Url Parsing in C++

#include <iostream>
#include <string>
#include <map>
#include <cstdlib>
#include <regex>
#include <stdexcept>

// A simple URL parsing class
class URL {
public:
    URL(const std::string& url_string) {
        parse(url_string);
    }

    std::string scheme;
    std::string user;
    std::string password;
    std::string host;
    std::string port;
    std::string path;
    std::string query;
    std::string fragment;

private:
    void parse(const std::string& url_string) {
        std::regex url_regex(
            R"(^(([^:/?#]+):)?(//((([^:@]*):?([^:@]*))?@)?([^:/?#]*):?(\d*))?((/[^?#]*)?(\?[^#]*)?(#.*)?))",
            std::regex::extended
        );

        std::smatch match;
        if (std::regex_match(url_string, match, url_regex)) {
            scheme = match[2];
            user = match[6];
            password = match[7];
            host = match[8];
            port = match[9];
            path = match[11];
            query = match[12];
            fragment = match[13];
        } else {
            throw std::runtime_error("Invalid URL");
        }
    }
};

// Function to parse query string into a map
std::map<std::string, std::string> parse_query(const std::string& query) {
    std::map<std::string, std::string> result;
    std::regex param_regex("([^&=]+)=([^&]*)");
    auto begin = std::sregex_iterator(query.begin() + 1, query.end(), param_regex);
    auto end = std::sregex_iterator();
    for (std::sregex_iterator i = begin; i != end; ++i) {
        std::smatch match = *i;
        result[match[1]] = match[2];
    }
    return result;
}

int main() {
    // We'll parse this example URL, which includes a
    // scheme, authentication info, host, port, path,
    // query params, and query fragment.
    std::string s = "postgres://user:pass@host.com:5432/path?k=v#f";

    // Parse the URL and ensure there are no errors.
    URL u(s);

    // Accessing the scheme is straightforward.
    std::cout << u.scheme << std::endl;

    // User contains all authentication info
    std::cout << u.user << ":" << u.password << std::endl;
    std::cout << u.user << std::endl;
    std::cout << u.password << std::endl;

    // The Host contains both the hostname and the port,
    // if present.
    std::cout << u.host << ":" << u.port << std::endl;
    std::cout << u.host << std::endl;
    std::cout << u.port << std::endl;

    // Here we extract the path and the fragment after
    // the #.
    std::cout << u.path << std::endl;
    std::cout << u.fragment << std::endl;

    // To get query params in a string of k=v format,
    // use query. You can also parse query params
    // into a map.
    std::cout << u.query << std::endl;
    auto m = parse_query(u.query);
    for (const auto& pair : m) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

This C++ program demonstrates URL parsing using a custom URL class and regular expressions. Here’s a breakdown of what the program does:

We define a URL class that parses a URL string into its components.
The parse_query function is used to parse the query string into a map.
In the main function, we create a sample URL string.
We create a URL object by parsing the string.
We then print out various components of the URL:
- The scheme
- User and password information
- Host and port
- Path and fragment
- Raw query string
Finally, we parse the query string into a map and print out the key-value pairs.

To compile and run this program:

$ g++ -std=c++11 url_parsing.cpp -o url_parsing
$ ./url_parsing

This will output the different pieces of the URL that we extracted.

Note that C++ doesn’t have built-in URL parsing libraries like some other languages, so we’ve implemented a basic parser using regular expressions. For production use, you might want to use a more robust third-party library for URL parsing.

Number Parsing in C++

Directories in C++

Learn X By Example

Title here

Url Parsing in C++