Unify UUID/GUID generation code across base and blink

base/guid.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_GUID_H_
 #define BASE_GUID_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/base_export.h"
 #include "build/build_config.h"
 
 namespace base {
 
-// Generate a 128-bit random GUID of the form: "%08X-%04X-%04X-%04X-%012llX".
+// Generate a 128-bit (pseudo) random GUID in the form of version 4 as described
+// in RFC 4122, section 4.4.
+// The format of GUID version 4 must be xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx,
+// where y is one of [8, 9, A, B].
+// The hexadecimal values "a" through "f" are output as lower case characters.
 // If GUID generation fails an empty string is returned.
-// The POSIX implementation uses pseudo random number generation to create
-// the GUID.  The Windows implementation uses system services.
 BASE_EXPORT std::string GenerateGUID();
 
-// Returns true if the input string conforms to the GUID format.
+// Returns true if the input string conforms to the version 4 GUID format.
+// Note that this does NOT check if the hexadecimal values "a" through "f"
+// are in lower case characters, as Version 4 RFC says onput they're
+// case insensitive. (Use IsValidGUIDOutputString for checking if the
+// given string is valid output string)
 BASE_EXPORT bool IsValidGUID(const std::string& guid);
 
-#if defined(OS_POSIX)
+// Returns true if the input string is valid version 4 GUID output string.
+// This also checks if the hexadecimal values "a" through "f" are in lower
+// case characters.
+BASE_EXPORT bool IsValidGUIDOutputString(const std::string& guid);
+
 // For unit testing purposes only.  Do not use outside of tests.
 BASE_EXPORT std::string RandomDataToGUIDString(const uint64_t bytes[2]);
-#endif
 
 }  // namespace base
 
 #endif  // BASE_GUID_H_