curl download c++11

curl.cpp

#include <cstdio>
#include <curl/curl.h>
#include <curl/easy.h>
#include <string>
#include <cassert>
#include <stdexcept>
#include <sstream>
#include <iostream>

void download(const std::string& url, const std::string& filename) {
	auto curl = curl_easy_init();
	assert(curl);
	auto fp = fopen(filename.c_str(), "wb");
	curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite);
	curl_easy_setopt(curl, CURLOPT_ACCEPT_ENCODING, "gzip");
	curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
	if (CURLE_OK != curl_easy_perform(curl)) {
		throw std::runtime_error("Cannot perform download " + url + " -> " + filename);
	}
	curl_easy_cleanup(curl);
	fclose(fp);
}

std::string getStringFromUrl(const std::string& url) {
	std::stringstream ss;
	auto curl = curl_easy_init();
	assert(curl);
	curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
	curl_easy_setopt(curl, CURLOPT_WRITEDATA, &ss);
	curl_easy_setopt(curl, CURLOPT_ACCEPT_ENCODING, "gzip");
	auto fn = static_cast<size_t (*)(void*, size_t, size_t, void*)>([](void* ptr, size_t size, size_t nmemb, void* stream) {
		std::stringstream& ss = *reinterpret_cast<std::stringstream*>(stream);
		ss.write(reinterpret_cast<char*>(ptr), size * nmemb);
		return size * nmemb;
	});
	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fn);
	if (CURLE_OK != curl_easy_perform(curl)) {
		throw std::runtime_error("Cannot perform download " + url);
	}
	curl_easy_cleanup(curl);
	return ss.str();
}

int main(int argc, char* argv[]) {
	if (argc == 2) {
		std::cout << getStringFromUrl(argv[1]);
	} else if (argc == 3) {
		download(argv[1], argv[2]);
	} else {
		return 1;
	}
	return 0;
}