/*
 * Copyright (c) 2002 by Cliff Green. All rights reserved. Individual files
 * may be covered by other copyrights (as noted in the file itself).
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that this entire copyright notice is duplicated in all such
 * copies.
 *
 * This software is provided "as is" and without any expressed or implied
 * warranties, including, without limitation, the implied warranties of
 * merchantibility and fitness for any particular purpose.
*/
//----------------------------------------------------------------------
// Source file:   pal.cpp
// Written by:    Cliff Green, 2002
// Compiler:      Metrowerks CodeWarrior Pro 6, g++ 3.0.4
// History:
//   Modified:    Mar. 5, 2002
//   By:          Cliff Green
//   Comments:    See header file.
//----------------------------------------------------------------------
// This commentheader supports documentation tools such as Doc++ and
// Doxygen: http://www.doxygen.org/
//----------------------------------------------------------------------
/// PalCtr class implementation, performs palindrome detection and counting.
/**
 *  Keeps track of how many palindromes have been detected
 *  by calling the isPalindrome method.
 */

#include "pal.h"

#include <cctype>   // standard C++ header for traditional ctype.h
#include <cstring>  // standard C++ header for traditional string.h

// Note that C library headers with C++ std header names do not work
// consistently in VC++ 5 / 6 - the traditional versions of C library
// headers might need to be used, such as <ctype.h>

// Utility function to count the number of alpha chars in a C string

int strlen_alpha (char const* s) {
   int cnt(0);
   while (*s != '\0') {
      if (std::isalpha(*s)) {
         ++cnt;
      }
      ++s;
   }
   return cnt;
}

// Note pre-condition documentation in header file

bool PalCtr::isPalindrome (char const* begPtr) {

   if (strlen_alpha(begPtr) < 1) { // sanitize the input
      return false;
   }
// At this point nothing will blow up inside this function. Also
// note the char const type safety, and the C++ style of variable
// initialization.

   // Compute beginning and end pointers
   char const* endPtr (begPtr + std::strlen(begPtr) - 1);
   while (begPtr < endPtr) {
      if (!std::isalpha(*begPtr)) {
         ++begPtr;
         continue;
      }
      if (!std::isalpha(*endPtr)) {
         --endPtr;
         continue;
      }
      if (std::toupper(*begPtr) != std::toupper(*endPtr)) {
         return false;
      }
      ++begPtr;
      --endPtr;
   }
   ++ mCnt;
   return true;
}