/* Copyright (c) 2000, 2025, Oracle and/or its affiliates.

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

   it under the terms of the GNU General Public License, version 2.0,

   as published by the Free Software Foundation.

   This program is designed to work with certain software (including

   but not limited to OpenSSL) that is licensed under separate terms,

   as designated in a particular file or component or in included license

   documentation.  The authors of MySQL hereby grant you an additional

   permission to link the program and your derivative works with the

   separately licensed software that they have either included with

   the program or referenced in the documentation.

   Without limiting anything contained in the foregoing, this file,

   which is part of C Driver for MySQL (Connector/C), is also subject to the

   Universal FOSS Exception, version 1.0, a copy of which can be found at

   http://oss.oracle.com/licenses/universal-foss-exception.

   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, version 2.0, 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 St, Fifth Floor, Boston, MA 02110-1301  USA */

/*

  str2int(src, radix, lower, upper, &val)

  converts the string pointed to by src to an integer and stores it in

  val.  It skips leading spaces and tabs (but not newlines, formfeeds,

  backspaces), then it accepts an optional sign and a sequence of digits

  in the specified radix.  The result should satisfy lower <= *val <= upper.

  The result is a pointer to the first character after the number;

  trailing spaces will NOT be skipped.

  If an error is detected, the result will be nullptr, the value put

  in val will be 0, and errno will be set to

        EDOM  if there are no digits

        ERANGE  if the result would overflow or otherwise fail to lie

                within the specified bounds.

  Check that the bounds are right for your machine.

  This looks amazingly complicated for what you probably thought was an

  easy task.  Coping with integer overflow and the asymmetric range of

  twos complement machines is anything but easy.

  So that users of atoi and atol can check whether an error occurred,

  I have taken a wholly unprecedented step: errno is CLEARED if this

  call has no problems.

*/

#include "str2int.h"

#include <cerrno>

#include <climits>

#include "mysql/strings/m_ctype.h"

#define char_val(X)                      \

  (X >= '0' && X <= '9'   ? X - '0'      \

   : X >= 'A' && X <= 'Z' ? X - 'A' + 10 \

   : X >= 'a' && X <= 'z' ? X - 'a' + 10 \

                          : '\177')

const char *str2int(const char *src, int radix, long int lower, long int upper,

                    long int *val) {

  int sign;   /* is number negative (+1) or positive (-1) */

  int n;      /* number of digits yet to be converted */

  long limit; /* "largest" possible valid input */

  long scale; /* the amount to multiply next digit by */

  long sofar; /* the running value */

  int d;      /* (negative of) next digit */

  const char *start;

  int digits[32]; /* Room for numbers */

  /*  Make sure *val is sensible in case of error  */

  *val = 0;

  /*  Check that the radix is in the range 2..36  */

#ifndef NDEBUG

  if (radix < 2 || radix > 36) {

    errno = EDOM;

    return nullptr;

  }

#endif

  /*  The basic problem is: how do we handle the conversion of

      a number without resorting to machine-specific code to

      check for overflow?  Obviously, we have to ensure that

      no calculation can overflow.  We are guaranteed that the

      "lower" and "upper" arguments are valid machine integers.

      On sign-and-magnitude, twos-complement, and ones-complement

      machines all, if +|n| is representable, so is -|n|, but on

      twos complement machines the converse is not true.  So the

      "maximum" representable number has a negative representative.

      Limit is set to min(-|lower|,-|upper|); this is the "largest"

      number we are concerned with. */

  /*  Calculate Limit using Scale as a scratch variable  */

  if ((limit = lower) > 0) limit = -limit;

  if ((scale = upper) > 0) scale = -scale;

  if (scale < limit) limit = scale;

  /*  Skip leading spaces and check for a sign.

      Note: because on a 2s complement machine MinLong is a valid

      integer but |MinLong| is not, we have to keep the current

      converted value (and the scale!) as *negative* numbers,

      so the sign is the opposite of what you might expect.

      */

  while (my_isspace(&my_charset_latin1, *src)) src++;

  sign = -1;

  if (*src == '+')

    src++;

  else if (*src == '-')

    src++, sign = 1;

  /*  Skip leading zeros so that we never compute a power of radix

      in scale that we won't have a need for.  Otherwise sticking

      enough 0s in front of a number could cause the multiplication

      to overflow when it neededn't.

      */

  start = src;

  while (*src == '0') src++;

  /*  Move over the remaining digits.  We have to convert from left

      to left in order to avoid overflow.  Answer is after last digit.

      */

  for (n = 0; (digits[n] = char_val(*src)) < radix && n < 20; n++, src++)

    ;

  /*  Check that there is at least one digit  */

  if (start == src) {

    errno = EDOM;

    return nullptr;

  }

  /*  The invariant we want to maintain is that src is just

      to the right of n digits, we've converted k digits to

      sofar, scale = -radix**k, and scale < sofar < 0.  Now

      if the final number is to be within the original

      Limit, we must have (to the left)*scale+sofar >= Limit,

      or (to the left)*scale >= Limit-sofar, i.e. the digits

      to the left of src must form an integer <= (Limit-sofar)/(scale).

      In particular, this is true of the next digit.  In our

      incremental calculation of Limit,

      IT IS VITAL that (-|N|)/(-|D|) = |N|/|D|

      */

  for (sofar = 0, scale = -1; --n >= 1;) {

    if ((long)-(d = digits[n]) < limit) {

      errno = ERANGE;

      return nullptr;

    }

    limit = (limit + d) / radix, sofar += d * scale;

    scale *= radix;

  }

  if (n == 0) {

    if ((long)-(d = digits[n]) < limit) /* get last digit */

    {

      errno = ERANGE;

      return nullptr;

    }

    sofar += d * scale;

  }

  /*  Now it might still happen that sofar = -32768 or its equivalent,

      so we can't just multiply by the sign and check that the result

      is in the range lower..upper.  All of this caution is a right

      pain in the neck.  If only there were a standard routine which

      says generate thus and such a signal on integer overflow...

      But not enough machines can do it *SIGH*.

      */

  if (sign < 0) {

    if (sofar < -LONG_MAX || (sofar = -sofar) > upper) {

      errno = ERANGE;

      return nullptr;

    }

  } else if (sofar < lower) {

    errno = ERANGE;

    return nullptr;

  }

  *val = sofar;

  errno = 0; /* indicate that all went well */

  return src;

}