string_view vs string.cpp

// string_view_vs_string_test.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <vector>
#include <fstream>
#include <string_view>
#include <unordered_map>
#include <chrono>
#include <benchmark/benchmark.h>

// This is not optimized and dosent have to be
std::vector<std::string> read_header_raw(const std::string& filename) {

	std::vector<std::string> raw_cards;
	std::ifstream input_file_stream(filename);

	if (input_file_stream.is_open()) {
		std::istreambuf_iterator<char> inp_iter(input_file_stream); // Iterators for traversing the entire stream
		std::istreambuf_iterator<char> end_of_file;

		while (inp_iter != end_of_file) {
			std::string raw_card;

			for (int i = 0; i < 80; i++) raw_card.push_back(*inp_iter++);
			raw_cards.push_back(raw_card);

		}

		return raw_cards;
	}
}

// String_View based
inline std::string_view getKey(std::string_view card) {

	std::string_view my_str = card;
	return my_str.substr(0, 8); // Returns a view rather than actual string

	//return std::string_view(card.data(), 8);
}

// String based
inline std::string getKey_str(const std::string& card) {
	return card.substr(0, 8);
}



static void TEST_STRING(benchmark::State& state) {

	// Runs only once
	auto raw_cards = read_header_raw("FITS_HEADER.txt");
	 int count = 0;
	std::unordered_map<std::string, size_t> fast_lookup;
	
	 
	for (auto _ : state) {
		for (auto&raw_card : raw_cards) {
			benchmark::DoNotOptimize(fast_lookup[getKey_str(raw_card)] = count++);
		}
	}
}
static void TEST_STRING_VIEW(benchmark::State& state) {

	// Runs only once
	auto raw_cards = read_header_raw("FITS_HEADER.txt");
	 int count = 0;
	std::unordered_map<std::string_view, size_t> fast_lookup;

	
	for (auto _ : state) {
		for (auto&raw_card : raw_cards) {
			benchmark::DoNotOptimize(fast_lookup[getKey(raw_card)] = count++);
		}
	}
}

BENCHMARK(TEST_STRING)->Unit(benchmark::kMicrosecond);
BENCHMARK(TEST_STRING_VIEW)->Unit(benchmark::kMicrosecond);
BENCHMARK_MAIN();