ref: 6033931b02f9a9bbe33a84f9c777bb8ce9260b2f
dir: /sys/man/2/gio/
.TH GIO 2
.SH NAME
gopen, gclose, gseek, gread, gwrite, fd2gio \- Programmable streams
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.br
.B #include <gio.h>
.PP
.ft L
.nf
typedef 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;
} ReadWriter;
.fi
.PP
.B
int gopen(ReadWriter *r, void *aux)
.PP
.B
int gclose(int gfd)
.PP
.B
vlong gseek(int gfd, vlong offset, int whence)
.PP
.B
long gread(int gfd, void *buf, long nbytes, vlong offset)
.PP
.B
long gwrite(int gfd, void *buf, long nbytes, vlong offset)
.PP
.B
int fd2gio(int fd)
.SH DESCRIPTION
.I gopen
takes a ReadWriter struct and creates a new instance of a gio fd.
.I aux
is an auxillary argument that may or may not be optional depending on how the gio stream is implemented.
.I gclose
closes a gio fd and frees any resources allocated to it.
.I gseek
changes the fd in a similar way to
.IR seek (2).
.I gread
and
.I gwrite
are the gio equivalents to
.IR pread (2)
and
.IR pwrite (2).
They are functionally equivalent and have nearly the same usage.
.I fd2gio
takes a Plan 9 file descriptor and returns a gio descriptor made from that fd.
.SH SOURCE
.B /sys/src/libgio
.SH NOTES
The gio functions automatically lock the ReadWriter struct in use hopefully making things work better with
.IR thread (2).
.SH BUGS
Things get interesting with
.IR rfork (2)
when you disable shared memory.
.br
The file descriptor table is poorly implemented.
.br
You cannot easily mix gio file descriptors with functions that want Plan 9 ones.
.br
.SH SEE ALSO
.IR read (2),
.IR seek (2),
.IR open (2)
.SH DIAGNOSTICS
By default, no. Users can have their methods set
.I errstr,
and
.I gopen,
.I gclose,
.I gread,
and
.I gwrite
will return -2 if a function pointer is nil.
.SH HISTORY
First appeared as part of
.IR ngfs (8)
in September 2015; imported into 9front February 2016.