Function LookupCaseFold

extern/re2/re2/parse.cc:272–297

Searches the case folding tables and returns the CaseFold* that contains r. If there isn't one, returns the CaseFold* with smallest f->lo bigger than r. If there isn't one, returns NULL.

// If there isn't one, returns the CaseFold* with smallest f->lo bigger than r.
// If there isn't one, returns NULL.
const CaseFold* LookupCaseFold(const CaseFold *f, int n, Rune r) {
  const CaseFold* ef = f + n;

  // Binary search for entry containing r.
  while (n > 0) {
    int m = n/2;
    if (f[m].lo <= r && r <= f[m].hi)
      return &f[m];
    if (r < f[m].lo) {
      n = m;
    } else {
      f += m+1;
      n -= m+1;
    }
  }

  // There is no entry that contains r, but f points
  // where it would have been.  Unless f points at
  // the end of the array, it points at the next entry
  // after r.
  if (f < ef)
    return f;

  // No entry contains r; no entry contains runes > r.
  return NULL;
}

// Returns the result of applying the fold f to the rune r.
Rune ApplyFold(const CaseFold *f, Rune r) {