first commit: echo server

include/event/Epoll.hpp

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+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   Epoll.hpp                                          :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: acossari <acossari@student.codam.nl>       +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/08/26 11:34:23 by acossari          #+#    #+#             */
+/*   Updated: 2026/08/26 11:34:25 by acossari         ###   ########.fr       */
+/*                                                                            */
+/* ************************************************************************** */
+
+#pragma once
+
+#include <sys/epoll.h>
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <exception>
+#include <span>
+#include <string>
+
+#include "net/FileDescriptor.hpp"
+
+namespace webserv {
+
+class Epoll final {
+  public:
+    class Error : public std::exception {
+      public:
+        explicit Error(std::string message);
+        const char* what() const noexcept override;
+
+      private:
+        std::string msg_;
+    };
+
+    // wait() returns at most this many ready events per call. Smaller batches
+    // require more calls, while larger batches delay the next loop iteration.
+    // The value is a middle ground. Excess events remain for later calls.
+    static constexpr std::size_t EVENT_BATCH_CAPACITY = 256;
+
+    Epoll();
+
+    void add(int fd, std::uint32_t events, std::uint64_t token);
+    void modify(int fd, std::uint32_t events, std::uint64_t token);
+    void remove(int fd) noexcept;
+
+    std::span<const epoll_event> wait(int timeoutMillis);
+
+  private:
+    FileDescriptor fd_;
+    std::array<epoll_event, EVENT_BATCH_CAPACITY> events_{};
+};
+
+}  // namespace webserv