Factoring GUID generation from metrics to base

base/rand_util_posix.cc

 // Copyright (c) 2008 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.
 
 #include "base/rand_util.h"
 #include "base/rand_util_c.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <unistd.h>
 
 #include "base/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/stringprintf.h"
 
 namespace {
 
 // We keep the file descriptor for /dev/urandom around so we don't need to
 // reopen it (which is expensive), and since we may not even be able to reopen
 // it if we are later put in a sandbox. This class wraps the file descriptor so
 // we can use LazyInstance to handle opening it on the first access.
 class URandomFd {
  public:
   URandomFd() {
@@ skipping 22 matching lines @@
 
   int urandom_fd = g_urandom_fd.Pointer()->fd();
   bool success = file_util::ReadFromFD(urandom_fd,
                                        reinterpret_cast<char*>(&number),
                                        sizeof(number));
   CHECK(success);
 
   return number;
 }
 
+// TODO(cmasone): Once we're comfortable this works, migrate Windows code to
+// use this as well.
+std::string RandomBytesToGUIDString(const uint64 bytes[2]) {
+  return StringPrintf("%08X-%04X-%04X-%04X-%012llX",
+                      static_cast<unsigned int>(bytes[0] >> 32),
+                      static_cast<unsigned int>((bytes[0] >> 16) & 0x0000ffff),
+                      static_cast<unsigned int>(bytes[0] & 0x0000ffff),
+                      static_cast<unsigned int>(bytes[1] >> 48),
+                      bytes[1] & 0x0000ffffffffffffULL);
+}
+
+std::string GenerateGUID() {
+  uint64 sixteen_bytes[2] = { base::RandUint64(), base::RandUint64() };
+  return RandomBytesToGUIDString(sixteen_bytes);
+}
+
 }  // namespace base
 
 int GetUrandomFD(void) {
   return g_urandom_fd.Pointer()->fd();
 }