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<head>
<title>ioproc(3) - Plan 9 from User Space</title>
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<tr><td width=20><td>
<tr><td width=20><td><b>IOPROC(3)</b><td align=right><b>IOPROC(3)</b>
<tr><td width=20><td colspan=2>
<br>
<p><font size=+1><b>NAME </b></font><br>
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closeioproc, iocall, ioclose, iointerrupt, iodial, ioopen, ioproc,
ioread, ioread9pmsg, ioreadn, iorecvfd, iosendfd, iosleep, iowrite
– slave I/O processes for threaded programs<br>
</table>
<p><font size=+1><b>SYNOPSIS </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>#include <u.h><br>
#include <libc.h><br>
#include <thread.h><br>
typedef struct Ioproc Ioproc;<br>
Ioproc* ioproc(void);<br>
int ioclose(Ioproc *io, int fd);<br>
int iodial(Ioproc *io, char *addr, char *local, char *dir, char
*cdfp);<br>
int ioopen(Ioproc *io, char *file, int omode);<br>
long ioread(Ioproc *io, int fd, void *a, long n);<br>
int ioread9pmsg(Ioproc *io, int fd, void *a, uint n);<br>
long ioreadn(Ioproc *io, int fd, void *a, long n);<br>
int iorecvfd(int socket);<br>
int iosendfd(int socket, int fd);<br>
int iosleep(int milli);<br>
long iowrite(Ioproc *io, int fd, void *a, long n);<br>
void iointerrupt(Ioproc *io);<br>
void closeioproc(Ioproc *io);<br>
long iocall(Ioproc *io, long (*op)(va_list *arg), ...);<br>
</font></tt>
</table>
<p><font size=+1><b>DESCRIPTION </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
These routines provide access to I/O in slave procs. Since the
I/O itself is done in a slave proc, other threads in the calling
proc can run while the calling thread waits for the I/O to complete.
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<i>Ioproc</i> forks a new slave proc and returns a pointer to the <tt><font size=+1>Ioproc</font></tt>
associated with it. <i>Ioproc</i> uses <i>mallocz</i> and <i>proccreate</i>; if either
fails, it calls <i>sysfatal</i> rather than return an error.
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<i>Ioclose</i>, <i>iodial</i>, <i>ioopen</i>, <i>ioread</i>, <i>ioread9pmsg</i>, <i>ioreadn</i>, <i>iorecvfd</i>,
<i>iosendfd</i>, <i>iosleep</i>, and <i>iowrite</i> execute the similarly named library
or system calls (see <a href="../man2/close.html"><i>close</i>(2)</a>, <a href="../man3/dial.html"><i>dial</i>(3)</a>, <a href="../man3/open.html"><i>open</i>(3)</a>, <a href="../man3/read.html"><i>read</i>(3)</a>, <a href="../man3/fcall.html"><i>fcall</i>(3)</a>,
<a href="../man3/sendfd.html"><i>sendfd</i>(3)</a>, and <a href="../man3/sleep.html"><i>sleep</i>(3)</a>) in the slave process associated with
<i>io</i>. It is an error to execute more than one call at a time in
an I/O
proc.
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<i>Iointerrupt</i> interrupts the call currently executing in the I/O
proc. If no call is executing, <i>iointerrupt</i> is a no-op.
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<i>Closeioproc</i> terminates the I/O proc and frees the associated <tt><font size=+1>Ioproc
.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
</font></tt>
<i>Iocall</i> is a primitive that may be used to implement more slave
I/O routines. <i>Iocall</i> arranges for <i>op</i> to be called in <i>io</i>’s proc,
with <i>arg</i> set to the variable parameter list, returning the value
that <i>op</i> returns.<br>
</table>
<p><font size=+1><b>EXAMPLE </b></font><br>
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Relay messages between two file descriptors, counting the total
number of bytes seen:<br>
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<tt><font size=+1>int tot;<br>
void<br>
relaythread(void *v)<br>
{<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
int *fd, n;<br>
char buf[1024];<br>
Ioproc *io;<br>
fd = v;<br>
io = ioproc();<br>
while((n = ioread(io, fd[0], buf, sizeof buf)) > 0){<br>
if(iowrite(io, fd[1], buf, n) != n)<br>
sysfatal("iowrite: %r");<br>
tot += n;<br>
}<br>
closeioproc(io);<br>
</table>
}<br>
void<br>
relay(int fd0, int fd1)<br>
{<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
int fd[4];<br>
fd[0] = fd[3] = fd0;<br>
fd[1] = fd[2] = fd1;<br>
threadcreate(relaythread, fd, 8192);<br>
threadcreate(relaythread, fd+2, 8192);<br>
</table>
}<br>
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</font></tt>
</table>
If the two <i>relaythread</i> instances were running in different procs,
the common access to <i>tot</i> would be unsafe.
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Implement <i>ioread</i>:<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>static long<br>
_ioread(va_list *arg)<br>
{<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
int fd;<br>
void *a;<br>
long n;<br>
fd = va_arg(*arg, int);<br>
a = va_arg(*arg, void*);<br>
n = va_arg(*arg, long);<br>
return read(fd, a, n);<br>
</table>
}<br>
long<br>
ioread(Ioproc *io, int fd, void *a, long n)<br>
{<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
return iocall(io, _ioread, fd, a, n);<br>
</table>
}<br>
</font></tt>
</table>
</table>
<p><font size=+1><b>SOURCE </b></font><br>
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<tt><font size=+1>/usr/local/plan9/src/libthread<br>
</font></tt>
</table>
<p><font size=+1><b>SEE ALSO </b></font><br>
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<a href="../man3/dial.html"><i>dial</i>(3)</a>, <a href="../man3/open.html"><i>open</i>(3)</a>, <a href="../man3/read.html"><i>read</i>(3)</a>, <a href="../man3/thread.html"><i>thread</i>(3)</a><br>
</table>
<p><font size=+1><b>BUGS </b></font><br>
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<i>Iointerrupt</i> is currently unimplemented.<br>
</table>
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