Abseil常用函数
简介
Abseil是基于STL标准往上封装的公共库，它是较轻量级的库。
Abseil 简要组成部分如下：
- base Abseil Fundamentals ：包含初始化代码和其它部分依赖的代码。除了 C++ 标准库外不依赖外部代码
- algorithm ：C++ <algorithm> 库的增强
- container ：STL 风格容器
- debugging ：内存泄露检查
- memory ：智能指针和内存管理
- meta ：用 C++11 兼容代码支持 C++14 和 C++17 版本的 <type_traits> 库
- numeric ：支持 C++11 兼容的 128 位整数
- strings ：string 相关函数增强
- synchronization ：同步原语和抽象支持
- time ：时间方面的计算
- types ：非容器类型的工具类型
字符串
#include <iostream>
#include <absl/strings/str_join.h>
#include <absl/strings/str_split.h>
#include <absl/strings/str_cat.h>
#include <absl/strings/str_replace.h>
#include <absl/strings/str_format.h>
#include <absl/strings/substitute.h>
#include <absl/strings/string_view.h>
int main() {
//字符串分隔数组
std::cout << "---split----" << std::endl;
std::vector<std::string> v=absl::StrSplit("abc,123",",");
for(int i=0;i<v.size();i++)
{
std::cout << v[i] << "";
}
std::cout << std::endl;
//将数组合并成字符串
std::cout << "---join----" << std::endl;
std::vector<std::string> strVector={"zhangsan","lisi","wangwu"};
std::string newStr=absl::StrJoin(strVector,"|");
std::cout << newStr << std::endl;
//将两个字符串拼接在一起
std::cout << "---cat----" << std::endl;
std::string strCat1="hello,";
std::string strCat2="world";
std::string newStrCat=absl::StrCat(strCat1,strCat2);
std::cout << newStrCat << std::endl;
//替换字符串第一种方式
std::cout << "---Replace1----" << std::endl;
std::string strReplace="zhangsan hello world";
std::string newStrReplace1=absl::StrReplaceAll(strReplace,{{"zhangsan","lisi"}});
std::cout << newStrReplace1 << std::endl;
//替换字符串第二种方式
std::cout << "---Replace2----" << std::endl;
std::vector<std::pair<const absl::string_view, std::string>> replacements;
replacements.push_back({"&", "&"});
replacements.push_back({"<", "<"});
replacements.push_back({">", ">"});
replacements.push_back({"&", "&"});
std::string newStrReplace2 = absl::StrReplaceAll("if (ptr < &foo)", replacements);
std::cout << newStrReplace2 << std::endl;
//字符串格式化
//格式化占位符参考：https://abseil.io/docs/cpp/guides/format
std::cout << "---StrFormat----" << std::endl;
std::string newFormat = absl::StrFormat("Welcome to %s, Number %d!", "The Village", 6);
std::cout << newFormat << std::endl;
//替代字符串
std::cout << "---Substitute----" << std::endl;
std::string newSubStitute = absl::Substitute("$1 purchased $0 $2 for $$10. Thanks $1!", 5, "Bob", "Apples");
std::cout << newSubStitute << std::endl;
//string_view 它提供一个字符串的视图，即可以通过这个类以各种方法“观测”字符串，但不允许修改字符串
absl::string_view strView="hello world";
return 0;
}
容器
无序容器
flat_hash_map和flat_hash_set可替换到 std::unordered_set和 std::unordered_map ,内部使用hash实现。
#include <iostream>
#include <absl/container/flat_hash_map.h>
#include <absl/container/flat_hash_set.h>
#include <vector>
int main() {
// 默认构造函数
//没有添加元素进行。
absl::flat_hash_set<std::string> set1;
absl::flat_hash_map<int, std::string> map1;
// 构造函数初始化列表
absl::flat_hash_set<std::string> set2 = {{"huey"}, {"dewey"}, {"louie"},};
absl::flat_hash_map<int, std::string> map2 =
{{1, "huey"}, {2, "dewey"}, {3, "louie"},};
//将set2复制到set3中
absl::flat_hash_set<std::string> set3(set2);
absl::flat_hash_map<int, std::string> map3(map2);
//赋值操作
absl::flat_hash_set<std::string> set4;
set4 = set3;
absl::flat_hash_map<int, std::string> map4;
map4 = map3;
// 移动构造函数
//移动是有效的
absl::flat_hash_set<std::string> set5(std::move(set4));
absl::flat_hash_map<int, std::string> map5(std::move(map4));
//移动赋值运算符
//如果分配器是兼容的，可能是有效的
absl::flat_hash_set<std::string> set6;
set6 = std::move(set5);
absl::flat_hash_map<int, std::string> map6;
map6 = std::move(map5);
// 范围的构造函数
std::vector<std::string> v = {"a", "b"};
absl::flat_hash_set<std::string> set7(v.begin(), v.end());
std::vector<std::pair<int, std::string>> v1 = {{1, "a"}, {2, "b"}};
absl::flat_hash_map<int, std::string> map7(v1.begin(), v1.end());
return 0;
}
BTREE容器
#include <iostream>
#include <absl/container/btree_map.h>
#include <absl/container/btree_set.h>
#include <vector>
//heliang
int main() {
absl::btree_set<std::string> set1;
absl::btree_map<int, std::string> map1;
// Initializer List constructor
absl::btree_set<std::string> set2 = {{"huey"}, {"dewey"}, {"louie"},};
absl::btree_map<int, std::string> map2 =
{{1, "huey"}, {2, "dewey"}, {3, "louie"},};
// Copy constructor
absl::btree_set<std::string> set3(set2);
absl::btree_map<int, std::string> map3(map2);
// Copy assignment operator
// Hash functor and Comparator are copied as well
absl::btree_set<std::string> set4;
set4 = set3;
absl::btree_map<int, std::string> map4;
map4 = map3;
// Move constructor
// Move is guaranteed efficient
absl::btree_set<std::string> set5(std::move(set4));
absl::btree_map<int, std::string> map5(std::move(map4));
// Move assignment operator
// May be efficient if allocators are compatible
absl::btree_set<std::string> set6;
set6 = std::move(set5);
absl::btree_map<int, std::string> map6;
map6 = std::move(map5);
// Range constructor
std::vector<std::string> v = {"a", "b"};
absl::btree_set<std::string> set7(v.begin(), v.end());
std::vector<std::pair<int, std::string>> v1 = {{1, "a"}, {2, "b"}};
absl::btree_map<int, std::string> map7(v1.begin(), v1.end());
return 0;
}
时间
#include <iostream>
#include <absl/time/time.h>
#include <absl/time/clock.h>
//heliang
int main() {
//当前的绝对时间
absl::Time t1= absl::Now();
//转换Time对象
time_t tt = time(NULL);
absl::Time timeT1 = absl::FromTimeT(tt);
auto tp = std::chrono::system_clock::from_time_t(123);
absl::Time chronoT2 = absl::FromChrono(tp);
int64_t unix_micros = 1674387176;
absl::Time unixT3= absl::FromUnixMicros(unix_micros);
//输出时间
absl::TimeZone utc = absl::UTCTimeZone();
//转换unix时间戳
uint64_t millis=absl::ToTimeT(t1);
std::cout << millis << "\n";
absl::Duration hour=absl::Hours(8);
//+8小时的误差
std::string newTime=absl::FormatTime("%Y-%m-%d %H:%M:%S",t1+hour, utc);
std::cout << newTime << "\n";
//将字符串转时间
absl::Time parseTime;
std::string strDate="2023-01-03 21:00:21";
absl::ParseTime("%Y-%m-%d %H:%M:%S",strDate,&parseTime, nullptr);
std::cout << absl::FormatTime("%Y-%m-%d %H:%M:%S",parseTime, utc) << std::endl;
return 0;
}
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