cashew: add local byte counters

src/procfs_byte_counter.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 SRC_PROCFS_BYTE_COUNTER_H_
+#define SRC_PROCFS_BYTE_COUNTER_H_
+
+#include <stdio.h>
+
+#include <glib.h>
+#include <sys/socket.h>
+#include <linux/netdevice.h>
+
+#include <string>
+
+#include <base/basictypes.h>  // NOLINT
+
+#include "src/byte_counter.h"
+
+namespace cashew {
+
+// a procfs-based implementation of the ByteCounter interface
+class ProcfsByteCounter: public ByteCounter {
+  public:
+    explicit ProcfsByteCounter(const std::string& interface);
+    virtual ~ProcfsByteCounter();
+    virtual const std::string& GetInterface() const;
+    virtual uint64 GetRxBytes() const;
+    virtual uint64 GetTxBytes() const;
+    virtual void SetDelegate(ByteCounterDelegate *delegate);
+
+  private:
+    // interface name
+    const std::string interface_;
+
+    // file pointer for open /proc/net/dev virtual file
+    // can be NULL
+    FILE *proc_net_dev_fp_;
+
+    // ReadStats timer glib source id
+    guint read_stats_source_id_;
+
+    // counter: received bytes
+    uint64 counter_rx_bytes_;
+
+    // counter: transmitted byes
+    uint64 counter_tx_bytes_;
+
+    // baseline stats against which we'll compare our next update
+    // updated with each sample so as to better handle wraparound
+    //
+    // these stats are maintained by the device driver starting from kernel boot
+    // or module load time and have aribitrary values relative to when our
+    // logical |counter_rx_bytes_| and |counter_tx_bytes_| counters were started
+    struct net_device_stats baseline_stats_;
+
+    // have our baseline device stats been initialized?
+    // this becomes true after the first call to OnStatsUpdate
+    bool baseline_initialized_;
+
+    // delegate
+    ByteCounterDelegate *delegate_;
+
+    // open /proc/net/dev
+    // stores resulting fp in |proc_net_dev_fp_|
+    // returns true on success and false on failure
+    bool OpenProcNetDev();
+
+    // close /proc/net/dev
+    // clears |proc_net_dev_fp_|
+    // ok to call even if file isn't open
+    void CloseProcNetDev();
+
+    // glib integration: static wrapper for ReadStats
+    // takes object ptr as data and invokes object->ReadStats
+    static gboolean StaticReadStatsCallback(gpointer data);
+
+    // read stats for |interface_| from /proc/net/dev
+    // returns true on success and false on failure
+    bool ReadStats();
+
+    // new stats are available, update counter
+    void OnStatsUpdate(const struct net_device_stats& stats);
+
+    DISALLOW_COPY_AND_ASSIGN(ProcfsByteCounter);
+};
+
+}  // namespace cashew
+
+#endif  // SRC_PROCFS_BYTE_COUNTER_H_