Removing uses of X11 native key events.
[chromium-blink-merge.git] / content / common / inter_process_time_ticks_converter.h
blob8b005408d58a0a2d04f3e233251617f91b1322cf
1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef CONTENT_COMMON_INTER_PROCESS_TIME_TICKS_CONVERTER_H_
6 #define CONTENT_COMMON_INTER_PROCESS_TIME_TICKS_CONVERTER_H_
8 #include "base/time/time.h"
9 #include "content/common/content_export.h"
11 namespace content {
13 class LocalTimeDelta;
14 class LocalTimeTicks;
15 class RemoteTimeDelta;
16 class RemoteTimeTicks;
18 // On Windows, TimeTicks are not consistent between processes. Often, the values
19 // on one process have a static offset relative to another. Occasionally, these
20 // offsets shift while running.
22 // To combat this, any TimeTicks values sent from the remote process to the
23 // local process must be tweaked in order to appear monotonic.
25 // In order to properly tweak ticks, we need 4 reference points:
27 // - |local_lower_bound|: A known point, recorded on the local process, that
28 // occurs before any remote values that will be
29 // converted.
30 // - |remote_lower_bound|: The equivalent point on the remote process. This
31 // should be recorded immediately after
32 // |local_lower_bound|.
33 // - |local_upper_bound|: A known point, recorded on the local process, that
34 // occurs after any remote values that will be
35 // converted.
36 // - |remote_upper_bound|: The equivalent point on the remote process. This
37 // should be recorded immediately before
38 // |local_upper_bound|.
40 // Once these bounds are determined, values within the remote process's range
41 // can be converted to the local process's range. The values are converted as
42 // follows:
44 // 1. If the remote's range exceeds the local's range, it is scaled to fit.
45 // Any values converted will have the same scale factor applied.
47 // 2. The remote's range is shifted so that it is centered within the
48 // local's range. Any values converted will be shifted the same amount.
49 class CONTENT_EXPORT InterProcessTimeTicksConverter {
50 public:
51 InterProcessTimeTicksConverter(const LocalTimeTicks& local_lower_bound,
52 const LocalTimeTicks& local_upper_bound,
53 const RemoteTimeTicks& remote_lower_bound,
54 const RemoteTimeTicks& remote_upper_bound);
56 // Returns the value within the local's bounds that correlates to
57 // |remote_ms|.
58 LocalTimeTicks ToLocalTimeTicks(const RemoteTimeTicks& remote_ms) const;
60 // Returns the equivalent delta after applying remote-to-local scaling to
61 // |remote_delta|.
62 LocalTimeDelta ToLocalTimeDelta(const RemoteTimeDelta& remote_delta) const;
64 // Returns true iff the TimeTicks are converted by adding a constant, without
65 // scaling. This is the case whenever the remote timespan is smaller than the
66 // local timespan, which should be the majority of cases due to IPC overhead.
67 bool IsSkewAdditiveForMetrics() const;
69 // Returns the (remote time) - (local time) difference estimated by the
70 // converter. This is the constant that is subtracted from remote TimeTicks to
71 // get local TimeTicks when no scaling is applied.
72 base::TimeDelta GetSkewForMetrics() const;
74 private:
75 int64 Convert(int64 value) const;
77 // The local time which |remote_lower_bound_| is mapped to.
78 int64 local_base_time_;
80 int64 numerator_;
81 int64 denominator_;
83 int64 remote_lower_bound_;
84 int64 remote_upper_bound_;
87 class CONTENT_EXPORT LocalTimeDelta {
88 public:
89 int ToInt32() const { return value_; }
91 private:
92 friend class InterProcessTimeTicksConverter;
93 friend class LocalTimeTicks;
95 LocalTimeDelta(int value) : value_(value) {}
97 int value_;
100 class CONTENT_EXPORT LocalTimeTicks {
101 public:
102 static LocalTimeTicks FromTimeTicks(const base::TimeTicks& value) {
103 return LocalTimeTicks(value.ToInternalValue());
106 base::TimeTicks ToTimeTicks() {
107 return base::TimeTicks::FromInternalValue(value_);
110 LocalTimeTicks operator+(const LocalTimeDelta& delta) {
111 return LocalTimeTicks(value_ + delta.value_);
114 private:
115 friend class InterProcessTimeTicksConverter;
117 LocalTimeTicks(int64 value) : value_(value) {}
119 int64 value_;
122 class CONTENT_EXPORT RemoteTimeDelta {
123 public:
124 static RemoteTimeDelta FromRawDelta(int delta) {
125 return RemoteTimeDelta(delta);
128 private:
129 friend class InterProcessTimeTicksConverter;
130 friend class RemoteTimeTicks;
132 RemoteTimeDelta(int value) : value_(value) {}
134 int value_;
137 class CONTENT_EXPORT RemoteTimeTicks {
138 public:
139 static RemoteTimeTicks FromTimeTicks(const base::TimeTicks& ticks) {
140 return RemoteTimeTicks(ticks.ToInternalValue());
143 RemoteTimeDelta operator-(const RemoteTimeTicks& rhs) const {
144 return RemoteTimeDelta(value_ - rhs.value_);
147 private:
148 friend class InterProcessTimeTicksConverter;
150 RemoteTimeTicks(int64 value) : value_(value) {}
152 int64 value_;
155 } // namespace content
157 #endif // CONTENT_COMMON_INTER_PROCESS_TIME_TICKS_CONVERTER_H_