[windows] Make most file_win.cc functions use malloc for string conversions.

runtime/bin/directory_win.cc

Index: runtime/bin/directory_win.cc
diff --git a/runtime/bin/directory_win.cc b/runtime/bin/directory_win.cc
index efaaaf90a6e7ee6f08e5e94b2f5e6a0157d08900..4ebf512307e34d980015294ca2e015897f88fde3 100644
--- a/runtime/bin/directory_win.cc
+++ b/runtime/bin/directory_win.cc
@@ -50,8 +50,8 @@ const char* PathBuffer::AsScopedString() const {
 
 
 bool PathBuffer::Add(const char* name) {
-  const wchar_t* wide_name = StringUtilsWin::Utf8ToWide(name);
-  return AddW(wide_name);
+  Utf8ToWideScope wide_name(name);
+  return AddW(wide_name.wide());
 }
 
 
@@ -377,8 +377,8 @@ static Directory::ExistsResult ExistsHelper(const wchar_t* dir_name) {
 
 
 Directory::ExistsResult Directory::Exists(const char* dir_name) {
-  const wchar_t* system_name = StringUtilsWin::Utf8ToWide(dir_name);
-  return ExistsHelper(system_name);
+  Utf8ToWideScope system_name(dir_name);
+  return ExistsHelper(system_name.wide());
 }
 
 
@@ -412,19 +412,19 @@ const char* Directory::Current() {
 
 
 bool Directory::SetCurrent(const char* path) {
-  const wchar_t* system_path = StringUtilsWin::Utf8ToWide(path);
-  bool result = SetCurrentDirectoryW(system_path) != 0;
+  Utf8ToWideScope system_path(path);
+  bool result = SetCurrentDirectoryW(system_path.wide()) != 0;
   return result;
 }
 
 
 bool Directory::Create(const char* dir_name) {
-  const wchar_t* system_name = StringUtilsWin::Utf8ToWide(dir_name);
-  int create_status = CreateDirectoryW(system_name, NULL);
+  Utf8ToWideScope system_name(dir_name);
+  int create_status = CreateDirectoryW(system_name.wide(), NULL);
   // If the directory already existed, treat it as a success.
   if ((create_status == 0) &&
       (GetLastError() == ERROR_ALREADY_EXISTS) &&
-      (ExistsHelper(system_name) == EXISTS)) {
+      (ExistsHelper(system_name.wide()) == EXISTS)) {
     return true;
   }
   return (create_status != 0);
@@ -446,8 +446,8 @@ const char* Directory::CreateTemp(const char* prefix) {
   // descriptor inherited from its parent directory.
   // The return value is Dart_ScopeAllocated.
   PathBuffer path;
-  const wchar_t* system_prefix = StringUtilsWin::Utf8ToWide(prefix);
-  if (!path.AddW(system_prefix)) {
+  Utf8ToWideScope system_prefix(prefix);
+  if (!path.AddW(system_prefix.wide())) {
     return NULL;
   }
 
@@ -481,16 +481,16 @@ const char* Directory::CreateTemp(const char* prefix) {
 
 bool Directory::Delete(const char* dir_name, bool recursive) {
   bool result = false;
-  const wchar_t* system_dir_name = StringUtilsWin::Utf8ToWide(dir_name);
+  Utf8ToWideScope system_dir_name(dir_name);
   if (!recursive) {
     if (File::GetType(dir_name, true) == File::kIsDirectory) {
-      result = (RemoveDirectoryW(system_dir_name) != 0);
+      result = (RemoveDirectoryW(system_dir_name.wide()) != 0);
     } else {
       SetLastError(ERROR_FILE_NOT_FOUND);
     }
   } else {
     PathBuffer path;
-    if (path.AddW(system_dir_name)) {
+    if (path.AddW(system_dir_name.wide())) {
       result = DeleteRecursively(&path);
     }
   }
@@ -499,13 +499,13 @@ bool Directory::Delete(const char* dir_name, bool recursive) {
 
 
 bool Directory::Rename(const char* path, const char* new_path) {
-  const wchar_t* system_path = StringUtilsWin::Utf8ToWide(path);
-  const wchar_t* system_new_path = StringUtilsWin::Utf8ToWide(new_path);
-  ExistsResult exists = ExistsHelper(system_path);
+  Utf8ToWideScope system_path(path);
+  Utf8ToWideScope system_new_path(new_path);
+  ExistsResult exists = ExistsHelper(system_path.wide());
   if (exists != EXISTS) {
     return false;
   }
-  ExistsResult new_exists = ExistsHelper(system_new_path);
+  ExistsResult new_exists = ExistsHelper(system_new_path.wide());
   // MoveFile does not allow replacing exising directories. Therefore,
   // if the new_path is currently a directory we need to delete it
   // first.
@@ -517,7 +517,7 @@ bool Directory::Rename(const char* path, const char* new_path) {
   }
   DWORD flags = MOVEFILE_WRITE_THROUGH;
   int move_status =
-      MoveFileExW(system_path, system_new_path, flags);
+      MoveFileExW(system_path.wide(), system_new_path.wide(), flags);
   return (move_status != 0);
 }