Method find

ext/src/llvm/StringRef.cpp:133–180

find - Search for the first string \arg Str in the string. \return - The index of the first occurrence of \arg Str, or npos if not found.

/// \return - The index of the first occurrence of \arg Str, or npos if not
/// found.
size_t StringRef::find(StringRef Str, size_t From) const {
  if (From > Length)
    return npos;

  const char *Start = Data + From;
  size_t Size = Length - From;

  const char *Needle = Str.data();
  size_t N = Str.size();
  if (N == 0)
    return From;
  if (Size < N)
    return npos;
  if (N == 1) {
    const char *Ptr = (const char *)::memchr(Start, Needle[0], Size);
    return Ptr == nullptr ? npos : Ptr - Data;
  }

  const char *Stop = Start + (Size - N + 1);

  // For short haystacks or unsupported needles fall back to the naive algorithm
  if (Size < 16 || N > 255) {
    do {
      if (std::memcmp(Start, Needle, N) == 0)
        return Start - Data;
      ++Start;
    } while (Start < Stop);
    return npos;
  }

  // Build the bad char heuristic table, with uint8_t to reduce cache thrashing.
  uint8_t BadCharSkip[256];
  std::memset(BadCharSkip, N, 256);
  for (unsigned i = 0; i != N-1; ++i)
    BadCharSkip[(uint8_t)Str[i]] = N-1-i;

  do {
    uint8_t Last = Start[N - 1];
    if (LLVM_UNLIKELY(Last == (uint8_t)Needle[N - 1]))
      if (std::memcmp(Start, Needle, N - 1) == 0)
        return Start - Data;

    // Otherwise skip the appropriate number of bytes.
    Start += BadCharSkip[Last];
  } while (Start < Stop);

  return npos;
}

size_t StringRef::find_lower(StringRef Str, size_t From) const {
  StringRef This = substr(From);