tesseract  4.1.1
unichar.h
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1 // File: unichar.h
3 // Description: Unicode character/ligature class.
4 // Author: Ray Smith
5 //
6 // (C) Copyright 2006, Google Inc.
7 // Licensed under the Apache License, Version 2.0 (the "License");
8 // you may not use this file except in compliance with the License.
9 // You may obtain a copy of the License at
10 // http://www.apache.org/licenses/LICENSE-2.0
11 // Unless required by applicable law or agreed to in writing, software
12 // distributed under the License is distributed on an "AS IS" BASIS,
13 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 // See the License for the specific language governing permissions and
15 // limitations under the License.
16 //
18 
19 #ifndef TESSERACT_CCUTIL_UNICHAR_H_
20 #define TESSERACT_CCUTIL_UNICHAR_H_
21 
22 #include <memory.h>
23 #include <cstring>
24 #include <string>
25 #include <vector>
26 #include "platform.h"
27 
28 // Maximum number of characters that can be stored in a UNICHAR. Must be
29 // at least 4. Must not exceed 31 without changing the coding of length.
30 #define UNICHAR_LEN 30
31 
32 // TODO(rays) Move these to the tesseract namespace.
33 // A UNICHAR_ID is the unique id of a unichar.
34 using UNICHAR_ID = int;
35 
36 // A variable to indicate an invalid or uninitialized unichar id.
37 static const int INVALID_UNICHAR_ID = -1;
38 // A special unichar that corresponds to INVALID_UNICHAR_ID.
39 static const char INVALID_UNICHAR[] = "__INVALID_UNICHAR__";
40 
42  DIR_NEUTRAL = 0, // Text contains only neutral characters.
43  DIR_LEFT_TO_RIGHT = 1, // Text contains no Right-to-Left characters.
44  DIR_RIGHT_TO_LEFT = 2, // Text contains no Left-to-Right characters.
45  DIR_MIX = 3, // Text contains a mixture of left-to-right
46  // and right-to-left characters.
47 };
48 
49 namespace tesseract {
50 
51 using char32 = signed int;
52 
53 // The UNICHAR class holds a single classification result. This may be
54 // a single Unicode character (stored as between 1 and 4 utf8 bytes) or
55 // multiple Unicode characters representing the NFKC expansion of a ligature
56 // such as fi, ffl etc. These are also stored as utf8.
57 class UNICHAR {
58  public:
59  UNICHAR() {
60  memset(chars, 0, UNICHAR_LEN);
61  }
62 
63  // Construct from a utf8 string. If len<0 then the string is null terminated.
64  // If the string is too long to fit in the UNICHAR then it takes only what
65  // will fit.
66  UNICHAR(const char* utf8_str, int len);
67 
68  // Construct from a single UCS4 character.
69  explicit UNICHAR(int unicode);
70 
71  // Default copy constructor and operator= are OK.
72 
73  // Get the first character as UCS-4.
74  int first_uni() const;
75 
76  // Get the length of the UTF8 string.
77  int utf8_len() const {
78  int len = chars[UNICHAR_LEN - 1];
79  return len >= 0 && len < UNICHAR_LEN ? len : UNICHAR_LEN;
80  }
81 
82  // Get a UTF8 string, but NOT nullptr terminated.
83  const char* utf8() const {
84  return chars;
85  }
86 
87  // Get a terminated UTF8 string: Must delete[] it after use.
88  char* utf8_str() const;
89 
90  // Get the number of bytes in the first character of the given utf8 string.
91  static int utf8_step(const char* utf8_str);
92 
93  // A class to simplify iterating over and accessing elements of a UTF8
94  // string. Note that unlike the UNICHAR class, const_iterator does NOT COPY or
95  // take ownership of the underlying byte array. It also does not permit
96  // modification of the array (as the name suggests).
97  //
98  // Example:
99  // for (UNICHAR::const_iterator it = UNICHAR::begin(str, str_len);
100  // it != UNICHAR::end(str, len);
101  // ++it) {
102  // tprintf("UCS-4 symbol code = %d\n", *it);
103  // char buf[5];
104  // int char_len = it.get_utf8(buf); buf[char_len] = '\0';
105  // tprintf("Char = %s\n", buf);
106  // }
108  using CI = const_iterator;
109 
110  public:
111  // Step to the next UTF8 character.
112  // If the current position is at an illegal UTF8 character, then print an
113  // error message and step by one byte. If the current position is at a
114  // nullptr value, don't step past it.
116 
117  // Return the UCS-4 value at the current position.
118  // If the current position is at an illegal UTF8 value, return a single
119  // space character.
120  int operator*() const;
121 
122  // Store the UTF-8 encoding of the current codepoint into buf, which must be
123  // at least 4 bytes long. Return the number of bytes written.
124  // If the current position is at an illegal UTF8 value, writes a single
125  // space character and returns 1.
126  // Note that this method does not null-terminate the buffer.
127  int get_utf8(char* buf) const;
128  // Returns the number of bytes of the current codepoint. Returns 1 if the
129  // current position is at an illegal UTF8 value.
130  int utf8_len() const;
131  // Returns true if the UTF-8 encoding at the current position is legal.
132  bool is_legal() const;
133 
134  // Return the pointer into the string at the current position.
135  const char* utf8_data() const {
136  return it_;
137  }
138 
139  // Iterator equality operators.
140  friend bool operator==(const CI& lhs, const CI& rhs) {
141  return lhs.it_ == rhs.it_;
142  }
143  friend bool operator!=(const CI& lhs, const CI& rhs) {
144  return !(lhs == rhs);
145  }
146 
147  private:
148  friend class UNICHAR;
149  explicit const_iterator(const char* it) : it_(it) {}
150 
151  const char* it_; // Pointer into the string.
152  };
153 
154  // Create a start/end iterator pointing to a string. Note that these methods
155  // are static and do NOT create a copy or take ownership of the underlying
156  // array.
157  static const_iterator begin(const char* utf8_str, int byte_length);
158  static const_iterator end(const char* utf8_str, int byte_length);
159 
160  // Converts a utf-8 string to a vector of unicodes.
161  // Returns an empty vector if the input contains invalid UTF-8.
162  static std::vector<char32> UTF8ToUTF32(const char* utf8_str);
163  // Converts a vector of unicodes to a utf8 string.
164  // Returns an empty string if the input contains an invalid unicode.
165  static std::string UTF32ToUTF8(const std::vector<char32>& str32);
166 
167  private:
168  // A UTF-8 representation of 1 or more Unicode characters.
169  // The last element (chars[UNICHAR_LEN - 1]) is a length if
170  // its value < UNICHAR_LEN, otherwise it is a genuine character.
171  char chars[UNICHAR_LEN]{};
172 };
173 
174 } // namespace tesseract
175 
176 #endif // TESSERACT_CCUTIL_UNICHAR_H_
tesseract::UNICHAR::const_iterator::operator!=
friend bool operator!=(const CI &lhs, const CI &rhs)
Definition: unichar.h:143
tesseract::UNICHAR::const_iterator::get_utf8
int get_utf8(char *buf) const
Definition: unichar.cpp:178
tesseract::UNICHAR::UTF8ToUTF32
static std::vector< char32 > UTF8ToUTF32(const char *utf8_str)
Definition: unichar.cpp:215
tesseract::UNICHAR::utf8
const char * utf8() const
Definition: unichar.h:83
tesseract::UNICHAR::const_iterator
Definition: unichar.h:107
tesseract::UNICHAR::const_iterator::utf8_data
const char * utf8_data() const
Definition: unichar.h:135
tesseract
Definition: altorenderer.cpp:25
tesseract::UNICHAR::UNICHAR
UNICHAR()
Definition: unichar.h:59
DIR_LEFT_TO_RIGHT
@ DIR_LEFT_TO_RIGHT
Definition: unichar.h:43
tesseract::UNICHAR::begin
static const_iterator begin(const char *utf8_str, int byte_length)
Definition: unichar.cpp:204
UNICHAR_ID
int UNICHAR_ID
Definition: unichar.h:34
tesseract::UNICHAR::first_uni
int first_uni() const
Definition: unichar.cpp:98
tesseract::UNICHAR
Definition: unichar.h:57
tesseract::char32
signed int char32
Definition: unichar.h:51
tesseract::UNICHAR::const_iterator::utf8_len
int utf8_len() const
Definition: unichar.cpp:190
tesseract::UNICHAR::const_iterator::operator*
int operator*() const
Definition: unichar.cpp:167
tesstrain_utils.int
int
Definition: tesstrain_utils.py:154
tesseract::UNICHAR::utf8_str
char * utf8_str() const
Definition: unichar.cpp:129
tesseract::UNICHAR::UTF32ToUTF8
static std::string UTF32ToUTF8(const std::vector< char32 > &str32)
Definition: unichar.cpp:232
StrongScriptDirection
StrongScriptDirection
Definition: unichar.h:41
UNICHAR_LEN
#define UNICHAR_LEN
Definition: unichar.h:30
DIR_RIGHT_TO_LEFT
@ DIR_RIGHT_TO_LEFT
Definition: unichar.h:44
DIR_NEUTRAL
@ DIR_NEUTRAL
Definition: unichar.h:42
tesseract::UNICHAR::const_iterator::operator++
const_iterator & operator++()
Definition: unichar.cpp:153
tesseract::UNICHAR::const_iterator::is_legal
bool is_legal() const
Definition: unichar.cpp:200
tesseract::UNICHAR::utf8_len
int utf8_len() const
Definition: unichar.h:77
DIR_MIX
@ DIR_MIX
Definition: unichar.h:45
tesseract::UNICHAR::end
static const_iterator end(const char *utf8_str, int byte_length)
Definition: unichar.cpp:208
tesseract::UNICHAR::utf8_step
static int utf8_step(const char *utf8_str)
Definition: unichar.cpp:138
tesseract::UNICHAR::const_iterator::operator==
friend bool operator==(const CI &lhs, const CI &rhs)
Definition: unichar.h:140
platform.h