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Tsirkin" , Fam Zheng , philmd@linaro.org, Albert Esteve Subject: [PATCH v7 1/4] uuid: add a hash function Date: Thu, 7 Sep 2023 09:43:15 +0200 Message-ID: <20230907074318.528064-2-aesteve@redhat.com> In-Reply-To: <20230907074318.528064-1-aesteve@redhat.com> References: <20230907074318.528064-1-aesteve@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=aesteve@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Add hash function to uuid module using the djb2 hash algorithm. Add a couple simple unit tests for the hash function, checking collisions for similar UUIDs. Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Albert Esteve --- include/qemu/uuid.h | 2 ++ tests/unit/test-uuid.c | 27 +++++++++++++++++++++++++++ util/uuid.c | 15 +++++++++++++++ 3 files changed, 44 insertions(+) diff --git a/include/qemu/uuid.h b/include/qemu/uuid.h index dc40ee1fc9..e24a1099e4 100644 --- a/include/qemu/uuid.h +++ b/include/qemu/uuid.h @@ -96,4 +96,6 @@ int qemu_uuid_parse(const char *str, QemuUUID *uuid); QemuUUID qemu_uuid_bswap(QemuUUID uuid); +uint32_t qemu_uuid_hash(const void *uuid); + #endif diff --git a/tests/unit/test-uuid.c b/tests/unit/test-uuid.c index c111de5fc1..aedc125ae9 100644 --- a/tests/unit/test-uuid.c +++ b/tests/unit/test-uuid.c @@ -171,6 +171,32 @@ static void test_uuid_unparse_strdup(void) } } +static void test_uuid_hash(void) +{ + QemuUUID uuid; + int i; + + for (i = 0; i < 100; i++) { + qemu_uuid_generate(&uuid); + /* Obtain the UUID hash */ + uint32_t hash_a = qemu_uuid_hash(&uuid); + int data_idx = g_random_int_range(0, 15); + /* Change a single random byte of the UUID */ + if (uuid.data[data_idx] < 0xFF) { + uuid.data[data_idx]++; + } else { + uuid.data[data_idx]--; + } + /* Obtain the UUID hash again */ + uint32_t hash_b = qemu_uuid_hash(&uuid); + /* + * Both hashes shall be different (avoid collision) + * for any change in the UUID fields + */ + g_assert_cmpint(hash_a, !=, hash_b); + } +} + int main(int argc, char **argv) { g_test_init(&argc, &argv, NULL); @@ -179,6 +205,7 @@ int main(int argc, char **argv) g_test_add_func("/uuid/parse", test_uuid_parse); g_test_add_func("/uuid/unparse", test_uuid_unparse); g_test_add_func("/uuid/unparse_strdup", test_uuid_unparse_strdup); + g_test_add_func("/uuid/hash", test_uuid_hash); return g_test_run(); } diff --git a/util/uuid.c b/util/uuid.c index b1108dde78..b366961bc6 100644 --- a/util/uuid.c +++ b/util/uuid.c @@ -116,3 +116,18 @@ QemuUUID qemu_uuid_bswap(QemuUUID uuid) bswap16s(&uuid.fields.time_high_and_version); return uuid; } + +/* djb2 hash algorithm */ +uint32_t qemu_uuid_hash(const void *uuid) +{ + QemuUUID *qid = (QemuUUID *) uuid; + uint32_t h = 5381; + int i; + + for (i = 0; i < ARRAY_SIZE(qid->data); i++) { + h = (h << 5) + h + qid->data[i]; + } + + return h; +} +