Generalize the net module's LoadLog facility from a passive container, to an event stream (NetLog).

net/base/net_log.h

Index: net/base/net_log.h
===================================================================
--- net/base/net_log.h	(revision 40318)
+++ net/base/net_log.h	(working copy)
@@ -1,32 +1,37 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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 NET_BASE_LOAD_LOG_H_
-#define NET_BASE_LOAD_LOG_H_
+#ifndef NET_BASE_NET_LOG_H_
+#define NET_BASE_NET_LOG_H_
 
 #include <string>
 #include <vector>
 
-#include "base/ref_counted.h"
+#include "base/scoped_ptr.h"
 #include "base/time.h"
+#include "net/base/net_log.h"
 
 namespace net {
 
-// LoadLog stores information associated with an individual request. This
-// includes event traces (used to build up profiling information), error
-// return codes from network modules, and arbitrary text messages.
+// NetLog is the destination for log messages generated by the network stack.
+// Each log message has a "source" field which identifies the specific entity
+// that generated the message (for example, which URLRequest or which
+// SocketStream).
 //
-// Note that LoadLog is NOT THREADSAFE, however it is RefCountedThreadSafe so
-// that it can be AddRef() / Release() across threads.
-class LoadLog : public base::RefCountedThreadSafe<LoadLog> {
+// To avoid needing to pass in the "source id" to the logging functions, NetLog
+// is usually accessed through a BoundNetLog, which will always pass in a
+// specific source ID.
+//
+// Note that NetLog is NOT THREADSAFE.
+class NetLog {
  public:
    // TODO(eroman): Really, EventType and EventPhase should be
    // Event::Type and Event::Phase, to be consisent with Entry.
    // But there lots of consumers to change!
   enum EventType {
 #define EVENT_TYPE(label) TYPE_ ## label,
-#include "net/base/load_log_event_type_list.h"
+#include "net/base/net_log_event_type_list.h"
 #undef EVENT_TYPE
   };
 
@@ -35,7 +40,6 @@
   enum EventPhase {
     PHASE_NONE,
     PHASE_BEGIN,
-    // TODO(eroman): DEPRECATED: Use TYPE_STRING_LITERAL instead.
     PHASE_END,
   };
 
@@ -47,6 +51,28 @@
     EventPhase phase;
   };
 
+  // The "source" identifies the entity that generated the log message.
+  enum SourceType {
+    SOURCE_NONE,
+    SOURCE_URL_REQUEST,
+    SOURCE_SOCKET_STREAM,
+    SOURCE_INIT_PROXY_RESOLVER,
+    SOURCE_CONNECT_JOB,
+  };
+
+  // Identifies the entity that generated this log. The |id| field should
+  // uniquely identify the source, and is used by log observers to infer
+  // message groupings. Can use NetLog::NextID() to create unique IDs.
+  struct Source {
+    Source() : type(SOURCE_NONE), id(-1) {}
+    Source(SourceType type, int id) : type(type), id(id) {}
+
+    SourceType type;
+    int id;
+  };
+
+  // TODO(eroman): generalize the entries so events can specify multiple
+  //               parameters, and TYPE_STRING is rarely needed.
   struct Entry {
     enum Type {
       // This entry describes an event trace.
@@ -62,22 +88,8 @@
       TYPE_STRING_LITERAL,
     };
 
-    Entry(base::TimeTicks time, int error_code)
-        : type(TYPE_ERROR_CODE), time(time), error_code(error_code) {
-    }
+    Source source;
 
-    Entry(base::TimeTicks time, const Event& event)
-        : type(TYPE_EVENT), time(time), event(event) {
-    }
-
-    Entry(base::TimeTicks time, const std::string& string)
-        : type(TYPE_STRING), time(time), string(string) {
-    }
-
-    Entry(base::TimeTicks time, const char* literal)
-        : type(TYPE_STRING_LITERAL), time(time), literal(literal) {
-    }
-
     Type type;
     base::TimeTicks time;
 
@@ -89,108 +101,138 @@
     const char* literal;  // valid when (type == TYPE_STRING_LITERAL).
   };
 
-  // Ordered set of entries that were logged.
-  // TODO(eroman): use a StackVector or array to avoid allocations.
-  typedef std::vector<Entry> EntryList;
+  NetLog() {}
+  virtual ~NetLog() {}
 
-  // Value for max_num_entries to indicate the LoadLog has no size limit.
-  static const size_t kUnbounded = static_cast<size_t>(-1);
+  // Adds a message to the log.
+  virtual void AddEntry(const Entry& entry) = 0;
 
-  // Creates a log, which can hold up to |max_num_entries| entries.
-  // If |max_num_entries| is |kUnbounded|, then the log can grow arbitrarily
-  // large.
-  //
-  // If entries are dropped because the log has grown too large, the final entry
-  // will be overwritten.
-  explicit LoadLog(size_t max_num_entries);
+  // Returns a unique ID which can be used as a source ID.
+  virtual int NextID() = 0;
 
-  // --------------------------------------------------------------------------
+  // Returns true if more complicated messages should be sent to the log.
+  // TODO(eroman): This is a carry-over from refactoring; figure out
+  //               something better.
+  virtual bool HasListener() const = 0;
 
-  // The public interface for adding events to the log are static methods.
-  // This makes it easier to deal with optionally NULL LoadLog.
+  // Returns a C-String symbolic name for |event_type|.
+  static const char* EventTypeToString(EventType event_type);
 
-  // Adds an instantaneous event to the log.
-  // TODO(eroman): DEPRECATED: use AddStringLiteral() instead.
-  static void AddEvent(LoadLog* log, EventType event_type) {
-    if (log)
-      log->Add(Entry(base::TimeTicks::Now(), Event(event_type, PHASE_NONE)));
-  }
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NetLog);
+};
 
-  // Adds the start of an event to the log. Presumably this event type measures
-  // a time duration, and will be matched by a call to EndEvent(event_type).
-  static void BeginEvent(LoadLog* log, EventType event_type) {
-    if (log)
-      log->Add(Entry(base::TimeTicks::Now(), Event(event_type, PHASE_BEGIN)));
-  }
+// Helper that binds a Source to a NetLog, and exposes convenience methods to
+// output log messages without needing to pass in the source.
+class BoundNetLog {
+ public:
+  BoundNetLog() : net_log_(NULL) {}
 
-  // Adds the end of an event to the log. Presumably this event type measures
-  // a time duration, and we are matching an earlier call to
-  // BeginEvent(event_type).
-  static void EndEvent(LoadLog* log, EventType event_type) {
-    if (log)
-      log->Add(Entry(base::TimeTicks::Now(), Event(event_type, PHASE_END)));
-  }
+  // TODO(eroman): This is a complete hack to allow passing in NULL in
+  // place of a BoundNetLog. I added this while refactoring to simplify the
+  // task of updating all the callers.
+  BoundNetLog(int) : net_log_(NULL) {}
 
-  // |literal| should be a string literal (i.e. lives in static storage).
-  static void AddStringLiteral(LoadLog* log, const char* literal) {
-    if (log)
-      log->Add(Entry(base::TimeTicks::Now(), literal));
+  BoundNetLog(const NetLog::Source& source, NetLog* net_log)
+      : source_(source), net_log_(net_log) {
   }
 
-  static void AddString(LoadLog* log, const std::string& string) {
-    if (log)
-      log->Add(Entry(base::TimeTicks::Now(), string));
-  }
+  void AddEntry(const NetLog::Entry& entry) const;
 
-  static void AddErrorCode(LoadLog* log, int error) {
-    if (log)
-      log->Add(Entry(base::TimeTicks::Now(), error));
-  }
+  // Convenience methods that call through to the NetLog, passing in the
+  // currently bound source.
+  void AddEvent(NetLog::EventType event_type) const;
+  bool HasListener() const;
+  void BeginEvent(NetLog::EventType event_type) const;
+  void BeginEventWithString(NetLog::EventType event_type,
+                            const std::string& string) const;
+  void AddEventWithInteger(NetLog::EventType event_type, int integer) const;
+  void EndEvent(NetLog::EventType event_type) const;
+  void AddStringLiteral(const char* literal) const;
+  void AddString(const std::string& string) const;
+  void AddErrorCode(int error) const;
 
-  static bool IsUnbounded(const LoadLog* log) {
-    return log && log->is_unbounded();
-  }
+  // Helper to create a BoundNetLog given a NetLog and a SourceType. Takes care
+  // of creating a unique source ID, and handles the case of NULL net_log.
+  static BoundNetLog Make(NetLog* net_log, NetLog::SourceType source_type);
 
-  // --------------------------------------------------------------------------
+  const NetLog::Source& source() const { return source_; }
+  NetLog* net_log() const { return net_log_; }
 
+ private:
+  NetLog::Source source_;
+  NetLog* net_log_;
+};
+
+// CapturingNetLog is an implementation of NetLog that saves messages to a
+// bounded buffer.
+class CapturingNetLog : public NetLog {
+ public:
+  // Ordered set of entries that were logged.
+  typedef std::vector<Entry> EntryList;
+
+  enum { kUnbounded = -1 };
+
+  // Creates a CapturingNetLog that logs a maximum of |max_num_entries|
+  // messages.
+  explicit CapturingNetLog(size_t max_num_entries)
+      : next_id_(0), max_num_entries_(max_num_entries) {}
+
+  // NetLog implementation:
+  virtual void AddEntry(const Entry& entry);
+  virtual int NextID();
+  virtual bool HasListener() const { return true; }
+
   // Returns the list of all entries in the log.
-  const EntryList& entries() const {
-    return entries_;
-  }
+  const EntryList& entries() const { return entries_; }
 
-  // Returns the number of entries that were dropped from the log because the
-  // maximum size had been reached.
-  size_t num_entries_truncated() const {
-    return num_entries_truncated_;
+  void Clear();
+
+ private:
+  int next_id_;
+  size_t max_num_entries_;
+  EntryList entries_;
+
+  DISALLOW_COPY_AND_ASSIGN(CapturingNetLog);
+};
+
+// Helper class that exposes a similar API as BoundNetLog, but uses a
+// CapturingNetLog rather than the more generic NetLog.
+//
+// CapturingBoundNetLog can easily be converted to a BoundNetLog using the
+// bound() method.
+class CapturingBoundNetLog {
+ public:
+  CapturingBoundNetLog(const NetLog::Source& source, CapturingNetLog* net_log)
+      : source_(source), capturing_net_log_(net_log) {
   }
 
-  // Returns the bound on the size of the log.
-  size_t max_num_entries() const {
-    return max_num_entries_;
+  explicit CapturingBoundNetLog(size_t max_num_entries)
+      : capturing_net_log_(new CapturingNetLog(max_num_entries)) {}
+
+  // The returned BoundNetLog is only valid while |this| is alive.
+  BoundNetLog bound() const {
+    return BoundNetLog(source_, capturing_net_log_.get());
   }
 
-  bool is_unbounded() const {
-    return max_num_entries_ == kUnbounded;
+  // Returns the list of all entries in the log.
+  const CapturingNetLog::EntryList& entries() const {
+    return capturing_net_log_->entries();
   }
 
-  // Returns a C-String symbolic name for |event|.
-  static const char* EventTypeToString(EventType event_type);
+  void Clear();
 
-  void Add(const Entry& entry);
+  // Sends all of captured messages to |net_log|, using the same source ID
+  // as |net_log|.
+  void AppendTo(const BoundNetLog& net_log) const;
 
-  // Copies all entries from |log|, appending it to the end of |this|.
-  void Append(const LoadLog* log);
-
  private:
-  friend class base::RefCountedThreadSafe<LoadLog>;
+  NetLog::Source source_;
+  scoped_ptr<CapturingNetLog> capturing_net_log_;
 
-  ~LoadLog() {}
-
-  EntryList entries_;
-  size_t num_entries_truncated_;
-  size_t max_num_entries_;;
+  DISALLOW_COPY_AND_ASSIGN(CapturingBoundNetLog);
 };
 
 }  // namespace net
 
-#endif  // NET_BASE_LOAD_LOG_H_
+#endif  // NET_BASE_NET_LOG_H_