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1 // Copyright 2008 The RE2 Authors. All Rights Reserved. | |
2 // Use of this source code is governed by a BSD-style | |
3 // license that can be found in the LICENSE file. | |
4 | |
5 // Unicode case folding tables. | |
6 | |
7 // The Unicode case folding tables encode the mapping from one Unicode point | |
8 // to the next largest Unicode point with equivalent folding. The largest | |
9 // point wraps back to the first. For example, the tables map: | |
10 // | |
11 // 'A' -> 'a' | |
12 // 'a' -> 'A' | |
13 // | |
14 // 'K' -> 'k' | |
15 // 'k' -> 'K' (Kelvin symbol) | |
16 // 'K' -> 'K' | |
17 // | |
18 // Like everything Unicode, these tables are big. If we represent the table | |
19 // as a sorted list of uint32 pairs, it has 2049 entries and is 16 kB. | |
20 // Most table entries look like the ones around them: | |
21 // 'A' maps to 'A'+32, 'B' maps to 'B'+32, etc. | |
22 // Instead of listing all the pairs explicitly, we make a list of ranges | |
23 // and deltas, so that the table entries for 'A' through 'Z' can be represented | |
24 // as a single entry { 'A', 'Z', +32 }. | |
25 // | |
26 // In addition to blocks that map to each other (A-Z mapping to a-z) | |
27 // there are blocks of pairs that individually map to each other | |
28 // (for example, 0100<->0101, 0102<->0103, 0104<->0105, ...). | |
29 // For those, the special delta value EvenOdd marks even/odd pairs | |
30 // (if even, add 1; if odd, subtract 1), and OddEven marks odd/even pairs. | |
31 // | |
32 // In this form, the table has 274 entries, about 3kB. If we were to split | |
33 // the table into one for 16-bit codes and an overflow table for larger ones, | |
34 // we could get it down to about 1.5kB, but that's not worth the complexity. | |
35 // | |
36 // The grouped form also allows for efficient fold range calculations | |
37 // rather than looping one character at a time. | |
38 | |
39 #ifndef RE2_UNICODE_CASEFOLD_H__ | |
40 #define RE2_UNICODE_CASEFOLD_H__ | |
41 | |
42 #include "util/util.h" | |
43 | |
44 namespace re2 { | |
45 | |
46 enum { | |
47 EvenOdd = 1, | |
48 OddEven = -1, | |
49 EvenOddSkip = 1<<30, | |
50 OddEvenSkip, | |
51 }; | |
52 | |
53 struct CaseFold { | |
54 Rune lo; | |
55 Rune hi; | |
56 int32 delta; | |
57 }; | |
58 | |
59 extern const CaseFold unicode_casefold[]; | |
60 extern const int num_unicode_casefold; | |
61 | |
62 extern const CaseFold unicode_tolower[]; | |
63 extern const int num_unicode_tolower; | |
64 | |
65 // Returns the CaseFold* in the tables that contains rune. | |
66 // If rune is not in the tables, returns the first CaseFold* after rune. | |
67 // If rune is larger than any value in the tables, returns NULL. | |
68 extern const CaseFold* LookupCaseFold(const CaseFold*, int, Rune rune); | |
69 | |
70 // Returns the result of applying the fold f to the rune r. | |
71 extern Rune ApplyFold(const CaseFold *f, Rune r); | |
72 | |
73 } // namespace re2 | |
74 | |
75 #endif // RE2_UNICODE_CASEFOLD_H__ | |
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