1 files changed, 47 insertions, 0 deletions
diff --git a/format/commitgraph/edges.go b/format/commitgraph/edges.go
new file mode 100644
index 00000000..277735d0
--- /dev/null
+++ b/format/commitgraph/edges.go
@@ -0,0 +1,47 @@
+package commitgraph
+
+import (
+	"encoding/binary"
+
+	"codeberg.org/lindenii/furgit/internal/intconv"
+)
+
+func (reader *Reader) decodeExtraEdgeList(layer *layer, edgeStart uint32) ([]Position, error) {
+	if len(layer.chunkExtraEdges) == 0 {
+		return nil, &ErrMalformed{Path: layer.path, Reason: "missing EDGE chunk"}
+	}
+
+	out := make([]Position, 0)
+
+	cur := edgeStart
+	for {
+		off64 := uint64(cur) * 4
+
+		off, err := intconv.Uint64ToInt(off64)
+		if err != nil {
+			return nil, err
+		}
+
+		if off+4 > len(layer.chunkExtraEdges) {
+			return nil, &ErrMalformed{Path: layer.path, Reason: "EDGE index out of range"}
+		}
+
+		word := binary.BigEndian.Uint32(layer.chunkExtraEdges[off : off+4])
+		parentGlobal := word & parentLastMask
+
+		parentPos, err := reader.globalToPosition(parentGlobal)
+		if err != nil {
+			return nil, err
+		}
+
+		out = append(out, parentPos)
+
+		if word&parentExtraMask != 0 {
+			break
+		}
+
+		cur++
+	}
+
+	return out, nil
+}