+line_t *new_line();
+line_t *next_line(line_t *prev);
+page_t *new_page();
+page_t *next_page(page_t *prev);
+document_t *new_document();
+int is_utf8(char ch);
+int next_nonblank(cstring_t *text, int i);
+int next_blank(cstring_t *text, int i);
+document_t *markdown_load(FILE *input);
+