metrics: refactor counters
The metrics daemon had counter classes that represented
persistent, tagged values, and UMA stats. To create some
derived UMA stats we need to separate persistency and UMA stats,
and the tagging doesn't help either.
This rewrite is supposed to keep the same functionality.
BUG=chromium:339588
TEST=ran and checked a few histograms
BRANCH=none
Change-Id: Ia1121ab2db391d71edffab9f52afe29ce17686ba
Reviewed-on: https://chromium-review.googlesource.com/188082
Tested-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Commit-Queue: Luigi Semenzato <semenzato@chromium.org>
diff --git a/metrics/persistent_integer.h b/metrics/persistent_integer.h
new file mode 100644
index 0000000..7d920b5
--- /dev/null
+++ b/metrics/persistent_integer.h
@@ -0,0 +1,65 @@
+// Copyright (c) 2014 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_PERSISTENT_INTEGER_H_
+#define METRICS_PERSISTENT_INTEGER_H_
+
+#include <base/basictypes.h>
+#include <string>
+
+namespace chromeos_metrics {
+
+// PersistentIntegers is a named 64-bit integer value backed by a file.
+// The in-memory value acts as a write-through cache of the file value.
+// If the backing file doesn't exist or has bad content, the value is 0.
+
+class PersistentInteger {
+ public:
+ PersistentInteger(const std::string& name);
+
+ // Virtual only because of mock.
+ virtual ~PersistentInteger();
+
+ // Sets the value. This writes through to the backing file.
+ void Set(int64 v);
+
+ // Gets the value. May sync from backing file first.
+ int64 Get();
+
+ // Returns the name of the object.
+ std::string Name() { return name_; }
+
+ // Convenience function for Get() followed by Set(0).
+ int64 GetAndClear();
+
+ // Convenience function for v = Get, Set(v + x).
+ // Virtual only because of mock.
+ virtual void Add(int64 x);
+
+ // After calling with |testing| = true, changes some behavior for the purpose
+ // of testing. For instance: instances created while testing use the current
+ // directory for the backing files.
+ static void SetTestingMode(bool testing);
+
+ private:
+ static const int kVersion = 1001;
+
+ // Writes |value| to the backing file, creating it if necessary.
+ void Write(int64 value);
+
+ // Reads the value from the backing file, stores it in |value_|, and returns
+ // true if the backing file is valid. Returns false otherwise.
+ bool Read();
+
+ int64 value_;
+ int32 version_;
+ std::string name_;
+ std::string backing_file_name_;
+ bool synced_;
+ static bool testing_;
+};
+
+}
+
+#endif // METRICS_PERSISTENT_INTEGER_H_