content/common/inter_process_time_ticks_converter.cc

   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
   9 namespace content {
  10
  11 InterProcessTimeTicksConverter::InterProcessTimeTicksConverter(
  12     const LocalTimeTicks& local_lower_bound,
  13     const LocalTimeTicks& local_upper_bound,
  14     const RemoteTimeTicks& remote_lower_bound,
  15     const RemoteTimeTicks& remote_upper_bound)
  16     : remote_lower_bound_(remote_lower_bound.value_),
  17       remote_upper_bound_(remote_upper_bound.value_) {
  18   int64 target_range = local_upper_bound.value_ - local_lower_bound.value_;
  19   int64 source_range = remote_upper_bound.value_ - remote_lower_bound.value_;
  20   if (source_range <= target_range) {
  21     // We fit!  Just shift the midpoints to match.
  22     numerator_ = 1;
  23     denominator_ = 1;
  24     offset_ = ((local_upper_bound.value_ + local_lower_bound.value_) -
  25                (remote_upper_bound.value_ + remote_lower_bound.value_)) / 2;
  26     return;
  27   }
  28   // Set up scaling factors, and then deduce shift.
  29   numerator_ = target_range;
  30   denominator_ = source_range;
  31   // Find out what we need to shift by to make this really work.
  32   offset_ = local_lower_bound.value_ - Convert(remote_lower_bound.value_);
  33   DCHECK_GE(local_upper_bound.value_, Convert(remote_upper_bound.value_));
  34 }
  35
  36 LocalTimeTicks InterProcessTimeTicksConverter::ToLocalTimeTicks(
  37     const RemoteTimeTicks& remote_ms) {
  38   DCHECK_LE(remote_lower_bound_, remote_ms.value_);
  39   DCHECK_GE(remote_upper_bound_, remote_ms.value_);
  40   RemoteTimeDelta remote_delta = remote_ms - remote_lower_bound_;
  41   return LocalTimeTicks(remote_lower_bound_ + offset_ +
  42                         ToLocalTimeDelta(remote_delta).value_);
  43 }
  44
  45 LocalTimeDelta InterProcessTimeTicksConverter::ToLocalTimeDelta(
  46     const RemoteTimeDelta& remote_delta) {
  47   DCHECK_GE(remote_upper_bound_, remote_lower_bound_ + remote_delta.value_);
  48   return LocalTimeDelta(Convert(remote_delta.value_));
  49 }
  50
  51 int64 InterProcessTimeTicksConverter::Convert(int64 value) {
  52   if (value <= 0) {
  53     return value;
  54   }
  55   return numerator_ * value / denominator_;
  56 }
  57
  58 }  // namespace content