8271506: Add ResourceHashtable support for deleting selected entries

Reviewed-by: iklam, stuefe

src/hotspot/share/utilities/resourceHash.hpp

@@ -56,7 +56,12 @@ class ResourceHashtableBase : public STORAGE {
  private:
   int _number_of_entries;
 
-  Node** bucket_at(unsigned index) const {
+  Node** bucket_at(unsigned index) {
+    Node** t = table();
+    return &t[index];
+  }
+
+  const Node* const* bucket_at(unsigned index) const {
     Node** t = table();
     return &t[index];
   }
@@ -210,6 +215,32 @@ class ResourceHashtableBase : public STORAGE {
       ++bucket;
     }
   }
+
+  // ITER contains bool do_entry(K const&, V const&), which will be
+  // called for each entry in the table.  If do_entry() returns true,
+  // the entry is deleted.
+  template<class ITER>
+  void unlink(ITER* iter) {
+    const unsigned sz = table_size();
+    for (unsigned index = 0; index < sz; index++) {
+      Node** ptr = bucket_at(index);
+      while (*ptr != NULL) {
+        Node* node = *ptr;
+        // do_entry must clean up the key and value in Node.
+        bool clean = iter->do_entry(node->_key, node->_value);
+        if (clean) {
+          *ptr = node->_next;
+          if (ALLOC_TYPE == ResourceObj::C_HEAP) {
+            delete node;
+          }
+          _number_of_entries --;
+        } else {
+          ptr = &(node->_next);
+        }
+      }
+    }
+  }
+
 };
 
 template<unsigned TABLE_SIZE, typename K, typename V>

test/hotspot/gtest/utilities/test_resourceHash.cpp

@@ -60,6 +60,21 @@ class CommonResourceHashtableTest : public ::testing::Test {
     }
   };
 
+  class DeleterTestIter {
+    int _val;
+   public:
+    DeleterTestIter(int i) : _val(i) {}
+
+    bool do_entry(K const& k, V const& v) {
+      if ((uintptr_t) k == (uintptr_t) _val) {
+        // Delete me!
+        return true;
+      } else {
+        return false; // continue iteration
+      }
+    }
+  };
+
 };
 
 class SmallResourceHashtableTest : public CommonResourceHashtableTest {
@@ -233,6 +248,15 @@ class GenericResourceHashtableTest : public CommonResourceHashtableTest {
         ASSERT_FALSE(rh.remove(as_K(index)));
       }
       rh.iterate(&et);
+
+      // Add more entries in and then delete one.
+      for (uintptr_t i = 10; i > 0; --i) {
+        uintptr_t index = i - 1;
+        ASSERT_TRUE(rh.put(as_K(index), index));
+      }
+      DeleterTestIter dt(5);
+      rh.unlink(&dt);
+      ASSERT_FALSE(rh.get(as_K(5)));
     }
   };
 };