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Optimize initialization of tz database

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* Defer expensive parts of the initialization
* The deferment can be turned off with -DLAZY_INIT=0
This commit is contained in:
Howard Hinnant 2016-04-05 11:56:09 -07:00
parent e8f95dddb7
commit e79634f61d
2 changed files with 40 additions and 21 deletions
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43
tz.cpp
View File

@ -1249,6 +1249,9 @@ Zone::zonelet::zonelet(const zonelet& i)
}
Zone::Zone(const std::string& s)
#if LAZY_INIT
: adjusted_(new std::once_flag{})
#endif
{
try
{
@ -1566,24 +1569,22 @@ Zone::adjust_infos(const std::vector<Rule>& rules)
const zonelet* prev_zonelet = nullptr;
for (auto& z : zonelets_)
{
std::pair<const Rule*, const Rule*> eqr{};
std::istringstream in;
in.exceptions(std::ios::failbit | std::ios::badbit);
// Classify info as rule-based, has save, or neither
if (!z.u.rule_.empty())
{
// Find out if this zonelet has a rule or a save
auto i = std::lower_bound(rules.begin(), rules.end(), z.u.rule_,
[](const Rule& r, const std::string& nm)
{
return r.name() < nm;
});
if (i == rules.end() || i->name() != z.u.rule_)
eqr = std::equal_range(rules.data(), rules.data() + rules.size(), z.u.rule_);
if (eqr.first == eqr.second)
{
// The rule doesn't exist. Assume this is a save
try
{
using namespace std::chrono;
using string = std::string;
std::istringstream in(z.u.rule_);
in.exceptions(std::ios::failbit | std::ios::badbit);
in.str(z.u.rule_);
auto tmp = duration_cast<minutes>(parse_signed_time(in));
#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
z.u.rule_.~string();
@ -1608,13 +1609,6 @@ Zone::adjust_infos(const std::vector<Rule>& rules)
z.tag_ = zonelet::is_empty;
}
std::pair<const Rule*, const Rule*> eqr{};
if (z.tag_ == zonelet::has_rule)
{
eqr = std::equal_range(rules.data(), rules.data() + rules.size(), z.u.rule_);
assert(eqr.first != eqr.second);
}
minutes final_save{0};
if (z.tag_ == zonelet::has_save)
{
@ -1750,6 +1744,12 @@ Zone::get_info(std::chrono::system_clock::time_point tp, tz timezone) const
" is out of range:[" + std::to_string(static_cast<int>(min_year)) + ", "
+ std::to_string(static_cast<int>(max_year)) + "]");
auto tps = floor<seconds>(tp);
#if LAZY_INIT
std::call_once(*adjusted_, [this]()
{
const_cast<Zone*>(this)->adjust_infos(get_tzdb().rules);
});
#endif
auto i = std::upper_bound(zonelets_.begin(), zonelets_.end(), tps,
[timezone](second_point t, const zonelet& zl)
{
@ -1803,6 +1803,12 @@ operator<<(std::ostream& os, const Zone& z)
detail::save_stream _(os);
os.fill(' ');
os.flags(std::ios::dec | std::ios::left);
#if LAZY_INIT
std::call_once(*z.adjusted_, [&z]()
{
const_cast<Zone&>(z).adjust_infos(get_tzdb().rules);
});
#endif
os.width(35);
os << z.name_;
std::string indent;
@ -1909,9 +1915,8 @@ init_tzdb()
std::ifstream infile(path + "Makefile");
while (infile)
{
std::string version;
infile >> version;
if (version == "VERSION=")
infile >> line;
if (line == "VERSION=")
{
infile >> db.version;
break;
@ -1966,8 +1971,10 @@ init_tzdb()
std::sort(db.rules.begin(), db.rules.end());
Rule::split_overlaps(db.rules);
std::sort(db.zones.begin(), db.zones.end());
#if !LAZY_INIT
for (auto& z : db.zones)
z.adjust_infos(db.rules);
#endif
db.zones.shrink_to_fit();
std::sort(db.links.begin(), db.links.end());
db.links.shrink_to_fit();

18
tz.h
View File

@ -50,6 +50,10 @@ Technically any OS may use the mapping process but currently only Windows does u
#endif
#endif
#ifndef LAZY_INIT
# define LAZY_INIT 1
#endif
#include "date.h"
#include <algorithm>
@ -200,6 +204,9 @@ private:
std::string name_;
std::vector<zonelet> zonelets_;
#if LAZY_INIT
std::unique_ptr<std::once_flag> adjusted_;
#endif
public:
#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
@ -207,15 +214,20 @@ public:
Zone& operator=(Zone&&) = default;
#else // defined(_MSC_VER) || (_MSC_VER >= 1900)
Zone(Zone&& src)
:
name_(std::move(src.name_)),
zonelets_(std::move(src.zonelets_))
: name_(std::move(src.name_))
, zonelets_(std::move(src.zonelets_))
#if LAZY_INIT
, adjusted_(std::move(src.adjusted_))
#endif
{}
Zone& operator=(Zone&& src)
{
name_ = std::move(src.name_);
zonelets_ = std::move(src.zonelets_);
#if LAZY_INIT
adjusted_ = std::move(src.adjusted_);
#endif
return *this;
}
#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)