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doscan.c

/* __gmp_doscan -- formatted input internals.

   THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY.  THEY'RE ALMOST
   CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN
   FUTURE GNU MP RELEASES.

Copyright 2001, 2002 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.

The GNU MP Library 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 Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

#include "config.h"

#if HAVE_STDARG
#include <stdarg.h>
#else
#include <varargs.h>
#endif

#include <ctype.h>
#include <stddef.h>    /* for ptrdiff_t */
#include <stdio.h>
#include <string.h>

#if HAVE_LOCALE_H
#include <locale.h>    /* for localeconv */
#endif

#if HAVE_INTTYPES_H
# include <inttypes.h> /* for intmax_t */
#else
# if HAVE_STDINT_H
#  include <stdint.h>
# endif
#endif

#if HAVE_SYS_TYPES_H
#include <sys/types.h> /* for quad_t */
#endif

#include "gmp.h"
#include "gmp-impl.h"


/* Change this to "#define TRACE(x) x" for some traces. */
#define TRACE(x)


/* It's necessary to parse up the string to recognise the GMP extra types F,
   Q and Z.  Other types and conversions are passed across to the standard
   sscanf or fscanf via funs->scan, for ease of implemenation.  This is
   essential in the case of something like glibc %p where the pointer format
   isn't actually documented.

   Because funs->scan doesn't get the whole input it can't put the right
   values in for %n, so that's handled in __gmp_doscan.  Neither sscanf nor
   fscanf directly indicate how many characters were read, so an extra %n is
   appended to each run for that.  For fscanf this merely supports our %n
   output, but for sscanf it lets funs->step move us along the input string.

   Whitespace and literal matches in the format string, including %%, are
   handled directly within __gmp_doscan.  This is reasonably efficient, and
   avoids some suspicious behaviour observed in various system libc's.
   GLIBC 2.2.4 for instance returns 0 on sscanf(" "," x") or on sscanf(" ",
   " x%d",&n), whereas we think they should return EOF, since end-of-string
   is reached when a match of "x" is required.

   For standard % conversions, funs->scan is called once for each
   conversion.  If we had vfscanf and vsscanf and could rely on their fixed
   text matching behaviour then we could call them with multiple consecutive
   standard conversions.  But plain fscanf and sscanf work fine, and parsing
   one field at a time shouldn't be too much of a slowdown.

   gmpscan reads a gmp type.  It's only used from one place, but is a
   separate subroutine to avoid a big chunk of complicated code in the
   middle of __gmp_doscan.  Within gmpscan a couple of loopbacks make it
   possible to share code for parsing integers, rationals and floats.

   In gmpscan normally one char of lookahead is maintained, but when width
   is reached that stops, on the principle that an fgetc/ungetc of a char
   past where we're told to stop would be undesirable.  "chars" is how many
   characters have been read so far, including the current c.  When
   chars==width and another character is desired then a jump is done to the
   "convert" stage.  c is invalid and mustn't be unget'ed in this case;
   chars is set to width+1 to indicate that.

   gmpscan normally returns the number of characters read.  -1 means an
   invalid field, like a "-" or "+" alone.  -2 means EOF reached before any
   matching characters were read.

   Consideration was given to using a separate code for gmp_fscanf and
   gmp_sscanf.  The sscanf case could zip across a string making literal
   matches or recognising digits in gmpscan, rather than making a function
   call fun->get per character.  The fscanf could use getc rather than fgetc
   too, which might help those systems where getc is a macro or otherwise
   inlined.  But none of this scanning and converting will be particularly
   fast, so the two are done together to keep it a bit simpler for now.

   Enhancements:

   A way to read the GLIBC printf %a format that we support in gmp_printf
   would be good.  That would probably be good for plain GLIBC scanf too, so
   perhaps we can simply follow its lead if it gets such a feature in the
   future.  */


struct gmp_doscan_params_t {
  int   base;
  int   ignore;
  char  type;
  int   width;
};


#define GET(c)                  \
  do {                          \
    ASSERT (chars <= width);    \
    chars++;                    \
    if (chars > width)          \
      goto convert;             \
    (c) = (*funs->get) (data);  \
  } while (0)

/* store into "s", extending if necessary */
#define STORE(c)                                                        \
  do {                                                                  \
    ASSERT (s_upto <= s_alloc);                                         \
    if (s_upto >= s_alloc)                                              \
      {                                                                 \
        size_t  s_alloc_new = s_alloc + S_ALLOC_STEP;                   \
        s = __GMP_REALLOCATE_FUNC_TYPE (s, s_alloc, s_alloc_new, char); \
        s_alloc = s_alloc_new;                                          \
      }                                                                 \
    s[s_upto++] = c;                                                    \
  } while (0)

#define S_ALLOC_STEP  512

static int
gmpscan (const struct gmp_doscan_funs_t *funs, void *data,
         const struct gmp_doscan_params_t *p, void *dst)
{
  int     chars, c, base, first, width, seen_point, seen_digit;
  size_t  s_upto, s_alloc;
  char    *s;
  int     invalid = 0;

  TRACE (printf ("gmpscan\n"));

  ASSERT (p->type == 'F' || p->type == 'Q' || p->type == 'Z');

  c = (*funs->get) (data);
  if (c == EOF)
    return -2;

  chars = 1;
  first = 1;
  seen_point = 0;
  seen_digit = 0;
  width = (p->width == 0 ? INT_MAX-1 : p->width);
  base = p->base;
  s_alloc = S_ALLOC_STEP;
  s = __GMP_ALLOCATE_FUNC_TYPE (s_alloc, char);
  s_upto = 0;

 another:
  if (c == '-')
    {
      STORE (c);
      goto get_for_sign;
    }
  else if (c == '+')
    {
      /* don't store '+', it's not accepted by mpz_set_str etc */
    get_for_sign:
      GET (c);
    }

  if (base == 0)
    {
      base = 10;
      if (c == '0')
        {
          seen_digit = 1;
          base = 8;
          STORE (c);
          GET (c);
          if (c == 'x' || c == 'X')
            {
              base = 16;
            store_get_digits:
              STORE (c);
              GET (c);
            }
        }
    }

 digits:
  for (;;)
    {
      if (base == 16)
        {
          if (! (isascii (c) && isxdigit (c)))
            break;
        }
      else
        {
          if (! (isascii (c) && isdigit (c)))
            break;
          if (base == 8 && (c == '8' || c == '9'))
            break;
        }

      seen_digit = 1;
      STORE (c);
      GET (c);
    }

  if (first)
    {
      /* decimal point */
      if (p->type == 'F' && ! seen_point)
        {
#if HAVE_LOCALECONV
          /* For a multi-character decimal point, if the first character is
             present then all of it must be, otherwise the input is
             considered invalid.  */
          const char  *point;
          int         pc;
          point = localeconv()->decimal_point;
          pc = *point++;
          if (c == pc)
            {
              for (;;)
                {
                  STORE (c);
                  GET (c);
                  pc = *point++;
                  if (pc == '\0')
                    break;
                  if (c != pc)
                    goto invalid;
                }
              seen_point = 1;
              goto digits;
            }
#else
          if (c == '.')
            {
              seen_point = 1;
              goto store_get_digits;
            }
#endif
        }

      /* exponent */
      if (p->type == 'F' && (c == 'e' || c == 'E'))
        {
          /* must have at least one digit in the mantissa, just an exponent
             is not good enough */
          if (! seen_digit)
            goto invalid;

        exponent:
          first = 0;
          STORE (c);
          GET (c);
          goto another;
        }

      /* denominator */
      if (p->type == 'Q' && c == '/')
        {
          /* must have at least one digit in the numerator */
          if (! seen_digit)
            goto invalid;

          /* now look for at least one digit in the denominator */
          seen_digit = 0;

          /* allow the base to be redetermined for "%i" */
          base = p->base;
          goto exponent;
        }
    }

 convert:
  if (! seen_digit)
    {
    invalid:
      invalid = 1;
      goto done;
    }

  if (! p->ignore)
    {
      STORE ('\0');
      TRACE (printf ("  convert \"%s\"\n", s));

      /* We ought to have parsed out a valid string above, so just test
         mpz_set_str etc with an ASSERT.  */
      switch (p->type) {
      case 'F':
        ASSERT (p->base == 10);
        ASSERT_NOCARRY (mpf_set_str ((mpf_ptr) dst, s, 10));
        break;
      case 'Q':
        ASSERT_NOCARRY (mpq_set_str ((mpq_ptr) dst, s, p->base));
        break;
      case 'Z':
        ASSERT_NOCARRY (mpz_set_str ((mpz_ptr) dst, s, p->base));
        break;
      default:
        ASSERT (0);
        /*FALLTHRU*/
        break;
      }
    }

 done:
  ASSERT (chars <= width+1);
  if (chars != width+1)
    {
      (*funs->unget) (c, data);
      TRACE (printf ("  ungetc %d, to give %d chars\n", c, chars-1));
    }
  chars--;

  (*__gmp_free_func) (s, s_alloc);

  if (invalid)
    {
      TRACE (printf ("  invalid\n"));
      return -1;
    }

  TRACE (printf ("  return %d chars (cf width %d)\n", chars, width));
  return chars;
}


/* Read and discard whitespace, if any.  Return number of chars skipped.
   Whitespace skipping never provokes the EOF return from __gmp_doscan, so
   it's not necessary to watch for EOF from funs->get, */
static int
skip_white (const struct gmp_doscan_funs_t *funs, void *data)
{
  int  c;
  int  ret = 0;

  do
    {
      c = (funs->get) (data);
      ret++;
    }
  while (isascii (c) && isspace (c));

  (funs->unget) (c, data);
  ret--;

  TRACE (printf ("  skip white %d\n", ret));
  return ret;
}


int
__gmp_doscan (const struct gmp_doscan_funs_t *funs, void *data,
              const char *orig_fmt, va_list orig_ap)
{
  struct gmp_doscan_params_t  param;
  va_list     ap;
  char        *alloc_fmt;
  const char  *fmt, *this_fmt, *end_fmt;
  size_t      orig_fmt_len, alloc_fmt_size, len;
  int         new_fields, new_chars;
  char        fchar;
  int         fields = 0;
  int         chars = 0;

  TRACE (printf ("__gmp_doscan \"%s\"\n", orig_fmt);
         if (funs->scan == (gmp_doscan_scan_t) sscanf)
           printf ("  s=\"%s\"\n", (const char *) data));

  /* Don't modify orig_ap, if va_list is actually an array and hence call by
     reference.  It could be argued that it'd be more efficient to leave
     callers to make a copy if they care, but doing so here is going to be a
     very small part of the total work, and we may as well keep applications
     out of trouble.  */
  va_copy (ap, orig_ap);

  /* Parts of the format string are going to be copied so that a " %n" can
     be appended.  alloc_fmt is some space for that.  orig_fmt_len+4 will be
     needed if fmt consists of a single "%" specifier, but otherwise is an
     overestimate.  We're not going to be very fast here, so use
     __gmp_allocate_func rather than TMP_ALLOC.  */
  orig_fmt_len = strlen (orig_fmt);
  alloc_fmt_size = orig_fmt_len + 4;
  alloc_fmt = __GMP_ALLOCATE_FUNC_TYPE (alloc_fmt_size, char);

  fmt = orig_fmt;
  end_fmt = orig_fmt + orig_fmt_len;

  for (;;)
    {
    next:
      fchar = *fmt++;

      if (fchar == '\0')
        break;

      if (isascii (fchar) && isspace (fchar))
        {
          chars += skip_white (funs, data);
          continue;
        }

      if (fchar != '%')
        {
          int  c;
        literal:
          c = (funs->get) (data);
          if (c != fchar)
            {
              (funs->unget) (c, data);
              if (c == EOF)
                {
                eof_no_match:
                  if (fields == 0)
                    fields = EOF;
                }
              goto done;
            }
          chars++;
          continue;
        }

      param.type = '\0';
      param.base = 10;
      param.ignore = 0;
      param.width = 0;

      this_fmt = fmt-1;
      TRACE (printf ("  this_fmt \"%s\"\n", this_fmt));

      for (;;)
        {
          ASSERT (fmt <= end_fmt);

          fchar = *fmt++;
          switch (fchar) {

          case '\0':  /* unterminated % sequence */
            ASSERT (0);
            goto done;

          case '%':   /* literal % */
            goto literal;

          case '[':   /* character range */
            fchar = *fmt++;
            if (fchar == '^')
              fchar = *fmt++;
            /* ']' allowed as the first char (possibly after '^') */
            if (fchar == ']')
              fchar = *fmt++;
            for (;;)
              {
                ASSERT (fmt <= end_fmt);
                if (fchar == '\0')
                  {
                    /* unterminated % sequence */
                    ASSERT (0);
                    goto done;
                  }
                if (fchar == ']')
                  break;
                fchar = *fmt++;
              }
            /*FALLTHRU*/
          case 'c':   /* characters */
          case 's':   /* string of non-whitespace */
          case 'p':   /* pointer */
          libc_type:
            len = fmt - this_fmt;
            memcpy (alloc_fmt, this_fmt, len);
            alloc_fmt[len++] = '%';
            alloc_fmt[len++] = 'n';
            alloc_fmt[len] = '\0';

            TRACE (printf ("  scan \"%s\"\n", alloc_fmt);
                   if (funs->scan == (gmp_doscan_scan_t) sscanf)
                     printf ("  s=\"%s\"\n", (const char *) data));

            new_chars = -1;
            if (param.ignore)
              {
                new_fields = (*funs->scan) (data, alloc_fmt, &new_chars);
                ASSERT (new_fields == 0 || new_fields == EOF);
              }
            else
              {
                new_fields = (*funs->scan) (data, alloc_fmt,
                                            va_arg (ap, void *), &new_chars);
                ASSERT (new_fields==0 || new_fields==1 || new_fields==EOF);

                if (new_fields == 0)
                  goto done;  /* invalid input */

                if (new_fields == 1)
                  ASSERT (new_chars != -1);
              }
            TRACE (printf ("  new_fields %d   new_chars %d\n",
                           new_fields, new_chars));

            if (new_fields == -1)
              goto eof_no_match;  /* EOF before anything matched */

            /* Wnder param.ignore, when new_fields==0 we don't know if
               it's a successful match or an invalid field.  new_chars
               won't have been assigned if it was an invalid field.  */
            if (new_chars == -1)
              goto done;  /* invalid input */

            chars += new_chars;
            (*funs->step) (data, new_chars);

          increment_fields:
            if (! param.ignore)
              fields++;
            goto next;

          case 'd':   /* decimal */
          case 'e':   /* float */
          case 'E':   /* float */
          case 'f':   /* float */
          case 'g':   /* float */
          case 'G':   /* float */
          case 'u':   /* decimal */
          numeric:
            if (param.type != 'F' && param.type != 'Q' && param.type != 'Z')
              goto libc_type;

            chars += skip_white (funs, data);

            new_chars = gmpscan (funs, data, &param,
                                 param.ignore ? NULL : va_arg (ap, void*));
            if (new_chars == -2)
              goto eof_no_match;
            if (new_chars == -1)
              goto done;

            ASSERT (new_chars >= 0);
            chars += new_chars;
            goto increment_fields;

          case 'a':   /* glibc allocate string */
          case '\'':  /* glibc digit groupings */
            break;

          case 'F':   /* mpf_t */
          case 'j':   /* intmax_t */
          case 'L':   /* long long */
          case 'q':   /* quad_t */
          case 'Q':   /* mpq_t */
          case 't':   /* ptrdiff_t */
          case 'z':   /* size_t */
          case 'Z':   /* mpz_t */
          set_type:
            param.type = fchar;
            break;

          case 'h':   /* short or char */
            if (param.type != 'h')
              goto set_type;
            param.type = 'H';   /* internal code for "hh" */
            break;

          case 'i':
            param.base = 0;
            goto numeric;

          case 'l':   /* long, long long, double or long double */
            if (param.type != 'l')
              goto set_type;
            param.type = 'L';   /* "ll" means "L" */
            break;

          case 'n':
            if (! param.ignore)
              {
                void  *p;
                p = va_arg (ap, void *);
                TRACE (printf ("  store %%n to %p\n", p));
                switch (param.type) {
                case '\0': * (int       *) p = chars; break;
                case 'F':  mpf_set_si ((mpf_ptr) p, (long) chars); break;
                case 'H':  * (char      *) p = chars; break;
                case 'h':  * (short     *) p = chars; break;
#if HAVE_INTMAX_T
                case 'j':  * (intmax_t  *) p = chars; break;
#else
                case 'j':  ASSERT_FAIL (intmax_t not available); break;
#endif
                case 'l':  * (long      *) p = chars; break;
#if HAVE_QUAD_T && HAVE_LONG_LONG
                case 'q':
                  ASSERT_ALWAYS (sizeof (quad_t) == sizeof (long long));
                  /*FALLTHRU*/
#else
                case 'q':  ASSERT_FAIL (quad_t not available); break;
#endif
#if HAVE_LONG_LONG
                case 'L':  * (long long *) p = chars; break;
#else
                case 'L':  ASSERT_FAIL (long long not available); break;
#endif
                case 'Q':  mpq_set_si ((mpq_ptr) p, (long) chars, 1L); break;
#if HAVE_PTRDIFF_T
                case 't':  * (ptrdiff_t *) p = chars; break;
#else
                case 't':  ASSERT_FAIL (ptrdiff_t not available); break;
#endif
                case 'z':  * (size_t    *) p = chars; break;
                case 'Z':  mpz_set_si ((mpz_ptr) p, (long) chars); break;
                default: ASSERT (0); break;
                }
              }
            goto next;

          case 'o':
            param.base = 8;
            goto numeric;

          case 'x':
          case 'X':
            param.base = 16;
            goto numeric;

          case '0': case '1': case '2': case '3': case '4':
          case '5': case '6': case '7': case '8': case '9':
            param.width = 0;
            do {
              param.width = param.width * 10 + (fchar-'0');
              fchar = *fmt++;
            } while (isascii (fchar) && isdigit (fchar));
            fmt--; /* unget the non-digit */
            break;

          case '*':
            param.ignore = 1;
            break;

          default:
            /* something invalid in a % sequence */
            ASSERT (0);
            goto next;
          }
        }
    }

 done:
  (*__gmp_free_func) (alloc_fmt, alloc_fmt_size);
  return fields;
}

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