cidr_utils.cpp

#include "cidr_utils.h"
#include <arpa/inet.h>
#include <netinet/in.h>

namespace netcidr {

static bool parse_cidr(const std::string& cidr, uint32_t& net, uint32_t& mask) {
    // Split at /
    auto slash = cidr.find('/');
    if (slash == std::string::npos) 
        return false;
    std::string ip = cidr.substr(0, slash);
    std::string bits = cidr.substr(slash+1);
    int prefix = std::stoi(bits);

    if (prefix < 0 || prefix > 32) 
        return false;
    in_addr addr{};
    if (inet_pton(AF_INET, ip.c_str(), &addr) != 1) 
        return false;
    uint32_t h = ntohl(addr.s_addr);
    uint32_t m = (prefix == 0) ? 0 : (0xFFFFFFFFu << (32 - prefix));
    net = h & m;
    mask = m;
    return true;
}

std::vector<uint32_t> enumerate_ipv4_hosts(const std::string& cidr) {
    uint32_t net=0, mask=0;
    if (!parse_cidr(cidr, net, mask)) 
        return {};
    uint32_t first = net;
    uint32_t last = net | (~mask);
    std::vector<uint32_t> out;
    // enumerate from first to last inclusive
    for (uint32_t ip = first; ip <= last; ++ip) {
        out.push_back(ip);
        if (ip == 0xFFFFFFFFu) 
            break;
    }
    return out;
}

std::string ip_to_string(uint32_t ip) {
    in_addr a{};
    a.s_addr = htonl(ip);
    char buf[INET_ADDRSTRLEN];
    if (!inet_ntop(AF_INET, &a, buf, sizeof(buf))) 
        return "0.0.0.0";
    return std::string(buf);
}

uint32_t ip_from_string(const std::string& s) {
    in_addr a{};
    if (inet_pton(AF_INET, s.c_str(), &a) != 1) 
        return 0;
    return ntohl(a.s_addr);
}

} // namespace netcidr