ref: 20a1d2268d69a0bbe66d0f21999649133878377c
dir: /sys/man/2/ioproc/
.TH IOPROC 2 .SH NAME closeioproc, iocall, ioclose, ioflush, iointerrupt, iodial, ioopen, ioproc, ioread, ioreadn, iosleep, iowrite \- slave I/O processes for threaded programs .SH SYNOPSIS .PP .de XX .ift .sp 0.5 .ifn .sp .. .EX .ta \w'Ioproc* 'u #include <u.h> #include <libc.h> #include <thread.h> .sp typedef struct Ioproc Ioproc; .sp Ioproc* ioproc(void); .XX int ioopen(Ioproc *io, char *file, int omode); int ioclose(Ioproc *io, int fd); long ioread(Ioproc *io, int fd, void *a, long n); long ioreadn(Ioproc *io, int fd, void *a, long n); long iowrite(Ioproc *io, int fd, void *a, long n); int iodial(Ioproc *io, char *addr, char *local, char *dir, int *cdfp); int iosleep(Ioproc *io, long n); .XX int ioflush(Ioproc *io); void iointerrupt(Ioproc *io); void closeioproc(Ioproc *io); .XX long iocall(Ioproc *io, long (*op)(va_list *arg), ...); .EE .SH DESCRIPTION .PP 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. .PP .I Ioproc forks a new slave proc and returns a pointer to the .B Ioproc associated with it. .I Ioproc uses .I mallocz and .IR proccreate ; if either fails, it calls .I sysfatal rather than return an error. .PP .IR Ioopen , .IR ioclose , .IR ioread , .IR ioreadn , .IR iowrite , .IR iosleep , and .IR iodial execute the similarly named library or system calls (see .IR open (2), .IR read (2), and .IR dial (2)) in the slave process associated with .IR io . .PP .I Iointerrupt interrupts the next or currently executing call in the I/O proc. If there was no call executing, the interrupt will stay pending and the next I/O call will get interrupted. .PP .I Ioflush executes a non-op in the I/O proc. It is commonly called after .IR iointerrupt to clear a pending interrupt. .PP .I Closeioproc terminates the I/O proc and frees the associated .BR Ioproc . .PP .I Iocall is a primitive that may be used to implement more slave I/O routines. .I Iocall arranges for .I op to be called in .IR io 's proc, with .I arg set to the variable parameter list, returning the value that .I op returns. .SH EXAMPLE Relay messages between two file descriptors, counting the total number of bytes seen: .IP .EX .ta +\w'xxxx'u +\w'xxxx'u +\w'xxxx'u int tot; void relaythread(void *v) { 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); } void relay(int fd0, int fd1) { int fd[4]; fd[0] = fd[3] = fd0; fd[1] = fd[2] = fd1; threadcreate(relaythread, fd, 8192); threadcreate(relaythread, fd+2, 8192); } .EE .LP If the two .I relaythread instances were running in different procs, the common access to .I tot would be unsafe. .PP Implement .IR ioread : .IP .EX static long _ioread(va_list *arg) { 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); } long ioread(Ioproc *io, int fd, void *a, long n) { return iocall(io, _ioread, fd, a, n); } .EE .SH SOURCE .B /sys/src/libthread/io*.c .SH SEE ALSO .IR dial (2), .IR open (2), .IR read (2), .IR sleep (2), .IR thread (2)