Replace RE2 import with a dependency

third_party/re2/re2/testing/string_generator.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.
-
-// String generator: generates all possible strings of up to
-// maxlen letters using the set of letters in alpha.
-// Fetch strings using a Java-like Next()/HasNext() interface.
-
-#ifndef RE2_TESTING_STRING_GENERATOR_H__
-#define RE2_TESTING_STRING_GENERATOR_H__
-
-#include <string>
-#include <vector>
-#include "util/util.h"
-#include "util/random.h"
-#include "re2/stringpiece.h"
-
-namespace re2 {
-
-class StringGenerator {
- public:
-  StringGenerator(int maxlen, const vector<string>& alphabet);
-  ~StringGenerator();
-  const StringPiece& Next();
-  bool HasNext() { return hasnext_; }
-
-  // Resets generator to start sequence over.
-  void Reset();
-
-  // Causes generator to emit random strings for next n calls to Next().
-  void Random(int32 seed, int n);
-
-  // Causes generator to emit a NULL as the next call.
-  void GenerateNULL();
-
- private:
-  bool IncrementDigits();
-  bool RandomDigits();
-
-  // Global state.
-  int maxlen_;               // Maximum length string to generate.
-  vector<string> alphabet_;  // Alphabet, one string per letter.
-
-  // Iteration state.
-  StringPiece sp_;           // Last StringPiece returned by Next().
-  string s_;                 // String data in last StringPiece returned by Next().
-  bool hasnext_;             // Whether Next() can be called again.
-  vector<int> digits_;       // Alphabet indices for next string.
-  bool generate_null_;       // Whether to generate a NULL StringPiece next.
-  bool random_;              // Whether generated strings are random.
-  int nrandom_;              // Number of random strings left to generate.
-  ACMRandom* acm_;           // Random number generator
-  DISALLOW_COPY_AND_ASSIGN(StringGenerator);
-};
-
-}  // namespace re2
-
-#endif  // RE2_TESTING_STRING_GENERATOR_H__