From eb9c10efbc88ea486a08f80c4fa1bc3df6785347 Mon Sep 17 00:00:00 2001
From: John Kerl <kerl.john.r@gmail.com>
Date: Wed, 26 Aug 2020 22:16:55 -0400
Subject: [PATCH] mappers cat & tac

---
 go/src/mapping/channel_mapper.go |  5 ++---
 go/src/mapping/mapper_cat.go     | 18 ++++++++++++++++++
 go/src/mapping/mapper_tac.go     | 30 ++++++++++++++++++++++++++++++
 go/src/stream/stream.go          |  4 +++-
 4 files changed, 53 insertions(+), 4 deletions(-)
 create mode 100644 go/src/mapping/mapper_cat.go
 create mode 100644 go/src/mapping/mapper_tac.go

diff --git a/go/src/mapping/channel_mapper.go b/go/src/mapping/channel_mapper.go
index 0b0dc8b03..53c014456 100644
--- a/go/src/mapping/channel_mapper.go
+++ b/go/src/mapping/channel_mapper.go
@@ -11,10 +11,9 @@ func ChannelMapper(
 ) {
 	for {
 		lrec := <-inrecs
-		if lrec == nil {
-			outrecs <- nil
+		recordMapper.Map(lrec, outrecs)
+		if lrec == nil { // end of stream
 			break
 		}
-		recordMapper.Map(lrec, outrecs)
 	}
 }
diff --git a/go/src/mapping/mapper_cat.go b/go/src/mapping/mapper_cat.go
new file mode 100644
index 000000000..faf8b6f5f
--- /dev/null
+++ b/go/src/mapping/mapper_cat.go
@@ -0,0 +1,18 @@
+package mapping
+
+import (
+	"containers"
+)
+
+type MapperCat struct {
+	// stateless
+}
+
+func NewMapperCat() *MapperCat {
+	return &MapperCat {
+	}
+}
+
+func (this *MapperCat) Map(inrec *containers.Lrec, outrecs chan<- *containers.Lrec) {
+	outrecs <- inrec
+}
diff --git a/go/src/mapping/mapper_tac.go b/go/src/mapping/mapper_tac.go
new file mode 100644
index 000000000..359e79aac
--- /dev/null
+++ b/go/src/mapping/mapper_tac.go
@@ -0,0 +1,30 @@
+package mapping
+
+import (
+	// System:
+	"container/list"
+	// Miller:
+	"containers"
+)
+
+type MapperTac struct {
+	lrecs *list.List
+}
+
+func NewMapperTac() *MapperTac {
+	return &MapperTac {
+		list.New(),
+	}
+}
+
+func (this *MapperTac) Map(inrec *containers.Lrec, outrecs chan<- *containers.Lrec) {
+	if inrec != nil {
+		this.lrecs.PushFront(inrec)
+	} else {
+		// end of stream
+		for e := this.lrecs.Front(); e != nil; e = e.Next() {
+			outrecs <- e.Value.(*containers.Lrec)
+		}
+		outrecs <- nil
+	}
+}
diff --git a/go/src/stream/stream.go b/go/src/stream/stream.go
index 761747dde..6ddbaf56e 100644
--- a/go/src/stream/stream.go
+++ b/go/src/stream/stream.go
@@ -26,7 +26,9 @@ func Stream(filenames []string) error {
 	outrecs := make(chan *containers.Lrec, 1)
 	donechan := make(chan bool, 1)
 
-	recordMapper := mapping.NewMapperFoo();
+	//recordMapper := mapping.NewMapperFoo();
+	//recordMapper := mapping.NewMapperCat();
+	recordMapper := mapping.NewMapperTac();
 
 	go input.ChannelReader(reader, inrecs, echan)
 	go mapping.ChannelMapper(inrecs, recordMapper, outrecs)