std::basic_string<CharT,Traits,Allocator>::max_size
来自cppreference.com
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size_type max_size() const; |
(C++11 起为 noexcept) (C++20 起为 constexpr) |
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返回字符串由于系统或库实现限制而有能力保有的最大元素数，即最大字符串的 std::distance(begin(), end())。
参数
（无）
返回值
最大字符数。
复杂度
常数。
示例
运行此代码
#include <array>
#include <climits>
#include <iomanip>
#include <iostream>
#include <locale>
#include <string>
#include <typeinfo>
#include <boost/core/demangle.hpp>
template<typename T>
void print_basic_string_max_size()
{
std::basic_string<T> s;
auto max_size = s.max_size();
std::cout.imbue(std::locale("en_US.UTF-8"));
std::cout << "basic_string<" << boost::core::demangle(typeid(T).name())
<< ">:\n\t" << max_size << " = ";
std::cout << std::setprecision(3) << (double) max_size << " = ";
std::cout.imbue(std::locale("C"));
std::cout << std::hex << std::setfill('0') << "0x"
<< std::setw(sizeof(typename decltype(s)::size_type) << 1)
<< max_size << '\n' << std::dec;
};
int main()
{
std::cout << "指针大小: " << CHAR_BIT * sizeof(void*) << " 位\n"
"最大大小:\n";
print_basic_string_max_size<char>();
print_basic_string_max_size<char16_t>();
print_basic_string_max_size<char32_t>();
print_basic_string_max_size<wchar_t>();
print_basic_string_max_size<long>();
using CharT = std::array<char, 01232>;
print_basic_string_max_size<CharT>();
}
可能的输出：
指针大小: 64 位
最大大小:
basic_string<char>:
9,223,372,036,854,775,807 = 9.22e+18 = 0x7fffffffffffffff
basic_string<char16_t>:
4,611,686,018,427,387,903 = 4.61e+18 = 0x3fffffffffffffff
basic_string<char32_t>:
2,305,843,009,213,693,951 = 2.31e+18 = 0x1fffffffffffffff
basic_string<wchar_t>:
2,305,843,009,213,693,951 = 2.31e+18 = 0x1fffffffffffffff
basic_string<long>:
1,152,921,504,606,846,975 = 1.15e+18 = 0x0fffffffffffffff
basic_string<std::array<char, 666ul>>:
13,848,906,962,244,407 = 1.38e+16 = 0x00313381ec031337
参阅
| 返回字符数 (公开成员函数) | |
| 返回字符数 ( std::basic_string_view<CharT,Traits> 的公开成员函数)
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