infdahai commented on code in PR #1489:
URL:
https://github.com/apache/incubator-kvrocks/pull/1489#discussion_r1234260165
##########
src/server/server.cc:
##########
@@ -1753,3 +1755,52 @@ std::list<std::pair<std::string, uint32_t>>
Server::GetSlaveHostAndPort() {
slave_threads_mu_.unlock();
return result;
}
+
+// The numeric cursor consists of a 32-bit hash, a 16-bit time stamp, and a
16-bit counter, with the highest bit set to
+// 1 to prevent a zero cursor from occurring. The hash is used to prevent
information leakage. The time_stamp is used to
+// prevent the generation of the same cursor in the extremely short period
before and after a restart.
+static uint64_t GetNumberCursor(const std::string &key_name, uint16_t counter)
{
+ auto hash = static_cast<uint32_t>(std::hash<std::string>{}(key_name));
+ auto time_stamp = static_cast<uint16_t>(util::GetTimeStamp());
+ // set first bit 1, so number cursor not be 0
+ return static_cast<uint64_t>(hash) | static_cast<uint64_t>(time_stamp) << 32
| static_cast<uint64_t>(counter) << 48 |
+ static_cast<uint64_t>(1) << 63;
+}
+
+static size_t GetIndexFromNumberCursor(uint64_t number_cursor) { return
(number_cursor >> 48) % CURSOR_DICT_SIZE; }
Review Comment:
hi @jihuayu can I ask why the counter puts the high bit? I mean maybe we
don't need to move the bit here.
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