1 files changed, 52 insertions, 0 deletions
diff --git a/cfa635/state.go b/cfa635/state.go
new file mode 100644
index 0000000..fc324d5
--- /dev/null
+++ b/cfa635/state.go
@@ -0,0 +1,52 @@
+// Copyright 2022 Benjamin Barenblat
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+package cfa635
+
+// State represents the state of the CFA635 LCD.
+type LCDState [4][20]byte
+
+func ClearedLCDState() *LCDState {
+	var r LCDState
+	for y := range r {
+		for x := range r[y] {
+			r[y][x] = 0x20
+		}
+	}
+	return &r
+}
+
+func Update(m *Module, old, new *LCDState) error {
+	if *old == *new {
+		return nil
+	}
+
+	for y := range old {
+		var first, last int
+
+		for ; first < len(old[y]) && new[y][first] == old[y][first]; first++ {
+		}
+		if first == len(old[y]) {
+			continue
+		}
+
+		for last = len(old[y]) - 1; last > first && new[y][last] == old[y][last]; last-- {
+		}
+		if err := m.Put(first, y, new[y][first:last+1]); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}