src: remove static variables from string_search

These variables can as well be stack-allocated. This avoids
relying on global state that is not protected by mutexes.

Thanks to Stephen Belanger for reviewing this change in its original PR.

Refs: ayojs/ayo#82

PR-URL: #20541
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

node.gyp

@@ -346,7 +346,6 @@
        'src/spawn_sync.cc',
        'src/string_bytes.cc',
        'src/string_decoder.cc',
        'src/string_search.cc',
        'src/stream_base.cc',
        'src/stream_pipe.cc',
        'src/stream_wrap.cc',

src/string_search.h

@@ -80,12 +80,12 @@ class StringSearchBase {
  static const int kBMMinPatternLength = 8;

  // Store for the BoyerMoore(Horspool) bad char shift table.
  static int kBadCharShiftTable[kUC16AlphabetSize];
  int bad_char_shift_table_[kUC16AlphabetSize];
  // Store for the BoyerMoore good suffix shift table.
  static int kGoodSuffixShiftTable[kBMMaxShift + 1];
  int good_suffix_shift_table_[kBMMaxShift + 1];
  // Table used temporarily while building the BoyerMoore good suffix
  // shift table.
  static int kSuffixTable[kBMMaxShift + 1];
  int suffix_table_[kBMMaxShift + 1];
};

template <typename Char>
@@ -152,26 +152,6 @@ class StringSearch : private StringSearchBase {
    return bad_char_occurrence[equiv_class];
  }

  // Store for the BoyerMoore(Horspool) bad char shift table.
  // Return a table covering the last kBMMaxShift+1 positions of
  // pattern.
  int* bad_char_table() { return kBadCharShiftTable; }

  // Store for the BoyerMoore good suffix shift table.
  int* good_suffix_shift_table() {
    // Return biased pointer that maps the range  [start_..pattern_.length()
    // to the kGoodSuffixShiftTable array.
    return kGoodSuffixShiftTable - start_;
  }

  // Table used temporarily while building the BoyerMoore good suffix
  // shift table.
  int* suffix_table() {
    // Return biased pointer that maps the range  [start_..pattern_.length()
    // to the kSuffixTable array.
    return kSuffixTable - start_;
  }

  // The pattern to search for.
  Vector pattern_;
  // Pointer to implementation of the search.
@@ -345,8 +325,8 @@ size_t StringSearch<Char>::BoyerMooreSearch(
  // Only preprocess at most kBMMaxShift last characters of pattern.
  size_t start = start_;

  int* bad_char_occurrence = bad_char_table();
  int* good_suffix_shift = good_suffix_shift_table();
  int* bad_char_occurrence = bad_char_shift_table_;
  int* good_suffix_shift = good_suffix_shift_table_ - start_;

  Char last_char = pattern_[pattern_length - 1];
  size_t index = start_index;
@@ -397,8 +377,8 @@ void StringSearch<Char>::PopulateBoyerMooreTable() {

  // Biased tables so that we can use pattern indices as table indices,
  // even if we only cover the part of the pattern from offset start.
  int* shift_table = good_suffix_shift_table();
  int* suffix_table = this->suffix_table();
  int* shift_table = good_suffix_shift_table_ - start_;
  int* suffix_table = suffix_table_ - start_;

  // Initialize table.
  for (size_t i = start; i < pattern_length; i++) {
@@ -462,7 +442,7 @@ size_t StringSearch<Char>::BoyerMooreHorspoolSearch(
    size_t start_index) {
  const size_t subject_length = subject.length();
  const size_t pattern_length = pattern_.length();
  int* char_occurrences = bad_char_table();
  int* char_occurrences = bad_char_shift_table_;
  int64_t badness = -pattern_length;

  // How bad we are doing without a good-suffix table.
@@ -511,7 +491,7 @@ template <typename Char>
void StringSearch<Char>::PopulateBoyerMooreHorspoolTable() {
  const size_t pattern_length = pattern_.length();

  int* bad_char_occurrence = bad_char_table();
  int* bad_char_occurrence = bad_char_shift_table_;

  // Only preprocess at most kBMMaxShift last characters of pattern.
  const size_t start = start_;