Implementation of dynamic strings in C.

char s[] = "test";
// typedef "str" used to mark dynamic string
str j = str_new(s);

// get length of string (stored in int-sized header appended to char pointer)
int len = str_len(j);

// copy string
str cpy = str_cpy(j);

// concatenate string
str j1 = str_new("test");
// must reassign pointer
j = str_cat(j, j1);

printf("The new string is \"%s\"\n", j); // will print "testtest"

// erase characters between [0..3] inclusive
j = str_cut(j, 0, 4);

// get substring between [4..7] inclusive
str sub = str_sub(j, 4, 8);