environ.c

gcc-fortran,linux使用fortran的编译软件。很好用的。

  {"GFORTRAN_FPU_PRECISION", 0, &options.fpu_precision, init_precision,
   show_precision,
   "Precision of intermediate results.  Values are 24, 53 and 64.", 0},

  /* GFORTRAN_CONVERT_UNIT - Set the default data conversion for
   unformatted I/O.  */
  {"GFORTRAN_CONVERT_UNIT", 0, 0, init_unformatted, show_string,
   "Set format for unformatted files", 0},

  {NULL, 0, NULL, NULL, NULL, NULL, 0}
};


/* init_variables()-- Initialize most runtime variables from
 * environment variables. */

void
init_variables (void)
{
  variable *v;

  for (v = variable_table; v->name; v++)
    v->init (v);
}


/* check_buffered()-- Given an unit number n, determine if an override
 * for the stream exists.  Returns zero for unbuffered, one for
 * buffered or two for not set. */

int
check_buffered (int n)
{
  char name[22 + sizeof (n) * 3];
  variable v;
  int rv;

  if (options.all_unbuffered)
    return 0;

  sprintf (name, "GFORTRAN_UNBUFFERED_%d", n);

  v.name = name;
  v.value = 2;
  v.var = &rv;

  init_boolean (&v);

  return rv;
}


void
show_variables (void)
{
  variable *v;
  int n;

  /* TODO: print version number.  */
  st_printf ("GNU Fortran 95 runtime library version "
	     "UNKNOWN" "\n\n");

  st_printf ("Environment variables:\n");
  st_printf ("----------------------\n");

  for (v = variable_table; v->name; v++)
    {
      n = st_printf ("%s", v->name);
      print_spaces (25 - n);

      if (v->show == show_integer)
	st_printf ("Integer ");
      else if (v->show == show_boolean)
	st_printf ("Boolean ");
      else
	st_printf ("String  ");

      v->show (v);
      st_printf ("%s\n\n", v->desc);
    }

  /* System error codes */

  st_printf ("\nRuntime error codes:");
  st_printf ("\n--------------------\n");

  for (n = ERROR_FIRST + 1; n < ERROR_LAST; n++)
    if (n < 0 || n > 9)
      st_printf ("%d  %s\n", n, translate_error (n));
    else
      st_printf (" %d  %s\n", n, translate_error (n));

  st_printf ("\nCommand line arguments:\n");
  st_printf ("  --help               Print this list\n");

  /* st_printf("  --resume <dropfile>  Resume program execution from dropfile\n"); */

  sys_exit (0);
}

/* This is the handling of the GFORTRAN_CONVERT_UNITS environment variable.
   It is called from environ.c to parse this variable, and from
   open.c to determine if the user specified a default for an
   unformatted file.
   The syntax of the environment variable is, in bison grammar:

   GFORTRAN_CONVERT_UNITS: mode | mode ';' exception ;
   mode: 'native' | 'swap' | 'big_endian' | 'little_endian' ;
   exception: mode ':' unit_list | unit_list ;
   unit_list: unit_spec | unit_list unit_spec ;
   unit_spec: INTEGER | INTEGER '-' INTEGER ;
*/

/* Defines for the tokens.  Other valid tokens are ',', ':', '-'.  */


#define NATIVE   257
#define SWAP     258
#define BIG      259
#define LITTLE   260
/* Some space for additional tokens later.  */
#define INTEGER  273
#define END      (-1)
#define ILLEGAL  (-2)

typedef struct
{
  int unit;
  unit_convert conv;
} exception_t;


static char *p;            /* Main character pointer for parsing.  */
static char *lastpos;      /* Auxiliary pointer, for backing up.  */
static int unit_num;       /* The last unit number read.  */
static int unit_count;     /* The number of units found. */
static int do_count;       /* Parsing is done twice - first to count the number
			      of units, then to fill in the table.  This
			      variable controls what to do.  */
static exception_t *elist; /* The list of exceptions to the default. This is
			      sorted according to unit number.  */
static int n_elist;        /* Number of exceptions to the default.  */

static unit_convert endian; /* Current endianness.  */

static unit_convert def; /* Default as specified (if any).  */

/* Search for a unit number, using a binary search.  The
   first argument is the unit number to search for.  The second argument
   is a pointer to an index.
   If the unit number is found, the function returns 1, and the index
   is that of the element.
   If the unit number is not found, the function returns 0, and the
   index is the one where the element would be inserted.  */

static int
search_unit (int unit, int *ip)
{
  int low, high, mid;

  low = -1;
  high = n_elist;
  while (high - low > 1)
    {
      mid = (low + high) / 2;
      if (unit <= elist[mid].unit)
	high = mid;
      else
	low = mid;
    }
  *ip = high;
  if (elist[high].unit == unit)
    return 1;
  else
    return 0;
}

/* This matches a keyword.  If it is found, return the token supplied,
   otherwise return ILLEGAL.  */

static int
match_word (const char *word, int tok)
{
  int res;

  if (strncasecmp (p, word, strlen (word)) == 0)
    {
      p += strlen (word);
      res = tok;
    }
  else
    res = ILLEGAL;
  return res;

}

/* Match an integer and store its value in unit_num.  This only works
   if p actually points to the start of an integer.  The caller has
   to ensure this.  */

static int
match_integer (void)
{
  unit_num = 0;
  while (isdigit (*p))
    unit_num = unit_num * 10 + (*p++ - '0');
  return INTEGER;

}

/* This reads the next token from the GFORTRAN_CONVERT_UNITS variable.
   Returned values are the different tokens.  */

static int
next_token (void)
{
  int result;

  lastpos = p;
  switch (*p)
    {
    case '\0':
      result = END;
      break;
      
    case ':':
    case ',': 
    case '-':
    case ';':
      result = *p;
      p++;
      break;

    case 'b':
    case 'B':
      result = match_word ("big_endian", BIG);
      break;

    case 'l':
    case 'L':
      result = match_word ("little_endian", LITTLE);
      break;

    case 'n':
    case 'N':
      result = match_word ("native", NATIVE);
      break;

    case 's':
    case 'S':
      result = match_word ("swap", SWAP);
      break;

    case '1': case '2': case '3': case '4': case '5':
    case '6': case '7': case '8': case '9':
      result = match_integer ();
      break;

    default:
      result = ILLEGAL;
      break;
    }
  return result;
}

/* Back up the last token by setting back the character pointer.  */

static void
push_token (void)
{
  p = lastpos;
}

/* This is called when a unit is identified.  If do_count is nonzero,
   increment the number of units by one.  If do_count is zero,
   put the unit into the table.  */

static void
mark_single (int unit)
{
  int i,j;

  if (do_count)
    {
      unit_count++;
      return;
    }
  if (search_unit (unit, &i))
    {
      elist[unit].conv = endian;
    }
  else
    {
      for (j=n_elist; j>=i; j--)
	elist[j+1] = elist[j];
    
      n_elist += 1;
      elist[i].unit = unit;
      elist[i].conv = endian;
    }
}

/* This is called when a unit range is identified.  If do_count is
   nonzero, increase the number of units.  If do_count is zero,
   put the unit into the table.  */

static void
mark_range (int unit1, int unit2)
{
  int i;
  if (do_count)
    unit_count += abs (unit2 - unit1) + 1;
  else
    {
      if (unit2 < unit1)
	for (i=unit2; i<=unit1; i++)
	  mark_single (i);
      else
	for (i=unit1; i<=unit2; i++)
	  mark_single (i);
    }
}

/* Parse the GFORTRAN_CONVERT_UNITS variable.  This is called
   twice, once to count the units and once to actually mark them in
   the table.  When counting, we don't check for double occurences
   of units.  */

static int
do_parse (void)
{
  int tok, def;
  int unit1;
  int continue_ulist;
  char *start;

  unit_count = 0;

  def = 0;
  start = p;

  /* Parse the string.  First, let's look for a default.  */
  tok = next_token ();
  switch (tok)
    {
    case NATIVE:
      endian = CONVERT_NATIVE;
      break;

    case SWAP:
      endian = CONVERT_SWAP;
      break;

    case BIG:
      endian = CONVERT_BIG;
      break;

    case LITTLE:
      endian = CONVERT_LITTLE;
      break;

    case INTEGER:
      /* A leading digit means that we are looking at an exception.
	 Reset the position to the beginning, and continue processing
	 at the exception list.  */
      p = start;
      goto exceptions;
      break;

    case END:
      goto end;
      break;

    default:
      goto error;
      break;
    }

  tok = next_token ();
  switch (tok)
    {
    case ';':
      def = endian;
      break;

    case ':':
      /* This isn't a default after all.  Reset the position to the
	 beginning, and continue processing at the exception list.  */
      p = start;
      goto exceptions;
      break;

    case END:
      goto end;
      break;

    default:
      goto error;
      break;
    }

 exceptions:

  /* Loop over all exceptions.  */
  while(1)
    {
      tok = next_token ();
      switch (tok)
	{
	case LITTLE:
	  if (next_token () != ':')
	    goto error;
	  endian = CONVERT_LITTLE;
	  break;

	case BIG:
	  if (next_token () != ':')
	    goto error;
	  endian = CONVERT_BIG;
	  break;

	case INTEGER:
	  push_token ();
	  break;

	case END:
	  goto end;
	  break;

	default:
	  goto error;
	  break;
	}
      /* We arrive here when we want to parse a list of
	 numbers.  */
      continue_ulist = 1;
      do
	{
	  tok = next_token ();
	  if (tok != INTEGER)
	    goto error;

	  unit1 = unit_num;
	  tok = next_token ();
	  /* The number can be followed by a - and another number,
	     which means that this is a unit range, a comma
	     or a semicolon.  */
	  if (tok == '-')
	    {
	      if (next_token () != INTEGER)
		goto error;

	      mark_range (unit1, unit_num);
	      tok = next_token ();
	      if (tok == END)
		goto end;
	      else if (tok == ';')
		continue_ulist = 0;
	      else if (tok != ',')
		goto error;
	    }
	  else
	    {
	      mark_single (unit1);
	      switch (tok)
		{
		case ';':
		  continue_ulist = 0;
		  break;

		case ',':
		  break;

		case END:
		  goto end;
		  break;

		default:
		  goto error;
		}
	    }
	} while (continue_ulist);
    }
 end:
  return 0;
 error:
  def = CONVERT_NONE;
  return -1;
}

void init_unformatted (variable * v)
{
  char *val;
  val = getenv (v->name);
  def = CONVERT_NONE;
  n_elist = 0;

  if (val == NULL)
    return;
  do_count = 1;
  p = val;
  do_parse ();
  if (do_count <= 0)
    {
      n_elist = 0;
      elist = NULL;
    }
  else
    {
      elist = get_mem (unit_count * sizeof (exception_t));
      do_count = 0;
      p = val;
      do_parse ();
    }
}

/* Get the default conversion for for an unformatted unit.  */

unit_convert
get_unformatted_convert (int unit)
{
  int i;

  if (elist == NULL)
    return def;
  else if (search_unit (unit, &i))
    return elist[i].conv;
  else
    return def;
}