third_party/gmp/mpz/get_str.c

/* mpz_get_str (string, base, mp_src) -- Convert the multiple precision
   number MP_SRC to a string STRING of base BASE.  If STRING is NULL
   allocate space for the result.  In any case, return a pointer to the
   result.  If STRING is not NULL, the caller must ensure enough space is
   available to store the result.

Copyright 1991, 1993, 1994, 1996, 2000-2002, 2005, 2012, 2017 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 either:

  * the GNU Lesser General Public License as published by the Free
    Software Foundation; either version 3 of the License, or (at your
    option) any later version.

or

  * the GNU General Public License as published by the Free Software
    Foundation; either version 2 of the License, or (at your option) any
    later version.

or both in parallel, as here.

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 General Public License
for more details.

You should have received copies of the GNU General Public License and the
GNU Lesser General Public License along with the GNU MP Library.  If not,
see https://www.gnu.org/licenses/.  */

#include <string.h> /* for strlen */
#include "gmp-impl.h"
#include "longlong.h"

char *
mpz_get_str (char *res_str, int base, mpz_srcptr x)
{
  mp_ptr xp;
  mp_size_t x_size = SIZ (x);
  char *return_str;
  size_t str_size;
  size_t alloc_size = 0;
  const char *num_to_text;
  int i;
  TMP_DECL;

  num_to_text = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  if (base > 1)
    {
      if (base <= 36)
	num_to_text = "0123456789abcdefghijklmnopqrstuvwxyz";
      else if (UNLIKELY (base > 62))
	return NULL;
    }
  else if (base > -2)
    {
      base = 10;
    }
  else
    {
      base = -base;
      if (UNLIKELY (base > 36))
	return NULL;
    }

  /* allocate string for the user if necessary */
  if (res_str == NULL)
    {
      /* digits, null terminator, possible minus sign */
      MPN_SIZEINBASE (alloc_size, PTR(x), ABS(x_size), base);
      alloc_size += 1 + (x_size<0);
      res_str = __GMP_ALLOCATE_FUNC_TYPE (alloc_size, char);
    }
  return_str = res_str;

  if (x_size < 0)
    {
      *res_str++ = '-';
      x_size = -x_size;
    }

  /* mpn_get_str clobbers its input on non power-of-2 bases */
  TMP_MARK;
  xp = PTR (x);
  if (! POW2_P (base))
    {
      xp = TMP_ALLOC_LIMBS (x_size | 1);  /* |1 in case x_size==0 */
      MPN_COPY (xp, PTR (x), x_size);
    }

  str_size = mpn_get_str ((unsigned char *) res_str, base, xp, x_size);
  ASSERT (alloc_size == 0 || str_size <= alloc_size - (SIZ(x) < 0));

  /* Convert result to printable chars.  */
  for (i = 0; i < str_size; i++)
    res_str[i] = num_to_text[(int) res_str[i]];
  res_str[str_size] = 0;

  TMP_FREE;

  /* if allocated then resize down to the actual space required */
  if (alloc_size != 0)
    {
      size_t  actual_size = str_size + 1 + (res_str - return_str);
      ASSERT (actual_size == strlen (return_str) + 1);
      __GMP_REALLOCATE_FUNC_MAYBE_TYPE (return_str, alloc_size, actual_size,
					char);
    }
  return return_str;
}