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/* Copyright (C) 2000 MySQL AB
This program 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; version 2 of the License.
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 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 (char *)0, 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 occured,
I have taken a wholly unprecedented step: errno is CLEARED if this
call has no problems.
*/
#include "m_string.h"
#include "m_ctype.h"
#include <errno.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')
char *str2int(register const char *src, register 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 */
register int d; /* (negative of) next digit */
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 */
if (radix < 2 || radix > 36) {
errno=EDOM;
return (char *)0;
}
/* 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=(char*) 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 (char *)0;
}
/* 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 (char *)0;
}
limit = (limit+d)/radix, sofar += d*scale; scale *= radix;
}
if (n == 0)
{
if ((long) -(d=digits[n]) < limit) /* get last digit */
{
errno=ERANGE;
return (char *)0;
}
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 (char *)0;
}
}
else if (sofar < lower)
{
errno=ERANGE;
return (char *)0;
}
*val = sofar;
errno=0; /* indicate that all went well */
return (char*) src;
}
/* Theese are so slow compared with ordinary, optimized atoi */
#ifdef WANT_OUR_ATOI
int atoi(const char *src)
{
long val;
str2int(src, 10, (long) INT_MIN, (long) INT_MAX, &val);
return (int) val;
}
long atol(const char *src)
{
long val;
str2int(src, 10, LONG_MIN, LONG_MAX, &val);
return val;
}
#endif /* WANT_OUR_ATOI */
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