diff --git a/include/enc-util.h b/include/enc-util.h
new file mode 100644
index 0000000..5ec7b78
--- /dev/null
+++ b/include/enc-util.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2019 - 2020 Andri Yngvason
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#pragma once
+
+#include "rfb-proto.h"
+
+#include <stdint.h>
+
+struct vec;
+
+int encode_rect_count(struct vec* dst, uint32_t count);
+int encode_rect_head(struct vec* dst, enum rfb_encodings encoding,
+		uint32_t x, uint32_t y, uint32_t width, uint32_t height);
+uint32_t calc_bytes_per_cpixel(const struct rfb_pixel_format* fmt);
diff --git a/meson.build b/meson.build
index 851525b..4df7b67 100644
--- a/meson.build
+++ b/meson.build
@@ -66,6 +66,7 @@ sources = [
 	'src/stream.c',
 	'src/display.c',
 	'src/tight.c',
+	'src/enc-util.c',
 ]
 
 dependencies = [
diff --git a/src/enc-util.c b/src/enc-util.c
new file mode 100644
index 0000000..922f00c
--- /dev/null
+++ b/src/enc-util.c
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2019 - 2020 Andri Yngvason
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "enc-util.h"
+#include "rfb-proto.h"
+#include "vec.h"
+
+#include <arpa/inet.h>
+
+int encode_rect_count(struct vec* dst, uint32_t count)
+{
+	struct rfb_server_fb_update_msg msg = {
+		.type = RFB_SERVER_TO_CLIENT_FRAMEBUFFER_UPDATE,
+		.n_rects = htons(count),
+	};
+
+	return vec_append(dst, &msg, sizeof(msg));
+}
+
+int encode_rect_head(struct vec* dst, enum rfb_encodings encoding,
+		uint32_t x, uint32_t y, uint32_t width, uint32_t height)
+{
+	struct rfb_server_fb_rect head = {
+		.encoding = htonl(encoding),
+		.x = htons(x),
+		.y = htons(y),
+		.width = htons(width),
+		.height = htons(height),
+	};
+
+	return vec_append(dst, &head, sizeof(head));
+}
+
+uint32_t calc_bytes_per_cpixel(const struct rfb_pixel_format* fmt)
+{
+	return fmt->bits_per_pixel == 32 ? fmt->depth / 8
+	                                 : fmt->bits_per_pixel / 8;
+}