Import of the watch repository from Pebble

src/fw/util/packbits.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * 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
+ *
+ *     http://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.
+ */
+
+#include "packbits.h"
+
+#include <string.h>
+
+void packbits_unpack(const char* src, int src_length, uint8_t* dest) {
+  int length = 0;
+  while (length < src_length) {
+    int8_t header = *((int8_t*) src++);
+    length++;
+
+    if (header >= 0) {
+      int count = header + 1;
+      memcpy(dest, src, count);
+
+      dest += count;
+      src += count;
+      length += count;
+    } else {
+      int count = 1 - header;
+      memset(dest, *src, count);
+
+      dest += count;
+      src += 1;
+      length += 1;
+    }
+  }
+}