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utf8_validator.hpp
1 /*
2  * The following code is adapted from code originally written by Bjoern
3  * Hoehrmann <bjoern@hoehrmann.de>. See
4  * http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
5  *
6  * The original license:
7  *
8  * Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
9  *
10  * Permission is hereby granted, free of charge, to any person obtaining a copy
11  * of this software and associated documentation files (the "Software"), to deal
12  * in the Software without restriction, including without limitation the rights
13  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
14  * copies of the Software, and to permit persons to whom the Software is
15  * furnished to do so, subject to the following conditions:
16  *
17  * The above copyright notice and this permission notice shall be included in
18  * all copies or substantial portions of the Software.
19  *
20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
23  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
24  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
25  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
26  * SOFTWARE.
27 */
28 
29 #ifndef UTF8_VALIDATOR_HPP
30 #define UTF8_VALIDATOR_HPP
31 
32 #include <websocketpp/common/stdint.hpp>
33 
34 #include <string>
35 
36 namespace websocketpp {
37 namespace utf8_validator {
38 
39 /// State that represents a valid utf8 input sequence
40 static unsigned int const utf8_accept = 0;
41 /// State that represents an invalid utf8 input sequence
42 static unsigned int const utf8_reject = 1;
43 
44 /// Lookup table for the UTF8 decode state machine
45 static uint8_t const utf8d[] = {
46  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 00..1f
47  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 20..3f
48  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 40..5f
49  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 60..7f
50  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, // 80..9f
51  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, // a0..bf
52  8,8,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, // c0..df
53  0xa,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x4,0x3,0x3, // e0..ef
54  0xb,0x6,0x6,0x6,0x5,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8, // f0..ff
55  0x0,0x1,0x2,0x3,0x5,0x8,0x7,0x1,0x1,0x1,0x4,0x6,0x1,0x1,0x1,0x1, // s0..s0
56  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1,1,0,1,0,1,1,1,1,1,1, // s1..s2
57  1,2,1,1,1,1,1,2,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1, // s3..s4
58  1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,3,1,3,1,1,1,1,1,1, // s5..s6
59  1,3,1,1,1,1,1,3,1,3,1,1,1,1,1,1,1,3,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // s7..s8
60 };
61 
62 /// Decode the next byte of a UTF8 sequence
63 /**
64  * @param [out] state The decoder state to advance
65  * @param [out] codep The codepoint to fill in
66  * @param [in] byte The byte to input
67  * @return The ending state of the decode operation
68  */
69 inline uint32_t decode(uint32_t * state, uint32_t * codep, uint8_t byte) {
70  uint32_t type = utf8d[byte];
71 
72  *codep = (*state != utf8_accept) ?
73  (byte & 0x3fu) | (*codep << 6) :
74  (0xff >> type) & (byte);
75 
76  *state = utf8d[256 + *state*16 + type];
77  return *state;
78 }
79 
80 /// Provides streaming UTF8 validation functionality
81 class validator {
82 public:
83  /// Construct and initialize the validator
84  validator() : m_state(utf8_accept),m_codepoint(0) {}
85 
86  /// Advance the state of the validator with the next input byte
87  /**
88  * @param byte The byte to advance the validation state with
89  * @return Whether or not the byte resulted in a validation error.
90  */
91  bool consume (uint8_t byte) {
92  if (utf8_validator::decode(&m_state,&m_codepoint,byte) == utf8_reject) {
93  return false;
94  }
95  return true;
96  }
97 
98  /// Advance validator state with input from an iterator pair
99  /**
100  * @param begin Input iterator to the start of the input range
101  * @param end Input iterator to the end of the input range
102  * @return Whether or not decoding the bytes resulted in a validation error.
103  */
104  template <typename iterator_type>
105  bool decode (iterator_type begin, iterator_type end) {
106  for (iterator_type it = begin; it != end; ++it) {
107  unsigned int result = utf8_validator::decode(
108  &m_state,
109  &m_codepoint,
110  static_cast<uint8_t>(*it)
111  );
112 
113  if (result == utf8_reject) {
114  return false;
115  }
116  }
117  return true;
118  }
119 
120  /// Return whether the input sequence ended on a valid utf8 codepoint
121  /**
122  * @return Whether or not the input sequence ended on a valid codepoint.
123  */
124  bool complete() {
125  return m_state == utf8_accept;
126  }
127 
128  /// Reset the validator to decode another message
129  void reset() {
130  m_state = utf8_accept;
131  m_codepoint = 0;
132  }
133 private:
134  uint32_t m_state;
135  uint32_t m_codepoint;
136 };
137 
138 /// Validate a UTF8 string
139 /**
140  * convenience function that creates a validator, validates a complete string
141  * and returns the result.
142  */
143 inline bool validate(std::string const & s) {
144  validator v;
145  if (!v.decode(s.begin(),s.end())) {
146  return false;
147  }
148  return v.complete();
149 }
150 
151 } // namespace utf8_validator
152 } // namespace websocketpp
153 
154 #endif // UTF8_VALIDATOR_HPP
bool decode(iterator_type begin, iterator_type end)
Advance validator state with input from an iterator pair.
Provides streaming UTF8 validation functionality.
bool consume(uint8_t byte)
Advance the state of the validator with the next input byte.
void reset()
Reset the validator to decode another message.
void handle_accept(connection_ptr con, lib::error_code const &ec)
Handler callback for start_accept.
bool complete()
Return whether the input sequence ended on a valid utf8 codepoint.
validator()
Construct and initialize the validator.