cpp17.string.view.org

string_view

A wrapper/view from a tradiciona std::string.

source code from: https://skebanga.github.io/string-view/

“… C++17 makes it easy by introducing a new type called std::string_view. From now on, if you are writing a function that accepts a string, use an std::string_view as parameter type. No need to use an std::string_view reference. A string_view is very cheap to copy, so it’s perfectly fine to pass by value. Basically, a string_view just contains a pointer to a string, and its length. A string_view parameter accepts any kind of string, such as a C++ std::string, a C-style const char* string, and a string literal, all without any copying involved! …”

source from: http://www.nuonsoft.com/blog/2018/06/06/c17-stdstring_view/

#include <iostream>
#include <string_view>

using namespace std;

void* operator new(std::size_t n)
{
    	std::cout << "[allocating " << n << " bytes]\n";
    	return malloc(n);
}

bool compare(const std::string& s1, const std::string& s2)
{
    	if (s1 == s2)
	{
    	    return true;
	}
    	std::cout << '\"' << s1 << "\" does not match \"" << s2 << "\"\n";
    	return false;
}

bool compare_v2(std::string_view s1, std::string_view s2)
{
    	if (s1 == s2)
	{
    	    return true;
	}
    	std::cout << '\"' << s1 << "\" does not match \"" << s2 << "\"\n";
    	return false;
}


void processString(string_view myString)
{
   	 cout << myString; if (myString.size() >= 4)
   	 {
   	     cout << "   (Substring: " << myString.substr(2, 2) << ")";
   	 }
   	 cout << endl;
}

int main()
{
    	string str = "this is my input string";

	compare(str, "this is the first test string");
    	compare(str, "this is the second test string");
    	compare(str, "this is the third test string");
	
	cout << "-------------------------------------------" << endl;
	
	compare_v2(str, "this is the first test string");
    	compare_v2(str, "this is the second test string");
    	compare_v2(str, "this is the third test string");
	
	cout << "-------------------------------------------" << endl;
	
	string myString1 = "Hello";
    	const char* myString2 = "C++";
    	processString(myString1);  // C++ string
    	processString(myString2);  // C-style string
    	processString("World!");   // String literal

    	return 0;
}