libgio -- Programmable Virtual Files or Streams Synopsis	libgio is a small library to approximate Go's io.Reader and	io.Writer interfaces, Common Lisp's grey-streams, and OpenVMS's	programmable I/O. libgio takes a struct with the methods to read	or write to the stream, open and close the stream, and some other	stuff, and returns a libgio file descriptor. You can then use this	descriptor to read, write, seek, open, and close the stream. Note	that these are not normal file descriptors, but they look like it,	and basically feel like it. libgio is, by default, thread safe and	locks the ReadWriter struct on every operation. As a user of	libgio you shouldn't need to add any locks in your methods unless	those functions need to keep some other data safe. History	libgio was initially implemented as part of ngfs's volume manager	to allow most operations be able to happen on disk, mirror, span,	p1p, and p2p devices. This reduced the amount of code that needed	to be written and made sure that all features could work no matter	the vdev. This also made adding vdev types much easier because you	didn't have to edit much code. The difference between libgio and	gio.c in ngfs is the libgio lengths and offsets are bytes while	gio.c's are blocks. Bugs	yes. -------------------------------------------------------------------------- Usage struct ReadWriter {	RWLock; int (*open)(ReadWriter*); int (*close)(ReadWriter*); long	(*pread)(ReadWriter*, void*, long, vlong); long	(*pwrite)(ReadWriter*, void*, long, vlong); void *aux; u64int	offset; u64int length;}; int gopen(ReadWriter*, void *aux)	This function takes a ReadWriter struct and auxillary data, and	creates a gio file descriptor. int gclose(int gio_fd)	This destroys the gio file descriptor. long gread(int gio_fd, void *buf, long len, vlong off)	This is functionally the same as pread, but operates on a gio fd. long gwrite(int gio_fd, void *buf, long len, vlong off)	This is functionally the same as pwrite, but operates on a gio fd. vlong gseek(int gio_fd, vlong off, int whence)	This is functionally the same as seek but operates on a gio fd. int fd2gio(int fd)	This takes a system fd and returns a gio fd.