gcc/libgfortran/io/read.c

/* Copyright (C) 2002, 2003, 2005, 2007, 2008 Free Software Foundation, Inc.
   Contributed by Andy Vaught
   F2003 I/O support contributed by Jerry DeLisle

This file is part of the GNU Fortran 95 runtime library (libgfortran).

Libgfortran 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 2, or (at your option)
any later version.

In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file.  (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combine
executable.)

Libgfortran 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 Libgfortran; see the file COPYING.  If not, write to
the Free Software Foundation, 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */

#include "io.h"
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <stdlib.h>

typedef unsigned char uchar;

/* read.c -- Deal with formatted reads */


/* set_integer()-- All of the integer assignments come here to
 * actually place the value into memory.  */

void
set_integer (void *dest, GFC_INTEGER_LARGEST value, int length)
{
  switch (length)
    {
#ifdef HAVE_GFC_INTEGER_16
    case 16:
      {
	GFC_INTEGER_16 tmp = value;
	memcpy (dest, (void *) &tmp, length);
      }
      break;
#endif
    case 8:
      {
	GFC_INTEGER_8 tmp = value;
	memcpy (dest, (void *) &tmp, length);
      }
      break;
    case 4:
      {
	GFC_INTEGER_4 tmp = value;
	memcpy (dest, (void *) &tmp, length);
      }
      break;
    case 2:
      {
	GFC_INTEGER_2 tmp = value;
	memcpy (dest, (void *) &tmp, length);
      }
      break;
    case 1:
      {
	GFC_INTEGER_1 tmp = value;
	memcpy (dest, (void *) &tmp, length);
      }
      break;
    default:
      internal_error (NULL, "Bad integer kind");
    }
}


/* max_value()-- Given a length (kind), return the maximum signed or
 * unsigned value */

GFC_UINTEGER_LARGEST
max_value (int length, int signed_flag)
{
  GFC_UINTEGER_LARGEST value;
#if defined HAVE_GFC_REAL_16 || defined HAVE_GFC_REAL_10
  int n;
#endif

  switch (length)
    {
#if defined HAVE_GFC_REAL_16 || defined HAVE_GFC_REAL_10
    case 16:
    case 10:
      value = 1;
      for (n = 1; n < 4 * length; n++)
        value = (value << 2) + 3;
      if (! signed_flag)
        value = 2*value+1;
      break;
#endif
    case 8:
      value = signed_flag ? 0x7fffffffffffffff : 0xffffffffffffffff;
      break;
    case 4:
      value = signed_flag ? 0x7fffffff : 0xffffffff;
      break;
    case 2:
      value = signed_flag ? 0x7fff : 0xffff;
      break;
    case 1:
      value = signed_flag ? 0x7f : 0xff;
      break;
    default:
      internal_error (NULL, "Bad integer kind");
    }

  return value;
}


/* convert_real()-- Convert a character representation of a floating
 * point number to the machine number.  Returns nonzero if there is a
 * range problem during conversion.  TODO: handle not-a-numbers and
 * infinities.  */

int
convert_real (st_parameter_dt *dtp, void *dest, const char *buffer, int length)
{
  errno = 0;

  switch (length)
    {
    case 4:
      {
	GFC_REAL_4 tmp =
#if defined(HAVE_STRTOF)
	  strtof (buffer, NULL);
#else
	  (GFC_REAL_4) strtod (buffer, NULL);
#endif
	memcpy (dest, (void *) &tmp, length);
      }
      break;
    case 8:
      {
	GFC_REAL_8 tmp = strtod (buffer, NULL);
	memcpy (dest, (void *) &tmp, length);
      }
      break;
#if defined(HAVE_GFC_REAL_10) && defined (HAVE_STRTOLD)
    case 10:
      {
	GFC_REAL_10 tmp = strtold (buffer, NULL);
	memcpy (dest, (void *) &tmp, length);
      }
      break;
#endif
#if defined(HAVE_GFC_REAL_16) && defined (HAVE_STRTOLD)
    case 16:
      {
	GFC_REAL_16 tmp = strtold (buffer, NULL);
	memcpy (dest, (void *) &tmp, length);
      }
      break;
#endif
    default:
      internal_error (&dtp->common, "Unsupported real kind during IO");
    }

  if (errno == EINVAL)
    {
      generate_error (&dtp->common, LIBERROR_READ_VALUE,
		      "Error during floating point read");
      next_record (dtp, 1);
      return 1;
    }

  return 0;
}


/* read_l()-- Read a logical value */

void
read_l (st_parameter_dt *dtp, const fnode *f, char *dest, int length)
{
  char *p;
  size_t w;

  w = f->u.w;

  p = gfc_alloca (w);

  if (read_block_form (dtp, p, &w) == FAILURE)
    return;

  while (*p == ' ')
    {
      if (--w == 0)
	goto bad;
      p++;
    }

  if (*p == '.')
    {
      if (--w == 0)
	goto bad;
      p++;
    }

  switch (*p)
    {
    case 't':
    case 'T':
      set_integer (dest, (GFC_INTEGER_LARGEST) 1, length);
      break;
    case 'f':
    case 'F':
      set_integer (dest, (GFC_INTEGER_LARGEST) 0, length);
      break;
    default:
    bad:
      generate_error (&dtp->common, LIBERROR_READ_VALUE,
		      "Bad value on logical read");
      next_record (dtp, 1);
      break;
    }
}


static inline gfc_char4_t
read_utf8 (st_parameter_dt *dtp, size_t *nbytes) 
{
  static const uchar masks[6] = { 0x7F, 0x1F, 0x0F, 0x07, 0x02, 0x01 };
  static const uchar patns[6] = { 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };
  static uchar buffer[6];
  size_t i, nb, nread;
  gfc_char4_t c;
  int status;
  char *s;

  *nbytes = 1;
  s = (char *) &buffer[0];
  status = read_block_form (dtp, s, nbytes);
  if (status == FAILURE)
    return 0;

  /* If this is a short read, just return.  */
  if (*nbytes == 0)
    return 0;

  c = buffer[0];
  if (c < 0x80)
    return c;

  /* The number of leading 1-bits in the first byte indicates how many
     bytes follow.  */
  for (nb = 2; nb < 7; nb++)
    if ((c & ~masks[nb-1]) == patns[nb-1])
      goto found;
  goto invalid;
	
 found:
  c = (c & masks[nb-1]);
  nread = nb - 1;

  s = (char *) &buffer[1];
  status = read_block_form (dtp, s, &nread);
  if (status == FAILURE)
    return 0;
  /* Decode the bytes read.  */
  for (i = 1; i < nb; i++)
    {
      gfc_char4_t n = *s++;

      if ((n & 0xC0) != 0x80)
	goto invalid;

      c = ((c << 6) + (n & 0x3F));
    }

  /* Make sure the shortest possible encoding was used.  */
  if (c <=      0x7F && nb > 1) goto invalid;
  if (c <=     0x7FF && nb > 2) goto invalid;
  if (c <=    0xFFFF && nb > 3) goto invalid;
  if (c <=  0x1FFFFF && nb > 4) goto invalid;
  if (c <= 0x3FFFFFF && nb > 5) goto invalid;

  /* Make sure the character is valid.  */
  if (c > 0x7FFFFFFF || (c >= 0xD800 && c <= 0xDFFF))
    goto invalid;

  return c;
      
 invalid:
  generate_error (&dtp->common, LIBERROR_READ_VALUE, "Invalid UTF-8 encoding");
  return (gfc_char4_t) '?';
}


static void
read_utf8_char1 (st_parameter_dt *dtp, char *p, int len, size_t width)
{
  gfc_char4_t c;
  char *dest;
  size_t nbytes;
  int i, j;

  len = ((int) width < len) ? len : (int) width;

  dest = (char *) p;

  /* Proceed with decoding one character at a time.  */
  for (j = 0; j < len; j++, dest++)
    {
      c = read_utf8 (dtp, &nbytes);

      /* Check for a short read and if so, break out.  */
      if (nbytes == 0)
	break;

      *dest = c > 255 ? '?' : (uchar) c;
    }

  /* If there was a short read, pad the remaining characters.  */
  for (i = j; i < len; i++)
    *dest++ = ' ';
  return;
}

static void
read_default_char1 (st_parameter_dt *dtp, char *p, int len, size_t width)
{
  char *s;
  int m, n, status;

  s = gfc_alloca (width);

  status = read_block_form (dtp, s, &width);
  
  if (status == FAILURE)
    return;
  if (width > (size_t) len)
     s += (width - len);

  m = ((int) width > len) ? len : (int) width;
  memcpy (p, s, m);

  n = len - width;
  if (n > 0)
    memset (p + m, ' ', n);
}


static void
read_utf8_char4 (st_parameter_dt *dtp, void *p, int len, size_t width)
{
  gfc_char4_t *dest;
  size_t nbytes;
  int i, j;

  len = ((int) width < len) ? len : (int) width;

  dest = (gfc_char4_t *) p;

  /* Proceed with decoding one character at a time.  */
  for (j = 0; j < len; j++, dest++)
    {
      *dest = read_utf8 (dtp, &nbytes);

      /* Check for a short read and if so, break out.  */
      if (nbytes == 0)
	break;
    }

  /* If there was a short read, pad the remaining characters.  */
  for (i = j; i < len; i++)
    *dest++ = (gfc_char4_t) ' ';
  return;
}


static void
read_default_char4 (st_parameter_dt *dtp, char *p, int len, size_t width)
{
  char *s;
  gfc_char4_t *dest;
  int m, n, status;

  s = gfc_alloca (width);

  status = read_block_form (dtp, s, &width);
  
  if (status == FAILURE)
    return;
  if (width > (size_t) len)
     s += (width - len);

  m = ((int) width > len) ? len : (int) width;
  
  dest = (gfc_char4_t *) p;
  
  for (n = 0; n < m; n++, dest++, s++)
    *dest = (unsigned char ) *s;

  for (n = 0; n < len - (int) width; n++, dest++)
    *dest = (unsigned char) ' ';
}


/* read_a()-- Read a character record into a KIND=1 character destination,
   processing UTF-8 encoding if necessary.  */

void
read_a (st_parameter_dt *dtp, const fnode *f, char *p, int length)
{
  int wi;
  size_t w;

  wi = f->u.w;
  if (wi == -1) /* '(A)' edit descriptor  */
    wi = length;
  w = wi;

  /* Read in w characters, treating comma as not a separator.  */
  dtp->u.p.sf_read_comma = 0;

  if (dtp->u.p.current_unit->flags.encoding == ENCODING_UTF8)
    read_utf8_char1 (dtp, p, length, w);
  else
    read_default_char1 (dtp, p, length, w);

  dtp->u.p.sf_read_comma = 1;
  if (dtp->common.flags & IOPARM_DT_HAS_F2003)
    dtp->u.p.sf_read_comma = dtp->u.p.decimal_status == DECIMAL_COMMA ? 0 : 1;
}


/* read_a_char4()-- Read a character record into a KIND=4 character destination,
   processing UTF-8 encoding if necessary.  */

void
read_a_char4 (st_parameter_dt *dtp, const fnode *f, char *p, int length)
{
  int wi;
  size_t w;

  wi = f->u.w;
  if (wi == -1) /* '(A)' edit descriptor  */
    wi = length;
  w = wi;

  /* Read in w characters, treating comma as not a separator.  */
  dtp->u.p.sf_read_comma = 0;

  if (dtp->u.p.current_unit->flags.encoding == ENCODING_UTF8)
    read_utf8_char4 (dtp, p, length, w);
  else
    read_default_char4 (dtp, p, length, w);
  
  dtp->u.p.sf_read_comma = 1;
  if (dtp->common.flags & IOPARM_DT_HAS_F2003)
    dtp->u.p.sf_read_comma = dtp->u.p.decimal_status == DECIMAL_COMMA ? 0 : 1;
}

/* eat_leading_spaces()-- Given a character pointer and a width,
 * ignore the leading spaces.  */

static char *
eat_leading_spaces (int *width, char *p)
{
  for (;;)
    {
      if (*width == 0 || *p != ' ')
	break;

      (*width)--;
      p++;
    }

  return p;
}


static char
next_char (st_parameter_dt *dtp, char **p, int *w)
{
  char c, *q;

  if (*w == 0)
    return '\0';

  q = *p;
  c = *q++;
  *p = q;

  (*w)--;

  if (c != ' ')
    return c;
  if (dtp->u.p.blank_status != BLANK_UNSPECIFIED)
    return ' ';  /* return a blank to signal a null */ 

  /* At this point, the rest of the field has to be trailing blanks */

  while (*w > 0)
    {
      if (*q++ != ' ')
	return '?';
      (*w)--;
    }

  *p = q;
  return '\0';
}


/* read_decimal()-- Read a decimal integer value.  The values here are
 * signed values. */

void
read_decimal (st_parameter_dt *dtp, const fnode *f, char *dest, int length)
{
  GFC_UINTEGER_LARGEST value, maxv, maxv_10;
  GFC_INTEGER_LARGEST v;
  int w, negative; 
  size_t wu;
  char c, *p;

  wu = f->u.w;

  p = gfc_alloca (wu);

  if (read_block_form (dtp, p, &wu) == FAILURE)
    return;

  w = wu;

  p = eat_leading_spaces (&w, p);
  if (w == 0)
    {
      set_integer (dest, (GFC_INTEGER_LARGEST) 0, length);
      return;
    }

  maxv = max_value (length, 1);
  maxv_10 = maxv / 10;

  negative = 0;
  value = 0;

  switch (*p)
    {
    case '-':
      negative = 1;
      /* Fall through */

    case '+':
      p++;
      if (--w == 0)
	goto bad;
      /* Fall through */

    default:
      break;
    }

  /* At this point we have a digit-string */
  value = 0;

  for (;;)
    {
      c = next_char (dtp, &p, &w);
      if (c == '\0')
	break;
	
      if (c == ' ')
        {
	  if (dtp->u.p.blank_status == BLANK_NULL) continue;
	  if (dtp->u.p.blank_status == BLANK_ZERO) c = '0';
        }
        
      if (c < '0' || c > '9')
	goto bad;

      if (value > maxv_10 && compile_options.range_check == 1)
	goto overflow;

      c -= '0';
      value = 10 * value;

      if (value > maxv - c && compile_options.range_check == 1)
	goto overflow;
      value += c;
    }

  v = value;
  if (negative)
    v = -v;

  set_integer (dest, v, length);
  return;

 bad:
  generate_error (&dtp->common, LIBERROR_READ_VALUE,
		  "Bad value during integer read");
  next_record (dtp, 1);
  return;

 overflow:
  generate_error (&dtp->common, LIBERROR_READ_OVERFLOW,
		  "Value overflowed during integer read");
  next_record (dtp, 1);

}


/* read_radix()-- This function reads values for non-decimal radixes.
 * The difference here is that we treat the values here as unsigned
 * values for the purposes of overflow.  If minus sign is present and
 * the top bit is set, the value will be incorrect. */

void
read_radix (st_parameter_dt *dtp, const fnode *f, char *dest, int length,
	    int radix)
{
  GFC_UINTEGER_LARGEST value, maxv, maxv_r;
  GFC_INTEGER_LARGEST v;
  int w, negative;
  char c, *p;
  size_t wu;

  wu = f->u.w;

  p = gfc_alloca (wu);

  if (read_block_form (dtp, p, &wu) == FAILURE)
    return;

  w = wu;

  p = eat_leading_spaces (&w, p);
  if (w == 0)
    {
      set_integer (dest, (GFC_INTEGER_LARGEST) 0, length);
      return;
    }

  maxv = max_value (length, 0);
  maxv_r = maxv / radix;

  negative = 0;
  value = 0;

  switch (*p)
    {
    case '-':
      negative = 1;
      /* Fall through */

    case '+':
      p++;
      if (--w == 0)
	goto bad;
      /* Fall through */

    default:
      break;
    }

  /* At this point we have a digit-string */
  value = 0;

  for (;;)
    {
      c = next_char (dtp, &p, &w);
      if (c == '\0')
	break;
      if (c == ' ')
        {
	  if (dtp->u.p.blank_status == BLANK_NULL) continue;
	  if (dtp->u.p.blank_status == BLANK_ZERO) c = '0';
        }

      switch (radix)
	{
	case 2:
	  if (c < '0' || c > '1')
	    goto bad;
	  break;

	case 8:
	  if (c < '0' || c > '7')
	    goto bad;
	  break;

	case 16:
	  switch (c)
	    {
	    case '0':
	    case '1':
	    case '2':
	    case '3':
	    case '4':
	    case '5':
	    case '6':
	    case '7':
	    case '8':
	    case '9':
	      break;

	    case 'a':
	    case 'b':
	    case 'c':
	    case 'd':
	    case 'e':
	    case 'f':
	      c = c - 'a' + '9' + 1;
	      break;

	    case 'A':
	    case 'B':
	    case 'C':
	    case 'D':
	    case 'E':
	    case 'F':
	      c = c - 'A' + '9' + 1;
	      break;

	    default:
	      goto bad;
	    }

	  break;
	}

      if (value > maxv_r)
	goto overflow;

      c -= '0';
      value = radix * value;

      if (maxv - c < value)
	goto overflow;
      value += c;
    }

  v = value;
  if (negative)
    v = -v;

  set_integer (dest, v, length);
  return;

 bad:
  generate_error (&dtp->common, LIBERROR_READ_VALUE,
		  "Bad value during integer read");
  next_record (dtp, 1);
  return;

 overflow:
  generate_error (&dtp->common, LIBERROR_READ_OVERFLOW,
		  "Value overflowed during integer read");
  next_record (dtp, 1);

}


/* read_f()-- Read a floating point number with F-style editing, which
   is what all of the other floating point descriptors behave as.  The
   tricky part is that optional spaces are allowed after an E or D,
   and the implicit decimal point if a decimal point is not present in
   the input.  */

void
read_f (st_parameter_dt *dtp, const fnode *f, char *dest, int length)
{
  size_t wu;
  int w, seen_dp, exponent;
  int exponent_sign, val_sign;
  int ndigits;
  int edigits;
  int i;
  char *p, *buffer;
  char *digits;
  char scratch[SCRATCH_SIZE];

  val_sign = 1;
  seen_dp = 0;
  wu = f->u.w;

  p = gfc_alloca (wu);

  if (read_block_form (dtp, p, &wu) == FAILURE)
    return;

  w = wu;

  p = eat_leading_spaces (&w, p);
  if (w == 0)
    goto zero;

  /* Optional sign */

  if (*p == '-' || *p == '+')
    {
      if (*p == '-')
        val_sign = -1;
      p++;
      w--;
    }

  exponent_sign = 1;
  p = eat_leading_spaces (&w, p);
  if (w == 0)
    goto zero;

  /* A digit, a '.' or a exponent character ('e', 'E', 'd' or 'D')
     is required at this point */

  if (!isdigit (*p) && *p != '.' && *p != ',' && *p != 'd' && *p != 'D'
      && *p != 'e' && *p != 'E')
    goto bad_float;

  /* Remember the position of the first digit.  */
  digits = p;
  ndigits = 0;

  /* Scan through the string to find the exponent.  */
  while (w > 0)
    {
      switch (*p)
	{
	case ',':
	  if ((dtp->common.flags & IOPARM_DT_HAS_F2003)
	      && (dtp->u.p.decimal_status == DECIMAL_COMMA && *p == ','))
		*p = '.';
	  else
	    goto bad_float;
	  /* Fall through */
	case '.':
	  if (seen_dp)
	    goto bad_float;
	  seen_dp = 1;
	  /* Fall through */

	case '0':
	case '1':
	case '2':
	case '3':
	case '4':
	case '5':
	case '6':
	case '7':
	case '8':
	case '9':
	case ' ':
	  ndigits++;
	  p++;
	  w--;
	  break;

	case '-':
	  exponent_sign = -1;
	  /* Fall through */

	case '+':
	  p++;
	  w--;
	  goto exp2;

	case 'd':
	case 'e':
	case 'D':
	case 'E':
	  p++;
	  w--;
	  goto exp1;

	default:
	  goto bad_float;
	}
    }

  /* No exponent has been seen, so we use the current scale factor */
  exponent = -dtp->u.p.scale_factor;
  goto done;

 bad_float:
  generate_error (&dtp->common, LIBERROR_READ_VALUE,
		  "Bad value during floating point read");
  next_record (dtp, 1);
  return;

  /* The value read is zero */
 zero:
  switch (length)
    {
      case 4:
	*((GFC_REAL_4 *) dest) = 0;
	break;

      case 8:
	*((GFC_REAL_8 *) dest) = 0;
	break;

#ifdef HAVE_GFC_REAL_10
      case 10:
	*((GFC_REAL_10 *) dest) = 0;
	break;
#endif

#ifdef HAVE_GFC_REAL_16
      case 16:
	*((GFC_REAL_16 *) dest) = 0;
	break;
#endif

      default:
	internal_error (&dtp->common, "Unsupported real kind during IO");
    }
  return;

  /* At this point the start of an exponent has been found */
 exp1:
  while (w > 0 && *p == ' ')
    {
      w--;
      p++;
    }

  switch (*p)
    {
    case '-':
      exponent_sign = -1;
      /* Fall through */

    case '+':
      p++;
      w--;
      break;
    }

  if (w == 0)
    goto bad_float;

  /* At this point a digit string is required.  We calculate the value
     of the exponent in order to take account of the scale factor and
     the d parameter before explict conversion takes place. */
 exp2:
  if (!isdigit (*p))
    goto bad_float;

  exponent = *p - '0';
  p++;
  w--;

  if (dtp->u.p.blank_status == BLANK_UNSPECIFIED) /* Normal processing of exponent */
    {
      while (w > 0 && isdigit (*p))
        {
          exponent = 10 * exponent + *p - '0';
          p++;
          w--;
        }
        
      /* Only allow trailing blanks */

      while (w > 0)
        {
          if (*p != ' ')
  	  goto bad_float;
          p++;
          w--;
        }
    }    
  else  /* BZ or BN status is enabled */
    {
      while (w > 0)
        {
          if (*p == ' ')
            {
	      if (dtp->u.p.blank_status == BLANK_ZERO) *p = '0';
	      if (dtp->u.p.blank_status == BLANK_NULL)
                {
                  p++;
                  w--;
                  continue;
                }
            }
          else if (!isdigit (*p))
            goto bad_float;

          exponent = 10 * exponent + *p - '0';
          p++;
          w--;
        }
    }

  exponent = exponent * exponent_sign;

 done:
  /* Use the precision specified in the format if no decimal point has been
     seen.  */
  if (!seen_dp)
    exponent -= f->u.real.d;

  if (exponent > 0)
    {
      edigits = 2;
      i = exponent;
    }
  else
    {
      edigits = 3;
      i = -exponent;
    }

  while (i >= 10)
    {
      i /= 10;
      edigits++;
    }

  i = ndigits + edigits + 1;
  if (val_sign < 0)
    i++;

  if (i < SCRATCH_SIZE) 
    buffer = scratch;
  else
    buffer = get_mem (i);

  /* Reformat the string into a temporary buffer.  As we're using atof it's
     easiest to just leave the decimal point in place.  */
  p = buffer;
  if (val_sign < 0)
    *(p++) = '-';
  for (; ndigits > 0; ndigits--)
    {
      if (*digits == ' ')
        {
	  if (dtp->u.p.blank_status == BLANK_ZERO) *digits = '0';
	  if (dtp->u.p.blank_status == BLANK_NULL)
            {
              digits++;
              continue;
            } 
        }
      *p = *digits;
      p++;
      digits++;
    }
  *(p++) = 'e';
  sprintf (p, "%d", exponent);

  /* Do the actual conversion.  */
  convert_real (dtp, dest, buffer, length);

  if (buffer != scratch)
     free_mem (buffer);

}


/* read_x()-- Deal with the X/TR descriptor.  We just read some data
 * and never look at it. */

void
read_x (st_parameter_dt * dtp, int n)
{
  if (dtp->common.flags & IOPARM_DT_HAS_F2003)
    {
      if ((dtp->u.p.pad_status == PAD_NO || is_internal_unit (dtp))
	  && dtp->u.p.current_unit->bytes_left < n)
	n = dtp->u.p.current_unit->bytes_left;
    }
  else
    {
      if (is_internal_unit (dtp) && dtp->u.p.current_unit->bytes_left < n)
	n = dtp->u.p.current_unit->bytes_left;
    }

  dtp->u.p.sf_read_comma = 0;
  if (n > 0)
    read_sf (dtp, &n, 1);
  dtp->u.p.sf_read_comma = 1;
  dtp->u.p.current_unit->strm_pos += (gfc_offset) n;
}