/* This program uses code from "Algorithms in C, Third Edition,"
 *               by Robert Sedgewick, Addison-Wesley, 1998.
 */

#include <string.h>

/* return the length of string s, i.e., the number of 
 * characters up to and not including the first occurrence of 
 * the NULL character. */
int strlen1(char * s)
{
   int counter = 0;
   while (s[counter] != 0)
   {
      counter++;
   }
   
   return counter;
}

/* copy the contents of source to the target string. */
void strcpy1(char * target, char * source)
{
   int counter = 0;
   while (source[counter] != 0)
   {
      target[counter] = source[counter];
      counter++;
   }
}

/* ASCII-based comparison of the two strings. 
 * Return values:
 * 0, if the two srings have the same contents.
 * less than 0, if the ASCII code of s1 is less than the ASCII code
 *     of s2 at the first position where s1 and s2 differ.
 * greater than 0, if the ASCII code of s1 is greater than the ASCII code
 *     of s2 at the first position where s1 and s2 differ.
 */
int strcmp1_unoptimized(char * s1, char * s2)
{
   int counter = 0;
   while ((s1[counter] != 0) && (s2[counter] != 0))
   {
      if (s1[counter] != s2[counter])
      {
         return s1[counter] - s2[counter];
      }
      counter++;
   }
   
   return s1[counter] - s2[counter];
}

/* ASCII-based comparison of the two strings. 
 * Return values:
 * 0, if the two srings have the same contents.
 * less than 0, if the ASCII code of s1 is less than the ASCII code
 *     of s2 at the first position where s1 and s2 differ.
 * greater than 0, if the ASCII code of s1 is greater than the ASCII code
 *     of s2 at the first position where s1 and s2 differ.
 */
int strcmp1(char * s1, char * s2)
{
   int counter = 0;
   while (s1[counter] != 0)
   {
      if (s1[counter] != s2[counter])
      {
         break;
      }
      counter++;
   }
   
   return s1[counter] - s2[counter];
}

/* ASCII-based comparison of the first N letters of two strings. 
 * Return values:
 * 0, if the two srings have the same contents.
 * less than 0, if the ASCII code of s1 is less than the ASCII code
 *     of s2 at the first position where s1 and s2 differ.
 * greater than 0, if the ASCII code of s1 is greater than the ASCII code
 *     of s2 at the first position where s1 and s2 differ.
 */
int strncmp1(char * s1, char * s2, int N)
{
   int counter;
   for (counter = 0; counter < N; counter++)
   {
      if ((s1[counter] == 0) || (s2[counter] == 0) || (s1[counter] != s2[counter]))
      {
         return s1[counter] - s2[counter];
      }
   }

   return 0;
}


char * strcat1(char * a, char * b)
{
   int a_index = strlen(a);
   int b_index = 0;
   
   while(1)
   {
      char current = b[b_index];
      a[a_index] = current;
      
      if (current == 0)
      {
         break;
      }
      a_index++;
      b_index++;
   }

   return a;
}