1 /* Copyright (C) 2000-2023 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18 #include <stdint.h>
19
20 /* Tables indexed by a wide character are compressed through the use
21 of a multi-level lookup. The compression effect comes from blocks
22 that don't need particular data and from blocks that can share their
23 data. */
24
25 /* Bit tables are accessed by cutting wc in four blocks of bits:
26 - the high 32-q-p bits,
27 - the next q bits,
28 - the next p bits,
29 - the next 5 bits.
30
31 +------------------+-----+-----+-----+
32 wc = + 32-q-p-5 | q | p | 5 |
33 +------------------+-----+-----+-----+
34
35 p and q are variable. For 16-bit Unicode it is sufficient to
36 choose p and q such that q+p+5 <= 16.
37
38 The table contains the following uint32_t words:
39 - q+p+5,
40 - s = upper exclusive bound for wc >> (q+p+5),
41 - p+5,
42 - 2^q-1,
43 - 2^p-1,
44 - 1st-level table: s offsets, pointing into the 2nd-level table,
45 - 2nd-level table: k*2^q offsets, pointing into the 3rd-level table,
46 - 3rd-level table: j*2^p words, each containing 32 bits of data.
47 */
48
49 static __inline int
50 __attribute ((always_inline))
51 wctype_table_lookup (const char *table, uint32_t wc)
52 {
53 uint32_t shift1 = ((const uint32_t *) table)[0];
54 uint32_t index1 = wc >> shift1;
55 uint32_t bound = ((const uint32_t *) table)[1];
56 if (index1 < bound)
57 {
58 uint32_t lookup1 = ((const uint32_t *) table)[5 + index1];
59 if (lookup1 != 0)
60 {
61 uint32_t shift2 = ((const uint32_t *) table)[2];
62 uint32_t mask2 = ((const uint32_t *) table)[3];
63 uint32_t index2 = (wc >> shift2) & mask2;
64 uint32_t lookup2 = ((const uint32_t *)(table + lookup1))[index2];
65 if (lookup2 != 0)
66 {
67 uint32_t mask3 = ((const uint32_t *) table)[4];
68 uint32_t index3 = (wc >> 5) & mask3;
69 uint32_t lookup3 = ((const uint32_t *)(table + lookup2))[index3];
70
71 return (lookup3 >> (wc & 0x1f)) & 1;
72 }
73 }
74 }
75 return 0;
76 }
77
78 /* Byte tables are similar to bit tables, except that the addressing
79 unit is a single byte, and no 5 bits are used as a word index. */
80
81 static __inline int
82 __attribute ((always_inline))
83 wcwidth_table_lookup (const char *table, uint32_t wc)
84 {
85 uint32_t shift1 = ((const uint32_t *) table)[0];
86 uint32_t index1 = wc >> shift1;
87 uint32_t bound = ((const uint32_t *) table)[1];
88 if (index1 < bound)
89 {
90 uint32_t lookup1 = ((const uint32_t *) table)[5 + index1];
91 if (lookup1 != 0)
92 {
93 uint32_t shift2 = ((const uint32_t *) table)[2];
94 uint32_t mask2 = ((const uint32_t *) table)[3];
95 uint32_t index2 = (wc >> shift2) & mask2;
96 uint32_t lookup2 = ((const uint32_t *)(table + lookup1))[index2];
97 if (lookup2 != 0)
98 {
99 uint32_t mask3 = ((const uint32_t *) table)[4];
100 uint32_t index3 = wc & mask3;
101 uint8_t lookup3 = ((const uint8_t *)(table + lookup2))[index3];
102
103 return lookup3;
104 }
105 }
106 }
107 return 0xff;
108 }
109
110 /* Mapping tables are similar to bit tables, except that the
111 addressing unit is a single signed 32-bit word, containing the
112 difference between the desired result and the argument, and no 5
113 bits are used as a word index. */
114
115 static __inline uint32_t
116 __attribute ((always_inline))
117 wctrans_table_lookup (const char *table, uint32_t wc)
118 {
119 uint32_t shift1 = ((const uint32_t *) table)[0];
120 uint32_t index1 = wc >> shift1;
121 uint32_t bound = ((const uint32_t *) table)[1];
122 if (index1 < bound)
123 {
124 uint32_t lookup1 = ((const uint32_t *) table)[5 + index1];
125 if (lookup1 != 0)
126 {
127 uint32_t shift2 = ((const uint32_t *) table)[2];
128 uint32_t mask2 = ((const uint32_t *) table)[3];
129 uint32_t index2 = (wc >> shift2) & mask2;
130 uint32_t lookup2 = ((const uint32_t *)(table + lookup1))[index2];
131 if (lookup2 != 0)
132 {
133 uint32_t mask3 = ((const uint32_t *) table)[4];
134 uint32_t index3 = wc & mask3;
135 int32_t lookup3 = ((const int32_t *)(table + lookup2))[index3];
136
137 return wc + lookup3;
138 }
139 }
140 }
141 return wc;
142 }