summaryrefslogtreecommitdiff
path: root/lib/strnumcmp-in.h
blob: 7e963bc16b20676a6fd346ba65c4ba75b295c400 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
/* Compare numeric strings.  This is an internal include file.

   Copyright (C) 1988, 1991-1993, 1995-1996, 1998-2000, 2003-2006, 2009-2011
   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 <http://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 of -1
   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