std::string_view (C++17)

In a Nutshell

A read-only string "view" that performs no copying or memory allocation. It only holds a pointer and a length, making it ideal for replacing const std::string& as a function parameter.

Header

#include <string_view>

Core API Cheat Sheet

Operation	Signature	Description
Construct	constexpr basic_string_view(const CharT* s, size_type count)	Construct from a pointer and length
Construct	constexpr basic_string_view(const CharT* s)	Construct from a C string
Length	constexpr size_type size() const	Return the number of characters
Empty check	constexpr bool empty() const	Check if it is empty
Element access	constexpr const CharT& operator[](size_type pos) const	Access the character at the specified position
Data pointer	constexpr const CharT* data() const	Return a pointer to the underlying character array
Remove prefix	constexpr void remove_prefix(size_type n)	Advance the starting position by n
Remove suffix	constexpr void remove_suffix(size_type n)	Move the ending position back by n
Substring	constexpr basic_string_view substr(size_type pos = 0, size_type count = npos) const	Return a substring view
Find	constexpr size_type find(basic_string_view v, size_type pos = 0) const	Find the position of a substring

Minimal Example

#include <iostream>
#include <string_view>
// Standard: C++17

void print(std::string_view sv) {
    std::cout << sv << "\n";
}

int main() {
    std::string s = "hello";
    print(s);                    // 接受 std::string
    print("world");              // 接受字符串字面量
    std::string_view sv = s;
    sv.remove_prefix(1);         // 变为 "ello"
    print(sv.substr(0, 2));      // 输出 "el"
}

Embedded Applicability: High

• Zero heap allocation; it only has two members (a pointer and a length), resulting in minimal memory overhead (typically 16 bytes).
• A TriviallyCopyable type, safe to use in interrupt contexts or for parsing DMA transfer buffers.
• Replaces const std::string& to avoid heap allocations caused by implicit std::string construction.
• Note on lifetime: never bind a temporary std::string to a string_view.

Compiler Support

GCC	Clang	MSVC
7.1	4.0	19.10

See Also

• cppreference: std::basic_string_view

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