Replace RE2 import with a dependency

third_party/re2/re2/unicode_casefold.h

-// Copyright 2008 The RE2 Authors.  All Rights Reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Unicode case folding tables.
-
-// The Unicode case folding tables encode the mapping from one Unicode point
-// to the next largest Unicode point with equivalent folding.  The largest
-// point wraps back to the first.  For example, the tables map:
-//
-//     'A' -> 'a'
-//     'a' -> 'A'
-//
-//     'K' -> 'k'
-//     'k' -> 'K'  (Kelvin symbol)
-//     'K' -> 'K'
-//
-// Like everything Unicode, these tables are big.  If we represent the table
-// as a sorted list of uint32 pairs, it has 2049 entries and is 16 kB.
-// Most table entries look like the ones around them:
-// 'A' maps to 'A'+32, 'B' maps to 'B'+32, etc.
-// Instead of listing all the pairs explicitly, we make a list of ranges
-// and deltas, so that the table entries for 'A' through 'Z' can be represented
-// as a single entry { 'A', 'Z', +32 }.
-//
-// In addition to blocks that map to each other (A-Z mapping to a-z)
-// there are blocks of pairs that individually map to each other
-// (for example, 0100<->0101, 0102<->0103, 0104<->0105, ...).
-// For those, the special delta value EvenOdd marks even/odd pairs
-// (if even, add 1; if odd, subtract 1), and OddEven marks odd/even pairs.
-//
-// In this form, the table has 274 entries, about 3kB.  If we were to split
-// the table into one for 16-bit codes and an overflow table for larger ones,
-// we could get it down to about 1.5kB, but that's not worth the complexity.
-//
-// The grouped form also allows for efficient fold range calculations
-// rather than looping one character at a time.
-
-#ifndef RE2_UNICODE_CASEFOLD_H__
-#define RE2_UNICODE_CASEFOLD_H__
-
-#include "util/util.h"
-
-namespace re2 {
-
-enum {
-  EvenOdd = 1,
-  OddEven = -1,
-  EvenOddSkip = 1<<30,
-  OddEvenSkip,
-};
-
-struct CaseFold {
-  Rune lo;
-  Rune hi;
-  int32 delta;
-};
-
-extern const CaseFold unicode_casefold[];
-extern const int num_unicode_casefold;
-
-extern const CaseFold unicode_tolower[];
-extern const int num_unicode_tolower;
-
-// Returns the CaseFold* in the tables that contains rune.
-// If rune is not in the tables, returns the first CaseFold* after rune.
-// If rune is larger than any value in the tables, returns NULL.
-extern const CaseFold* LookupCaseFold(const CaseFold*, int, Rune rune);
-
-// Returns the result of applying the fold f to the rune r.
-extern Rune ApplyFold(const CaseFold *f, Rune r);
-
-}  // namespace re2
-
-#endif  // RE2_UNICODE_CASEFOLD_H__