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

typedef struct
{
	char *text;
	size_t capacity;
	size_t size;
} String;

void init_string(String *str)
{
	str->text = NULL;
	str->size = 0;
	str->capacity = 0;
}

int init_string_by_literal(String *dest, const char *src)
{
	dest->size = dest->capacity = strlen(src)+1;
	dest->text = (char*)malloc(dest->capacity);
	
	if (dest->text == NULL) {
		init_string(dest);
		
		return 1;
	}
	
	strcpy(dest->text, src);
	
	return 0;
}

void destroy_string(String *str)
{
	free(str->text);
	init_string(str);
}

int append_string(String *dest, String src)
{
	if (src.size == 0) {
		return 0;
	}

	if (dest->text == NULL) {
		dest->text = (char*)malloc(src.capacity);
		strcpy(dest->text, src.text);
		dest->capacity = src.capacity;
		dest->size = src.size;

		return 0;
	}

	dest->size += src.size-1;

	if (dest->size > dest->capacity) {
		do {
			dest->capacity <<= 1;
		} while(dest->capacity < dest->size);

		dest->text = realloc(dest->text, dest->capacity);

		if (dest->text == NULL) {
			return 1;
		}
	}

	strcat(dest->text, src.text);

	return 0;
}

int main()
{
	String s1, s2, s3;
	
	if (init_string_by_literal(&s1, "Pera") != 0) {
		printf("Failed to init s1\n");
		
		return 1;
	}
	
	if (init_string_by_literal(&s2, ", ") != 0) {
		printf("Failed to init s2\n");
		
		return 2;
	}
	
	if (init_string_by_literal(&s3, "Mika") != 0) {
		printf("Failed to init s3\n");
		
		return 3;
	}
	
	if (append_string(&s1, s2) != 0) {
		printf("Failed to append s2 to s1\n");
		
		return 4;
	}
	
	if (append_string(&s1, s3) != 0) {
		printf("Failed to append s3 to s1\n");
		
		return 5;
	}
	
	printf("The resulting string is \"%s\"\n", s1.text);
	destroy_string(&s1);
	destroy_string(&s2);
	destroy_string(&s3);
	
	return 0;
}