c_cpp/lib/natsort/strnatcmp.c

   1 /* -*- mode: c; c-file-style: "k&r" -*-
   2
   3   strnatcmp.c -- Perform 'natural order' comparisons of strings in C.
   4   Copyright (C) 2000, 2004 by Martin Pool <mbp sourcefrog net>
   5
   6   This software is provided 'as-is', without any express or implied
   7   warranty.  In no event will the authors be held liable for any damages
   8   arising from the use of this software.
   9
  10   Permission is granted to anyone to use this software for any purpose,
  11   including commercial applications, and to alter it and redistribute it
  12   freely, subject to the following restrictions:
  13
  14   1. The origin of this software must not be misrepresented; you must not
  15      claim that you wrote the original software. If you use this software
  16      in a product, an acknowledgment in the product documentation would be
  17      appreciated but is not required.
  18   2. Altered source versions must be plainly marked as such, and must not be
  19      misrepresented as being the original software.
  20   3. This notice may not be removed or altered from any source distribution.
  21 */
  22
  23
  24 /* partial change history:
  25  *
  26  * 2004-10-10 mbp: Lift out character type dependencies into macros.
  27  *
  28  * Eric Sosman pointed out that ctype functions take a parameter whose
  29  * value must be that of an unsigned int, even on platforms that have
  30  * negative chars in their default char type.
  31  */
  32
  33 #include <stddef.h>     /* size_t */
  34 #include <ctype.h>
  35
  36 #include "strnatcmp.h"
  37
  38
  39 /* These are defined as macros to make it easier to adapt this code to
  40  * different characters types or comparison functions. */
  41 static inline int
  42 nat_isdigit(nat_char a)
  43 {
  44      return isdigit((unsigned char) a);
  45 }
  46
  47
  48 static inline int
  49 nat_isspace(nat_char a)
  50 {
  51      return isspace((unsigned char) a);
  52 }
  53
  54
  55 static inline nat_char
  56 nat_toupper(nat_char a)
  57 {
  58      return toupper((unsigned char) a);
  59 }
  60
  61
  62 static int
  63 compare_right(nat_char const *a, nat_char const *b)
  64 {
  65      int bias = 0;
  66
  67      /* The longest run of digits wins.  That aside, the greatest
  68         value wins, but we can't know that it will until we've scanned
  69         both numbers to know that they have the same magnitude, so we
  70         remember it in BIAS. */
  71      for (;; a++, b++) {
  72           if (!nat_isdigit(*a)  &&  !nat_isdigit(*b))
  73                return bias;
  74           if (!nat_isdigit(*a))
  75                return -1;
  76           if (!nat_isdigit(*b))
  77                return +1;
  78           if (*a < *b) {
  79                if (!bias)
  80                     bias = -1;
  81           } else if (*a > *b) {
  82                if (!bias)
  83                     bias = +1;
  84           } else if (!*a  &&  !*b)
  85                return bias;
  86      }
  87
  88      return 0;
  89 }
  90
  91
  92 static int
  93 compare_left(nat_char const *a, nat_char const *b)
  94 {
  95      /* Compare two left-aligned numbers: the first to have a
  96         different value wins. */
  97      for (;; a++, b++) {
  98           if (!nat_isdigit(*a)  &&  !nat_isdigit(*b))
  99                return 0;
 100           if (!nat_isdigit(*a))
 101                return -1;
 102           if (!nat_isdigit(*b))
 103                return +1;
 104           if (*a < *b)
 105                return -1;
 106           if (*a > *b)
 107                return +1;
 108      }
 109
 110      return 0;
 111 }
 112
 113
 114 static int
 115 strnatcmp0(nat_char const *a, nat_char const *b, int fold_case)
 116 {
 117      int ai, bi;
 118      nat_char ca, cb;
 119      int fractional, result;
 120
 121      ai = bi = 0;
 122      while (1) {
 123           ca = a[ai]; cb = b[bi];
 124
 125           /* skip over leading spaces or zeros */
 126           while (nat_isspace(ca))
 127                ca = a[++ai];
 128
 129           while (nat_isspace(cb))
 130                cb = b[++bi];
 131
 132           /* process run of digits */
 133           if (nat_isdigit(ca)  &&  nat_isdigit(cb)) {
 134                fractional = (ca == '0' || cb == '0');
 135
 136                if (fractional) {
 137                     if ((result = compare_left(a+ai, b+bi)) != 0)
 138                          return result;
 139                } else {
 140                     if ((result = compare_right(a+ai, b+bi)) != 0)
 141                          return result;
 142                }
 143           }
 144
 145           if (!ca && !cb) {
 146                /* The strings compare the same.  Perhaps the caller
 147                   will want to call strcmp to break the tie. */
 148                return 0;
 149           }
 150
 151           if (fold_case) {
 152                ca = nat_toupper(ca);
 153                cb = nat_toupper(cb);
 154           }
 155
 156           if (ca < cb)
 157                return -1;
 158
 159           if (ca > cb)
 160                return +1;
 161
 162           ++ai; ++bi;
 163      }
 164 }
 165
 166
 167 int
 168 strnatcmp(nat_char const *a, nat_char const *b) {
 169      return strnatcmp0(a, b, 0);
 170 }
 171
 172
 173 /* Compare, recognizing numeric string and ignoring case. */
 174 int
 175 strnatcasecmp(nat_char const *a, nat_char const *b) {
 176      return strnatcmp0(a, b, 1);
 177 }