util/uuid: add a hash function

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 <philmd@linaro.org>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
Message-Id: <20231002065706.94707-2-aesteve@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/util/uuid.c b/util/uuid.c
index b1108dd..d71aa79 100644
--- a/util/uuid.c
+++ b/util/uuid.c
@@ -116,3 +116,17 @@ 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;
+}