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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // FieldTrial is a class for handling details of statistical experiments | 5 // FieldTrial is a class for handling details of statistical experiments |
6 // performed by actual users in the field (i.e., in a shipped or beta product). | 6 // performed by actual users in the field (i.e., in a shipped or beta product). |
7 // All code is called exclusively on the UI thread currently. | 7 // All code is called exclusively on the UI thread currently. |
8 // | 8 // |
9 // The simplest example is an experiment to see whether one of two options | 9 // The simplest example is an experiment to see whether one of two options |
10 // produces "better" results across our user population. In that scenario, UMA | 10 // produces "better" results across our user population. In that scenario, UMA |
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506 static void CreateTrialsFromCommandLine( | 506 static void CreateTrialsFromCommandLine( |
507 const base::CommandLine& cmd_line, | 507 const base::CommandLine& cmd_line, |
508 const char* field_trial_handle_switch); | 508 const char* field_trial_handle_switch); |
509 | 509 |
510 #if defined(OS_WIN) | 510 #if defined(OS_WIN) |
511 // On Windows, we need to explicitly pass down any handles to be inherited. | 511 // On Windows, we need to explicitly pass down any handles to be inherited. |
512 // This function adds the shared memory handle to field trial state to the | 512 // This function adds the shared memory handle to field trial state to the |
513 // list of handles to be inherited. | 513 // list of handles to be inherited. |
514 static void AppendFieldTrialHandleIfNeeded( | 514 static void AppendFieldTrialHandleIfNeeded( |
515 base::HandlesToInheritVector* handles); | 515 base::HandlesToInheritVector* handles); |
| 516 #elif defined(OS_POSIX) |
| 517 // On POSIX, we also need to explicitly pass down this file descriptor that |
| 518 // should be shared with the child process. Returns kInvalidPlatformFile if no |
| 519 // handle exists or was not initialized properly. |
| 520 static PlatformFile GetFieldTrialHandle(); |
516 #endif | 521 #endif |
517 | 522 |
518 // Adds a switch to the command line containing the field trial state as a | 523 // Adds a switch to the command line containing the field trial state as a |
519 // string (if not using shared memory to share field trial state), or the | 524 // string (if not using shared memory to share field trial state), or the |
520 // shared memory handle + length. | 525 // shared memory handle + length. |
521 // Needs the |field_trial_handle_switch| argument to be passed in since base/ | 526 // Needs the |field_trial_handle_switch| argument to be passed in since base/ |
522 // can't depend on content/. | 527 // can't depend on content/. |
523 static void CopyFieldTrialStateToFlags(const char* field_trial_handle_switch, | 528 static void CopyFieldTrialStateToFlags(const char* field_trial_handle_switch, |
524 base::CommandLine* cmd_line); | 529 base::CommandLine* cmd_line); |
525 | 530 |
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550 // Return the number of active field trials. | 555 // Return the number of active field trials. |
551 static size_t GetFieldTrialCount(); | 556 static size_t GetFieldTrialCount(); |
552 | 557 |
553 private: | 558 private: |
554 // Allow tests to access our innards for testing purposes. | 559 // Allow tests to access our innards for testing purposes. |
555 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); | 560 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); |
556 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); | 561 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); |
557 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, | 562 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, |
558 DoNotAddSimulatedFieldTrialsToAllocator); | 563 DoNotAddSimulatedFieldTrialsToAllocator); |
559 | 564 |
560 #if defined(OS_WIN) | 565 // Takes in |handle_switch| from the command line which represents the shared |
561 // Takes in |handle| that should have been retrieved from the command line and | 566 // memory handle for field trials, parses it, and creates the field trials. |
562 // creates a SharedMemoryHandle from it, and then calls | 567 // Returns true on success, false on failure. |
563 // CreateTrialsFromSharedMemory(). Returns true on success, false on failure. | 568 static bool CreateTrialsFromHandleSwitch(const std::string& handle_switch); |
564 static bool CreateTrialsFromWindowsHandle(HANDLE handle); | 569 |
565 #endif | 570 // Takes an unmapped SharedMemoryHandle, creates a SharedMemory object from it |
| 571 // and maps it with the correct size. |
| 572 static bool CreateTrialsFromSharedMemoryHandle(SharedMemoryHandle shm_handle); |
566 | 573 |
567 // Expects a mapped piece of shared memory |shm| that was created from the | 574 // Expects a mapped piece of shared memory |shm| that was created from the |
568 // browser process's field_trial_allocator and shared via the command line. | 575 // browser process's field_trial_allocator and shared via the command line. |
569 // This function recreates the allocator, iterates through all the field | 576 // This function recreates the allocator, iterates through all the field |
570 // trials in it, and creates them via CreateFieldTrial(). Returns true if | 577 // trials in it, and creates them via CreateFieldTrial(). Returns true if |
571 // successful and false otherwise. | 578 // successful and false otherwise. |
572 static bool CreateTrialsFromSharedMemory( | 579 static bool CreateTrialsFromSharedMemory( |
573 std::unique_ptr<base::SharedMemory> shm); | 580 std::unique_ptr<base::SharedMemory> shm); |
574 | 581 |
575 // Instantiate the field trial allocator, add all existing field trials to it, | 582 // Instantiate the field trial allocator, add all existing field trials to it, |
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620 | 627 |
621 // List of observers to be notified when a group is selected for a FieldTrial. | 628 // List of observers to be notified when a group is selected for a FieldTrial. |
622 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; | 629 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; |
623 | 630 |
624 // Allocator in shared memory containing field trial data. Used in both | 631 // Allocator in shared memory containing field trial data. Used in both |
625 // browser and child processes, but readonly in the child. | 632 // browser and child processes, but readonly in the child. |
626 // In the future, we may want to move this to a more generic place if we want | 633 // In the future, we may want to move this to a more generic place if we want |
627 // to start passing more data other than field trials. | 634 // to start passing more data other than field trials. |
628 std::unique_ptr<FieldTrialAllocator> field_trial_allocator_ = nullptr; | 635 std::unique_ptr<FieldTrialAllocator> field_trial_allocator_ = nullptr; |
629 | 636 |
630 #if defined(OS_WIN) | |
631 // Readonly copy of the handle to the allocator. Needs to be a member variable | 637 // Readonly copy of the handle to the allocator. Needs to be a member variable |
632 // because it's needed from both CopyFieldTrialStateToFlags() and | 638 // because it's needed from both CopyFieldTrialStateToFlags() and |
633 // AppendFieldTrialHandleIfNeeded(). | 639 // AppendFieldTrialHandleIfNeeded(). |
634 HANDLE readonly_allocator_handle_ = nullptr; | 640 PlatformFile readonly_allocator_handle_ = kInvalidPlatformFile; |
635 #endif | |
636 | 641 |
637 // Tracks whether CreateTrialsFromCommandLine() has been called. | 642 // Tracks whether CreateTrialsFromCommandLine() has been called. |
638 bool create_trials_from_command_line_called_ = false; | 643 bool create_trials_from_command_line_called_ = false; |
639 | 644 |
640 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); | 645 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); |
641 }; | 646 }; |
642 | 647 |
643 } // namespace base | 648 } // namespace base |
644 | 649 |
645 #endif // BASE_METRICS_FIELD_TRIAL_H_ | 650 #endif // BASE_METRICS_FIELD_TRIAL_H_ |
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