/* BFD back-end for s-record objects.

   Copyright (C) 1990-2026 Free Software Foundation, Inc.

   Written by Steve Chamberlain of Cygnus Support <sac@cygnus.com>.

   This file is part of BFD, the Binary File Descriptor library.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, 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 more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

   MA 02110-1301, USA.  */

/* SUBSECTION

  S-Record handling

   DESCRIPTION

  Ordinary S-Records cannot hold anything but addresses and

  data, so that's all that we implement.

  The only interesting thing is that S-Records may come out of

  order and there is no header, so an initial scan is required

  to discover the minimum and maximum addresses used to create

  the vma and size of the only section we create.  We

  arbitrarily call this section ".text".

  When bfd_get_section_contents is called the file is read

  again, and this time the data is placed into a bfd_alloc'd

  area.

  Any number of sections may be created for output, we save them

  up and output them when it's time to close the bfd.

  An s record looks like:

   EXAMPLE

  S<type><length><address><data><checksum>

   DESCRIPTION

  Where

  o length

  is the number of bytes following upto the checksum. Note that

  this is not the number of chars following, since it takes two

  chars to represent a byte.

  o type

  is one of:

  0) header record

  1) two byte address data record

  2) three byte address data record

  3) four byte address data record

  7) four byte address termination record

  8) three byte address termination record

  9) two byte address termination record

  o address

  is the start address of the data following, or in the case of

  a termination record, the start address of the image

  o data

  is the data.

  o checksum

  is the sum of all the raw byte data in the record, from the length

  upwards, modulo 256 and subtracted from 255.

   SUBSECTION

  Symbol S-Record handling

   DESCRIPTION

  Some ICE equipment understands an addition to the standard

  S-Record format; symbols and their addresses can be sent

  before the data.

  The format of this is:

  ($$ <modulename>

    (<space> <symbol> <address>)*)

  $$

  so a short symbol table could look like:

   EXAMPLE

  $$ flash.x

  $$ flash.c

    _port6 $0

    _delay $4

    _start $14

    _etext $8036

    _edata $8036

    _end $8036

  $$

   DESCRIPTION

  We allow symbols to be anywhere in the data stream - the module names

  are always ignored.  */

#include "sysdep.h"

#include "bfd.h"

#include "libbfd.h"

#include "libiberty.h"

#include "safe-ctype.h"

/* Macros for converting between hex and binary.  */

static const char digs[] = "0123456789ABCDEF";

#define NIBBLE(x)    hex_value(x)

#define HEX(buffer) ((NIBBLE ((buffer)[0])<<4) + NIBBLE ((buffer)[1]))

#define TOHEX(d, x, ch) \

  d[1] = digs[(x) & 0xf]; \

  d[0] = digs[((x)>>4)&0xf]; \

  ch += ((x) & 0xff);

#define ISHEX(x)    hex_p(x)

/* The maximum number of address+data+crc bytes on a line is FF.  */

#define MAXCHUNK 0xff

/* Default size for a CHUNK.  */

#define DEFAULT_CHUNK 16

/* The number of data bytes we actually fit onto a line on output.

   This variable can be modified by objcopy's --srec-len parameter.

   For a 0x75 byte record you should set --srec-len=0x70.  */

unsigned int _bfd_srec_len = DEFAULT_CHUNK;

/* The type of srec output (free or forced to S3).

   This variable can be modified by objcopy's --srec-forceS3

   parameter.  */

bool _bfd_srec_forceS3 = false;

/* When writing an S-record file, the S-records can not be output as

   they are seen.  This structure is used to hold them in memory.  */

struct srec_data_list_struct

{

  struct srec_data_list_struct *next;

  bfd_byte *data;

  bfd_vma where;

  bfd_size_type size;

};

typedef struct srec_data_list_struct srec_data_list_type;

/* When scanning the S-record file, a linked list of srec_symbol

   structures is built to represent the symbol table (if there is

   one).  */

struct srec_symbol

{

  struct srec_symbol *next;

  const char *name;

  bfd_vma val;

};

/* The S-record tdata information.  */

typedef struct srec_data_struct

  {

    srec_data_list_type *head;

    srec_data_list_type *tail;

    unsigned int type;

    struct srec_symbol *symbols;

    struct srec_symbol *symtail;

    asymbol *csymbols;

  }

tdata_type;

/* Initialize by filling in the hex conversion array.  */

static void

srec_init (void)

{

  static bool inited = false;

  if (! inited)

    {

      inited = true;

      hex_init ();

    }

}

/* Set up the S-record tdata information.  */

static bool

srec_mkobject (bfd *abfd)

{

  tdata_type *tdata;

  srec_init ();

  tdata = (tdata_type *) bfd_alloc (abfd, sizeof (tdata_type));

  if (tdata == NULL)

    return false;

  abfd->tdata.srec_data = tdata;

  tdata->type = 1;

  tdata->head = NULL;

  tdata->tail = NULL;

  tdata->symbols = NULL;

  tdata->symtail = NULL;

  tdata->csymbols = NULL;

  return true;

}

/* Read a byte from an S record file.  Set *ERRORPTR if an error

   occurred.  Return EOF on error or end of file.  */

static int

srec_get_byte (bfd *abfd, bool *errorptr)

{

  bfd_byte c;

  if (bfd_read (&c, 1, abfd) != 1)

    {

      if (bfd_get_error () != bfd_error_file_truncated)

  *errorptr = true;

      return EOF;

    }

  return (int) (c & 0xff);

}

/* Report a problem in an S record file.  FIXME: This probably should

   not call fprintf, but we really do need some mechanism for printing

   error messages.  */

static void

srec_bad_byte (bfd *abfd,

         unsigned int lineno,

         int c,

         bool error)

{

  if (c == EOF)

    {

      if (! error)

  bfd_set_error (bfd_error_file_truncated);

    }

  else

    {

      char buf[40];

      if (! ISPRINT (c))

  sprintf (buf, "\\%03o", (unsigned int) c & 0xff);

      else

  {

    buf[0] = c;

    buf[1] = '\0';

  }

      _bfd_error_handler

  /* xgettext:c-format */

  (_("%pB:%d: unexpected character `%s' in S-record file"),

   abfd, lineno, buf);

      bfd_set_error (bfd_error_bad_value);

    }

}

/* Add a new symbol found in an S-record file.  */

static bool

srec_new_symbol (bfd *abfd, const char *name, bfd_vma val)

{

  struct srec_symbol *n;

  n = (struct srec_symbol *) bfd_alloc (abfd, sizeof (* n));

  if (n == NULL)

    return false;

  n->name = name;

  n->val = val;

  if (abfd->tdata.srec_data->symbols == NULL)

    abfd->tdata.srec_data->symbols = n;

  else

    abfd->tdata.srec_data->symtail->next = n;

  abfd->tdata.srec_data->symtail = n;

  n->next = NULL;

  ++abfd->symcount;

  return true;

}

/* Read the S record file and turn it into sections.  We create a new

   section for each contiguous set of bytes.  */

static bool

srec_scan (bfd *abfd)

{

  int c;

  unsigned int lineno = 1;

  bool error = false;

  bfd_byte *buf = NULL;

  size_t bufsize = 0;

  asection *sec = NULL;

  char *symbuf = NULL;

  if (bfd_seek (abfd, 0, SEEK_SET) != 0)

    goto error_return;

  while ((c = srec_get_byte (abfd, &error)) != EOF)

    {

      /* We only build sections from contiguous S-records, so if this

   is not an S-record, then stop building a section.  */

      if (c != 'S' && c != '\r' && c != '\n')

  sec = NULL;

      switch (c)

  {

  default:

    srec_bad_byte (abfd, lineno, c, error);

    goto error_return;

  case '\n':

    ++lineno;

    break;

  case '\r':

    break;

  case '$':

    /* Starting a module name, which we ignore.  */

    while ((c = srec_get_byte (abfd, &error)) != '\n'

     && c != EOF)

      ;

    if (c == EOF)

      {

        srec_bad_byte (abfd, lineno, c, error);

        goto error_return;

      }

    ++lineno;

    break;

  case ' ':

    do

      {

        bfd_size_type alc;

        char *p, *symname;

        bfd_vma symval;

        /* Starting a symbol definition.  */

        while ((c = srec_get_byte (abfd, &error)) != EOF

         && (c == ' ' || c == '\t'))

    ;

        if (c == '\n' || c == '\r')

    break;

        if (c == EOF)

    {

      srec_bad_byte (abfd, lineno, c, error);

      goto error_return;

    }

        alc = 10;

        symbuf = (char *) bfd_malloc (alc + 1);

        if (symbuf == NULL)

    goto error_return;

        p = symbuf;

        *p++ = c;

        while ((c = srec_get_byte (abfd, &error)) != EOF

         && ! ISSPACE (c))

    {

      if ((bfd_size_type) (p - symbuf) >= alc)

        {

          char *n;

          alc *= 2;

          n = (char *) bfd_realloc (symbuf, alc + 1);

          if (n == NULL)

      goto error_return;

          p = n + (p - symbuf);

          symbuf = n;

        }

      *p++ = c;

    }

        if (c == EOF)

    {

      srec_bad_byte (abfd, lineno, c, error);

      goto error_return;

    }

        *p++ = '\0';

        symname = (char *) bfd_alloc (abfd, (bfd_size_type) (p - symbuf));

        if (symname == NULL)

    goto error_return;

        strcpy (symname, symbuf);

        free (symbuf);

        symbuf = NULL;

        while ((c = srec_get_byte (abfd, &error)) != EOF

         && (c == ' ' || c == '\t'))

    ;

        if (c == EOF)

    {

      srec_bad_byte (abfd, lineno, c, error);

      goto error_return;

    }

        /* Skip a dollar sign before the hex value.  */

        if (c == '$')

    {

      c = srec_get_byte (abfd, &error);

      if (c == EOF)

        {

          srec_bad_byte (abfd, lineno, c, error);

          goto error_return;

        }

    }

        symval = 0;

        while (ISHEX (c))

    {

      symval <<= 4;

      symval += NIBBLE (c);

      c = srec_get_byte (abfd, &error);

      if (c == EOF)

        {

          srec_bad_byte (abfd, lineno, c, error);

          goto error_return;

        }

    }

        if (! srec_new_symbol (abfd, symname, symval))

    goto error_return;

      }

    while (c == ' ' || c == '\t')

      ;

    if (c == '\n')

      ++lineno;

    else if (c != '\r')

      {

        srec_bad_byte (abfd, lineno, c, error);

        goto error_return;

      }

    break;

  case 'S':

    {

      file_ptr pos;

      unsigned char hdr[3];

      unsigned int bytes, min_bytes;

      bfd_vma address;

      bfd_byte *data;

      unsigned char check_sum;

      /* Starting an S-record.  */

      pos = bfd_tell (abfd) - 1;

      if (bfd_read (hdr, 3, abfd) != 3)

        goto error_return;

      if (! ISHEX (hdr[1]) || ! ISHEX (hdr[2]))

        {

    if (! ISHEX (hdr[1]))

      c = hdr[1];

    else

      c = hdr[2];

    srec_bad_byte (abfd, lineno, c, error);

    goto error_return;

        }

      check_sum = bytes = HEX (hdr + 1);

      min_bytes = 3;

      if (hdr[0] == '2' || hdr[0] == '8')

        min_bytes = 4;

      else if (hdr[0] == '3' || hdr[0] == '7')

        min_bytes = 5;

      if (bytes < min_bytes)

        {

    /* xgettext:c-format */

    _bfd_error_handler (_("%pB:%d: byte count %d too small"),

            abfd, lineno, bytes);

    bfd_set_error (bfd_error_bad_value);

    goto error_return;

        }

      if (bytes * 2 > bufsize)

        {

    free (buf);

    buf = bfd_malloc (bytes * 2);

    if (buf == NULL)

      goto error_return;

    bufsize = bytes * 2;

        }

      if (bfd_read (buf, bytes * 2, abfd) != bytes * 2)

        goto error_return;

      /* Ignore the checksum byte.  */

      --bytes;

      address = 0;

      data = buf;

      switch (hdr[0])

        {

        case '0':

        case '5':

    /* Prologue--ignore the file name, but stop building a

       section at this point.  */

    sec = NULL;

    break;

        case '3':

    check_sum += HEX (data);

    address = HEX (data);

    data += 2;

    --bytes;

    /* Fall through.  */

        case '2':

    check_sum += HEX (data);

    address = (address << 8) | HEX (data);

    data += 2;

    --bytes;

    /* Fall through.  */

        case '1':

    check_sum += HEX (data);

    address = (address << 8) | HEX (data);

    data += 2;

    check_sum += HEX (data);

    address = (address << 8) | HEX (data);

    data += 2;

    bytes -= 2;

    if (sec != NULL

        && sec->vma + sec->size == address)

      {

        /* This data goes at the end of the section we are

           currently building.  */

        sec->size += bytes;

      }

    else

      {

        char secbuf[20];

        char *secname;

        size_t amt;

        flagword flags;

        sprintf (secbuf, ".sec%d", bfd_count_sections (abfd) + 1);

        amt = strlen (secbuf) + 1;

        secname = (char *) bfd_alloc (abfd, amt);

        strcpy (secname, secbuf);

        flags = SEC_HAS_CONTENTS | SEC_LOAD | SEC_ALLOC;

        sec = bfd_make_section_with_flags (abfd, secname, flags);

        if (sec == NULL)

          goto error_return;

        sec->vma = address;

        sec->lma = address;

        sec->size = bytes;

        sec->filepos = pos;

      }

    while (bytes > 0)

      {

        check_sum += HEX (data);

        data += 2;

        bytes--;

      }

    check_sum = 255 - (check_sum & 0xff);

    if (check_sum != HEX (data))

      {

        _bfd_error_handler

          /* xgettext:c-format */

          (_("%pB:%d: bad checksum in S-record file"),

           abfd, lineno);

        bfd_set_error (bfd_error_bad_value);

        goto error_return;

      }

    break;

        case '7':

    check_sum += HEX (data);

    address = HEX (data);

    data += 2;

    /* Fall through.  */

        case '8':

    check_sum += HEX (data);

    address = (address << 8) | HEX (data);

    data += 2;

    /* Fall through.  */

        case '9':

    check_sum += HEX (data);

    address = (address << 8) | HEX (data);

    data += 2;

    check_sum += HEX (data);

    address = (address << 8) | HEX (data);

    data += 2;

    /* This is a termination record.  */

    abfd->start_address = address;

    check_sum = 255 - (check_sum & 0xff);

    if (check_sum != HEX (data))

      {

        _bfd_error_handler

          /* xgettext:c-format */

          (_("%pB:%d: bad checksum in S-record file"),

           abfd, lineno);

        bfd_set_error (bfd_error_bad_value);

        goto error_return;

      }

    free (buf);

    return true;

        }

    }

    break;

  }

    }

  if (error)

    goto error_return;

  free (buf);

  return true;

 error_return:

  free (symbuf);

  free (buf);

  return false;

}

/* Check whether an existing file is an S-record file.  */

static bfd_cleanup

srec_object_p (bfd *abfd)

{

  bfd_byte b[4];

  srec_init ();

  if (bfd_seek (abfd, 0, SEEK_SET) != 0

      || bfd_read (b, 4, abfd) != 4)

    return NULL;

  if (b[0] != 'S' || !ISHEX (b[1]) || !ISHEX (b[2]) || !ISHEX (b[3]))

    {

      bfd_set_error (bfd_error_wrong_format);

      return NULL;

    }

  if (!srec_mkobject (abfd))

    return NULL;

  if (!srec_scan (abfd))

    {

      bfd_release (abfd, abfd->tdata.any);

      return NULL;

    }

  if (abfd->symcount > 0)

    abfd->flags |= HAS_SYMS;

  return _bfd_no_cleanup;

}

/* Check whether an existing file is an S-record file with symbols.  */

static bfd_cleanup

symbolsrec_object_p (bfd *abfd)

{

  char b[2];

  srec_init ();

  if (bfd_seek (abfd, 0, SEEK_SET) != 0

      || bfd_read (b, 2, abfd) != 2)

    return NULL;

  if (b[0] != '$' || b[1] != '$')

    {

      bfd_set_error (bfd_error_wrong_format);

      return NULL;

    }

  if (!srec_mkobject (abfd))

    return NULL;

  if (!srec_scan (abfd))

    {

      bfd_release (abfd, abfd->tdata.any);

      return NULL;

    }

  if (abfd->symcount > 0)

    abfd->flags |= HAS_SYMS;

  return _bfd_no_cleanup;

}

/* Read in the contents of a section in an S-record file.  */

static bool

srec_read_section (bfd *abfd, asection *section, bfd_byte *contents)

{

  int c;

  bfd_size_type sofar = 0;

  bool error = false;

  bfd_byte *buf = NULL;

  size_t bufsize = 0;

  if (bfd_seek (abfd, section->filepos, SEEK_SET) != 0)

    goto error_return;

  while ((c = srec_get_byte (abfd, &error)) != EOF)

    {

      bfd_byte hdr[3];

      unsigned int bytes;

      bfd_vma address;

      bfd_byte *data;

      if (c == '\r' || c == '\n')

  continue;

      /* This is called after srec_scan has already been called, so we

   ought to know the exact format.  */

      if (c != 'S')

  goto error_return;

      if (bfd_read (hdr, 3, abfd) != 3)

  goto error_return;

      BFD_ASSERT (ISHEX (hdr[1]) && ISHEX (hdr[2]));

      bytes = HEX (hdr + 1);

      if (bytes * 2 > bufsize)

  {

    free (buf);

    buf = bfd_malloc (bytes * 2);

    if (buf == NULL)

      goto error_return;

    bufsize = bytes * 2;

  }

      if (bfd_read (buf, bytes * 2, abfd) != bytes * 2)

  goto error_return;

      address = 0;

      data = buf;

      switch (hdr[0])

  {

  default:

    if (sofar != section->size)

      goto error_return;

    free (buf);

    return true;

  case '3':

    address = HEX (data);

    data += 2;

    --bytes;

    /* Fall through.  */

  case '2':

    address = (address << 8) | HEX (data);

    data += 2;

    --bytes;

    /* Fall through.  */

  case '1':

    address = (address << 8) | HEX (data);

    data += 2;

    address = (address << 8) | HEX (data);

    data += 2;

    bytes -= 2;

    if (address != section->vma + sofar)

      {

        /* We've come to the end of this section.  */

        if (sofar != section->size)

    goto error_return;

        free (buf);

        return true;

      }

    /* Don't consider checksum.  */

    --bytes;

    while (bytes-- != 0)

      {

        contents[sofar] = HEX (data);

        data += 2;

        ++sofar;

      }

    break;

  }

    }

  if (error)

    goto error_return;

  if (sofar != section->size)

    goto error_return;

  free (buf);

  return true;

 error_return:

  free (buf);

  return false;

}

/* Get the contents of a section in an S-record file.  */

static bool

srec_get_section_contents (bfd *abfd,

         asection *section,

         void * location,

         file_ptr offset,

         bfd_size_type count)

{

  if (count == 0)

    return true;

  if (offset + count < count

      || offset + count > section->size)

    {

      bfd_set_error (bfd_error_invalid_operation);

      return false;

    }

  if (section->used_by_bfd == NULL)

    {

      section->used_by_bfd = bfd_alloc (abfd, section->size);

      if (section->used_by_bfd == NULL)

  return false;

      if (! srec_read_section (abfd, section,

             (bfd_byte *) section->used_by_bfd))

  return false;

    }

  memcpy (location, (bfd_byte *) section->used_by_bfd + offset,

    (size_t) count);

  return true;

}

/* Set the architecture.  We accept an unknown architecture here.  */

static bool

srec_set_arch_mach (bfd *abfd, enum bfd_architecture arch, unsigned long mach)

{

  if (arch != bfd_arch_unknown)

    return bfd_default_set_arch_mach (abfd, arch, mach);

  abfd->arch_info = & bfd_default_arch_struct;

  return true;

}

/* We have to save up all the Srecords for a splurge before output.  */

static bool

srec_set_section_contents (bfd *abfd,

         sec_ptr section,

         const void * location,

         file_ptr offset,

         bfd_size_type bytes_to_do)

{

  int opb = bfd_octets_per_byte (abfd, NULL);

  tdata_type *tdata = abfd->tdata.srec_data;

  srec_data_list_type *entry;

  entry = (srec_data_list_type *) bfd_alloc (abfd, sizeof (* entry));

  if (entry == NULL)

    return false;

  if (bytes_to_do

      && (section->flags & SEC_ALLOC)

      && (section->flags & SEC_LOAD))

    {

      bfd_byte *data;

      data = (bfd_byte *) bfd_alloc (abfd, bytes_to_do);

      if (data == NULL)

  return false;

      memcpy ((void *) data, location, (size_t) bytes_to_do);

      /* If _bfd_srec_forceS3 is TRUE then always select S3 records,

   regardless of the size of the addresses.  */

      if (_bfd_srec_forceS3)

  tdata->type = 3;

      else if ((section->lma + (offset + bytes_to_do) / opb - 1) <= 0xffff)

  ;  /* The default, S1, is OK.  */

      else if ((section->lma + (offset + bytes_to_do) / opb - 1) <= 0xffffff

         && tdata->type <= 2)

  tdata->type = 2;

      else

  tdata->type = 3;

      entry->data = data;

      entry->where = section->lma + offset / opb;

      entry->size = bytes_to_do;

      /* Sort the records by address.  Optimize for the common case of

   adding a record to the end of the list.  */

      if (tdata->tail != NULL

    && entry->where >= tdata->tail->where)

  {

    tdata->tail->next = entry;

    entry->next = NULL;

    tdata->tail = entry;

  }

      else

  {

    srec_data_list_type **look;

    for (look = &tdata->head;

         *look != NULL && (*look)->where < entry->where;

         look = &(*look)->next)

      ;

    entry->next = *look;

    *look = entry;

    if (entry->next == NULL)

      tdata->tail = entry;

  }

    }

  return true;

}

/* Write a record of type, of the supplied number of bytes. The

   supplied bytes and length don't have a checksum. That's worked out

   here.  */

static bool

srec_write_record (bfd *abfd,

       unsigned int type,

       bfd_vma address,

       const bfd_byte *data,

       const bfd_byte *end)

{

  char buffer[2 * MAXCHUNK + 6];

  unsigned int check_sum = 0;

  const bfd_byte *src = data;

  char *dst = buffer;

  char *length;

  bfd_size_type wrlen;

  *dst++ = 'S';

  *dst++ = '0' + type;

  length = dst;

  dst += 2;     /* Leave room for dst.  */

  switch (type)

    {

    case 3:

    case 7:

      TOHEX (dst, (address >> 24), check_sum);

      dst += 2;

      /* Fall through.  */

    case 8:

    case 2:

      TOHEX (dst, (address >> 16), check_sum);

      dst += 2;

      /* Fall through.  */

    case 9:

    case 1:

    case 0:

      TOHEX (dst, (address >> 8), check_sum);

      dst += 2;

      TOHEX (dst, (address), check_sum);

      dst += 2;

      break;

    }

  for (src = data; src < end; src++)

    {

      TOHEX (dst, *src, check_sum);

      dst += 2;

    }

  /* Fill in the length.  */

  TOHEX (length, (dst - length) / 2, check_sum);

  check_sum &= 0xff;

  check_sum = 255 - check_sum;

  TOHEX (dst, check_sum, check_sum);

  dst += 2;

  *dst++ = '\r';

  *dst++ = '\n';

  wrlen = dst - buffer;

  return bfd_write (buffer, wrlen, abfd) == wrlen;

}

static bool

srec_write_header (bfd *abfd)

{

  unsigned int len = strlen (bfd_get_filename (abfd));

  /* I'll put an arbitrary 40 char limit on header size.  */

  if (len > 40)

    len = 40;

  return srec_write_record (abfd, 0, (bfd_vma) 0,

          (bfd_byte *) bfd_get_filename (abfd),

          (bfd_byte *) bfd_get_filename (abfd) + len);

}

static bool

srec_write_section (bfd *abfd,

        tdata_type *tdata,

        srec_data_list_type *list)

{

  unsigned int octets_written = 0;

  bfd_byte *location = list->data;

  /* Validate number of data bytes to write.  The srec length byte

     counts the address, data and crc bytes.  S1 (tdata->type == 1)

     records have two address bytes, S2 (tdata->type == 2) records

     have three, and S3 (tdata->type == 3) records have four.

     The total length can't exceed 255, and a zero data length will

     spin for a long time.  */

  if (_bfd_srec_len == 0)

    _bfd_srec_len = 1;

  else if (_bfd_srec_len > MAXCHUNK - tdata->type - 2)