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NAME
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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
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SYNOPSIS
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#include <u.h>
#include <libc.h>
#include <thread.h>
typedef struct Ioproc Ioproc;
Ioproc* ioproc(void);
int ioclose(Ioproc *io, int fd);
int iodial(Ioproc *io, char *addr, char *local, char *dir, char
*cdfp);
int ioopen(Ioproc *io, char *file, int omode);
long ioread(Ioproc *io, int fd, void *a, long n);
int ioread9pmsg(Ioproc *io, int fd, void *a, uint n);
long ioreadn(Ioproc *io, int fd, void *a, long n);
int iorecvfd(Ioproc *io, int socket);
int iosendfd(Ioproc *io, int socket, int fd);
int iosleep(Ioproc *io, long milli);
long iowrite(Ioproc *io, int fd, void *a, long n);
void iointerrupt(Ioproc *io);
void closeioproc(Ioproc *io);
long iocall(Ioproc *io, long (*op)(va_list *arg), ...);
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DESCRIPTION
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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.
Ioproc forks a new slave proc and returns a pointer to the Ioproc
associated with it. Ioproc uses mallocz and proccreate; if either
fails, it calls sysfatal rather than return an error.
Ioclose, iodial, ioopen, ioread, ioread9pmsg, ioreadn, iorecvfd,
iosendfd, iosleep, and iowrite execute the similarly named library
or system calls (see close(2), dial(3), open(3), read(3), fcall(3),
sendfd(3), and sleep(3)) in the slave process associated with
io. It is an error to execute more than one call at a time in
an I/O proc.
Iointerrupt interrupts the call currently executing in the I/O
proc. If no call is executing, iointerrupt is a no-op.
Closeioproc terminates the I/O proc and frees the associated Ioproc
.
Iocall is a primitive that may be used to implement more slave
I/O routines. Iocall arranges for op to be called in io’s proc,
with arg set to the variable parameter list, returning the value
that op returns.
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EXAMPLE
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Relay messages between two file descriptors, counting the total
number of bytes seen:
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int tot;
void
relaythread(void *v)
{
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int *fd, n;
char buf[1024];
Ioproc *io;
fd = v;
io = ioproc();
while((n = ioread(io, fd[0], buf, sizeof buf)) > 0){
if(iowrite(io, fd[1], buf, n) != n)
sysfatal("iowrite: %r");
tot += n;
}
closeioproc(io);
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}
void
relay(int fd0, int fd1)
{
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int fd[4];
fd[0] = fd[3] = fd0;
fd[1] = fd[2] = fd1;
threadcreate(relaythread, fd, 8192);
threadcreate(relaythread, fd+2, 8192);
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}
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The two relaythread instances are running in the same proc, so
the common access to tot is safe.
Implement ioread:
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static long
_ioread(va_list *arg)
{
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int fd;
void *a;
long n;
fd = va_arg(*arg, int);
a = va_arg(*arg, void*);
n = va_arg(*arg, long);
return read(fd, a, n);
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}
long
ioread(Ioproc *io, int fd, void *a, long n)
{
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return iocall(io, _ioread, fd, a, n);
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}
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SOURCE
SEE ALSO
BUGS
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Iointerrupt is currently unimplemented.
C99 disallows the use of pointers to va_list. This interface will
have to change to use pointers to a structure containing a va_list.
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