--- ray/src/common/rtprocess.h	2018/03/20 17:45:07	3.17
+++ ray/src/common/rtprocess.h	2020/02/28 05:18:49	3.18
@@ -1,4 +1,4 @@
-/* RCSid $Id: rtprocess.h,v 3.17 2018/03/20 17:45:07 greg Exp $ */
+/* RCSid $Id: rtprocess.h,v 3.18 2020/02/28 05:18:49 greg Exp $ */
 /*
  *   rtprocess.h 
  *   Routines to communicate with separate process via dual pipes
@@ -38,7 +38,29 @@ extern "C" {
    platform independent RT_PID.
 */
 
+/* On Unix, we can set flags and assign descriptors before opening a
+   process, coupling an existing input or output to the new process rather
+   than opening both pipes.  If PF_FILT_INP is passed in the flags member of
+   SUBPROC, then the given r stream will be attached to the standard input
+   of the child process, and subsequent reads from that descriptor in the
+   parent get data from the standard output of the child, instead.  The
+   returned w descriptor is set to -1, since there is no longer any way
+   to write to the input of the child.  The default r descriptor of 0 will
+   compel the child to act as a filter on the standard input of the parent.
+   Whatever r handle you specify, the child will filter its read operations.
+   Note that this should be called before anything has been buffered using r.
+   If PF_FILT_OUT is set in flags, then the given w stream will be
+   attached to the standard output of the child, and subsequent writes
+   to that descriptor in the parent send data to the standard input
+   of the child. The returned r descriptor is set to -1, since
+   there is no output to read from any longer in the child.  The
+   default w descriptor of 1 will cause the child to act as a filter
+   on the output of the parent.  Make sure to call fflush(stdout) first
+   if any data was buffered.  It is illegal to set both PF_FILT_INP and
+   PF_FILT_OUT, as a circular process is guaranteed to hang.
+*/
 
+
 #ifndef PIPE_BUF
   #ifdef PIPSIZ
     #define PIPE_BUF	PIPSIZ
@@ -50,15 +72,19 @@ extern "C" {
     #endif
   #endif
 #endif
+				/* process flags */
+#define PF_RUNNING	1		/* process is running */
+#define PF_FILT_INP	2		/* use assigned read descriptor */
+#define PF_FILT_OUT	4		/* use assigned write descriptor */
 
 typedef struct {
-	int r; /* read handle */
-	int w; /* write handle */
-	int running; /* doing something */
-	RT_PID pid; /* process ID */
+	int	flags;		/* what is being done */
+	int	r;		/* read handle */
+	int	w;		/* write handle */
+	RT_PID	pid;		/* process ID */
 } SUBPROC;
 
-#define SP_INACTIVE {-1,-1,0,0} /* for static initializations */
+#define SP_INACTIVE {0,0,1,-1}	/* for static initializations */
 
 #define close_process(pd)	close_processes(pd,1)
 
@@ -74,6 +100,7 @@ extern int win_kill(RT_PID pid, int sig /* ignored */)
 extern int win_nice(int inc);
 #endif
 
+extern SUBPROC	sp_inactive;
 
 #ifdef __cplusplus
 }