#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#define LITTLE_BUFFER_SIZE 50
/* safer_strcpy(dest, dest_end, src): copy a string into a buffer
* dest: destination buffer
* dest_end: past-the-end (should be dest + buffer size)
* src: source string
*
* - returns the address of the null terminator on success
* - returns NULL if the buffer is too small
*/
char *
safer_strcpy(char *dest, char *dest_end, const char *src)
{
char c;
do {
if (dest == dest_end) { // Out of space? Bail out
return NULL;
}
c = *src++; // Copy a character
*dest++ = c;
} while (c != '\0'); // Done when we copied NUL
return --dest; // Back up to be on the NUL
}
char*
checked_strcpy(char *dest, char *dest_end, const char *src)
{
char* cp = safer_strcpy(dest, dest_end, src);
if (cp == NULL) {
fprintf(stderr, "Buffer oveflow!\n");
exit(1);
}
}
int main() {
char str1[LITTLE_BUFFER_SIZE] = "Operating"; // Writeable buffer
const char *str2 = "Super Systems"; // Fixed literal
char str3[LITTLE_BUFFER_SIZE];
char *str4;
const char *scp;
char* dcp;
size_t l = strlen(str1);
printf("Length of str1: %zu\n", l);
scp = strstr(str2, " S"); // Find some substring
dcp = checked_strcpy(str1 + l, str1 + LITTLE_BUFFER_SIZE, scp);
dcp = checked_strcpy(dcp, str1 + LITTLE_BUFFER_SIZE, "!!!");
dcp = checked_strcpy(dcp, str1 + LITTLE_BUFFER_SIZE, " -- Awesome.");
printf("Multi-Concatenated string: %s\n", str1);
checked_strcpy(str3, str3 + LITTLE_BUFFER_SIZE, str1);
str3[5] = '\0'; // Shorten the string
printf("First 5 characters: %s\n", str3);
str4 = strdup(str3); // Make a duplicate of str3 on the heap
printf("Duplicated string: %s\n", str4);
free(str4); // Free the heap memory
return 0;
}
