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69 lines
2.7 KiB
C++
69 lines
2.7 KiB
C++
// Copyright 2018 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_METRICS_PERSISTENT_HISTOGRAM_STORAGE_H_
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#define BASE_METRICS_PERSISTENT_HISTOGRAM_STORAGE_H_
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#include "base/base_export.h"
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#include "base/files/file_path.h"
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#include "base/macros.h"
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#include "base/strings/string_piece.h"
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namespace base {
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// This class creates a fixed sized persistent memory to allow histograms to be
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// stored in it. When a PersistentHistogramStorage is destructed, histograms
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// recorded during its lifetime are persisted in the directory
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// |storage_base_dir_|/|allocator_name| (see the ctor for allocator_name).
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// Histograms are not persisted if the storage directory does not exist on
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// destruction. PersistentHistogramStorage should be instantiated as early as
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// possible in the process lifetime and should never be instantiated again.
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// Persisted histograms will eventually be reported by Chrome.
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class BASE_EXPORT PersistentHistogramStorage {
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public:
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enum class StorageDirManagement { kCreate, kUseExisting };
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// Creates a process-wide storage location for histograms that will be written
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// to a file within a directory provided by |set_storage_base_dir()| on
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// destruction.
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// The |allocator_name| is used both as an internal name for the allocator,
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// well as the leaf directory name for the file to which the histograms are
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// persisted. The string must be ASCII.
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// |storage_dir_management| specifies if this instance reuses an existing
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// storage directory, or is responsible for creating one.
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PersistentHistogramStorage(StringPiece allocator_name,
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StorageDirManagement storage_dir_management);
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~PersistentHistogramStorage();
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// The storage directory isn't always known during initial construction so
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// it's set separately. The last one wins if there are multiple calls to this
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// method.
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void set_storage_base_dir(const FilePath& storage_base_dir) {
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storage_base_dir_ = storage_base_dir;
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}
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// Disables histogram storage.
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void Disable() { disabled_ = true; }
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private:
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// Metrics files are written into directory
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// |storage_base_dir_|/|allocator_name| (see the ctor for allocator_name).
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FilePath storage_base_dir_;
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// The setting of the storage directory management.
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const StorageDirManagement storage_dir_management_;
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// A flag indicating if histogram storage is disabled. It starts with false,
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// but can be set to true by the caller who decides to throw away its
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// histogram data.
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bool disabled_ = false;
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DISALLOW_COPY_AND_ASSIGN(PersistentHistogramStorage);
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};
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} // namespace base
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#endif // BASE_METRICS_PERSISTENT_HISTOGRAM_STORAGE_H_
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