std::basic_string::resize

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::operator= basic_string::assign basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (C++11) basic_string::back (C++11) basic_string::data basic_string::c_str basic_string::operator basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (C++11)

Operations basic_string::clear basic_string::insert basic_string::erase basic_string::push_back basic_string::pop_back (C++11) basic_string::append basic_string::operator+= basic_string::compare basic_string::replace basic_string::substr basic_string::copy basic_string::resize basic_string::swap Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of Constants basic_string::npos

Non-member functions operator+ operator==operator!=operator<operator>operator<=operator>= swap(std::basic_string) operator<<operator>> getline stoistolstoll (C++11)(C++11)(C++11) stoulstoull (C++11)(C++11) stofstodstold (C++11)(C++11)(C++11) to_string (C++11) to_wstring (C++11) operator""s (C++14) Helper classes hash<std::string>hash<std::wstring>hash<std::u32string>hash<std::u16string> (C++11)(C++11)(C++11)(C++11)

 

void resize( size_type count );	(1)
void resize( size_type count, CharT ch );	(2)

Resizes the string to contain count characters.

If the current size is less than count, additional characters are appended.

If the current size is greater than count, the string is reduced to its first count elements.

The first version initializes new characters to CharT(), the second version initializes new characters to ch.

Parameters

count	-	new size of the string
ch	-	character to initialize the new characters with

Return value

(none)

Exceptions

std::length_error if count > max_size(). Any exceptions thrown by corresponding Allocator.

If an exception is thrown for any reason, this function has no effect (strong exception guarantee). (since C++11)

Example

Run this code

#include <iostream>
#include <stdexcept>
 
int main()
{
    std::cout << "Basic functionality:\n";
    const unsigned  desired_length(8);
    std::string     long_string( "Where is the end?" );
    std::string     short_string( "Ha" );
 
    // Shorten
    std::cout << "Before: \"" << long_string << "\"\n";
    long_string.resize( desired_length );
    std::cout << "After: \"" << long_string <<  "\"\n";
 
    // Lengthen
    std::cout << "Before: \"" << short_string <<  "\"\n";
    short_string.resize( desired_length, 'a' );
    std::cout << "After: \"" << short_string <<  "\"\n";
 
    std::cout  << "\nErrors:\n";
    {
        std::string s;    
 
        try {
            // size is OK, no length_error
            // (may throw bad_alloc)
            s.resize(s.max_size() - 1, 'x');
        } catch (const std::bad_alloc&) {
            std::cout << "1. bad alloc\n";
        }
 
        try {
            // size is OK, no length_error
            // (may throw bad_alloc)
            s.resize(s.max_size(), 'x');
        } catch (const std::bad_alloc& exc) {
            std::cout << "2. bad alloc\n";
        }
 
        try {
            // size is BAD, throw length_error
            s.resize(s.max_size() + 1, 'x');
        } catch (const std::length_error&) {
            std::cout << "3. length error\n";
        }
     }
}

Possible output:

Basic functionality:
Before: "Where is the end?"
After: "Where is"
Before: "Ha"
After: "Haaaaaaa"
 
Errors:
1. bad alloc
2. bad alloc
3. length error

Complexity

Linear in the size of the string.

See also

sizelength

returns the number of characters (public member function)