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/* Compare numeric strings. This is an internal include file.
Copyright (C) 1988-2023 Free Software Foundation, Inc.
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, either version 3 of the License, or
(at your option) any later version.
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, see <https://www.gnu.org/licenses/>. */
/* Written by Mike Haertel. */
#ifndef STRNUMCMP_IN_H
# define STRNUMCMP_IN_H 1
# include "strnumcmp.h"
# include <stddef.h>
# define NEGATION_SIGN '-'
# define NUMERIC_ZERO '0'
/* ISDIGIT differs from isdigit, as follows:
- Its arg may be any int or unsigned int; it need not be an unsigned char
or EOF.
- It's typically faster.
POSIX says that only '0' through '9' are digits. Prefer ISDIGIT to
isdigit unless it's important to use the locale's definition
of 'digit' even when the host does not conform to POSIX. */
# define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)
/* Compare strings A and B containing decimal fractions < 1.
DECIMAL_POINT is the decimal point. Each string
should begin with a decimal point followed immediately by the digits
of the fraction. Strings not of this form are treated as zero. */
/* The goal here, is to take two numbers a and b... compare these
in parallel. Instead of converting each, and then comparing the
outcome. Most likely stopping the comparison before the conversion
is complete. The algorithm used, in the old "sort" utility:
Algorithm: fraccompare
Action : compare two decimal fractions
accepts : char *a, char *b
returns : -1 if a<b, 0 if a=b, 1 if a>b.
implement:
if *a == decimal_point AND *b == decimal_point
find first character different in a and b.
if both are digits, return the difference *a - *b.
if *a is a digit
skip past zeros
if digit return 1, else 0
if *b is a digit
skip past zeros
if digit return -1, else 0
if *a is a decimal_point
skip past decimal_point and zeros
if digit return 1, else 0
if *b is a decimal_point
skip past decimal_point and zeros
if digit return -1, else 0
return 0 */
static inline int _GL_ATTRIBUTE_PURE
fraccompare (char const *a, char const *b, char decimal_point)
{
if (*a == decimal_point && *b == decimal_point)
{
while (*++a == *++b)
if (! ISDIGIT (*a))
return 0;
if (ISDIGIT (*a) && ISDIGIT (*b))
return *a - *b;
if (ISDIGIT (*a))
goto a_trailing_nonzero;
if (ISDIGIT (*b))
goto b_trailing_nonzero;
return 0;
}
else if (*a++ == decimal_point)
{
a_trailing_nonzero:
while (*a == NUMERIC_ZERO)
a++;
return ISDIGIT (*a);
}
else if (*b++ == decimal_point)
{
b_trailing_nonzero:
while (*b == NUMERIC_ZERO)
b++;
return - ISDIGIT (*b);
}
return 0;
}
/* Compare strings A and B as numbers without explicitly converting
them to machine numbers, to avoid overflow problems and perhaps
improve performance. DECIMAL_POINT is the decimal point and
THOUSANDS_SEP the thousands separator. A DECIMAL_POINT outside
'char' range causes comparisons to act as if there is no decimal point
character, and likewise for THOUSANDS_SEP. */
static inline int _GL_ATTRIBUTE_PURE
numcompare (char const *a, char const *b,
int decimal_point, int thousands_sep)
{
unsigned char tmpa = *a;
unsigned char tmpb = *b;
int tmp;
size_t log_a;
size_t log_b;
if (tmpa == NEGATION_SIGN)
{
do
tmpa = *++a;
while (tmpa == NUMERIC_ZERO || tmpa == thousands_sep);
if (tmpb != NEGATION_SIGN)
{
if (tmpa == decimal_point)
do
tmpa = *++a;
while (tmpa == NUMERIC_ZERO);
if (ISDIGIT (tmpa))
return -1;
while (tmpb == NUMERIC_ZERO || tmpb == thousands_sep)
tmpb = *++b;
if (tmpb == decimal_point)
do
tmpb = *++b;
while (tmpb == NUMERIC_ZERO);
return - ISDIGIT (tmpb);
}
do
tmpb = *++b;
while (tmpb == NUMERIC_ZERO || tmpb == thousands_sep);
while (tmpa == tmpb && ISDIGIT (tmpa))
{
do
tmpa = *++a;
while (tmpa == thousands_sep);
do
tmpb = *++b;
while (tmpb == thousands_sep);
}
if ((tmpa == decimal_point && !ISDIGIT (tmpb))
|| (tmpb == decimal_point && !ISDIGIT (tmpa)))
return fraccompare (b, a, decimal_point);
tmp = tmpb - tmpa;
for (log_a = 0; ISDIGIT (tmpa); ++log_a)
do
tmpa = *++a;
while (tmpa == thousands_sep);
for (log_b = 0; ISDIGIT (tmpb); ++log_b)
do
tmpb = *++b;
while (tmpb == thousands_sep);
if (log_a != log_b)
return log_a < log_b ? 1 : -1;
if (!log_a)
return 0;
return tmp;
}
else if (tmpb == NEGATION_SIGN)
{
do
tmpb = *++b;
while (tmpb == NUMERIC_ZERO || tmpb == thousands_sep);
if (tmpb == decimal_point)
do
tmpb = *++b;
while (tmpb == NUMERIC_ZERO);
if (ISDIGIT (tmpb))
return 1;
while (tmpa == NUMERIC_ZERO || tmpa == thousands_sep)
tmpa = *++a;
if (tmpa == decimal_point)
do
tmpa = *++a;
while (tmpa == NUMERIC_ZERO);
return ISDIGIT (tmpa);
}
else
{
while (tmpa == NUMERIC_ZERO || tmpa == thousands_sep)
tmpa = *++a;
while (tmpb == NUMERIC_ZERO || tmpb == thousands_sep)
tmpb = *++b;
while (tmpa == tmpb && ISDIGIT (tmpa))
{
do
tmpa = *++a;
while (tmpa == thousands_sep);
do
tmpb = *++b;
while (tmpb == thousands_sep);
}
if ((tmpa == decimal_point && !ISDIGIT (tmpb))
|| (tmpb == decimal_point && !ISDIGIT (tmpa)))
return fraccompare (a, b, decimal_point);
tmp = tmpa - tmpb;
for (log_a = 0; ISDIGIT (tmpa); ++log_a)
do
tmpa = *++a;
while (tmpa == thousands_sep);
for (log_b = 0; ISDIGIT (tmpb); ++log_b)
do
tmpb = *++b;
while (tmpb == thousands_sep);
if (log_a != log_b)
return log_a < log_b ? -1 : 1;
if (!log_a)
return 0;
return tmp;
}
}
#endif
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