fuse_bufvec
int (*write_buf) (const char *, struct fuse_bufvec *buf, off_t off,
int (*read_buf) (const char *, struct fuse_bufvec **bufp,
struct fuse_bufvec **bufp, size_t size, off_t off,
struct fuse_bufvec *buf, off_t off,
((struct fuse_bufvec) { \
size_t fuse_buf_size(const struct fuse_bufvec *bufv);
ssize_t fuse_buf_copy(struct fuse_bufvec *dst, struct fuse_bufvec *src,
int fuse_reply_data(fuse_req_t req, struct fuse_bufvec *bufv,
off_t offset, struct fuse_bufvec *bufv,
struct fuse_bufvec *bufv, off_t off,
off_t offset, struct fuse_bufvec *bufv);