typedef struct{
	int nSize;
	int nMaxCapacity;
	char* szStr;
} StringBuilder;

StringBuilder* Initialize(int nCapacity);
void Append(StringBuilder *strBuilder, char* szStr);
void Clear(StringBuilder *strBuilder);

int _tmain(int argc, _TCHAR* argv[])
{
	StringBuilder* strBuilder = Initialize(1);
	Append(strBuilder, "I'm the string! :)\0");
	printf("%s", strBuilder);
	Clear(strBuilder);

	getchar();

	return 0;
}

StringBuilder* Initialize(int nCapacity)
{
	StringBuilder* strBuilder = (StringBuilder*)malloc(sizeof(StringBuilder));
	strBuilder->nMaxCapacity = nCapacity;
	strBuilder->nSize = 0;
	strBuilder->szStr = (char*)malloc(1);
	strBuilder->szStr = "\0";

	return strBuilder;
}

void Clear(StringBuilder *strBuilder)
{
	if(strBuilder != NULL)
		free(strBuilder);
}

void Append(StringBuilder *strBuilder, char* szStr)
{
	if(strBuilder->nSize + strlen(szStr) > strBuilder->nMaxCapacity)
		if((strBuilder->nMaxCapacity * 2) <= 2147483647)
		{
			strBuilder = (StringBuilder*)realloc(strBuilder, (strBuilder->nMaxCapacity * 2));
			strBuilder->nMaxCapacity = strBuilder->nMaxCapacity * 2;
		}
		else
			return; // overflow
	else
		strBuilder = (StringBuilder*)realloc(strBuilder, strBuilder->nSize + strlen(szStr));

	strBuilder->nSize += strlen(szStr);
	strBuilder->szStr = (char*)realloc(strBuilder->szStr, strBuilder->nSize + 2);

	strcat(strBuilder->szStr, szStr);
}