1/* -*- buffer-read-only: t -*- vi: set ro: */
2/* DO NOT EDIT! GENERATED AUTOMATICALLY! */
3#line 1
4/* Substring search in a NUL terminated string of 'char' elements,
5   using the Knuth-Morris-Pratt algorithm.
6   Copyright (C) 2005-2010 Free Software Foundation, Inc.
7   Written by Bruno Haible <bruno@clisp.org>, 2005.
8
9   This program is free software; you can redistribute it and/or modify
10   it under the terms of the GNU General Public License as published by
11   the Free Software Foundation; either version 3, or (at your option)
12   any later version.
13
14   This program is distributed in the hope that it will be useful,
15   but WITHOUT ANY WARRANTY; without even the implied warranty of
16   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17   GNU General Public License for more details.
18
19   You should have received a copy of the GNU General Public License
20   along with this program; if not, write to the Free Software Foundation,
21   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
22
23/* Before including this file, you need to define:
24     CANON_ELEMENT(c)        A macro that canonicalizes an element right after
25                             it has been fetched from one of the two strings.
26                             The argument is an 'unsigned char'; the result
27                             must be an 'unsigned char' as well.  */
28
29/* Knuth-Morris-Pratt algorithm.
30   See http://en.wikipedia.org/wiki/Knuth-Morris-Pratt_algorithm
31   Return a boolean indicating success:
32   Return true and set *RESULTP if the search was completed.
33   Return false if it was aborted because not enough memory was available.  */
34static bool
35knuth_morris_pratt_unibyte (const char *haystack, const char *needle,
36                            const char **resultp)
37{
38  size_t m = strlen (needle);
39
40  /* Allocate the table.  */
41  size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
42  if (table == NULL)
43    return false;
44  /* Fill the table.
45     For 0 < i < m:
46       0 < table[i] <= i is defined such that
47       forall 0 < x < table[i]: needle[x..i-1] != needle[0..i-1-x],
48       and table[i] is as large as possible with this property.
49     This implies:
50     1) For 0 < i < m:
51          If table[i] < i,
52          needle[table[i]..i-1] = needle[0..i-1-table[i]].
53     2) For 0 < i < m:
54          rhaystack[0..i-1] == needle[0..i-1]
55          and exists h, i <= h < m: rhaystack[h] != needle[h]
56          implies
57          forall 0 <= x < table[i]: rhaystack[x..x+m-1] != needle[0..m-1].
58     table[0] remains uninitialized.  */
59  {
60    size_t i, j;
61
62    /* i = 1: Nothing to verify for x = 0.  */
63    table[1] = 1;
64    j = 0;
65
66    for (i = 2; i < m; i++)
67      {
68        /* Here: j = i-1 - table[i-1].
69           The inequality needle[x..i-1] != needle[0..i-1-x] is known to hold
70           for x < table[i-1], by induction.
71           Furthermore, if j>0: needle[i-1-j..i-2] = needle[0..j-1].  */
72        unsigned char b = CANON_ELEMENT ((unsigned char) needle[i - 1]);
73
74        for (;;)
75          {
76            /* Invariants: The inequality needle[x..i-1] != needle[0..i-1-x]
77               is known to hold for x < i-1-j.
78               Furthermore, if j>0: needle[i-1-j..i-2] = needle[0..j-1].  */
79            if (b == CANON_ELEMENT ((unsigned char) needle[j]))
80              {
81                /* Set table[i] := i-1-j.  */
82                table[i] = i - ++j;
83                break;
84              }
85            /* The inequality needle[x..i-1] != needle[0..i-1-x] also holds
86               for x = i-1-j, because
87                 needle[i-1] != needle[j] = needle[i-1-x].  */
88            if (j == 0)
89              {
90                /* The inequality holds for all possible x.  */
91                table[i] = i;
92                break;
93              }
94            /* The inequality needle[x..i-1] != needle[0..i-1-x] also holds
95               for i-1-j < x < i-1-j+table[j], because for these x:
96                 needle[x..i-2]
97                 = needle[x-(i-1-j)..j-1]
98                 != needle[0..j-1-(x-(i-1-j))]  (by definition of table[j])
99                    = needle[0..i-2-x],
100               hence needle[x..i-1] != needle[0..i-1-x].
101               Furthermore
102                 needle[i-1-j+table[j]..i-2]
103                 = needle[table[j]..j-1]
104                 = needle[0..j-1-table[j]]  (by definition of table[j]).  */
105            j = j - table[j];
106          }
107        /* Here: j = i - table[i].  */
108      }
109  }
110
111  /* Search, using the table to accelerate the processing.  */
112  {
113    size_t j;
114    const char *rhaystack;
115    const char *phaystack;
116
117    *resultp = NULL;
118    j = 0;
119    rhaystack = haystack;
120    phaystack = haystack;
121    /* Invariant: phaystack = rhaystack + j.  */
122    while (*phaystack != '\0')
123      if (CANON_ELEMENT ((unsigned char) needle[j])
124          == CANON_ELEMENT ((unsigned char) *phaystack))
125        {
126          j++;
127          phaystack++;
128          if (j == m)
129            {
130              /* The entire needle has been found.  */
131              *resultp = rhaystack;
132              break;
133            }
134        }
135      else if (j > 0)
136        {
137          /* Found a match of needle[0..j-1], mismatch at needle[j].  */
138          rhaystack += table[j];
139          j -= table[j];
140        }
141      else
142        {
143          /* Found a mismatch at needle[0] already.  */
144          rhaystack++;
145          phaystack++;
146        }
147  }
148
149  freea (table);
150  return true;
151}
152
153#undef CANON_ELEMENT
154