Refactor AppendToFile and WriteFileDescriptor

base/files/file_util.h

Index: base/files/file_util.h
diff --git a/base/files/file_util.h b/base/files/file_util.h
index feebeed919697e3ec12c231f63a60868eb1b0a7a..607bb758ee5c4855459f42e6431380b726cf9488 100644
--- a/base/files/file_util.h
+++ b/base/files/file_util.h
@@ -326,14 +326,18 @@ BASE_EXPORT int WriteFile(const FilePath& filename, const char* data,
                           int size);
 
 #if defined(OS_POSIX)
-// Append the data to |fd|. Does not close |fd| when done.
-BASE_EXPORT int WriteFileDescriptor(const int fd, const char* data, int size);
+// Append |data| to |fd|. Does not close |fd| when done.  Returns true if all of

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

nit: appends

+// |data| was written, false otherwise.  In case of error, guarantees that the
+// last system error is preserved.
+BASE_EXPORT bool WriteFileDescriptor(const int fd, const char* data, int size);
 #endif
 
-// Append the given buffer into the file. Returns the number of bytes written,
-// or -1 on error.
-BASE_EXPORT int AppendToFile(const FilePath& filename,
-                             const char* data, int size);
+// Append |data| to |filename|.  Returns true if all of |data| was written,
+// false otherwise.  In case of error, guarantees that the last system error is

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

I'm a on the fence about the last error bit. There is only one place on all the
file related code from base where we explicitly preserve last error (and it is
actually not a documented feature). It seems like all callers are happy not
knowing the exact reason for the failure, as the current code doesn't preserve
it.

It is quite easy to preserve the error... just a few extra lines, but then we
start to lose uniformity as almost nowhere else the error is preserved (it may,
but it may not). On the other hand, it makes the code more flexible.

Brett, any opinion?

+// preserved.
+BASE_EXPORT bool AppendToFile(const FilePath& filename,
+                              const char* data,
+                              int size);
 
 // Gets the current working directory for the process.
 BASE_EXPORT bool GetCurrentDirectory(FilePath* path);