text: ///////////////////////////////////////////////////////////////////////
  // File:        unichar.h
  // Description: Unicode character/ligature class.
  // Author:      Ray Smith
  // Created:     Wed Jun 28 17:05:01 PDT 2006
  //
  // (C) Copyright 2006, Google Inc.
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  // http://www.apache.org/licenses/LICENSE-2.0
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  //
  ///////////////////////////////////////////////////////////////////////
  
  #ifndef TESSERACT_CCUTIL_UNICHAR_H__
  #define TESSERACT_CCUTIL_UNICHAR_H__
  
  #include <memory.h>
  #include <string.h>
  
  // Maximum number of characters that can be stored in a UNICHAR. Must be
  // at least 4. Must not exceed 31 without changing the coding of length.
  #define UNICHAR_LEN 30
  
  // A UNICHAR_ID is the unique id of a unichar.
  typedef int UNICHAR_ID;
  
  // A variable to indicate an invalid or uninitialized unichar id.
  static const int INVALID_UNICHAR_ID = -1;
  // A special unichar that corresponds to INVALID_UNICHAR_ID.
  static const char INVALID_UNICHAR[] = "__INVALID_UNICHAR__";
  
  enum StrongScriptDirection {
    DIR_NEUTRAL = 0,        // Text contains only neutral characters.
    DIR_LEFT_TO_RIGHT = 1,  // Text contains no Right-to-Left characters.
    DIR_RIGHT_TO_LEFT = 2,  // Text contains no Left-to-Right characters.
    DIR_MIX = 3,            // Text contains a mixture of left-to-right
                            // and right-to-left characters.
  };
  
  // The UNICHAR class holds a single classification result. This may be
  // a single Unicode character (stored as between 1 and 4 utf8 bytes) or
  // multple Unicode characters representing the NFKC expansion of a ligature
  // such as fi, ffl etc. These are also stored as utf8.
  class UNICHAR {
   public:
    UNICHAR() {
      memset(chars, 0, UNICHAR_LEN);
    }
  
    // Construct from a utf8 string. If len<0 then the string is null terminated.
    // If the string is too long to fit in the UNICHAR then it takes only what
    // will fit.
    UNICHAR(const char* utf8_str, int len);
  
    // Construct from a single UCS4 character.
    explicit UNICHAR(int unicode);
  
    // Default copy constructor and operator= are OK.
  
    // Get the first character as UCS-4.
    int first_uni() const;
  
    // Get the length of the UTF8 string.
    int utf8_len() const {
      int len = chars[UNICHAR_LEN - 1];
      return len >=0 && len < UNICHAR_LEN ? len : UNICHAR_LEN;
    }
  
    // Get a UTF8 string, but NOT NULL terminated.
    const char* utf8() const {
      return chars;
    }
  
    // Get a terminated UTF8 string: Must delete[] it after use.
    char* utf8_str() const;
  
    // Get the number of bytes in the first character of the given utf8 string.
    static int utf8_step(const char* utf8_str);
  
   private:
    // A UTF-8 representation of 1 or more Unicode characters.
    // The last element (chars[UNICHAR_LEN - 1]) is a length if
    // its value < UNICHAR_LEN, otherwise it is a genuine character.
    char chars[UNICHAR_LEN];
  };
  
  #endif  // TESSERACT_CCUTIL_UNICHAR_H__
  