TH READV 2
SH NAME
readv, writev, preadv, pwritev \- scatter/gather read and write
SH SYNOPSIS
B #include <u.h>
br
B #include <libc.h>
PP
nf
ft L
typedef
struct IOchunk
{
void *addr;
ulong len;
} IOchunk;
fi
PP
B
long readv(int fd, IOchunk *io, int nio)
PP
B
long preadv(int fd, IOchunk *io, int nio, vlong off)
PP
B
long writev(int fd, IOchunk *io, int nio)
PP
B
long pwritev(int fd, IOchunk *io, int nio, vlong off)
SH DESCRIPTION
These functions supplement the standard read and write operations of
IR read (2)
with facilities for scatter/gather I/O.
The set of I/O buffers is collected into an array of
B IOchunk
structures passed as an argument.
PP
I Readv
reads data from
I fd
and returns the total number of bytes received.
The received data is stored in the successive
I nio
elements of the
B IOchunk
array, storing
IB io [0].len
bytes at
IB io [0].addr\f1,
the next
IB io [1].len
at
IB io [1].addr\f1,
and so on.
I Preadv
does the same, but implicitly seeks to I/O offset
I off
by analogy with
IR readv .
PP
I Writev
and
I pwritev
are the analogous write routines.
SH SOURCE
B /sys/src/libc/9sys/readv.c
br
B /sys/src/libc/9sys/writev.c
SH SEE ALSO
IR intro (2),
IR read (2)
SH DIAGNOSTICS
These functions set
IR errstr .
SH BUGS
The implementations use
IR malloc (2)
to build a single buffer for a standard call to
B read
or
BR write .
They are placeholders for possible future system calls.
