/* XMUTIL.C Xmodem utility procedures.  Includes CRC generation and other
 *    utility routines not in xmsend.c (send state machine) and
 *    xmrecv.c (receive state machine)
 *  GOAL:  Provide high level interfaces to interrupt handler routines.
 *         Includes init() which sits between interrupt handler and cterm.
 *  NOTE:  Do no printf's in this file.
 */

#include "commint.h"   /* defines and structs for Turbo C int handler */
#include "cterm.h"     /* project header goes here */
#include "commn.h"     /* definition of S_INIT structure */

#define MAXJUNK  100   /* used by eat_noise */

/* Messages posted by A_Send_End and A_Recv_End */
char user_msg[] = "Terminated by user";
char nonak[]    = "No initial NAK/CRC received";
char cancel[]   = "Cancel Received";
char badcomm[]  = "Problem Reading/Writing to comm port";
char badread[]  = "Problem reading disk file";
char badwrite[] = "Problem writing disk file";
char eof_msg[]  = "File successfully transferred";
char giveup[]   = "Retries exhausted by NAK's and/or timeouts";

/* ------- External references */
extern int crc;                     /* external flag for CRC or Checksum */
extern void interrupt rxrdy_IH();   /* in module commint.c */
extern unsigned char getcomch();
extern S_INIT cur_config;

/* Calls the following from commint.c module:
extern int Remove_IH();
extern int Inst_IH();         */
/* Calls the following from ctermx.c module:
extern int Config_Comm();     */

/* Export to xmsend and xmrecv routines */
unsigned crcaccum;
unsigned char checksum;
int crc = 1;                  /* flag for CRC (!0) or checksum  (0) */

void updcrc( unsigned char c)
{
  unsigned shifter, i, flag;

  if (crc) {
    for (shifter = 0x80; shifter; shifter >>= 1) {
      flag = (crcaccum & 0x8000);
      crcaccum <<= 1;
      crcaccum |= (shifter & c) ? 1 : 0;
      if (flag)
        crcaccum ^= 0x1021;
    }
  }
  else
    checksum += c;
}

/* ---------- read_comm ------------------------
 * Does:  Reads data from the comm port already opened.
 * Pass:  by ref - number of bytes to read (returns actually read).
 *        pointer to buffer for data
 *        time to wait (in msecs) for completion. 0 = 1 test
 * Uses:  TurboC 1.5+ specific delay() function.
 *        Test show that delay() works reliably at 10 msecs (not 1)
 * Priority:  If all char's read, returns before time expires.
 *    Any time a receive error is detected, return immediately.
 * Returns: 0 if all read, TIMEOUT (define) if timeout.
 */
int read_comm( int *num, unsigned char *buf, int wait )
{
  int toread = *num;
  int redok  = 0;
  unsigned char *cptr = buf;
  int wait10ms  = wait / 10;

  if (wait10ms == 0)
    wait10ms = 1;         /* add 1 in case under 10 */

  do {
    if (incomm() != 0)
    {
      /* Data is waiting.  Move it into buffer and get count read */
      *cptr = getcomch();                /* Send to users buffer */
      cptr++;
      redok++;
    }
    else
      if ( wait10ms ) {
        delay(10);             /* Borland says 1 millisecond per... */
        wait10ms--;
      }
  }
  while (!( (redok == toread) || (wait10ms == 0)  ));

  *num = redok;    /* return the actual number read via *num ref param */
  return ( (wait10ms > 0) ? 0 : TIMEOUT );
}


/* ---------- close_comm ------------------------
 * Does:  Closes the comm port previously opened by removing our interrupt
 *        handler and returning the UART to the previous (saved) state.
 */
int close_comm()
{
  Remove_IH();
}

/* init ----- initialize params and installs interrupt handler.
 * Pass:  Comm port number (1 or 2) to install and configure, bbsmode flag.
 * Does:  Installs interrupt handler and sets comm port.
 *        Sets comm parameters per struct passed.
 *        Config_Comm publishes global baud rate for receiver timing.
 */
int init_comm( int comnum, int bbsconf )
{
  int retval;

  retval = Inst_IH(rxrdy_IH, comnum);
  if (retval != 0) {
    Remove_IH();           /* this could probably waste somebody else */
    return(1);             /* was exit(1) */
  }

  if (bbsconf == 0) {
    cur_config.ubits.lctrl = sev1even;
  }
  else
    cur_config.ubits.lctrl = ate1none;

  Config_Comm(comnum, cur_config);
  return(0);
}