1 /////////////////////////////////////////////////////////////////////// 2 // 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 // 17 /////////////////////////////////////////////////////////////////////// 18 19 #ifndef TESSERACT_CCUTIL_UNICHAR_H_ 20 #define TESSERACT_CCUTIL_UNICHAR_H_ 21 22 #include "export.h" 23 24 #include <memory.h> 25 #include <cstring> 26 #include <string> 27 #include <vector> 28 29 namespace tesseract { 30 31 // Maximum number of characters that can be stored in a UNICHAR. Must be 32 // at least 4. Must not exceed 31 without changing the coding of length. 33 #define UNICHAR_LEN 30 34 35 // A UNICHAR_ID is the unique id of a unichar. 36 using UNICHAR_ID = int; 37 38 // A variable to indicate an invalid or uninitialized unichar id. 39 static const int INVALID_UNICHAR_ID = -1; 40 // A special unichar that corresponds to INVALID_UNICHAR_ID. 41 static const char INVALID_UNICHAR[] = "__INVALID_UNICHAR__"; 42 43 enum StrongScriptDirection { 44 DIR_NEUTRAL = 0, // Text contains only neutral characters. 45 DIR_LEFT_TO_RIGHT = 1, // Text contains no Right-to-Left characters. 46 DIR_RIGHT_TO_LEFT = 2, // Text contains no Left-to-Right characters. 47 DIR_MIX = 3, // Text contains a mixture of left-to-right 48 // and right-to-left characters. 49 }; 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 TESS_API UNICHAR { 58 public: UNICHAR()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. utf8_len()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. utf8()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 // } 107 class TESS_API const_iterator { 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. 115 const_iterator &operator++(); 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. utf8_data()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; const_iterator(const char * it)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_ 177