void ds_putchar (struct string *, int ch);
void ds_concat (struct string *, const char *);
void ds_concat_buffer (struct string *, const char *buf, size_t len);
void ds_putchar (struct string *, int ch);
void ds_concat (struct string *, const char *);
void ds_concat_buffer (struct string *, const char *buf, size_t len);