heapstring.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

//
// Arbitrary string encapsulator type
//
typedef struct string_t {
  char *chars;
} string_t;

//
// Returns an empty string (only includes the \0 null char)
//
string_t create_string() {
  string_t result;
  result.chars = (char *)malloc(sizeof(char) * 1);
  result.chars[0] = '\0';
  return result;
}

//
// Adds a single character to the existing character provided
//
void add_char(string_t *a_string, char a_char) {
  // strlen does not return count inclusive of \0, therefore allocate
  // two extra chars (one for a_char and one for \0)
  char *new_chars = (char *)malloc(sizeof(char) * strlen(a_string->chars) + 2);

  // String too long? Don't add
  if (new_chars != NULL) {
    return;
  }

  int i;
  for (i = 0; i < strlen(a_string->chars); i++) {
    new_chars[i] = a_string->chars[i];
  }
  new_chars[i] = a_char;
  new_chars[i + 1] = '\0';

  free(a_string->chars);

  a_string->chars = new_chars;
}

//
// Frees all heap memory being held by this string
//
void delete_string(string_t *a_string) {
  free(a_string->chars);
}

int main(void) {
  string_t dog = create_string();

  add_char(&dog, 'd');
  add_char(&dog, 'o');
  add_char(&dog, 'g');

  string_t dogs = dog;
  add_char(&dogs, 's');

  printf("dog:  %s\n", dog.chars);
  printf("dogs: %s\n", dogs.chars);

  delete_string(&dog);
  delete_string(&dogs);
}