/*-

 * Copyright (c) 2023 Christos Zoulas

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS

 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS

 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

 * POSSIBILITY OF SUCH DAMAGE.

 */

/*

 * Parse SIM-H tape files

 * http://simh.trailing-edge.com/docs/simh_magtape.pdf

 */

#ifndef TEST

#include "file.h"

#ifndef lint

FILE_RCSID("@(#)$File: is_simh.c,v 1.11 2025/05/31 23:31:45 christos Exp $")

#endif

#include <string.h>

#include <stddef.h>

#include "magic.h"

#else

#include <stdint.h>

#include <sys/types.h>

#include <string.h>

#include <stddef.h>

#define CAST(a, b) (a)(b)

#endif

#ifdef DEBUG

#include <stdio.h>

#define DPRINTF(fmt, ...) printf(fmt, __VA_ARGS__)

#else

#define DPRINTF(fmt, ...)

#endif

/*

 * if SIMH_TAPEMARKS == 0:

 *  check all the records and tapemarks

 * otherwise:

 *  check only up-to the number of tapemarks specified

 */

#ifndef SIMH_TAPEMARKS

#define SIMH_TAPEMARKS 10

#endif

typedef union {

  char s[4];

  uint32_t u;

} myword; 

static myword simh_bo;

#define NEED_SWAP (simh_bo.u == CAST(uint32_t, 0x01020304))

/*

 * swap an int

 */

static uint32_t

swap4(uint32_t sv)

{

  myword d, s;

  s.u = sv;

  d.s[0] = s.s[3];

  d.s[1] = s.s[2];

  d.s[2] = s.s[1];

  d.s[3] = s.s[0];

  return d.u;

}

static uint32_t

getlen(const unsigned char **uc, int *err)

{

  uint32_t n;

  memcpy(&n, *uc, sizeof(n));

  *err = 0;

  *uc += sizeof(n);

  if (NEED_SWAP)

    n = swap4(n);

  if (n == 0xffffffff)  /* check for End of Medium */

    return n;

  /* Check bits 25 to 28 are not used */

  *err = ((n & 0x00ffffff) != (n & 0x0fffffff));

  n &= 0x00ffffff;  /* keep only the record len */

  if (n & 1)

    n++;

  return n;

}

static int

simh_parse(const unsigned char *uc, const unsigned char *ue)

{

  uint32_t nbytes, cbytes;

  const unsigned char *orig_uc = uc;

  size_t nt = 0, nr = 0;

  int err = 0;

  (void)memcpy(simh_bo.s, "\01\02\03\04", 4);

  while (ue - uc >= CAST(ptrdiff_t, sizeof(nbytes))) {

    nbytes = getlen(&uc, &err);

    if (err)

      return 0;

    if ((nt > 0 || nr > 0) && nbytes == 0xFFFFFFFF)

      /* EOM after at least one record or tapemark */

      break;

    if (nbytes == 0) {

      nt++; /* count tapemarks */

#if SIMH_TAPEMARKS

      if (nt == SIMH_TAPEMARKS)

        break;

#endif

      continue;

    }

    /* handle a data record */

    uc += nbytes;

    if (ue - uc < CAST(ptrdiff_t, sizeof(nbytes)))

      break;

    cbytes = getlen(&uc, &err);

    if (err)

      return 0;

    if (nbytes != cbytes)

      return 0;

    nr++;

  }

  if (nt * sizeof(uint32_t) == CAST(size_t, uc - orig_uc))

    return 0;  /* All examined data was tapemarks (0) */

  if (nr == 0)    /* No records */

    return 0;

  return 1;

}

#ifndef TEST

int

file_is_simh(struct magic_set *ms, const struct buffer *b)

{

  const unsigned char *uc = CAST(const unsigned char *, b->fbuf);

  const unsigned char *ue = uc + b->flen;

  int mime = ms->flags & MAGIC_MIME;

  if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)) != 0)

    return 0;

  if (!simh_parse(uc, ue))

    return 0;

  if (mime == MAGIC_MIME_ENCODING)

    return 1;

  if (mime) {

    if (file_printf(ms, "application/SIMH-tape-data") == -1)

      return -1;

    return 1;

  }

  if (file_printf(ms, "SIMH tape data") == -1)

    return -1;

  return 1;

}

#else

#include <sys/types.h>

#include <sys/stat.h>

#include <stdio.h>

#include <fcntl.h>

#include <unistd.h>

#include <stdlib.h>

#include <stdint.h>

#include <err.h>

int

main(int argc, char *argv[])

{

  int fd;

  struct stat st;

  unsigned char *p;

  if ((fd = open(argv[1], O_RDONLY)) == -1)

    err(EXIT_FAILURE, "Can't open `%s'", argv[1]);

  if (fstat(fd, &st) == -1)

    err(EXIT_FAILURE, "Can't stat `%s'", argv[1]);

  if ((p = CAST(char *, malloc(st.st_size))) == NULL)

    err(EXIT_FAILURE, "Can't allocate %jd bytes",

        (intmax_t)st.st_size);

  if (read(fd, p, st.st_size) != st.st_size)

    err(EXIT_FAILURE, "Can't read %jd bytes",

        (intmax_t)st.st_size);

  printf("is simh %d\n", simh_parse(p, p + st.st_size));

  return 0;

}

#endif