referrer.cc | Explore in Territory

// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/net/referrer.h"

#include <limits.h>
#include <stddef.h>

#include <memory>
#include <optional>
#include <utility>

#include "base/check_op.h"
#include "base/compiler_specific.h"
#include "base/values.h"

namespace chrome_browser_net {

//------------------------------------------------------------------------------
// Smoothing parameter for updating subresource_use_rate_.

// We always combine our old expected value, weighted by some factor W (we use
// kWeightingForOldConnectsExpectedValue), with the new expected value Enew.
// The new "expected value" is the number of actual connections made due to the
// current navigations.
// That means that IF we end up needing to connect, we should apply the formula:
// Eupdated = Eold * W  +  Enew * (1 - W)
// If we visit the containing url, but don't end up needing a connection, then
// Enew == 0, so we use the formula:
// Eupdated = Eold * W
// To achieve the above updating algorithm, we end up doing the multiplication
// by W every time we contemplate doing a preconnection (i.e., when we navigate
// to the containing URL, and consider doing a preconnection), and then IFF we
// learn that we really needed a connection to the subresource, we complete the
// above algorithm by adding the (1 - W) for each connection we make.

// We weight the new expected value by a factor which is in the range of 0.0 to
// 1.0.
static const double kWeightingForOldConnectsExpectedValue = …;

// To estimate the expected value of the number of connections that we'll need
// when a referrer is navigated to, we start with the following low initial
// value.
// Each time we do indeed (again) need the subresource, this value will get
// increased.
// Each time we navigate to the refererrer but never end up needing this
// subresource, the value will decrease.
// Very conservative is 0.0, which will mean that we have to wait for a while
// before doing much speculative acvtivity.  We do persist results, so we'll
// save the asymptotic (correct?) learned answer in the long run.
// Some browsers blindly make 2 connections all the time, so we'll use that as
// a starting point.
static const double kInitialConnectsExpectedValue = …;

Referrer::Referrer() : … { … }

void Referrer::SuggestHost(const GURL& url) { … }

void Referrer::DeleteLeastUseful() { … }

void Referrer::Deserialize(const base::Value& value) { … }

std::unique_ptr<base::Value::List> Referrer::Serialize() const { … }

//------------------------------------------------------------------------------

ReferrerValue::ReferrerValue()
    : … { … }

void ReferrerValue::SubresourceIsNeeded() { … }

void ReferrerValue::ReferrerWasObserved() { … }

}  // namespace chrome_browser_net
chromium/chrome/browser/net/referrer.cc
