lib: crc: add CRC-32K/4.2

This adds the best HD=4 CRC32 polynomial. The discovery
is the result of research by Philip Koopman of Carnegie
Mellon University, and is well documented at
https://users.ece.cmu.edu/~koopman/crc/.

The user is given the option of trading 1024B of RAM to
improve the execution speed. The unit tests are parameterized
with this KConfig option.

Signed-off-by: JP Hutchins <jp@intercreate.io>

include/zephyr/sys/crc.h

@@ -5,6 +5,7 @@
  * Copyright (c) 2015 Runtime Inc
  * Copyright (c) 2018 Google LLC.
  * Copyright (c) 2022 Meta
+ * Copyright (c) 2024 Intercreate, Inc.
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -69,6 +70,7 @@ enum crc_type {
 	CRC24_PGP,   /**< Use @ref crc24_pgp */
 	CRC32_C,     /**< Use @ref crc32_c */
 	CRC32_IEEE,  /**< Use @ref crc32_ieee */
+	CRC32_K_4_2, /**< Use @ref crc32_k_4_2_update */
 };
 
 /**
@@ -263,6 +265,32 @@ uint32_t crc32_ieee_update(uint32_t crc, const uint8_t *data, size_t len);
 uint32_t crc32_c(uint32_t crc, const uint8_t *data,
 		 size_t len, bool first_pkt, bool last_pkt);
 
+/**
+ * @brief Update a CRC-32K/4.2 (*op) (Koopman) checksum. This is a good HD=4
+ * checksum up to 2,147,483,615 bits and HD=5/6 up to 6,167 bits.
+ *
+ * Hamming Distance and properties:
+ *
+ * - Polynomial: 0x93a409eb
+ * - reflect-in: false
+ * - initial value (xor-in): provided by caller as crc argument (0xFFFFFFFF is OK)
+ * - reflect-out: false
+ * - xor-out: 0
+ * - HD=4 @ 2,147,483,615 bits
+ * - HD=5 @ 6,167 bits
+ * - HD=6 @ 6,167 bits
+ * - HD=7 @ 148 bits
+ *
+ * Reference: https://users.ece.cmu.edu/~koopman/crc/crc32.html
+ *
+ * @param crc       CRC32 checksum that needs to be updated.
+ * @param data      Pointer to data on which the CRC should be calculated.
+ * @param len       Data length.
+ *
+ * @return CRC32 value.
+ */
+uint32_t crc32_k_4_2_update(uint32_t crc, const uint8_t *data, size_t len);
+
 /**
  * @brief Compute CCITT variant of CRC 8
  *
@@ -378,7 +406,7 @@ uint32_t crc24_pgp_update(uint32_t crc, const uint8_t *data, size_t len);
  * @param type CRC algorithm to use.
  * @param src Input bytes for the computation
  * @param len Length of the input in bytes
- * @param seed Value to seed the CRC with
+ * @param seed Seed or existing CRC value to update
  * @param poly The polynomial to use omitting the leading coefficient
  * @param reflect Should we use reflected/reversed values or not
  * @param first Whether this is the first packet in the stream.
@@ -425,6 +453,8 @@ static inline uint32_t crc_by_type(enum crc_type type, const uint8_t *src, size_
 		return crc32_c(seed, src, len, first, last);
 	case CRC32_IEEE:
 		return crc32_ieee_update(seed, src, len);
+	case CRC32_K_4_2:
+		return crc32_k_4_2_update(seed, src, len);
 	default:
 		break;
 	}

lib/crc/CMakeLists.txt

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 zephyr_sources_ifdef(CONFIG_CRC
+  crc32k_4_2_sw.c
   crc32c_sw.c
   crc32_sw.c
   crc24_sw.c

lib/crc/Kconfig

@@ -1,4 +1,5 @@
 # Copyright (c) 2016,2023 Intel Corporation
+# Copyright (c) 2024 Intercreate, Inc.
 # SPDX-License-Identifier: Apache-2.0
 #
 config CRC
@@ -13,4 +14,10 @@ config CRC_SHELL
 	select POSIX_C_LIB_EXT
 	help
 	  Enable CRC checking for memory regions from the shell.
+
+config CRC32_K_4_2_TABLE_256
+	bool "Use 256-length table for CRC32-K/4.2"
+	help
+	  Enable the 256-length instead of 16-length table for CRC32-K/4.2.
+
 endif # CRC

lib/crc/crc32k_4_2_sw.c

@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2024 Intercreate, Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/sys/crc.h>
+
+uint32_t crc32_k_4_2_update(uint32_t crc, const uint8_t *const data, const size_t len)
+{
+
+#if defined(CONFIG_CRC32_K_4_2_TABLE_256)
+
+	/**
+	 * CRC table generated from polynomial 0x93a409eb CRC-32K/4.2 (*op) (Koopman)
+	 *
+	 * pycrc --width 32 --poly 0x93a409eb --reflect-in False --xor-in 0 --reflect-out False
+	 * --xor-out 0 --generate table --table-idx-width 8
+	 */
+	static const uint32_t table[256] = {
+		0x00000000, 0x93a409eb, 0xb4ec1a3d, 0x274813d6, 0xfa7c3d91, 0x69d8347a, 0x4e9027ac,
+		0xdd342e47, 0x675c72c9, 0xf4f87b22, 0xd3b068f4, 0x4014611f, 0x9d204f58, 0x0e8446b3,
+		0x29cc5565, 0xba685c8e, 0xceb8e592, 0x5d1cec79, 0x7a54ffaf, 0xe9f0f644, 0x34c4d803,
+		0xa760d1e8, 0x8028c23e, 0x138ccbd5, 0xa9e4975b, 0x3a409eb0, 0x1d088d66, 0x8eac848d,
+		0x5398aaca, 0xc03ca321, 0xe774b0f7, 0x74d0b91c, 0x0ed5c2cf, 0x9d71cb24, 0xba39d8f2,
+		0x299dd119, 0xf4a9ff5e, 0x670df6b5, 0x4045e563, 0xd3e1ec88, 0x6989b006, 0xfa2db9ed,
+		0xdd65aa3b, 0x4ec1a3d0, 0x93f58d97, 0x0051847c, 0x271997aa, 0xb4bd9e41, 0xc06d275d,
+		0x53c92eb6, 0x74813d60, 0xe725348b, 0x3a111acc, 0xa9b51327, 0x8efd00f1, 0x1d59091a,
+		0xa7315594, 0x34955c7f, 0x13dd4fa9, 0x80794642, 0x5d4d6805, 0xcee961ee, 0xe9a17238,
+		0x7a057bd3, 0x1dab859e, 0x8e0f8c75, 0xa9479fa3, 0x3ae39648, 0xe7d7b80f, 0x7473b1e4,
+		0x533ba232, 0xc09fabd9, 0x7af7f757, 0xe953febc, 0xce1bed6a, 0x5dbfe481, 0x808bcac6,
+		0x132fc32d, 0x3467d0fb, 0xa7c3d910, 0xd313600c, 0x40b769e7, 0x67ff7a31, 0xf45b73da,
+		0x296f5d9d, 0xbacb5476, 0x9d8347a0, 0x0e274e4b, 0xb44f12c5, 0x27eb1b2e, 0x00a308f8,
+		0x93070113, 0x4e332f54, 0xdd9726bf, 0xfadf3569, 0x697b3c82, 0x137e4751, 0x80da4eba,
+		0xa7925d6c, 0x34365487, 0xe9027ac0, 0x7aa6732b, 0x5dee60fd, 0xce4a6916, 0x74223598,
+		0xe7863c73, 0xc0ce2fa5, 0x536a264e, 0x8e5e0809, 0x1dfa01e2, 0x3ab21234, 0xa9161bdf,
+		0xddc6a2c3, 0x4e62ab28, 0x692ab8fe, 0xfa8eb115, 0x27ba9f52, 0xb41e96b9, 0x9356856f,
+		0x00f28c84, 0xba9ad00a, 0x293ed9e1, 0x0e76ca37, 0x9dd2c3dc, 0x40e6ed9b, 0xd342e470,
+		0xf40af7a6, 0x67aefe4d, 0x3b570b3c, 0xa8f302d7, 0x8fbb1101, 0x1c1f18ea, 0xc12b36ad,
+		0x528f3f46, 0x75c72c90, 0xe663257b, 0x5c0b79f5, 0xcfaf701e, 0xe8e763c8, 0x7b436a23,
+		0xa6774464, 0x35d34d8f, 0x129b5e59, 0x813f57b2, 0xf5efeeae, 0x664be745, 0x4103f493,
+		0xd2a7fd78, 0x0f93d33f, 0x9c37dad4, 0xbb7fc902, 0x28dbc0e9, 0x92b39c67, 0x0117958c,
+		0x265f865a, 0xb5fb8fb1, 0x68cfa1f6, 0xfb6ba81d, 0xdc23bbcb, 0x4f87b220, 0x3582c9f3,
+		0xa626c018, 0x816ed3ce, 0x12cada25, 0xcffef462, 0x5c5afd89, 0x7b12ee5f, 0xe8b6e7b4,
+		0x52debb3a, 0xc17ab2d1, 0xe632a107, 0x7596a8ec, 0xa8a286ab, 0x3b068f40, 0x1c4e9c96,
+		0x8fea957d, 0xfb3a2c61, 0x689e258a, 0x4fd6365c, 0xdc723fb7, 0x014611f0, 0x92e2181b,
+		0xb5aa0bcd, 0x260e0226, 0x9c665ea8, 0x0fc25743, 0x288a4495, 0xbb2e4d7e, 0x661a6339,
+		0xf5be6ad2, 0xd2f67904, 0x415270ef, 0x26fc8ea2, 0xb5588749, 0x9210949f, 0x01b49d74,
+		0xdc80b333, 0x4f24bad8, 0x686ca90e, 0xfbc8a0e5, 0x41a0fc6b, 0xd204f580, 0xf54ce656,
+		0x66e8efbd, 0xbbdcc1fa, 0x2878c811, 0x0f30dbc7, 0x9c94d22c, 0xe8446b30, 0x7be062db,
+		0x5ca8710d, 0xcf0c78e6, 0x123856a1, 0x819c5f4a, 0xa6d44c9c, 0x35704577, 0x8f1819f9,
+		0x1cbc1012, 0x3bf403c4, 0xa8500a2f, 0x75642468, 0xe6c02d83, 0xc1883e55, 0x522c37be,
+		0x28294c6d, 0xbb8d4586, 0x9cc55650, 0x0f615fbb, 0xd25571fc, 0x41f17817, 0x66b96bc1,
+		0xf51d622a, 0x4f753ea4, 0xdcd1374f, 0xfb992499, 0x683d2d72, 0xb5090335, 0x26ad0ade,
+		0x01e51908, 0x924110e3, 0xe691a9ff, 0x7535a014, 0x527db3c2, 0xc1d9ba29, 0x1ced946e,
+		0x8f499d85, 0xa8018e53, 0x3ba587b8, 0x81cddb36, 0x1269d2dd, 0x3521c10b, 0xa685c8e0,
+		0x7bb1e6a7, 0xe815ef4c, 0xcf5dfc9a, 0x5cf9f571};
+
+	for (size_t i = 0; i < len; i++) {
+		crc = (crc << 8) ^ table[((crc >> 24) ^ data[i]) & 0xff];
+	}
+
+#else
+
+	/**
+	 * CRC table generated from polynomial 0x93a409eb CRC-32K/4.2 (*op) (Koopman)
+	 *
+	 * pycrc --width 32 --poly 0x93a409eb --reflect-in False --xor-in 0 --reflect-out False
+	 * --xor-out 0 --generate table --table-idx-width 4
+	 */
+	static const uint32_t table[16] = {0x00000000, 0x93a409eb, 0xb4ec1a3d, 0x274813d6,
+					   0xfa7c3d91, 0x69d8347a, 0x4e9027ac, 0xdd342e47,
+					   0x675c72c9, 0xf4f87b22, 0xd3b068f4, 0x4014611f,
+					   0x9d204f58, 0x0e8446b3, 0x29cc5565, 0xba685c8e};
+
+	for (size_t i = 0; i < len; i++) {
+		crc = (crc << 4) ^ table[((crc >> 28) ^ (data[i] >> 4)) & 0x0f];
+		crc = (crc << 4) ^ table[((crc >> 28) ^ data[i]) & 0x0f];
+	}
+
+#endif
+
+	return crc;
+}

lib/crc/crc_shell.c

@@ -32,6 +32,7 @@ static const char *const crc_types[] = {
 	[CRC24_PGP] = "24_pgp",
 	[CRC32_C] = "32_c",
 	[CRC32_IEEE] = "32_ieee",
+	[CRC32_K_4_2] = "32_k_4_2",
 };
 
 static int string_to_crc_type(const char *s)

tests/unit/crc/main.c

@@ -12,6 +12,28 @@
 #include "../../../lib/crc/crc32c_sw.c"
 #include "../../../lib/crc/crc7_sw.c"
 #include "../../../lib/crc/crc24_sw.c"
+#include "../../../lib/crc/crc32k_4_2_sw.c"
+
+ZTEST(crc, test_crc32_k_4_2)
+{
+	uint8_t test1[] = "A";
+	uint8_t test2[] = "123456789";
+	uint8_t test3[] = "Zephyr";
+
+	const uint32_t TEST2_CRC = 0x3ee83603;
+
+	zassert_equal(crc32_k_4_2_update(0xFFFFFFFF, test1, sizeof(test1) - 1), 0x2d098604);
+	zassert_equal(crc32_k_4_2_update(0xFFFFFFFF, test2, sizeof(test2) - 1), TEST2_CRC);
+	zassert_equal(crc32_k_4_2_update(0xFFFFFFFF, test3, sizeof(test3) - 1), 0xacf334b2);
+
+	/* test iteration */
+	uint32_t crc = 0xFFFFFFFF;
+
+	for (size_t i = 0; i < sizeof(test2) - 1; i++) {
+		crc = crc32_k_4_2_update(crc, &test2[i], 1);
+	}
+	zassert_equal(crc, TEST2_CRC);
+}
 
 ZTEST(crc, test_crc32c)
 {

tests/unit/crc/testcase.yaml

@@ -3,3 +3,9 @@ tests:
     tags:
       - crc
     type: unit
+  utilities.crc.table256:
+    tags:
+      - crc
+    type: unit
+    extra_configs:
+      - CONFIG_CRC32_K_4_2_TABLE_256=y