1 files changed, 105 insertions, 0 deletions
diff --git a/appl/alphabet/fs/compose.b b/appl/alphabet/fs/compose.b
new file mode 100644
index 00000000..09bef812
--- /dev/null
+++ b/appl/alphabet/fs/compose.b
@@ -0,0 +1,105 @@
+implement Compose, Fsmodule;
+include "sys.m";
+	sys: Sys;
+include "draw.m";
+include "sh.m";
+include "alphabet/reports.m";
+	Report: import Reports;
+include "alphabet/fs.m";
+	fs: Fs;
+	Value: import fs;
+	Cmpchan,
+	Nilentry, Option,
+	Next, Down, Skip, Quit: import Fs;
+
+Compose: module {};
+
+AinB:	con 1<<3;
+BinA:	con 1<<2;
+AoutB:	con 1<<1;
+BoutA:	con 1<<0;
+
+A:		con AinB|AoutB;
+AoverB:	con AinB|AoutB|BoutA;
+AatopB:	con AinB|BoutA;
+AxorB:	con AoutB|BoutA;
+
+B:		con BinA|BoutA;
+BoverA:	con BinA|BoutA|AoutB;
+BatopA:	con BinA|AoutB;
+BxorA:	con BoutA|AoutB;
+
+ops := array[] of {
+	AinB => "AinB",
+	BinA => "BinA",
+	AoutB => "AoutB",
+	BoutA => "BoutA",
+	A => "A",
+	AoverB => "AoverB",
+	AatopB => "AatopB",
+	AxorB => "AxorB",
+	B => "B",
+	BoverA => "BoverA",
+	BatopA => "BatopA",
+};
+
+badmod(p: string)
+{
+	sys->fprint(sys->fildes(2), "fs: size: cannot load %s: %r\n", p);
+	raise "fail:bad module";
+}
+
+types(): string
+{
+	return "ms-d";
+}
+
+init()
+{
+	sys = load Sys Sys->PATH;
+	fs = load Fs Fs->PATH;
+	if(fs == nil)
+		badmod(Fs->PATH);
+	fs->init();
+}
+
+run(nil: ref Draw->Context, nil: ref Report,
+			opts: list of Option, args: list of ref Value): ref Value
+{
+	c := chan of (ref Sys->Dir, ref Sys->Dir, chan of int);
+	s := (hd args).s().i;
+	for(i := 0; i < len ops; i++)
+		if(ops[i] == s)
+			break;
+	if(i == len ops){
+		sys->fprint(sys->fildes(2), "fs: join: bad op %q\n", s);
+		return nil;
+	}
+	spawn compose(c, i, opts != nil);
+	return ref Value.Vm(c);
+}
+
+compose(c: Cmpchan, op: int, dflag: int)
+{
+	t := array[4] of {* => 0};
+	if(op & AinB)
+		t[2r11] = 2r01;
+	if(op & BinA)
+		t[2r11] = 2r10;
+	if(op & AoutB)
+		t[2r01] = 2r01;
+	if(op & BoutA)
+		t[2r10] = 2r10;
+	if(dflag){
+		while(((d0, d1, reply) := <-c).t2 != nil){
+			x := (d1 != nil) << 1 | d0 != nil;
+			r := t[d0 != nil | (d1 != nil) << 1];
+			if(r == 0 && x == 2r11 && (d0.mode & d1.mode & Sys->DMDIR))
+				r = 2r11;
+			reply <-= r;
+		}
+	}else{
+		while(((d0, d1, reply) := <-c).t2 != nil)
+			reply <-= t[(d1 != nil) << 1 | d0 != nil];
+	}
+}