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.
4
5#include "content/common/inter_process_time_ticks_converter.h"
6
7#include "base/logging.h"
8#include "base/strings/string_number_conversions.h"
9
10namespace content {
11
12InterProcessTimeTicksConverter::InterProcessTimeTicksConverter(
13    const LocalTimeTicks& local_lower_bound,
14    const LocalTimeTicks& local_upper_bound,
15    const RemoteTimeTicks& remote_lower_bound,
16    const RemoteTimeTicks& remote_upper_bound)
17    : remote_lower_bound_(remote_lower_bound.value_),
18      remote_upper_bound_(remote_upper_bound.value_) {
19  int64 target_range = local_upper_bound.value_ - local_lower_bound.value_;
20  int64 source_range = remote_upper_bound.value_ - remote_lower_bound.value_;
21  DCHECK_GE(target_range, 0);
22  DCHECK_GE(source_range, 0);
23  if (source_range <= target_range) {
24    // We fit!  Center the source range on the target range.
25    numerator_ = 1;
26    denominator_ = 1;
27    local_base_time_ =
28        local_lower_bound.value_ + (target_range - source_range) / 2;
29    // When converting times, remote bounds should fall within local bounds.
30    DCHECK_LE(local_lower_bound.value_,
31              ToLocalTimeTicks(remote_lower_bound).value_);
32    DCHECK_GE(local_upper_bound.value_,
33              ToLocalTimeTicks(remote_upper_bound).value_);
34    return;
35  }
36
37  // Interpolate values so that remote range will be will exactly fit into the
38  // local range, if possible.
39  numerator_ = target_range;
40  denominator_ = source_range;
41  local_base_time_ = local_lower_bound.value_;
42  // When converting times, remote bounds should equal local bounds.
43  DCHECK_EQ(local_lower_bound.value_,
44            ToLocalTimeTicks(remote_lower_bound).value_);
45  DCHECK_EQ(local_upper_bound.value_,
46            ToLocalTimeTicks(remote_upper_bound).value_);
47  DCHECK_EQ(target_range, Convert(source_range));
48}
49
50LocalTimeTicks InterProcessTimeTicksConverter::ToLocalTimeTicks(
51    const RemoteTimeTicks& remote_ms) const {
52  // If input time is "null", return another "null" time.
53  if (remote_ms.value_ == 0)
54    return LocalTimeTicks(0);
55  DCHECK_LE(remote_lower_bound_, remote_ms.value_);
56  DCHECK_GE(remote_upper_bound_, remote_ms.value_);
57  RemoteTimeDelta remote_delta = remote_ms - remote_lower_bound_;
58  return LocalTimeTicks(local_base_time_ +
59                        ToLocalTimeDelta(remote_delta).value_);
60}
61
62LocalTimeDelta InterProcessTimeTicksConverter::ToLocalTimeDelta(
63    const RemoteTimeDelta& remote_delta) const {
64  DCHECK_GE(remote_upper_bound_, remote_lower_bound_ + remote_delta.value_);
65  return LocalTimeDelta(Convert(remote_delta.value_));
66}
67
68int64 InterProcessTimeTicksConverter::Convert(int64 value) const {
69  if (value <= 0) {
70    return value;
71  }
72  return numerator_ * value / denominator_;
73}
74
75bool InterProcessTimeTicksConverter::IsSkewAdditiveForMetrics() const {
76  return numerator_ == 1 && denominator_ == 1;
77}
78
79base::TimeDelta InterProcessTimeTicksConverter::GetSkewForMetrics() const {
80  return base::TimeTicks::FromInternalValue(remote_lower_bound_) -
81      base::TimeTicks::FromInternalValue(local_base_time_);
82}
83
84}  // namespace content
85