pw_checksum: CCITT CRC16 functions
Change-Id: I731445296690409cd97cad652f0827b50e36a58e
diff --git a/pw_checksum/ccitt_crc16_test.cc b/pw_checksum/ccitt_crc16_test.cc
new file mode 100644
index 0000000..19b9c9c
--- /dev/null
+++ b/pw_checksum/ccitt_crc16_test.cc
@@ -0,0 +1,68 @@
+// 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.
+
+#include "pw_checksum/ccitt_crc16.h"
+
+#include <string_view>
+
+#include "gtest/gtest.h"
+
+namespace pw::checksum {
+namespace {
+
+// The expected CRC16 values were calculated using
+//
+// http://www.sunshine2k.de/coding/javascript/crc/crc_js.html
+//
+// with polynomial 0x1021, initial value 0xFFFF.
+constexpr uint8_t kBytes[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+constexpr uint16_t kBufferCrc = 0x3B0A;
+
+constexpr std::string_view kString =
+ "In the beginning the Universe was created. This has made a lot of "
+ "people very angry and been widely regarded as a bad move.";
+constexpr uint16_t kStringCrc = 0xC184;
+
+TEST(Crc16, Empty) {
+ EXPECT_EQ(CcittCrc16(span<std::byte>()), kCcittCrc16DefaultInitialValue);
+}
+
+TEST(Crc16, ByteByByte) {
+ uint16_t crc = kCcittCrc16DefaultInitialValue;
+ for (size_t i = 0; i < sizeof(kBytes); i++) {
+ crc = CcittCrc16(std::byte{kBytes[i]}, crc);
+ }
+ EXPECT_EQ(crc, kBufferCrc);
+}
+
+TEST(Crc16, Buffer) {
+ EXPECT_EQ(CcittCrc16(as_bytes(span(kBytes))), kBufferCrc);
+}
+
+TEST(Crc16, String) {
+ EXPECT_EQ(CcittCrc16(as_bytes(span(kString))), kStringCrc);
+}
+
+extern "C" uint16_t CallChecksumCcittCrc16(const void* data, size_t size_bytes);
+
+TEST(Crc16FromC, Buffer) {
+ EXPECT_EQ(CallChecksumCcittCrc16(kBytes, sizeof(kBytes)), kBufferCrc);
+}
+
+TEST(Crc16FromC, String) {
+ EXPECT_EQ(CallChecksumCcittCrc16(kString.data(), kString.size()), kStringCrc);
+}
+
+} // namespace
+} // namespace pw::checksum