What's the best way to trim std::string?

Question

I\'m currently using the following code to right-trim all the std::strings in my programs:

std::string s;
s.erase(s.find_last_not_of(\" \\n\\r\\         


        

Answer 1

I guess if you start asking for the "best way" to trim a string, I'd say a good implementation would be one that:

1. Doesn't allocate temporary strings
2. Has overloads for in-place trim and copy trim
3. Can be easily customized to accept different validation sequences / logic

Obviously there are too many different ways to approach this and it definitely depends on what you actually need. However, the C standard library still has some very useful functions in , like memchr. There's a reason why C is still regarded as the best language for IO - its stdlib is pure efficiency.

inline const char* trim_start(const char* str)
{
    while (memchr(" \t\n\r", *str, 4))  ++str;
    return str;
}
inline const char* trim_end(const char* end)
{
    while (memchr(" \t\n\r", end[-1], 4)) --end;
    return end;
}
inline std::string trim(const char* buffer, int len) // trim a buffer (input?)
{
    return std::string(trim_start(buffer), trim_end(buffer + len));
}
inline void trim_inplace(std::string& str)
{
    str.assign(trim_start(str.c_str()),
        trim_end(str.c_str() + str.length()));
}

int main()
{
    char str [] = "\t \nhello\r \t \n";

    string trimmed = trim(str, strlen(str));
    cout << "'" << trimmed << "'" << endl;

    system("pause");
    return 0;
}