summaryrefslogtreecommitdiff
path: root/lib/unistr/u8-strchr.c
blob: 355a12c7fb48f8d4266ab940688c1801e60068cc (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
246
247
248
/* Search character in UTF-8 string.
   Copyright (C) 1999, 2002, 2006-2007, 2009-2024 Free Software Foundation,
   Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2002.

   This file is free software.
   It is dual-licensed under "the GNU LGPLv3+ or the GNU GPLv2+".
   You can redistribute it and/or modify it under either
     - the terms of the GNU Lesser General Public License as published
       by the Free Software Foundation, either version 3, or (at your
       option) any later version, or
     - the terms of the GNU General Public License as published by the
       Free Software Foundation; either version 2, or (at your option)
       any later version, or
     - the same dual license "the GNU LGPLv3+ or the GNU GPLv2+".

   This file 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
   Lesser General Public License and the GNU General Public License
   for more details.

   You should have received a copy of the GNU Lesser General Public
   License and of the GNU General Public License along with this
   program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "unistr.h"

#include <string.h>

uint8_t *
u8_strchr (const uint8_t *s, ucs4_t uc)
{
  uint8_t c[6];

  if (uc < 0x80)
    {
      uint8_t c0 = uc;

      if (false)
        {
          /* Unoptimized code.  */
          for (;;)
            {
              uint8_t s0 = *s;
              if (s0 == c0)
                return (uint8_t *) s;
              s++;
              if (s0 == 0)
                break;
            }
        }
      else
        {
          /* Optimized code.
             strchr() is often so well optimized, that it's worth the
             added function call.  */
          return (uint8_t *) strchr ((const char *) s, c0);
        }
    }
  else
      /* Loops equivalent to strstr, optimized for a specific length (2, 3, 4)
         of the needle.  We use an algorithm similar to Boyer-Moore which
         is documented in lib/unistr/u8-chr.c.  There is additional
         complication because we need to check after every byte for
         a NUL byte, but the idea is the same. */
    switch (u8_uctomb_aux (c, uc, 6))
      {
      case 2:
        if (*s == 0 || s[1] == 0)
          break;
        {
          uint8_t c0 = c[0];
          uint8_t c1 = c[1];
          /* Search for { c0, c1 }.  */
          uint8_t s1 = s[1];

          for (;;)
            {
              /* Here s[0] != 0, s[1] != 0.
                 Test whether s[0..1] == { c0, c1 }.  */
              if (s1 == c1)
                {
                  if (*s == c0)
                    return (uint8_t *) s;
                  else
                    /* Skip the search at s + 1, because s[1] = c1 < c0.  */
                    goto case2_skip2;
                }
              else
                {
                  if (s1 == c0)
                    goto case2_skip1;
                  else
                    /* Skip the search at s + 1, because s[1] != c0.  */
                    goto case2_skip2;
                }
             case2_skip2:
              s++;
              s1 = s[1];
              if (s[1] == 0)
                break;
             case2_skip1:
              s++;
              s1 = s[1];
              if (s[1] == 0)
                break;
            }
        }
        break;

      case 3:
        if (*s == 0 || s[1] == 0 || s[2] == 0)
          break;
        {
          uint8_t c0 = c[0];
          uint8_t c1 = c[1];
          uint8_t c2 = c[2];
          /* Search for { c0, c1, c2 }.  */
          uint8_t s2 = s[2];

          for (;;)
            {
              /* Here s[0] != 0, s[1] != 0, s[2] != 0.
                 Test whether s[0..2] == { c0, c1, c2 }.  */
              if (s2 == c2)
                {
                  if (s[1] == c1 && *s == c0)
                    return (uint8_t *) s;
                  else
                    /* If c2 != c1:
                         Skip the search at s + 1, because s[2] == c2 != c1.
                       Skip the search at s + 2, because s[2] == c2 < c0.  */
                    if (c2 == c1)
                      goto case3_skip1;
                    else
                      goto case3_skip3;
                }
              else
                {
                  if (s2 == c1)
                    goto case3_skip1;
                  else if (s2 == c0)
                    /* Skip the search at s + 1, because s[2] != c1.  */
                    goto case3_skip2;
                  else
                    /* Skip the search at s + 1, because s[2] != c1.
                       Skip the search at s + 2, because s[2] != c0.  */
                    goto case3_skip3;
                }
             case3_skip3:
              s++;
              s2 = s[2];
              if (s[2] == 0)
                break;
             case3_skip2:
              s++;
              s2 = s[2];
              if (s[2] == 0)
                break;
             case3_skip1:
              s++;
              s2 = s[2];
              if (s[2] == 0)
                break;
            }
        }
        break;

      case 4:
        if (*s == 0 || s[1] == 0 || s[2] == 0 || s[3] == 0)
          break;
        {
          uint8_t c0 = c[0];
          uint8_t c1 = c[1];
          uint8_t c2 = c[2];
          uint8_t c3 = c[3];
          /* Search for { c0, c1, c2, c3 }.  */
          uint8_t s3 = s[3];

          for (;;)
            {
              /* Here s[0] != 0, s[1] != 0, s[2] != 0, s[3] != 0.
                 Test whether s[0..3] == { c0, c1, c2, c3 }.  */
              if (s3 == c3)
                {
                  if (s[2] == c2 && s[1] == c1 && *s == c0)
                    return (uint8_t *) s;
                  else
                    /* If c3 != c2:
                         Skip the search at s + 1, because s[3] == c3 != c2.
                       If c3 != c1:
                         Skip the search at s + 2, because s[3] == c3 != c1.
                       Skip the search at s + 3, because s[3] == c3 < c0.  */
                    if (c3 == c2)
                      goto case4_skip1;
                    else if (c3 == c1)
                      goto case4_skip2;
                    else
                      goto case4_skip4;
                }
              else
                {
                  if (s3 == c2)
                    goto case4_skip1;
                  else if (s3 == c1)
                    /* Skip the search at s + 1, because s[3] != c2.  */
                    goto case4_skip2;
                  else if (s3 == c0)
                    /* Skip the search at s + 1, because s[3] != c2.
                       Skip the search at s + 2, because s[3] != c1.  */
                    goto case4_skip3;
                  else
                    /* Skip the search at s + 1, because s[3] != c2.
                       Skip the search at s + 2, because s[3] != c1.
                       Skip the search at s + 3, because s[3] != c0.  */
                    goto case4_skip4;
                }
             case4_skip4:
              s++;
              s3 = s[3];
              if (s[3] == 0)
                break;
             case4_skip3:
              s++;
              s3 = s[3];
              if (s[3] == 0)
                break;
             case4_skip2:
              s++;
              s3 = s[3];
              if (s[3] == 0)
                break;
             case4_skip1:
              s++;
              s3 = s[3];
              if (s[3] == 0)
                break;
            }
        }
        break;
      }

  return NULL;
}