1 files changed, 114 insertions, 0 deletions
diff --git a/appl/alphabet/main/filter.b b/appl/alphabet/main/filter.b
new file mode 100644
index 00000000..f532f529
--- /dev/null
+++ b/appl/alphabet/main/filter.b
@@ -0,0 +1,114 @@
+implement Filter, Mainmodule;
+include "sys.m";
+	sys: Sys;
+include "draw.m";
+include "sh.m";
+	sh: Sh;
+	Context: import sh;
+include "bufio.m";
+	bufio: Bufio;
+	Iobuf: import bufio;
+include "alphabet/reports.m";
+	reports: Reports;
+		Report, report: import reports;
+include "alphabet.m";
+	alphabet: Alphabet;
+		Value: import alphabet;
+
+Filter: module {};
+
+typesig(): string
+{
+	return "ffcs*";		# XXX option to suppress stderr?
+}
+
+init()
+{
+	sys = load Sys Sys->PATH;
+	alphabet = load Alphabet Alphabet->PATH;
+	reports = load Reports Reports->PATH;
+	bufio = load Bufio Bufio->PATH;
+	sh = load Sh Sh->PATH;
+	sh->initialise();
+}
+
+quit()
+{
+}
+
+run(drawctxt: ref Draw->Context, report: ref Reports->Report, nil: chan of string,
+		nil: list of (int, list of ref Value),
+		args: list of ref Value): ref Value
+{
+	f := chan of ref Sys->FD;
+	a: list of ref Sh->Listnode;
+	for(al := tl tl args; al != nil; al = tl al)
+		a = ref Sh->Listnode(nil, (hd al).s().i) :: a;
+	spawn filterproc(drawctxt, (hd args).f().i, f, (hd tl args).c().i, rev(a), report.start("filter"));
+	return ref Value.Vf(f);
+}
+
+filterproc(drawctxt: ref Draw->Context,
+	f0,
+	f1: chan of ref Sys->FD,
+	c: ref Sh->Cmd,
+	args: list of ref Sh->Listnode,
+	errorc: chan of string)
+{
+	(fd0, fd1) := startfilter(f0, f1, errorc);
+	sys->pipe(p := array[2] of ref Sys->FD);
+	spawn stderrproc(p[0], errorc);
+	p[0] = nil;
+
+	# i hate this stuff.
+	sys->pctl(Sys->FORKFD, nil);
+	sys->dup(fd0.fd, 0);
+	sys->dup(fd1.fd, 1);
+	sys->dup(p[1].fd, 2);
+	fd0 = fd1 = nil;
+	p = nil;
+	sys->pctl(Sys->NEWFD, 0::1::2::nil);
+	Context.new(drawctxt).run(ref Sh->Listnode(c, nil)::args, 0);
+	sys->fprint(sys->fildes(2), "");
+}
+
+# read side (when it's an argument):
+# 	read proposed new fd
+# 	write actual fd for them to write to (creating pipe in necessary)
+# 
+# write side (when you're returning it):
+# 	write a proposed new fd (or nil if no suggestion)
+# 	read actual fd for writing
+startfilter(f0, f1: chan of ref Sys->FD, errorc: chan of string): (ref Sys->FD, ref Sys->FD)
+{
+	f1 <-= nil;
+	if((fd1 := <-f1) == nil){
+		<-f0;
+		f0 <-= nil;
+		reports->quit(errorc);
+	}
+	if((fd0 := <-f0) == nil){
+		sys->pipe(p := array[2] of ref Sys->FD);
+		f0 <-= p[1];
+		fd0 = p[0];
+	}else
+		f0 <-= nil;
+	return (fd0, fd1);
+}
+
+stderrproc(fd: ref Sys->FD, errorc: chan of string)
+{
+	iob := bufio->fopen(fd, Sys->OREAD);
+	while((s := iob.gets('\n')) != nil)
+		if(len s > 1)
+			errorc <-= s[0:len s - 1];
+	errorc <-= nil;
+}
+
+rev[T](l: list of T): list of T
+{
+	r: list of T;
+	for(; l != nil; l = tl l)
+		r = hd l :: r;
+	return r;
+}
+\ No newline at end of file