token_metadata: Add get_predecessor

It is used to get the previous token of this token in the ring.

locator/token_metadata.cc

@@ -302,6 +302,17 @@ void token_metadata::remove_from_moving(inet_address endpoint) {
     invalidate_cached_rings();
 }
 
+token token_metadata::get_predecessor(token t) {
+    auto& tokens = sorted_tokens();
+    auto it = std::lower_bound(tokens.begin(), tokens.end(), t);
+    assert(it != tokens.end() && *it == t);
+    if (it == tokens.begin()) {
+        // If the token is the first element, its preprocessor is the last element
+        return tokens.back();
+    } else {
+        return *(--it);
+    }
+}
 
 /////////////////// class topology /////////////////////////////////////////////
 inline void topology::clear() {

locator/token_metadata.hh

@@ -810,15 +810,12 @@ public:
             lock.readLock().unlock();
         }
     }
+#endif
+public:
 
-    public Token getPredecessor(Token token)
-    {
-        List tokens = sortedTokens();
-        int index = Collections.binarySearch(tokens, token);
-        assert index >= 0 : token + " not found in " + StringUtils.join(tokenToEndpointMap.keySet(), ", ");
-        return (Token) (index == 0 ? tokens.get(tokens.size() - 1) : tokens.get(index - 1));
-    }
+    token get_predecessor(token t);
 
+#if 0
     public Token getSuccessor(Token token)
     {
         List tokens = sortedTokens();