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Does it matter anymore if I use boost::string_ref over std::string& ? I mean, is it really more efficient to use boost::string_ref over the std version when you are processing strings ? I don't really get the explanation offered here: http://www.boost.org/doc/libs/1_61_0/libs/utility/doc/html/string_ref.html . What really confuses me is the fact that std::string is also a handle class that only points to the allocated memory, and since c++11, with move semantics the copy operations noted in the article above are not going to happen. So, which one is more efficient ?
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std::string class in C++ C++ has in its definition a way to represent a sequence of characters as an object of the class. This class is called std:: string. String class stores the characters as a sequence of bytes with the functionality of allowing access to the single-byte character.
There is no functionality difference between string and std::string because they're the same type. That said, there are times where you would prefer std::string over string .
The std::string class manages the underlying storage for you, storing your strings in a contiguous manner. You can get access to this underlying buffer using the c_str() member function, which will return a pointer to null-terminated char array. This allows std::string to interoperate with C-string APIs.
Use std::string when you need to store a value. Use const char * when you want maximum flexibility, as almost everything can be easily converted to or from one. Save this answer.
The use case for string_ref (or string_view in recent Boost and C++17) is for substring references.
The case where
std::string
is a (a-typical) special case, where it does indeed resemble std::string const&.
Note also that operations on string_ref (like sref.substring(...)) automatically return more string_ref objects, instead of allocating a new std::string.
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I have never used it be it seems to me that its purpose is to provide an interface similar to std::string but without having to allocate a string for manipulation. Take the example given extract_part(): it is given a hard-coded C array "ABCDEFG", but because the initial function takes a std::string an allocation takes place (std::string will have its own version of "ABCDEFG"). Using string_ref, no allocation occurs, it uses the reference to the initial "ABCDEFG". The constraint is that the string is read-only.
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