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/*

 * loadserv.c -- serial line load server

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <stdarg.h>

#include <fcntl.h>

#include <unistd.h>

#include <termios.h>

#define SERIAL_PORT     "/dev/ttyS0"

#define SYN             ((unsigned char) 's')

#define ACK             ((unsigned char) 'a')

#define LINE_SIZE       520

static int debugCmds = 1;

static int debugData = 0;

static FILE *loadFile = NULL;

static int sfd = 0;

static struct termios origOptions;

static struct termios currOptions;

void serialClose(void);

void error(char *fmt, ...) {

  va_list ap;

  va_start(ap, fmt);

  printf("Error: ");

  vprintf(fmt, ap);

  printf("\n");

  va_end(ap);

  if (loadFile != NULL) {

    fclose(loadFile);

    loadFile = NULL;

  }

  if (sfd != 0) {

    serialClose();

    sfd = 0;

  }

  exit(1);

}

void serialOpen(void) {

  sfd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);

  if (sfd == -1) {

    error("cannot open serial port '%s'", SERIAL_PORT);

  }

  tcgetattr(sfd, &origOptions);

  currOptions = origOptions;

  cfsetispeed(&currOptions, B38400);

  cfsetospeed(&currOptions, B38400);

  currOptions.c_cflag |= (CLOCAL | CREAD);

  currOptions.c_cflag &= ~PARENB;

  currOptions.c_cflag &= ~CSTOPB;

  currOptions.c_cflag &= ~CSIZE;

  currOptions.c_cflag |= CS8;

  currOptions.c_cflag &= ~CRTSCTS;

  currOptions.c_lflag &= ~(ICANON | ECHO | ECHONL | ISIG | IEXTEN);

  currOptions.c_iflag &= ~(IGNBRK | BRKINT | IGNPAR | PARMRK);

  currOptions.c_iflag &= ~(INPCK | ISTRIP | INLCR | IGNCR | ICRNL);

  currOptions.c_iflag &= ~(IXON | IXOFF | IXANY);

  currOptions.c_oflag &= ~(OPOST | ONLCR | OCRNL | ONOCR | ONLRET | OFILL);

  tcsetattr(sfd, TCSANOW, &currOptions);

}

void serialClose(void) {

  tcsetattr(sfd, TCSANOW, &origOptions);

  close(sfd);

}

int serialSnd(unsigned char b) {

  int n;

  n = write(sfd, &b, 1);

  return n == 1;

}

int serialRcv(unsigned char *bp) {

  int n;

  n = read(sfd, bp, 1);

  return n == 1;

}

void connect(void) {

  unsigned char b;

  printf("SYN... ");

  fflush(stdout);

  while (!serialSnd(ACK)) ;

  tcdrain(sfd);

  printf("ACK... ");

  fflush(stdout);

  while (!serialRcv(&b)) ;

  if (b != ACK) {

    error("cannot synchronize with client");

  }

  printf("connected\n");

}

int main(int argc, char *argv[]) {

  char *loadName;

  unsigned char b;

  unsigned char cmd;

  char line[LINE_SIZE];

  int n, i;

  if (argc != 2) {

    printf("Usage: %s <file to be loaded>\n", argv[0]);

    exit(1);

  }

  loadName = argv[1];

  loadFile = fopen(loadName, "rt");

  if (loadFile == NULL) {

    error("cannot open file to be loaded '%s'", loadName);

  }

  /* open serial interface */

  serialOpen();

  /* wait for client to connect */

  printf("Waiting for client...\n");

  while (1) {

    if (serialRcv(&b) && b == SYN) {

      break;

    }

  }

  connect();

  fseek(loadFile, 0, SEEK_SET);

  /* connected, now handle requests */

  while (1) {

    while (!serialRcv(&cmd)) ;

    if (cmd == 'q') {

      /* quit */

      if (debugCmds) {

        printf("quit\n");

      }

      break;

    }

    if (cmd == SYN) {

      /* this happens if the client has been reset */

      connect();

      fseek(loadFile, 0, SEEK_SET);

      continue;

    }

    if (cmd != 'r') {

      /* unknown command */

      if (debugCmds) {

        printf("unknown... UNCMD\n");

      }

      continue;

    }

    /* only read requests get here */

    if (debugCmds) {

      printf("reading record... ");

      fflush(stdout);

    }

    if (fgets(line, LINE_SIZE, loadFile) == NULL) {

      if (debugCmds) {

        printf("RDERR\n");

      }

    } else {

      n = strlen(line);

      for (i = 0; i < n; i++) {

        while (!serialSnd(line[i])) ;

      }

      tcdrain(sfd);

      if (debugCmds) {

        printf("OK\n");

      }

      if (debugData) {

        printf("%s", line);

      }

    }

  }

  if (loadFile != NULL) {

    fclose(loadFile);

    loadFile = NULL;

  }

  if (sfd != 0) {

    serialClose();

    sfd = 0;

  }

  return 0;

}