first commit: echo server

include/net/ByteBuffer.hpp

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+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   ByteBuffer.hpp                                     :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: acossari <acossari@student.codam.nl>       +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/08/25 09:30:45 by acossari          #+#    #+#             */
+/*   Updated: 2026/08/25 13:26:00 by acossari         ###   ########.fr       */
+/*                                                                            */
+/* ************************************************************************** */
+
+#pragma once
+
+#include <cstddef>
+#include <span>
+#include <vector>
+
+namespace webserv {
+
+class ByteBuffer final {
+  public:
+    // The fixed 64 KiB capacity is also the maximum request-head size. It
+    // leaves room for large headers while keeping memory bounded. The server
+    // accepts at most 256 simultaneous connections, each with one receive and
+    // one send buffer. In the worst-case scenario, their storage is 32 MiB, a
+    // modest fixed ceiling for all connection buffers combined.
+    // The C++23 uz suffix makes 64 a std::size_t, so multiplication occurs in
+    // std::size_t instead of int and avoids implicit widening (clang-tidy).
+    static constexpr std::size_t CAPACITY = 64uz * 1024;
+
+    std::span<const char> readable() const {
+      return {storage_.data() + readPos_, writePos_ - readPos_};
+    }
+
+    std::span<char> writableTail() {
+      return {storage_.data() + writePos_, CAPACITY - writePos_};
+    }
+
+    // Makes count bytes already written in writableTail() readable. count must
+    // not exceed writableTail().size().
+    void commit(std::size_t count);
+
+    // Discards count bytes from the start of readable(). count must not exceed
+    // readable().size().
+    void consume(std::size_t count);
+
+    void compact();
+
+  private:
+    // C++17 guaranteed copy elision constructs this vector directly in
+    // storage_, with no temporary vector or move.
+    std::vector<char> storage_ = std::vector<char>(CAPACITY);
+
+    // Only bytes from readPos_ up to, but not including, writePos_ are live.
+    // Values outside this range can remain in storage_ and are ignored.
+    std::size_t readPos_ = 0;
+    std::size_t writePos_ = 0;
+};
+
+}  // namespace webserv