ex_5-5.c

   1 #include <string.h>
   2 #include <stdio.h>
   3
   4 /* print contents of array */
   5 void print_array(char s[])
   6 {
   7         int i;
   8         for(i = 0; i < strlen(s); i++)
   9                 printf("%c", s[i]);
  10         printf("\n");
  11 }
  12
  13 /*
  14
  15 Copy at most n chars of string source into string dest.
  16 Pad with '\0' if source has fewer chars than dest.
  17
  18 */
  19 char *ss_strncpy(char *dest, const char *source, int n)
  20 {
  21         char *d = dest;
  22         if(n >= 0 || n == '\0')
  23         {
  24                 while(--n >= 0 && (*dest++ = *source++) != '\0')
  25                         continue;
  26                 while(--n > 0)
  27                         *dest++ = '\0';
  28         }
  29
  30         return d;
  31 }
  32
  33 /*
  34
  35 Appends n chars of src into the end of dest.
  36
  37 If null encountered before n, then copy null and no more.
  38
  39 If n is zero or negative, then function has not effect.
  40
  41 */
  42 char *ss_strncat(char *dest, const char *source, size_t n)
  43 {
  44         while(*dest) { ++dest; } // find pointer val for end of string s
  45         while((--n >= 0) && (*dest++ = *source++) != '\0');
  46         return dest;
  47 }
  48
  49 /*
  50
  51 Compares contents of string s1 with contents of s2.
  52
  53 If s1 < s2 returns < 0
  54 If s1 == s2 returns 0
  55 If s1 > s2 returns > 0
  56
  57 */
  58 int ss_strncmp(const char *s1, const char *s2, size_t n)
  59 {
  60
  61         while(--n >= 0 && *s1 != '\0' && *s2 != '\0')
  62         {
  63
  64                 if(*s1++ == *s2++) { continue; }
  65                 if(*s1 > *s2)
  66                         return 1;
  67                 else
  68                         return -1;
  69         }
  70         return 0;
  71 }
  72
  73 int main()
  74 {
  75         char source[] = { "Destination after..." };
  76         char dest[] = { "This is the destination before..." };
  77
  78         print_array(dest);
  79
  80         char *ans;
  81
  82         ans = strncpy(dest, source, 20);
  83
  84         printf("%p\n", ans);
  85         print_array(dest);
  86
  87         printf("\n\n");
  88
  89         char source2[] = { "Destination after..." };
  90         char dest2[] = { "This is the destination before..." };
  91
  92         print_array(dest2);
  93
  94         ss_strncpy(dest2, source2, 20);
  95
  96         printf("%p\n", ans);
  97         print_array(dest2);
  98
  99         char info[] = { "Data To Append. " };
 100         char buffer[50] = { "Beginning of Buffer. " };
 101         int i;
 102         for(i = 0; i <= 2; ++i)
 103         {
 104                 strncat(buffer, info, strlen(info));
 105                 print_array(buffer);
 106         }
 107
 108         printf("\n");
 109
 110         char smaller[] = { "12345" };
 111         char bigger[] = { "67890" };
 112         int size_ans;
 113
 114         size_ans = ss_strncmp(smaller, bigger, 3);
 115         printf("%d\n", size_ans);
 116
 117         size_ans = ss_strncmp(bigger, bigger, 3);
 118         printf("%d\n", size_ans);
 119
 120         size_ans = ss_strncmp(bigger, smaller, 3);
 121         printf("%d\n", size_ans);
 122
 123         return 1;
 124 }