1 | // Copyright 2008 The RE2 Authors. All Rights Reserved. |
2 | // Use of this source code is governed by a BSD-style |
3 | // license that can be found in the LICENSE file. |
4 | |
5 | // String generator: generates all possible strings of up to |
6 | // maxlen letters using the set of letters in alpha. |
7 | // Fetch strings using a Java-like Next()/HasNext() interface. |
8 | |
9 | #include <stddef.h> |
10 | #include <stdint.h> |
11 | #include <string> |
12 | #include <vector> |
13 | |
14 | #include "util/test.h" |
15 | #include "util/logging.h" |
16 | #include "re2/testing/string_generator.h" |
17 | |
18 | namespace re2 { |
19 | |
20 | StringGenerator::StringGenerator(int maxlen, |
21 | const std::vector<std::string>& alphabet) |
22 | : maxlen_(maxlen), alphabet_(alphabet), |
23 | generate_null_(false), |
24 | random_(false), nrandom_(0) { |
25 | |
26 | // Degenerate case: no letters, no non-empty strings. |
27 | if (alphabet_.empty()) |
28 | maxlen_ = 0; |
29 | |
30 | // Next() will return empty string (digits_ is empty). |
31 | hasnext_ = true; |
32 | } |
33 | |
34 | // Resets the string generator state to the beginning. |
35 | void StringGenerator::Reset() { |
36 | digits_.clear(); |
37 | hasnext_ = true; |
38 | random_ = false; |
39 | nrandom_ = 0; |
40 | generate_null_ = false; |
41 | } |
42 | |
43 | // Increments the big number in digits_, returning true if successful. |
44 | // Returns false if all the numbers have been used. |
45 | bool StringGenerator::IncrementDigits() { |
46 | // First try to increment the current number. |
47 | for (int i = static_cast<int>(digits_.size()) - 1; i >= 0; i--) { |
48 | if (++digits_[i] < static_cast<int>(alphabet_.size())) |
49 | return true; |
50 | digits_[i] = 0; |
51 | } |
52 | |
53 | // If that failed, make a longer number. |
54 | if (static_cast<int>(digits_.size()) < maxlen_) { |
55 | digits_.push_back(0); |
56 | return true; |
57 | } |
58 | |
59 | return false; |
60 | } |
61 | |
62 | // Generates random digits_, return true if successful. |
63 | // Returns false if the random sequence is over. |
64 | bool StringGenerator::RandomDigits() { |
65 | if (--nrandom_ <= 0) |
66 | return false; |
67 | |
68 | std::uniform_int_distribution<int> random_len(0, maxlen_); |
69 | std::uniform_int_distribution<int> random_alphabet_index( |
70 | 0, static_cast<int>(alphabet_.size()) - 1); |
71 | |
72 | // Pick length. |
73 | int len = random_len(rng_); |
74 | digits_.resize(len); |
75 | for (int i = 0; i < len; i++) |
76 | digits_[i] = random_alphabet_index(rng_); |
77 | return true; |
78 | } |
79 | |
80 | // Returns the next string in the iteration, which is the one |
81 | // currently described by digits_. Calls IncrementDigits |
82 | // after computing the string, so that it knows the answer |
83 | // for subsequent HasNext() calls. |
84 | const StringPiece& StringGenerator::Next() { |
85 | CHECK(hasnext_); |
86 | if (generate_null_) { |
87 | generate_null_ = false; |
88 | sp_ = StringPiece(); |
89 | return sp_; |
90 | } |
91 | s_.clear(); |
92 | for (size_t i = 0; i < digits_.size(); i++) { |
93 | s_ += alphabet_[digits_[i]]; |
94 | } |
95 | hasnext_ = random_ ? RandomDigits() : IncrementDigits(); |
96 | sp_ = s_; |
97 | return sp_; |
98 | } |
99 | |
100 | // Sets generator up to return n random strings. |
101 | void StringGenerator::Random(int32_t seed, int n) { |
102 | rng_.seed(seed); |
103 | |
104 | random_ = true; |
105 | nrandom_ = n; |
106 | hasnext_ = nrandom_ > 0; |
107 | } |
108 | |
109 | void StringGenerator::GenerateNULL() { |
110 | generate_null_ = true; |
111 | hasnext_ = true; |
112 | } |
113 | |
114 | } // namespace re2 |
115 | |