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/* RCSid $Id: rtprocess.h,v 3.19 2020/02/28 16:23:47 greg Exp $ */
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/*
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* rtprocess.h
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* Routines to communicate with separate process via dual pipes
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*
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* WARNING: On Windows, there's a system header named <process.h>.
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*/
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#ifndef _RAD_PROCESS_H_
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#define _RAD_PROCESS_H_
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#include <errno.h>
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#include <stdio.h>
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#if defined(_WIN32) || defined(_WIN64)
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#include <windows.h> /* DWORD etc. */
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typedef DWORD RT_PID;
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#include <process.h> /* getpid() and others */
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#define getpid _getpid
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#define execv _execv
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#define execvp _execvp
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#else
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#include <sys/param.h>
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#include <sys/types.h>
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typedef pid_t RT_PID;
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#endif
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#include "paths.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* On Windows, a process ID is a DWORD. That might actually be the
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same thing as an int, but it's better not to assume anything.
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This means that we shouldn't rely on PIDs and file descriptors
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being the same type, so we have to describe processes with a struct,
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instead of the original int[3]. For that purpose, we typedef a
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platform independent RT_PID.
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*/
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/* On Unix, we can set flags and assign descriptors before opening a
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process, coupling an existing input or output to the new process rather
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than opening both pipes. If PF_FILT_INP is passed in the flags member of
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SUBPROC, then the given r stream will be attached to the standard input
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of the child process, and subsequent reads from that descriptor in the
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parent get data from the standard output of the child, instead. The
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returned w descriptor is set to -1, since there is no longer any way
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to write to the input of the child. The default r descriptor of 0 will
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compel the child to act as a filter on the standard input of the parent.
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Whatever r handle you specify, the child will filter its read operations.
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Note that this should be called before anything has been buffered using r.
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If PF_FILT_OUT is set in flags, then the given w stream will be
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attached to the standard output of the child, and subsequent writes
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to that descriptor in the parent send data to the standard input
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of the child. The returned r descriptor is set to -1, since
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there is no output to read from any longer in the child. The
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default w descriptor of 1 will cause the child to act as a filter
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on the output of the parent. Make sure to call fflush(stdout) first
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if any data was buffered. It is illegal to set both PF_FILT_INP and
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PF_FILT_OUT, as a circular process is guaranteed to hang.
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If you want behavior similar to popen(cmd, "w") (again Unix-only),
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keeping stdout open in parent, use a duplicate descriptor like so:
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{
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SUBPROC rtp = sp_inactive;
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FILE *fout;
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fflush(stdout);
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rtp.w = dup(fileno(stdout));
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rtp.flags |= PF_FILT_OUT;
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if (open_process(&rtp, cmd_argv) <= 0) {
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perror(cmd_argv[0]); exit(1);
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}
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fout = fdopen(rtp.w, "w");
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...write data to filter using fout until finished...
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fclose(fout);
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if (close_process(&rtp)) {
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perror(cmd_argv[0]); exit(1);
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}
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...can continue sending data directly to stdout...
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}
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We could also have called open_process() after fdopen() above, or after
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using fopen() on a file if we wanted to insert our filter before it.
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A similar sequence may be used to filter from stdin without closing
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it, though process termination becomes more difficult with two readers.
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Filtering input from a file works better, since the file is then read by
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the child only, as in:
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{
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SUBPROC rtp = sp_inactive;
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FILE *fin = fopen(fname, "r");
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if (fin == NULL) {
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open_error(fname); exit(1);
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}
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rtp.r = fileno(fin);
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rtp.flags |= PF_FILT_INP;
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if (open_process(&rtp, cmd_argv) <= 0) {
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perror(cmd_argv[0]); fclose(fin); exit(1);
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}
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...read filtered file data from fin until EOF...
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fclose(fin);
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if (close_process(&rtp)) {
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perror(cmd_argv[0]); exit(1);
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}
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}
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*/
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#ifndef PIPE_BUF
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#ifdef PIPSIZ
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#define PIPE_BUF PIPSIZ
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#else
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#ifdef PIPE_MAX
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#define PIPE_BUF PIPE_MAX
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#else
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#define PIPE_BUF 512 /* hyperconservative */
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#endif
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#endif
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#endif
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/* process flags */
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#define PF_RUNNING 1 /* process is running */
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#define PF_FILT_INP 2 /* use assigned read descriptor */
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#define PF_FILT_OUT 4 /* use assigned write descriptor */
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typedef struct {
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int flags; /* what is being done */
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int r; /* read handle */
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int w; /* write handle */
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RT_PID pid; /* process ID */
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} SUBPROC;
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#define SP_INACTIVE {0,0,1,-1} /* for static initializations */
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#define close_process(pd) close_processes(pd,1)
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extern int open_process(SUBPROC *pd, char *av[]);
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extern int close_processes(SUBPROC pd[], int nproc);
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extern int process(SUBPROC *pd, char *recvbuf, char *sendbuf, int nbr, int nbs);
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extern ssize_t readbuf(int fd, char *bpos, ssize_t siz);
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extern ssize_t writebuf(int fd, char *bpos, ssize_t siz);
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#if defined(_WIN32) || defined(_WIN64)
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/* any non-negative increment will send the process to IDLE_PRIORITY_CLASS. */
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extern int win_kill(RT_PID pid, int sig /* ignored */);
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extern int win_nice(int inc);
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#endif
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extern SUBPROC sp_inactive;
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#ifdef __cplusplus
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}
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#endif
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#endif /* _RAD_PROCESS_H_ */
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