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// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/field_trial.h"
#include "base/logging.h"
#include "base/rand_util.h"
#include "base/string_util.h"
using base::Time;
// static
const int FieldTrial::kNotParticipating = -1;
// static
const char FieldTrial::kPersistentStringSeparator('/');
//------------------------------------------------------------------------------
// FieldTrial methods and members.
FieldTrial::FieldTrial(const std::string& name,
const Probability total_probability)
: name_(name),
divisor_(total_probability),
random_(static_cast<Probability>(divisor_ * base::RandDouble())),
accumulated_group_probability_(0),
next_group_number_(0),
group_(kNotParticipating) {
FieldTrialList::Register(this);
}
int FieldTrial::AppendGroup(const std::string& name,
Probability group_probability) {
DCHECK(group_probability <= divisor_);
accumulated_group_probability_ += group_probability;
DCHECK(accumulated_group_probability_ <= divisor_);
if (group_ == kNotParticipating && accumulated_group_probability_ > random_) {
// This is the group that crossed the random line, so we do teh assignment.
group_ = next_group_number_;
if (name.empty())
StringAppendF(&group_name_, "_%d", group_);
else
group_name_ = name;
}
return next_group_number_++;
}
// static
std::string FieldTrial::MakeName(const std::string& name_prefix,
const std::string& trial_name) {
std::string big_string(name_prefix);
return big_string.append(FieldTrialList::FindFullName(trial_name));
}
std::string FieldTrial::MakePersistentString() const {
DCHECK_EQ(name_.find(kPersistentStringSeparator), std::string::npos);
DCHECK_EQ(group_name_.find(kPersistentStringSeparator), std::string::npos);
std::string persistent(name_);
persistent = persistent.append(1, kPersistentStringSeparator);
persistent = persistent.append(group_name_);
return persistent;
}
// static
FieldTrial* FieldTrial::RestorePersistentString(const std::string &persistent) {
size_t split_point = persistent.find(kPersistentStringSeparator);
if (std::string::npos == split_point)
return NULL; // Bogus string.
std::string new_name(persistent, 0, split_point);
std::string new_group_name(persistent, split_point + 1);
if (new_name.empty() || new_group_name.empty())
return NULL; // Incomplete string.
FieldTrial *field_trial;
field_trial = FieldTrialList::Find(new_name);
if (field_trial) {
// In single process mode, we may have already created the field trial.
if (field_trial->group_name_ != new_group_name)
return NULL; // Conflicting group name :-(.
} else {
const int kTotalProbability = 100;
field_trial = new FieldTrial(new_name, kTotalProbability);
field_trial->AppendGroup(new_group_name, kTotalProbability);
}
return field_trial;
}
//------------------------------------------------------------------------------
// FieldTrialList methods and members.
// static
FieldTrialList* FieldTrialList::global_ = NULL;
FieldTrialList::FieldTrialList()
: application_start_time_(Time::Now()) {
DCHECK(!global_);
global_ = this;
}
FieldTrialList::~FieldTrialList() {
AutoLock auto_lock(lock_);
while (!registered_.empty()) {
RegistrationList::iterator it = registered_.begin();
it->second->Release();
registered_.erase(it->first);
}
DCHECK(this == global_);
global_ = NULL;
}
// static
void FieldTrialList::Register(FieldTrial* trial) {
DCHECK(global_);
if (!global_)
return;
AutoLock auto_lock(global_->lock_);
DCHECK(!global_->PreLockedFind(trial->name()));
trial->AddRef();
global_->registered_[trial->name()] = trial;
}
// static
int FieldTrialList::FindValue(const std::string& name) {
FieldTrial* field_trial = Find(name);
if (field_trial)
return field_trial->group();
return FieldTrial::kNotParticipating;
}
// static
std::string FieldTrialList::FindFullName(const std::string& name) {
FieldTrial* field_trial = Find(name);
if (field_trial)
return field_trial->group_name();
return "";
}
// static
FieldTrial* FieldTrialList::Find(const std::string& name) {
if (!global_)
return NULL;
AutoLock auto_lock(global_->lock_);
return global_->PreLockedFind(name);
}
FieldTrial* FieldTrialList::PreLockedFind(const std::string& name) {
RegistrationList::iterator it = registered_.find(name);
if (registered_.end() == it)
return NULL;
return it->second;
}
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