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/*

 * diskserv.c -- serial line disk 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/tty01"

#define SYN             0x16

#define ACK             0x06

#define RESULT_OK       0x00

#define RESULT_UNCMD    0x01

#define RESULT_TOOBIG   0x02

#define RESULT_POSERR   0x03

#define RESULT_RDERR    0x04

#define RESULT_WRERR    0x05

static int debugCmds = 1;

static int debugData = 0;

static FILE *diskFile = NULL;

static unsigned int numSectors;

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 (diskFile != NULL) {

    fclose(diskFile);

    diskFile = 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);

  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");

}

void sendResult(unsigned char result) {

  while (!serialSnd(result)) ;

  tcdrain(sfd);

}

void showData(unsigned char buffer[512]) {

  int i, j;

  unsigned char c;

  for (i = 0; i < 32; i++) {

    printf("%03X   ", i * 16);

    for (j = 0; j < 16; j++) {

      c = buffer[i * 16 + j];

      printf("%02X ", c);

    }

    printf("  ");

    for (j = 0; j < 16; j++) {

      c = buffer[i * 16 + j];

      if (c >= 0x20 && c < 0x7F) {

        printf("%c", c);

      } else {

        printf(".");

      }

    }

    printf("\n");

  }

}

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

  char *diskName;

  int i;

  unsigned char b;

  unsigned char cmd;

  unsigned int sector;

  unsigned char buffer[512];

  if (argc != 2) {

    printf("Usage: %s <disk image file>\n", argv[0]);

    exit(1);

  }

  diskName = argv[1];

  diskFile = fopen(diskName, "r+b");

  if (diskFile == NULL) {

    error("cannot open disk image file '%s'", diskName);

  }

  fseek(diskFile, 0, SEEK_END);

  numSectors = ftell(diskFile) / 512;

  fseek(diskFile, 0, SEEK_SET);

  printf("Disk '%s' has 0x%08X sectors.\n", diskName, numSectors);

  /* open serial interface */

  serialOpen();

  /* wait for client to connect */

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

  while (1) {

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

      break;

    }

  }

  connect();

  /* connected, now handle requests */

  while (1) {

    while (!serialRcv(&cmd)) ;

    if (cmd == 'q') {

      /* for tests only, a real client would never quit */

      if (debugCmds) {

        printf("quit\n");

      }

      break;

    }

    if (cmd == SYN) {

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

      connect();

      continue;

    }

    if (cmd == 'c') {

      /* client asks for disk capacity */

      sendResult(RESULT_OK);

      for (i = 0; i < 4; i++) {

        b = (numSectors >> (8 * (3 - i))) & 0xFF;

        while (!serialSnd(b)) ;

      }

      tcdrain(sfd);

      if (debugCmds) {

        printf("capacity... OK\n");

      }

      continue;

    }

    if (cmd != 'r' && cmd != 'w') {

      /* unknown command */

      sendResult(RESULT_UNCMD);

      if (debugCmds) {

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

      }

      continue;

    }

    /* only read and write requests get here */

    sector = 0;

    for (i = 0; i < 4; i++) {

      while (!serialRcv(&b)) ;

      sector = (sector << 8) | b;

    }

    if (cmd == 'r') {

      if (debugCmds) {

        printf("reading sector 0x%08X... ", sector);

        fflush(stdout);

      }

      if (sector >= numSectors) {

        sendResult(RESULT_TOOBIG);

        if (debugCmds) {

          printf("TOOBIG\n");

        }

      } else

      if (fseek(diskFile, sector * 512, SEEK_SET) != 0) {

        sendResult(RESULT_POSERR);

        if (debugCmds) {

          printf("POSERR\n");

        }

      } else

      if (fread(buffer, 1, 512, diskFile) != 512) {

        sendResult(RESULT_RDERR);

        if (debugCmds) {

          printf("RDERR\n");

        }

      } else {

        sendResult(RESULT_OK);

        for (i = 0; i < 512; i++) {

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

        }

        tcdrain(sfd);

        if (debugCmds) {

          printf("OK\n");

        }

        if (debugData) {

          showData(buffer);

        }

      }

      continue;

    }

    if (cmd == 'w') {

      if (debugCmds) {

        printf("writing sector 0x%08X... ", sector);

        fflush(stdout);

      }

      for (i = 0; i < 512; i++) {

        while (!serialRcv(buffer + i)) ;

      }

      if (sector >= numSectors) {

        sendResult(RESULT_TOOBIG);

        if (debugCmds) {

          printf("TOOBIG\n");

        }

      } else

      if (fseek(diskFile, sector * 512, SEEK_SET) != 0) {

        sendResult(RESULT_POSERR);

        if (debugCmds) {

          printf("POSERR\n");

        }

      } else

      if (fwrite(buffer, 1, 512, diskFile) != 512) {

        sendResult(RESULT_WRERR);

        if (debugCmds) {

          printf("WRERR\n");

        }

      } else {

        sendResult(RESULT_OK);

        if (debugCmds) {

          printf("OK\n");

        }

        if (debugData) {

          showData(buffer);

        }

      }

      continue;

    }

  }

  if (diskFile != NULL) {

    fclose(diskFile);

    diskFile = NULL;

  }

  if (sfd != 0) {

    serialClose();

    sfd = 0;

  }

  return 0;

}