In this tutorial, you will learn another modern C++17 feature to work with strings. This feature is a std::string_view. The purpose of any kinds of string reference proposals is to bypass copying data that already owned someplace and of which only a non-mutating representation is required. The std::string_view is one such proposal. There was an earlier one named string_ref.
The std::string_view is a picture of the string and cannot be utilized to alter the original string value. When a std::string_view is constructed, there’s no need to replicate the data. Besides, the std::string_view is smaller than std::string on the heap.
How can you use std::string_view with C++ Builder?
- string_view lives in the <string_view> header file
Benefits of the string_view
- string_view is useful when you want to avoid unnecessary duplicates
- The creation of string_view from literals does not need a dynamic allocation.
The following code illustrates how string_view supports save memory by restricting unnecessary dynamic allocations:
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#ifdef _WIN32 #include <tchar.h> #else typedef char _TCHAR; #define _tmain main #endif #include <algorithm> #include <cstring> #include <iostream> #include <string> #include <string_view> // string_view // Unified way to view a string (memory and length) - without owning it // No allocation std::size_t parse(std::string_view str) { return std::count(str.begin(), str.end(), 'e'); } int _tmain(int argc, _TCHAR *argv[]) { const std::string str = "hello world"; const char* c = "Rio de Janeiro"; std::cout << "Occurrences of letter 'e': " << parse(std::string_view(str.data(), str.length())) << std::endl; std::cout << "Occurrences of letter 'e': " << parse(std::string_view(c, strlen(c))) << std::endl; system("pause"); return 0; } |
So, std::string_view is an extraordinary utility for great performance. But, the programmer must assure that std::string_view does not outlive the pointed-to character array.
Additional functions provided by std::string_view can be found here, on the official documentation.
Check out everything you need to know about Substring C++ in this informative blog.
Head over and check out the Windows string_view demo for C++Builder on GitHub.
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