metrics: Add guest mode detection to metrics library and client

metrics_library.h

 // Copyright (c) 2010 The Chromium OS 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 METRICS_LIBRARY_H_
 #define METRICS_LIBRARY_H_
 
 #include <sys/types.h>
 #include <string>
 
 #include <gtest/gtest_prod.h>  // for FRIEND_TEST
 
 class MetricsLibraryInterface {
  public:
   virtual void Init() = 0;
   virtual bool SendToUMA(const std::string& name, int sample,
                          int min, int max, int nbuckets) = 0;
   virtual bool SendEnumToUMA(const std::string& name, int sample, int max) = 0;
   virtual ~MetricsLibraryInterface() {}
 };
 
 // Library used to send metrics to both Autotest and Chrome/UMA.
 class MetricsLibrary : public MetricsLibraryInterface {
  public:
   MetricsLibrary();
 
   // Initializes the library.
   void Init();
 
+  // Returns whether or not the machine is running in guest mode.
+  bool IsGuestMode();
+
   // Returns whether or not metrics collection is enabled.
   bool AreMetricsEnabled();
 
   // Sends histogram data to Chrome for transport to UMA and returns
   // true on success. This method results in the equivalent of an
   // asynchronous non-blocking RPC to UMA_HISTOGRAM_CUSTOM_COUNTS
   // inside Chrome (see base/histogram.h).
   //
   // |sample| is the sample value to be recorded (|min| <= |sample| < |max|).
   // |min| is the minimum value of the histogram samples (|min| > 0).
@@ skipping 28 matching lines @@
 
   // Sends to Autotest and returns true on success.
   static bool SendToAutotest(const std::string& name, int value);
 
  private:
   friend class CMetricsLibraryTest;
   friend class MetricsLibraryTest;
   FRIEND_TEST(MetricsLibraryTest, AreMetricsEnabled);
   FRIEND_TEST(MetricsLibraryTest, FormatChromeMessage);
   FRIEND_TEST(MetricsLibraryTest, FormatChromeMessageTooLong);
+  FRIEND_TEST(MetricsLibraryTest, IsDeviceMounted);
   FRIEND_TEST(MetricsLibraryTest, SendMessageToChrome);
   FRIEND_TEST(MetricsLibraryTest, SendMessageToChromeUMAEventsBadFileLocation);
 
+  // Sets |*result| to whether or not the |mounts_file| indicates that
+  // the |device_name| is currently mounted.  Uses |buffer| of
+  // |buffer_size| to read the file.  Returns false if any error.
+  bool IsDeviceMounted(const char* device_name,
+                       const char* mounts_file,
+                       char* buffer, int buffer_size,

[petkov, 2010/10/01 16:13:09]

the buffer is allocated on the stack anyway. you may as well allocate it inside
IsDeviceMounted and remove it from the method prototype. This will also
eliminate some NULL checking code and extra testing.

+                       bool* result);
+
   // Sends message of size |length| to Chrome for transport to UMA and
   // returns true on success.
   bool SendMessageToChrome(int32_t length, const char* message);
 
   // Formats a name/value message for Chrome in |buffer| and returns the
   // length of the message or a negative value on error.
   //
   // Message format is: | LENGTH(binary) | NAME | \0 | VALUE | \0 |
   //
   // The arbitrary |format| argument covers the non-LENGTH portion of the
   // message. The caller is responsible to store the \0 character
   // between NAME and VALUE (e.g. "%s%c%d", name, '\0', value).
   int32_t FormatChromeMessage(int32_t buffer_size, char* buffer,
                               const char* format, ...);
 
   // Time at which we last checked if metrics were enabled.
   static time_t cached_enabled_time_;
 
   // Cached state of whether or not metrics were enabled.
   static bool cached_enabled_;
 
   const char* uma_events_file_;
   const char* consent_file_;
 };
 
 #endif  // METRICS_LIBRARY_H_