Refactored connection handling for better resource management

Author: abhiphile

src/conn.h

@@ -0,0 +1,71 @@
+#include <cstdint>
+#include <stddef.h>
+#include <vector>
+#include "command.h"
+#include "utils.h"
+
+#pragma once
+
+enum ConnState {
+  STATE_READ,
+  STATE_WRITE,
+  STATE_END
+};
+
+/**
+ * Conn struct: a structure that represents a connection
+ * 
+ * This struct contains the following fields:
+ *   int fd;                      : the file descriptor of the connection
+ *   ConnState state{};           : state of the connection -> whether the server needs to read from the socket, or send a reply.
+ *   size_t rbuf_roffset{};       : read buffer's read offset (used when consuming data on buffer)
+ *   size_t rbuf_woffset{};       : read bufer's write offset (used when reading from network to read buffer)
+ *   size_t wbuf_offset{};        : write buffer's write offset (used when writing data to the network)
+ *   size_t pending_write_len{};  : amount of data still pending in the write buffer
+ *   char* rbuf;                  : pointer to the read buffer
+ *   char* wbuf;                  : pointer to the write buffer
+ * 
+ */
+struct Conn {
+  Conn()
+  : Conn(-1)
+  {}
+
+  Conn(int fd)
+  : fd{fd},
+    state{STATE_READ},
+    rbuf(Consts::SIZE_HEADER_LEN + Consts::MAX_MSG_LEN),
+    wbuf(Consts::SIZE_HEADER_LEN + Consts::MAX_MSG_LEN)
+  {}
+
+  // Conn(const Conn& other) = delete;
+  // Conn& operator=(const Conn& other) = delete;
+
+  // Conn(Conn&& other) = default;
+  // Conn& operator=(Conn&& other) = default;
+
+  void reset() {
+    fd = -1;
+    state = STATE_READ;
+    rbuf_roffset = 0;
+    rbuf_woffset = 0;
+    wbuf_offset = 0;
+    pending_write_len = 0;
+    cmd.reset();
+  }
+
+  void init(int fd) {
+    reset();
+    this->fd = fd;
+  }
+
+  int fd;
+  ConnState state{};
+  size_t rbuf_roffset{};
+  size_t rbuf_woffset{};
+  size_t wbuf_offset{};
+  size_t pending_write_len{};
+  Command cmd{};
+  std::vector<char> rbuf;
+  std::vector<char> wbuf;
+};