Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 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 | uint32 lo; |
| 55 | uint32 hi; |
| 56 | int32 delta; |
| 57 | }; |
| 58 | |
| 59 | extern CaseFold unicode_casefold[]; |
| 60 | extern int num_unicode_casefold; |
| 61 | |
| 62 | extern CaseFold unicode_tolower[]; |
| 63 | extern 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 CaseFold* LookupCaseFold(CaseFold*, int, Rune rune); |
| 69 | |
| 70 | // Returns the result of applying the fold f to the rune r. |
| 71 | extern Rune ApplyFold(CaseFold *f, Rune r); |
| 72 | |
| 73 | } // namespace re2 |
| 74 | |
| 75 | #endif // RE2_UNICODE_CASEFOLD_H__ |