pw_checksum: CCITT CRC16 functions

Change-Id: I731445296690409cd97cad652f0827b50e36a58e
diff --git a/pw_checksum/BUILD b/pw_checksum/BUILD
new file mode 100644
index 0000000..e2170e4
--- /dev/null
+++ b/pw_checksum/BUILD
@@ -0,0 +1,44 @@
+# Copyright 2020 The Pigweed Authors
+#
+# 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.
+
+load(
+    "//pw_build:pigweed.bzl",
+    "pw_cc_library",
+    "pw_cc_test",
+)
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # Apache License 2.0
+
+pw_cc_library(
+    name = "pw_checksum",
+    srcs = [
+        "ccitt_crc16.cc",
+    ],
+    hdrs = [
+        "public/pw_checksum/ccitt_crc16.h",
+    ],
+    includes = ["public"],
+    deps = ["//pw_span"],
+)
+
+pw_cc_test(
+    name = "ccitt_crc16_test",
+    srcs = [
+        "ccitt_crc16_test.c",
+        "ccitt_crc16_test.cc",
+    ],
+    deps = [":pw_checksum"],
+)