More extraction of functionality

Extracting server and tty functions into separate headers.
Thread functions for new connections, tty data and client data
are also extracted and used as separate functional blocks.

tty.h

@@ -0,0 +1,62 @@
+#pragma once
+
+/* Handles communication with a tty device. */
+
+#include <common.h>
+#include <client.h>
+#include <termios.h>
+
+#define DEV_PATH 128
+
+typedef struct
+{
+	int fd;						/* tty file descriptor */
+	struct termios ttysetdef;	/* default tty termios settings */
+	struct termios ttyset;		/* tty termios settings */
+	char path[DEV_PATH];		/* tty device path */
+	char data[DATABUF_LEN];		/* buffer for data received from tty */
+} tty_t;
+
+/**
+ * Opens the tty device and configures it.
+ */
+int tty_open(tty_t *tty_dev);
+
+/**
+ * Closes the tty device.
+ */
+int tty_close(tty_t *tty_dev);
+
+/**
+ * Reconfigures the tty device.
+ */
+int tty_reconfigure(tty_t *tty_dev, struct termios newttyset);
+
+/**
+ * Reads incoming data from tty device to tty data buffer.
+ *
+ * Returns:
+ * - number of read bytes on success,
+ * - negative errno value set by an error while readin
+ */
+int tty_read(tty_t *tty_dev);
+
+/**
+ * Sends data from a buffer to tty device.
+ *
+ * Returns:
+ * - number of sent bytes on success,
+ * - negative errno value set by an error while sending
+ */
+int tty_write(tty_t *tty_dev, char *databuf, int datalen);
+
+/**
+ * Converts POSIX speed_t to a baud rate.  The values of the
+ * constants for speed_t are not themselves portable.
+ */
+int speed_to_baud(speed_t speed);
+
+/**
+ * Converts a numeric baud rate to a POSIX speed_t.
+ */
+speed_t baud_to_speed(int baud);