newpath string) error {
+	from, err := syscall.UTF16PtrFromString(oldpath)
+	if err != nil {
+		return err
+	}
+	to, err := syscall.UTF16PtrFromString(newpath)
+	if err != nil {
+		return err
+	}
+	return moveFileEx(from, to, _MOVEFILE_REPLACE_EXISTING)
+}

updates.go

@@ -108,7 +108,7 @@ func updateOldFileLocations() {
 		old := filepath.Join(cfg.DataDir, fi[i].Name(), "wallet.bin")
 		if fileExists(old) {
 			new := accountFilename("wallet.bin", account, netdir)
-			if err := os.Rename(old, new); err != nil {
+			if err := Rename(old, new); err != nil {
 				log.Errorf("Cannot move old %v for account %v to new location: %v",
 					"wallet.bin", account, err)
 				os.Exit(1)
@@ -119,7 +119,7 @@ func updateOldFileLocations() {
 		old = filepath.Join(cfg.DataDir, fi[i].Name(), "tx.bin")
 		if fileExists(old) {
 			new := accountFilename("tx.bin", account, netdir)
-			if err := os.Rename(old, new); err != nil {
+			if err := Rename(old, new); err != nil {
 				log.Errorf("Cannot move old %v for account %v to new location: %v",
 					"tx.bin", account, err)
 				os.Exit(1)
@@ -130,7 +130,7 @@ func updateOldFileLocations() {
 		old = filepath.Join(cfg.DataDir, fi[i].Name(), "utxo.bin")
 		if fileExists(old) {
 			new := accountFilename("utxo.bin", account, netdir)
-			if err := os.Rename(old, new); err != nil {
+			if err := Rename(old, new); err != nil {
 				log.Errorf("Cannot move old %v for account %v to new location: %v",
 					"utxo.bin", account, err)
 				os.Exit(1)