- Separate store buffer data in the isolate into the StoreBufferBlock and

runtime/vm/hash_set.h

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_HASH_SET_H_
+#define VM_HASH_SET_H_
+
+#include "vm/allocation.h"
+#include "platform/utils.h"
+
+namespace dart {
+
+class HashSet {
+ public:
+  HashSet(intptr_t size, intptr_t fill_ratio)
+      : keys_(new uword[size]),
+        size_mask_(size - 1),
+        growth_limit_((size * fill_ratio) / 100),
+        count_(0),
+        fill_ratio_(fill_ratio) {
+    ASSERT(Utils::IsPowerOfTwo(size));
+    ASSERT(fill_ratio < 100);
+    memset(keys_, 0, size * sizeof(*keys_));
+  }
+
+  ~HashSet() {
+    delete[] keys_;
+  }
+
+  intptr_t Size() const {
+    return size_mask_ + 1;
+  }
+
+  intptr_t Count() const {
+    return count_;
+  }
+
+  // Returns false if the caller should stop adding entries to this HashSet.
+  bool Add(uword value) {
+    ASSERT(value != 0);
+    ASSERT(count_ < growth_limit_);
+    intptr_t hash = Hash(value);
+    while (true) {
+      if (keys_[hash] == value) {
+        return true;
+      } else if (SlotIsEmpty(hash)) {
+        keys_[hash] = value;
+        count_++;
+        return (count_ < growth_limit_);
+      }
+      hash = (hash + 1) & size_mask_;
+      // Ensure that we do not end up looping forever.
+      ASSERT(hash != Hash(value));
+    }
+    UNREACHABLE();
+  }
+
+  bool Contains(uword value) const {
+    if (value == 0) {
+      return false;
+    }
+    intptr_t hash = Hash(value);
+    while (true) {
+      if (keys_[hash] == value) {
+        return true;
+      } else if (SlotIsEmpty(hash)) {
+        return false;
+      }
+      hash = (hash + 1) & size_mask_;
+      // Ensure that we do not end up looping forever.
+      ASSERT(hash != Hash(value));
+    }
+    UNREACHABLE();
+  }
+
+ private:
+  intptr_t Hash(uword value) const {
+    return value & size_mask_;
+  }
+
+  // Returns true if the given slot contains a value.
+  bool SlotIsEmpty(intptr_t index) const {
+    return keys_[index] == 0;
+  }
+
+  uword* keys_;
+  intptr_t size_mask_;
+  intptr_t growth_limit_;
+  intptr_t count_;
+  intptr_t fill_ratio_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(HashSet);
+};
+
+}  // namespace dart
+
+#endif  // VM_HASH_SET_H_