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/* $Id: rlink_cext.c 575 2014-07-27 20:55:41Z mueller $

 *

 * Copyright 2007-2014 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>

 *

 * This program is free software; you may redistribute and/or modify it under

 * the terms of the GNU General Public License as published by the Free

 * Software Foundation, either version 2, or at your option any later version.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY

 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * for complete details.

 *

 *  Revision History:

 * Date         Rev  Vers    Comment

 * 2014-07-27   575   1.3.2  add ssize_t -> int casts to avoid warnings

 *                           add fflush(stdout) after standart open/close msgs

 * 2011-03-05   366   1.3.1  add RLINK_CEXT_TRACE=2 trace level

 * 2010-12-29   351   1.3    rename cext_rriext -> rlink_cext; rename functions

 *                           cext_* -> rlink_cext_* and fifo file names

 *                           tb_cext_* -> rlink_cext_*

 * 2007-11-18    96   1.2    add 'read before write' logic to avoid deadlocks

 *                           under cygwin broken fifo (size=1 !) implementation

 * 2007-10-19    90   1.1    add trace option, controlled by setting an

 *                           the environment variable CEXT_RRIEXT_TRACE=1

 * 2007-09-23    84   1.0    Initial version

 */

#include <unistd.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <stdio.h>

#include <sched.h>

#include <stdlib.h>

#include <string.h>

#define CPREF 0x80

#define CESC  (CPREF|0x0f)

#define QRBUFSIZE 1024

static int fd_rx = -1;

static int fd_tx = -1;

static int io_trace = 0;

static char qr_buf[QRBUFSIZE];

static int  qr_pr  = 0;

static int  qr_pw  = 0;

static int  qr_nb  = 0;

static int  qr_eof = 0;

static int  qr_err = EAGAIN;

/* returns:

 *   <0          if error

 *   >=0 <=0xff  normal data

 *   == 0x100    idle

 *   0x1aahhll   if side band message seen

 *

 */

/* returns

 */

static void rlink_cext_dotrace(const char *text, int dat)

{

  int i;

  int mask = 0x80;

  printf("rlink_cext-I: %s   ", text);

  for (i=0; i<8; i++) {

    printf("%c", (dat&mask)?'1':'0' );

    mask >>= 1;

  }

  printf("\n");

}

static void rlink_cext_doread()

{

  char buf[1];

  ssize_t nbyte;

  nbyte = read(fd_rx, buf, 1);

  if (io_trace > 1) {

    printf("rlink_cext-I: read   rc=%d", (int)nbyte);

    if (nbyte < 0) printf(" errno=%d %s", errno, strerror(errno));

    printf("\n");

  }

  if (nbyte < 0) {

    qr_err = errno;

  } else if (nbyte == 0) {

    qr_err = EAGAIN;

    qr_eof = 1;

  } else {

    qr_err = EAGAIN;

    if (qr_nb < QRBUFSIZE) {

      if (io_trace) rlink_cext_dotrace("rcv8", (unsigned char) buf[0]);

      qr_buf[qr_pw++] = buf[0];

      if (qr_pw >= QRBUFSIZE) qr_pw = 0;

      qr_nb += 1;

    } else {

      printf("Buffer overflow\n"); /* FIXME: better error handling */

    }

  }

}

int rlink_cext_getbyte(int clk)

{

  char buf[1];

  ssize_t nbyte;

  int irc;

  int tdat;

  char* env_val;

  static int odat;

  static int nidle = 0;

  static int ncesc = 0;

  static int nside = -1;

  if (fd_rx < 0) {               /* fifo's not yet opened */

    fd_rx = open("rlink_cext_fifo_rx", O_RDONLY|O_NONBLOCK);

    if (fd_rx <= 0) {

      perror("rlink_cext-E: failed to open rlink_cext_fifo_rx");

      return -2;

    }

    printf("rlink_cext-I: connected to rlink_cext_fifo_rx\n");

    fflush(stdout);

    fd_tx = open("rlink_cext_fifo_tx", O_WRONLY);

    if (fd_tx <= 0) {

      perror("rlink_cext-E: failed to open rlink_cext_fifo_tx");

      return -2;

    }

    printf("rlink_cext-I: connected to rlink_cext_fifo_tx\n");

    fflush(stdout);

    nidle = 0;

    ncesc = 0;

    nside = -1;

    io_trace = 0;

    env_val = getenv("RLINK_CEXT_TRACE");

    if (env_val) {

      printf("rlink_cext-I: seen RLINK_CEXT_TRACE=%s\n", env_val);

      if (strcmp(env_val, "1") == 0) {

        printf("rlink_cext-I: set trace level to 1\n");

        io_trace = 1;

      } else if (strcmp(env_val, "2") == 0) {

        printf("rlink_cext-I: set trace level to 2\n");

        io_trace = 2;

      }

    }

  }

  rlink_cext_doread();

  if (qr_nb == 0) {                          /* no character to be processed */

    if (qr_eof != 0) {                       /* EOF seen */

      if (ncesc >= 2) {                     /*  two+ CESC seen  ? */

        printf("rlink_cext-I: seen EOF, wait for reconnect\n");

        fflush(stdout);

        close(fd_rx);

        close(fd_tx);

        fd_rx = -1;

        fd_tx = -1;

        usleep(500000);                     /* wait 0.5 sec */

        return 0x100;                       /* return idle, will reconnect */

      }

      printf("rlink_cext-I: seen EOF, schedule clock stop and exit\n");

      fflush(stdout);

      return -1;                            /* signal EOF seen */

    } else if (qr_err == EAGAIN) {          /* nothing read, return idle */

      if (nidle < 8 || (nidle%1024)==0) {

        irc = sched_yield();

        if (irc < 0) perror("rlink_cext-W: sched_yield failed");

      }

      nidle += 1;

      return 0x100;

    } else {                                /* must be a read error */

      errno = qr_err;

      perror("rlink_cext-E: read error on rlink_cext_fifo_rx");

      return -3;

    }

  }

  nidle = 0;

  tdat = (unsigned char) qr_buf[qr_pr++];

  if (qr_pr >= QRBUFSIZE) qr_pr = 0;

  qr_nb -= 1;

  if (tdat == CESC) {

    ncesc += 1;

    if (ncesc == 2) nside = 0;

  } else {

    ncesc = 0;

  }

  switch (nside) {

  case -1:                                  /* normal data */

    return tdat;

  case 0:                                    /* 2nd CESC, return it */

    nside += 1;

    return tdat;

  case 1:                                   /* get ADDR byte */

    nside += 1;

    odat = 0x1000000 | (tdat<<16);

    return 0x100;

  case 2:                                   /* get DL byte */

    nside += 1;

    odat |= tdat;

    return 0x100;

  case 3:                                   /* get DH byte */

    nside = -1;

    odat |= tdat<<8;

    return odat;

  }

}

int rlink_cext_putbyte(int dat)

{

  char buf[1];

  ssize_t nbyte;

  rlink_cext_doread();

  if (io_trace) rlink_cext_dotrace("snd8", dat);

  buf[0] = (unsigned char) dat;

  nbyte = write(fd_tx, buf, 1);

  if (io_trace > 1) {

    printf("rlink_cext-I: write  rc=%d", (int)nbyte);

    if (nbyte < 0) printf(" errno=%d %s", errno, strerror(errno));

    printf("\n");

  }

  if (nbyte < 0) {

    perror("rlink_cext-E: write error on rlink_cext_fifo_tx");

    return -3;

  }

  return 0;

}