From cd4517ba69e26c96a69e505e305a6d0152972982 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Krystian=20Bac=C5=82awski?= <krystian.baclawski@gmail.com>
Date: Mon, 13 Mar 2023 20:48:47 +0100
Subject: [PATCH] Parse DRNG (palette cycling) chunk in ILBM format

---
 tools/iff/ilbm/drng.go | 84 ++++++++++++++++++++++++++++++++++++++++++
 tools/iff/ilbm/ilbm.go |  1 +
 2 files changed, 85 insertions(+)
 create mode 100644 tools/iff/ilbm/drng.go

diff --git a/tools/iff/ilbm/drng.go b/tools/iff/ilbm/drng.go
new file mode 100644
index 00000000..7dfeed9c
--- /dev/null
+++ b/tools/iff/ilbm/drng.go
@@ -0,0 +1,84 @@
+package ilbm
+
+import (
+	"bytes"
+	"ghostown.pl/iff"
+	"log"
+	"text/template"
+)
+
+const drngTemplate = `{
+  Min: {{.Min}},
+  Max: {{.Max}},
+  Rate: {{.Rate}},
+  Flags: {{if .Flags}} RNG_ACTIVE {{- else}} NONE {{- end}},
+  DColor: { {{- range .Dcolor }} {{ .Cell}}: {{ printf "#%02x%02x%02x" .R .G .B}}, {{ end -}} },
+  DIndex:  { {{- range .Dindex }} {{.Cell}}: {{.Index}}, {{ end -}} }
+}`
+
+type DColor struct {
+	Cell uint8
+	R    uint8
+	G    uint8
+	B    uint8
+}
+
+type DIndex struct {
+	Cell  uint8
+	Index uint8
+}
+
+type DRNG struct {
+	Min    uint8
+	Max    uint8
+	Rate   int16
+	Flags  int16
+	Dcolor []DColor
+	Dindex []DIndex
+}
+
+func (drng DRNG) Name() string {
+	return "DRNG"
+}
+
+func (drng *DRNG) Read(r iff.Reader) {
+	drng.Min = r.ReadU8()
+	drng.Max = r.ReadU8()
+	drng.Rate = r.ReadI16()
+	drng.Flags = r.ReadI16()
+	ntrue := r.ReadU8()
+	nregs := r.ReadU8()
+
+	drng.Dcolor = make([]DColor, ntrue, ntrue)
+	for i := 0; uint8(i) < ntrue; i++ {
+		drng.Dcolor[i].Cell = r.ReadU8()
+		drng.Dcolor[i].R = r.ReadU8()
+		drng.Dcolor[i].G = r.ReadU8()
+		drng.Dcolor[i].B = r.ReadU8()
+	}
+
+	drng.Dindex = make([]DIndex, nregs, nregs)
+	for i := 0; uint8(i) < nregs; i++ {
+		drng.Dindex[i].Cell = r.ReadU8()
+		drng.Dindex[i].Index = r.ReadU8()
+	}
+}
+
+func (drng DRNG) String() string {
+	t, err := template.New("drng_chunk").Parse(drngTemplate)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var out bytes.Buffer
+	err = t.Execute(&out, drng)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	return out.String()
+}
+
+func makeDRNG() iff.Chunk {
+	return &DRNG{}
+}
diff --git a/tools/iff/ilbm/ilbm.go b/tools/iff/ilbm/ilbm.go
index 9217d9eb..36610d19 100644
--- a/tools/iff/ilbm/ilbm.go
+++ b/tools/iff/ilbm/ilbm.go
@@ -9,6 +9,7 @@ func init() {
 	iff.ParsedChunks["CMAP"] = makeCMAP
 	iff.ParsedChunks["BODY"] = makeBODY
 	iff.ParsedChunks["CAMG"] = makeCAMG
+	iff.ParsedChunks["DRNG"] = makeDRNG
 
 	// Ignore JUNK chunk
 	iff.IgnoredChunks["JUNK"] = true