crc: Add crc8 implementation and tests

Add crc8 implementation and unit tests for it.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>

include/sys/crc.h

@@ -55,6 +55,24 @@ extern "C" {
 u16_t crc16(const u8_t *src, size_t len, u16_t polynomial,
 	    u16_t initial_value, bool pad);
 
+/**
+ * @brief Generic function for computing CRC 8
+ *
+ * Compute CRC 8 by passing in the address of the input, the input length
+ * and polynomial used in addition to the initial value.
+ *
+ * @param src Input bytes for the computation
+ * @param len Length of the input in bytes
+ * @param polynomial The polynomial to use omitting the leading x^8
+ *        coefficient
+ * @param initial_value Initial value for the CRC computation
+ * @param reversed Should we use reflected/reversed values or not
+ *
+ * @return The computed CRC8 value
+ */
+u8_t crc8(const u8_t *src, size_t len, u8_t polynomial, u8_t initial_value,
+	  bool reversed);
+
 /**
  * @brief Compute the CRC-16/CCITT checksum of a buffer.
  *

lib/os/crc8_sw.c

@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2020 Intel Corporation
  * Copyright (c) 2017 Nordic Semiconductor ASA
  * Copyright (c) 2015 Runtime Inc
  *
@@ -24,3 +25,32 @@ u8_t crc8_ccitt(u8_t val, const void *buf, size_t cnt)
 	}
 	return val;
 }
+
+u8_t crc8(const u8_t *src, size_t len, u8_t polynomial, u8_t initial_value,
+	  bool reversed)
+{
+	u8_t crc = initial_value;
+	size_t i, j;
+
+	for (i = 0; i < len; i++) {
+		crc ^= src[i];
+
+		for (j = 0; j < 8; j++) {
+			if (reversed) {
+				if (crc & 0x01) {
+					crc = (crc >> 1) ^ polynomial;
+				} else {
+					crc >>= 1;
+				}
+			} else {
+				if (crc & 0x80) {
+					crc = (crc << 1) ^ polynomial;
+				} else {
+					crc <<= 1;
+				}
+			}
+		}
+	}
+
+	return crc;
+}

tests/unit/crc/main.c

@@ -122,6 +122,86 @@ void test_crc7_be(void)
 	zassert_equal(crc7_be(0, test2, sizeof(test2)), 0xEA, NULL);
 }
 
+void test_crc8(void)
+{
+	u8_t fcs, expected;
+
+	u8_t test0[] = { 0x00 };
+	u8_t test1[] = { 0xBE, 0xEF };
+	u8_t test2[] = { 0x07, 0x3F };        /* GSM 07.10 example */
+	u8_t test3[] = { 0x07, 0x3F, 0x89 };  /* GSM 07.10 example */
+	u8_t test4[] = { 0x03, 0x02, 0x0A, 0x38, 0x17, 0x00 };
+	u8_t test5[] = { 0x03, 0x3f, 0x01, 0x1c };  /* Our GSM 07.10 calc */
+
+	fcs = crc8(test0, sizeof(test0), 0x00, 0x00, false);
+	expected = 0x00;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test0, sizeof(test0), 0x31, 0x00, false);
+	expected = 0x00;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test1, sizeof(test1), 0x07, 0x00, false);
+	expected = 0x1a;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test1, sizeof(test1), 0x31, 0xff, false);
+	expected = 0x92;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test1, sizeof(test1), 0x07, 0x00, false);
+	expected = 0x1a;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test2, sizeof(test2), 0x31, 0x00, false);
+	expected = 0x45;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test2, sizeof(test2), 0x31, 0xff, false);
+	expected = 0xc4;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test2, sizeof(test2), 0x07, 0x00, false);
+	expected = 0xd6;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test2, sizeof(test2), 0x07, 0xff, false);
+	expected = 0x01;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test2, sizeof(test2), 0xe0, 0xff, true);
+	expected = 0x76;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test3, sizeof(test3), 0xe0, 0xff, true);
+	expected = 0xcf;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test3, sizeof(test3), 0x07, 0xff, false);
+	expected = 0xb1;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test4, sizeof(test4), 0x31, 0x00, false);
+	expected = 0x3a;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test4, sizeof(test4), 0x07, 0x00, false);
+	expected = 0xaf;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test4, sizeof(test4), 0x9b, 0xff, false);
+	expected = 0xf0;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test4, sizeof(test4), 0x1d, 0xfd, false);
+	expected = 0x49;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+
+	fcs = crc8(test5, sizeof(test5), 0xe0, 0xff, true);
+	expected = 0xcf;
+	zassert_equal(fcs, expected, "0x%02x vs 0x%02x", fcs, expected);
+}
+
 void test_main(void)
 {
 	ztest_test_suite(test_crc,
@@ -132,6 +212,7 @@ void test_main(void)
 			 ztest_unit_test(test_crc16_ccitt_for_ppp),
 			 ztest_unit_test(test_crc16_itu_t),
 			 ztest_unit_test(test_crc8_ccitt),
-			 ztest_unit_test(test_crc7_be));
+			 ztest_unit_test(test_crc7_be),
+			 ztest_unit_test(test_crc8));
 	ztest_run_test_suite(test_crc);
 }