#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <termios.h>
#include <fcntl.h>
#include <sys/file.h>
#include <sys/select.h>
#include "flow.h"
#define DATA_CANCEL 0xffffffff
static bool debug = false;
static void print_debug(const char* const msg, int en)
{
if (debug) {
if (errno == 0) {
fprintf(stderr, "%s", msg);
} else {
fprintf(stderr, "%s: %d\n", msg, en);
}
fflush(stderr);
}
}
void serial_debug(bool value)
{
debug = value;
}
//contains file descriptors used in managing a serial port
struct serial_config {
int port_fd; // file descriptor of serial port
/* a pipe is used to abort a serial read by writing something into the
* write end of the pipe */
int pipe_read_fd; // file descriptor, read end of pipe
int pipe_write_fd; // file descriptor, write end of pipe
};
int serial_open(
const char* const port_name,
int baud,
int char_size,
bool two_stop_bits,
int parity,
struct serial_config** serial)
{
int fd = open(port_name, O_RDWR | O_NOCTTY | O_NONBLOCK);
if (fd < 0) {
int en = errno;
print_debug("Error obtaining file descriptor for port", en);
if (en == EACCES) return -E_ACCESS_DENIED;
if (en == ENOENT) return -E_NO_PORT;
return -E_IO;
}
if (flock(fd, LOCK_EX | LOCK_NB) < 0) {
print_debug("Error acquiring lock on port", errno);
close(fd);
return -E_BUSY;
}
/* configure new port settings */
struct termios newtio;
/* initialize serial interface */
newtio.c_iflag = 0;
newtio.c_oflag = 0;
newtio.c_lflag = 0;
newtio.c_cflag = CREAD;
/* set speed */
speed_t bd;
switch (baud) {
case 50: bd = B50; break;
case 75: bd = B75; break;
case 110: bd = B110; break;
case 134: bd = B134; break;
case 150: bd = B150; break;
case 200: bd = B200; break;
case 300: bd = B300; break;
case 600: bd = B600; break;
case 1200: bd = B1200; break;
case 1800: bd = B1800; break;
case 2400: bd = B2400; break;
case 4800: bd = B4800; break;
case 9600: bd = B9600; break;
case 19200: bd = B19200; break;
case 38400: bd = B38400; break;
case 57600: bd = B57600; break;
case 115200: bd = B115200; break;
case 230400: bd = B230400; break;
default:
close(fd);
print_debug("Invalid baud rate", 0);
return -E_INVALID_SETTINGS;
}
if (cfsetspeed(&newtio, bd) < 0) {
print_debug("Error setting baud rate", errno);
close(fd);
return -E_IO;
}
/* set char size*/
switch (char_size) {
case 5: newtio.c_cflag |= CS5; break;
case 6: newtio.c_cflag |= CS6; break;
case 7: newtio.c_cflag |= CS7; break;
case 8: newtio.c_cflag |= CS8; break;
default:
close(fd);
print_debug("Invalid character size", 0);
return -E_INVALID_SETTINGS;
}
/* use two stop bits */
if (two_stop_bits){
newtio.c_cflag |= CSTOPB;
}
/* set parity */
switch (parity) {
case PARITY_NONE: break;
case PARITY_ODD: newtio.c_cflag |= (PARENB | PARODD); break;
case PARITY_EVEN: newtio.c_cflag |= PARENB; break;
default:
close(fd);
print_debug("Invalid parity", 0);
return -E_INVALID_SETTINGS;
}
if (tcflush(fd, TCIOFLUSH) < 0) {
print_debug("Error flushing serial settings", errno);
close(fd);
return -E_IO;
}
if (tcsetattr(fd, TCSANOW, &newtio) < 0) {
print_debug("Error applying serial settings", errno);
close(fd);
return -E_IO;
}
int pipe_fd[2];
if (pipe(pipe_fd) < 0) {
print_debug("Error opening pipe", errno);
close(fd);
return -E_IO;
}
if (fcntl(pipe_fd[0], F_SETFL, O_NONBLOCK) < 0 || fcntl(pipe_fd[1], F_SETFL, O_NONBLOCK) < 0) {
print_debug("Error setting pipe to non-blocking", errno);
close(fd);
close(pipe_fd[0]);
close(pipe_fd[1]);
return -E_IO;
}
struct serial_config* s = malloc(sizeof(s));
if (s == NULL) {
print_debug("Error allocating memory for serial configuration", errno);
close(fd);
close(pipe_fd[0]);
close(pipe_fd[1]);
return -E_IO;
}
s->port_fd = fd;
s->pipe_read_fd = pipe_fd[0];
s->pipe_write_fd = pipe_fd[1];
(*serial) = s;
return 0;
}
int serial_close(struct serial_config* const serial)
{
if (close(serial->pipe_write_fd) < 0) {
print_debug("Error closing write end of pipe", errno);
return -E_IO;
}
if (close(serial->pipe_read_fd) < 0) {
print_debug("Error closing read end of pipe", errno);
return -E_IO;
}
if (flock(serial->port_fd, LOCK_UN) < 0){
print_debug("Error releasing lock on port", errno);
return -E_IO;
}
if (close(serial->port_fd) < 0) {
print_debug("Error closing port", errno);
return -E_IO;
}
free(serial);
return 0;
}
int serial_read(struct serial_config* const serial, char* const buffer, size_t size)
{
int port = serial->port_fd;
int pipe = serial->pipe_read_fd;
fd_set rfds;
FD_ZERO(&rfds);
FD_SET(port, &rfds);
FD_SET(pipe, &rfds);
int nfds = pipe + 1;
if (pipe < port) nfds = port + 1;
int n = select(nfds, &rfds, NULL, NULL, NULL);
if (n < 0) {
print_debug("Error trying to call select on port and pipe", errno);
return -E_IO;
}
if (FD_ISSET(pipe, &rfds)) {
return -E_INTERRUPT;
} else if (FD_ISSET(port, &rfds)) {
int r = read(port, buffer, size);
// treat 0 bytes read as an error to avoid problems on disconnect
// anyway, after a poll there should be more than 0 bytes available to read
if (r <= 0) {
print_debug("Error data not available after select", errno);
return -E_IO;
}
return r;
} else {
print_debug("Select returned unknown read sets", 0);
return -E_IO;
}
}
int serial_cancel_read(struct serial_config* const serial)
{
int data = DATA_CANCEL;
//write to pipe to wake up any blocked read thread (self-pipe trick)
if (write(serial->pipe_write_fd, &data, 1) < 0) {
print_debug("Error writing to pipe during read cancel", errno);
return -E_IO;
}
return 0;
}
int serial_write(struct serial_config* const serial, char* const data, size_t size)
{
int r = write(serial->port_fd, data, size);
if (r < 0) {
print_debug("Error writing to port", errno);
return -E_IO;
}
return r;
}