add jhash.h, copied from linux/jhash.h

Allow using arbitrary length data as hashtable key: Copy jhash.h implementation from the linux kernel. Apply osmo_ prefix to all global symbols. Add jhash_test to ensure the code import works as intended. First application will be a hashtable keyed by umts_cell_id in osmo-hnbgw.git. Related: SYS#6773 Change-Id: I0c9652bbc9e2a18b1200e7d63bb6f64ded7d75fa
2024-05-23 02:59:53 +02:00 · 2024-05-23 02:59:53 +02:00 · 4f0dbac51c
parent d8ac068478
commit 4f0dbac51c
6 changed files with 265 additions and 2 deletions
--- a/include/osmocom/core/Makefile.am
+++ b/include/osmocom/core/Makefile.am
@ -27,6 +27,7 @@ osmocore_HEADERS = \
 	hashtable.h \
 	isdnhdlc.h \
 	it_q.h \
+	jhash.h \
 	linuxlist.h \
 	linuxrbtree.h \
 	log2.h \
--- a/include/osmocom/core/jhash.h
+++ b/include/osmocom/core/jhash.h
@ -0,0 +1,171 @@
+#pragma once
+#include <osmocom/core/bit32gen.h>
+
+/* Below is a partial copy of
+ * https://raw.githubusercontent.com/torvalds/linux/3eb3c33c1d87029a3832e205eebd59cfb56ba3a4/tools/include/linux/bitops.h
+ * with an osmo_ prefix applied to avoid any collisions.
+ */
+/* SPDX-License-Identifier: GPL-2.0 */
+/**
+ * rol32 - rotate a 32-bit value left
+ * @word: value to rotate
+ * @shift: bits to roll
+ */
+static inline uint32_t osmo_rol32(uint32_t word, unsigned int shift)
+{
+	return (word << shift) | (word >> ((-shift) & 31));
+}
+
+/* Below is a partial copy of
+ * https://raw.githubusercontent.com/torvalds/linux/22c033989c3eb9731ad0c497dfab4231b8e367d6/include/linux/unaligned/packed_struct.h
+ * with an osmo_ prefix applied to avoid any collisions.
+ */
+struct osmo_unaligned_cpu32 {
+	uint32_t x;
+} __attribute__((__packed__));
+
+static inline uint32_t osmo_get_unaligned_cpu32(const void *p)
+{
+	const struct osmo_unaligned_cpu32 *ptr = (const struct osmo_unaligned_cpu32 *)p;
+	return ptr->x;
+}
+
+/* Below is a partial copy of
+ * https://raw.githubusercontent.com/torvalds/linux/79e3ea5aab48c83de9410e43b52895406847eca7/tools/include/linux/jhash.h
+ * with an osmo_ prefix applied to avoid any collisions.
+ */
+/* jhash.h: Jenkins hash support.
+ *
+ * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
+ *
+ * https://burtleburtle.net/bob/hash/
+ *
+ * These are the credits from Bob's sources:
+ *
+ * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
+ *
+ * These are functions for producing 32-bit hashes for hash table lookup.
+ * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
+ * are externally useful functions.  Routines to test the hash are included
+ * if SELF_TEST is defined.  You can use this free for any purpose.  It's in
+ * the public domain.  It has no warranty.
+ *
+ * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
+ *
+ * I've modified Bob's hash to be useful in the Linux kernel, and
+ * any bugs present are my fault.
+ * Jozsef
+ */
+
+/* OSMO_JHASH_MIX -- mix 3 32-bit values reversibly. */
+#define OSMO_JHASH_MIX(a, b, c)			\
+{						\
+	a -= c;  a ^= osmo_rol32(c, 4);  c += b;	\
+	b -= a;  b ^= osmo_rol32(a, 6);  a += c;	\
+	c -= b;  c ^= osmo_rol32(b, 8);  b += a;	\
+	a -= c;  a ^= osmo_rol32(c, 16); c += b;	\
+	b -= a;  b ^= osmo_rol32(a, 19); a += c;	\
+	c -= b;  c ^= osmo_rol32(b, 4);  b += a;	\
+}
+
+/* OSMO_JHASH_FINAL - final mixing of 3 32-bit values (a,b,c) into c */
+#define OSMO_JHASH_FINAL(a, b, c)			\
+{						\
+	c ^= b; c -= osmo_rol32(b, 14);		\
+	a ^= c; a -= osmo_rol32(c, 11);		\
+	b ^= a; b -= osmo_rol32(a, 25);		\
+	c ^= b; c -= osmo_rol32(b, 16);		\
+	a ^= c; a -= osmo_rol32(c, 4);		\
+	b ^= a; b -= osmo_rol32(a, 14);		\
+	c ^= b; c -= osmo_rol32(b, 24);		\
+}
+
+/* An arbitrary initial parameter */
+#define JHASH_INITVAL		0xdeadbeef
+
+/* osmo_jhash - hash an arbitrary key
+ * @k: sequence of bytes as key
+ * @length: the length of the key
+ * @initval: the previous hash, or an arbitray value
+ *
+ * The generic version, hashes an arbitrary sequence of bytes.
+ * No alignment or length assumptions are made about the input key.
+ *
+ * Returns the hash value of the key. The result depends on endianness.
+ */
+static inline uint32_t osmo_jhash(const void *key, uint32_t length, uint32_t initval)
+{
+	uint32_t a, b, c;
+	const uint8_t *k = key;
+
+	/* Set up the internal state */
+	a = b = c = JHASH_INITVAL + length + initval;
+
+	/* All but the last block: affect some 32 bits of (a,b,c) */
+	while (length > 12) {
+		a += osmo_get_unaligned_cpu32(k);
+		b += osmo_get_unaligned_cpu32(k + 4);
+		c += osmo_get_unaligned_cpu32(k + 8);
+		OSMO_JHASH_MIX(a, b, c);
+		length -= 12;
+		k += 12;
+	}
+	/* Last block: affect all 32 bits of (c) */
+	/* All the case statements fall through */
+	switch (length) {
+	case 12: c += (uint32_t)k[11]<<24;
+	case 11: c += (uint32_t)k[10]<<16;
+	case 10: c += (uint32_t)k[9]<<8;
+	case 9:  c += k[8];
+	case 8:  b += (uint32_t)k[7]<<24;
+	case 7:  b += (uint32_t)k[6]<<16;
+	case 6:  b += (uint32_t)k[5]<<8;
+	case 5:  b += k[4];
+	case 4:  a += (uint32_t)k[3]<<24;
+	case 3:  a += (uint32_t)k[2]<<16;
+	case 2:  a += (uint32_t)k[1]<<8;
+	case 1:  a += k[0];
+		 OSMO_JHASH_FINAL(a, b, c);
+	case 0: /* Nothing left to add */
+		break;
+	}
+
+	return c;
+}
+
+/* osmo_jhash2 - hash an array of uint32_t's
+ * @k: the key which must be an array of uint32_t's
+ * @length: the number of uint32_t's in the key
+ * @initval: the previous hash, or an arbitray value
+ *
+ * Returns the hash value of the key.
+ */
+static inline uint32_t osmo_jhash2(const uint32_t *k, uint32_t length, uint32_t initval)
+{
+	uint32_t a, b, c;
+
+	/* Set up the internal state */
+	a = b = c = JHASH_INITVAL + (length<<2) + initval;
+
+	/* Handle most of the key */
+	while (length > 3) {
+		a += k[0];
+		b += k[1];
+		c += k[2];
+		OSMO_JHASH_MIX(a, b, c);
+		length -= 3;
+		k += 3;
+	}
+
+	/* Handle the last 3 uint32_t's: all the case statements fall through */
+	switch (length) {
+	case 3: c += k[2];
+	case 2: b += k[1];
+	case 1: a += k[0];
+		OSMO_JHASH_FINAL(a, b, c);
+	case 0:	/* Nothing left to add */
+		break;
+	}
+
+	return c;
+}
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@ -59,6 +59,7 @@ check_PROGRAMS = timer/timer_test sms/sms_test ussd/ussd_test		\
 		 osmo_io/osmo_io_test					\
 		 soft_uart/soft_uart_test				\
 		 rlp/rlp_test						\
+		 jhash/jhash_test					\
 		 $(NULL)

 if ENABLE_MSGFILE
@ -391,6 +392,7 @@ soft_uart_soft_uart_test_SOURCES = soft_uart/soft_uart_test.c
 rlp_rlp_test_SOURCES = rlp/rlp_test.c
 rlp_rlp_test_LDADD = $(top_builddir)/src/gsm/libosmogsm.la $(LDADD)

+jhash_jhash_test_SOURCES = jhash/jhash_test.c

 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
@ -505,6 +507,7 @@ EXTRA_DIST = testsuite.at $(srcdir)/package.m4 $(TESTSUITE)		\
 	     soft_uart/soft_uart_test.ok \
 	     rlp/rlp_test.ok \
 	     socket/socket_sctp_test.ok socket/socket_sctp_test.err \
+	     jhash/jhash_test.ok \
 	     $(NULL)

 if ENABLE_LIBSCTP
@ -729,8 +732,9 @@ endif
 	soft_uart/soft_uart_test \
 		>$(srcdir)/soft_uart/soft_uart_test.ok
 	rlp/rlp_test \
-		>$(srcdir)/rlp/rlp_test.ok \
-	$(NULL)
+		>$(srcdir)/rlp/rlp_test.ok
+	jhash/jhash_test \
+		>$(srcdir)/jhash/jhash_test.ok


 check-local: atconfig $(TESTSUITE)
--- a/tests/jhash/jhash_test.c
+++ b/tests/jhash/jhash_test.c
@ -0,0 +1,56 @@
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/hashtable.h>
+#include <osmocom/core/jhash.h>
+
+struct item {
+	const char blob[32];
+	struct hlist_node node;
+};
+
+struct item items[] = {
+	{ "blob one", },
+	{ "blob two and five are the same", },
+	{ "third blob", },
+	{ "fourth blob", },
+	{ "blob two and five are the same", },
+};
+
+uint32_t item_hash(const struct item *item)
+{
+	return osmo_jhash(item->blob, strlen(item->blob), 0);
+}
+
+int main(void)
+{
+	int i;
+	struct item *item;
+
+	DECLARE_HASHTABLE(haystack, 5);
+	hash_init(haystack);
+
+	printf("add:\n");
+	for (i = 0; i < ARRAY_SIZE(items); i++) {
+		uint32_t hash;
+		item = &items[i];
+		hash_add(haystack, &item->node, hash = item_hash(item));
+		printf("- adding items[%d]#%x = %s\n", i, hash, item->blob);
+	}
+
+	printf("list:\n");
+	hash_for_each (haystack, i, item, node)
+		printf("- %s [%d]\n", item->blob, (int)(item - items));
+
+	printf("find:\n");
+	for (i = 0; i < ARRAY_SIZE(items); i++) {
+		uint32_t hash;
+		struct item *needle = &items[i];
+		hash = item_hash(needle);
+		printf("- looking up items[%d]#%x = %s\n", i, hash, needle->blob);
+		hash_for_each_possible (haystack, item, node, hash)
+			printf("  - %s items[%d]\n",
+			       (item == needle) ? "found" : "not",
+			       (int)(item - items));
+	}
+
+	return 0;
+}
--- a/tests/jhash/jhash_test.ok
+++ b/tests/jhash/jhash_test.ok
@ -0,0 +1,25 @@
+add:
+- adding items[0]#b286bb61 = blob one
+- adding items[1]#ad4eb7b = blob two and five are the same
+- adding items[2]#6b8eae61 = third blob
+- adding items[3]#24a546dc = fourth blob
+- adding items[4]#ad4eb7b = blob two and five are the same
+list:
+- blob two and five are the same [4]
+- blob two and five are the same [1]
+- blob one [0]
+- fourth blob [3]
+- third blob [2]
+find:
+- looking up items[0]#b286bb61 = blob one
+  - found items[0]
+- looking up items[1]#ad4eb7b = blob two and five are the same
+  - not items[4]
+  - found items[1]
+- looking up items[2]#6b8eae61 = third blob
+  - found items[2]
+- looking up items[3]#24a546dc = fourth blob
+  - found items[3]
+- looking up items[4]#ad4eb7b = blob two and five are the same
+  - found items[4]
+  - not items[1]
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@ -547,3 +547,9 @@ AT_KEYWORDS([rlp])
 cat $abs_srcdir/rlp/rlp_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/rlp/rlp_test], [0], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([jhash])
+AT_KEYWORDS([jhash])
+cat $abs_srcdir/jhash/jhash_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/jhash/jhash_test], [0], [expout], [ignore])
+AT_CLEANUP