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std::basic_string::reserve

性病：基本[医]字符串：储备金

void reserve( size_type new_cap = 0 ​​

通知std::basic_string对象的计划更改大小，以便它可以适当地管理存储分配。

  • 如果new_cap大于当前capacity()，则分配新存储空间，以及capacity()等于或大于new_cap...

  • 如果new_cap比电流小capacity()，这是一个非绑定收缩请求。

  • 如果new_cap比电流小size()，这是一个非绑定收缩到适合的请求，相当于shrink_to_fit()%28自C++11%29。

如果发生容量更改，则所有迭代器和引用，包括过去的结束迭代器，都将失效。

参数

new_cap-new capacity of the string

返回值

%280%29

例外

抛出std::length_error如果new_cap大于max_size()...

引发的任何异常。std::allocator_traits<Allocator>::allocate()，如std::bad_alloc...

复杂性

最多是线性的size()那根绳子。

例

二次

#include <cassert>
#include <string>
 
int main()
{
    std::string s;
    std::string::size_type new_capacity{ 100u };
    assert(new_capacity > s.capacity()
 
    s.reserve(new_capacity
    assert(new_capacity <= s.capacity()
}

二次

另见

capacityreturns the number of characters that can be held in currently allocated storage (public member function)

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