+char *base64encode(char *data, size_t datalen);
+char *base64decode(char *data, size_t *datalen);
+int hexdigit(char c);
+int bbtreedel(struct btree **tree, void *item, int (*cmp)(void *, void *));
+void freebtree(struct btree **tree, void (*ffunc)(void *));
+int bbtreeput(struct btree **tree, void *item, int (*cmp)(void *, void *));
+void *btreeget(struct btree *tree, void *key, int (*cmp)(void *, void *));
+FILE *funstdio(void *pdata,
+ ssize_t (*read)(void *pdata, void *buf, size_t len),
+ ssize_t (*write)(void *pdata, const void *buf, size_t len),
+ off_t (*seek)(void *pdata, off_t offset, int whence),
+ int (*close)(void *pdata));