jihuayu commented on code in PR #1489:
URL:
https://github.com/apache/incubator-kvrocks/pull/1489#discussion_r1233985519
##########
src/server/server.cc:
##########
@@ -1753,3 +1755,50 @@ 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;
+}
+
+std::string Server::GenerateCursorFromKeyName(const std::string &key_name,
const char *prefix) {
+ if (!config_->redis_cursor_compatible) {
+ // add prefix for SCAN
+ return prefix + key_name;
+ }
+ auto counter = cursor_counter_.fetch_add(1);
+ auto number_cursor = GetNumberCursor(key_name, counter);
+ auto index = counter % CURSOR_DICT_SIZE;
+ cursor_dict_[index] = {number_cursor, key_name};
+ return std::to_string(number_cursor);
+}
+
+std::string Server::GetKeyNameFromCursor(const std::string &cursor) {
+ // When cursor is 0, cursor string is empty
+ if (cursor.empty() || !config_->redis_cursor_compatible) {
+ return cursor;
+ }
+
+ auto s = ParseInt<uint64_t>(cursor, 10);
+ // When Cursor 0 or not a Integer return empty string.
+ // Although the parameter 'cursor' is not expected to be 0, we still added a
check for 0 to increase the robustness of
+ // the code.
+ if (!s.IsOK() || *s == 0) {
+ return {};
+ }
+ auto cursor_num = *s;
+ // Because the index information is fully stored in the cursor, we can
directly obtain the index from the cursor.
+ auto index = (cursor_num >> 48) % CURSOR_DICT_SIZE;
Review Comment:
CURSOR_DICT_SIZE must less than 2**15, I add `static_assert` in .h file.
https://github.com/apache/incubator-kvrocks/pull/1489/files#diff-a57adfc622093e1a4bedd3c0d7727e6c42b126a015fd5f2c166aed385c2557b3R94
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