Refactor AppendToFile and WriteFileDescriptor

base/files/file_util_win.cc

Index: base/files/file_util_win.cc
diff --git a/base/files/file_util_win.cc b/base/files/file_util_win.cc
index b58619192378d50bab86a791dcdce665cf7a0545..f8583c38967a7620fe8019f7f171a687771c8b00 100644
--- a/base/files/file_util_win.cc
+++ b/base/files/file_util_win.cc
@@ -644,7 +644,7 @@ int WriteFile(const FilePath& filename, const char* data, int size) {
   return -1;
 }
 
-int AppendToFile(const FilePath& filename, const char* data, int size) {
+bool AppendToFile(const FilePath& filename, const char* data, int size) {
   ThreadRestrictions::AssertIOAllowed();
   base::win::ScopedHandle file(CreateFile(filename.value().c_str(),
                                           FILE_APPEND_DATA,
@@ -653,27 +653,29 @@ int AppendToFile(const FilePath& filename, const char* data, int size) {
                                           OPEN_EXISTING,
                                           0,
                                           NULL));
-  if (!file.IsValid()) {
-    DPLOG(WARNING) << "CreateFile failed for path "
-                   << UTF16ToUTF8(filename.value());
-    return -1;
-  }
+  if (!file.IsValid())
+    return false;
 
+  DWORD saved_error = 0;
   DWORD written;
-  BOOL result = ::WriteFile(file.Get(), data, size, &written, NULL);
-  if (result && static_cast<int>(written) == size)
-    return written;
 
-  if (!result) {
-    // WriteFile failed.
-    DPLOG(WARNING) << "writing file " << UTF16ToUTF8(filename.value())
-                   << " failed";
-  } else {
-    // Didn't write all the bytes.
-    DLOG(WARNING) << "wrote" << written << " bytes to "
-                  << UTF16ToUTF8(filename.value()) << " expected " << size;
+  // According to MSFT documentation the only time a partial write can occur is
+  // if we are writing to a pipe, which we aren't currently doing so if this

[rvargas (doing something else), 2014/10/01 20:01:14]

I don't think this code has enough context to know if this is a pipe or not. In
any case, there is |written| already, so why not see what it is and return false
if != size?

+  // call succeeds we can assume that all the data was written out to the file.
+  if (!::WriteFile(file.Get(), data, size, &written, NULL))
+    saved_error = ::GetLastError();
+
+  // Close the file now so that we can restore the write error, if any.
+  file.Close();
+
+  // Restore any error that occurred while writing the data.  This takes
+  // precedence over any errors that happened while closing the file.
+  if (saved_error != 0) {
+    ::SetLastError(saved_error);
+    return false;
   }
-  return -1;
+
+  return true;
 }
 
 // Gets the current working directory for the process.