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+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following
+// disclaimer in the documentation and/or other materials provided
+// with the distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived
+// from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_HYDROGEN_UNIQUE_H_
+#define V8_HYDROGEN_UNIQUE_H_
+
+#include "handles.h"
+#include "utils.h"
+#include "zone.h"
+
+namespace v8 {
+namespace internal {
+
+
+template <typename T>
+class UniqueSet;
+
+
+// Represents a handle to an object on the heap, but with the additional
+// ability of checking for equality and hashing without accessing the heap.
+//
+// Creating a Unique<T> requires first dereferencing the handle to obtain
+// the address of the object, which is used as the hashcode and the basis for
+// comparison. The object can be moved later by the GC, but comparison
+// and hashing use the old address of the object, without dereferencing it.
+//
+// Careful! Comparison of two Uniques is only correct if both were created
+// in the same "era" of GC or if at least one is a non-movable object.
+template <typename T>
+class Unique V8_FINAL {
+ public:
+ // TODO(titzer): make private and introduce some builder/owner class.
+ explicit Unique(Handle<T> handle) {
+ if (handle.is_null()) {
+ raw_address_ = NULL;
+ } else {
+ raw_address_ = reinterpret_cast<Address>(*handle);
+ ASSERT_NE(raw_address_, NULL);
+ }
+ handle_ = handle;
+ }
+
+ // Constructor for handling automatic up casting.
+ // Ex. Unique<JSFunction> can be passed when Unique<Object> is expected.
+ template <class S> Unique(Unique<S> uniq) {
+#ifdef DEBUG
+ T* a = NULL;
+ S* b = NULL;
+ a = b; // Fake assignment to enforce type checks.
+ USE(a);
+#endif
+ raw_address_ = uniq.raw_address_;
+ handle_ = uniq.handle_; // Creates a new handle sharing the same location.
+ }
+
+ template <typename U>
+ bool operator==(const Unique<U>& other) const {
+ return raw_address_ == other.raw_address_;
+ }
+
+ template <typename U>
+ bool operator!=(const Unique<U>& other) const {
+ return raw_address_ != other.raw_address_;
+ }
+
+ intptr_t Hashcode() const {
+ return reinterpret_cast<intptr_t>(raw_address_);
+ }
+
+ bool IsNull() {
+ return raw_address_ == NULL;
+ }
+
+ // Don't do this unless you have access to the heap!
+ // No, seriously! You can compare and hash and set-ify uniques that were
+ // all created at the same time; please don't dereference.
+ Handle<T> handle() {
+ return handle_;
+ }
+
+ friend class UniqueSet<T>; // Uses internal details for speed.
+ template <class U>
+ friend class Unique; // For comparing raw_address values.
+
+ private:
+ Address raw_address_;
+ Handle<T> handle_;
+};
+
+
+template <typename T>
+class UniqueSet V8_FINAL : public ZoneObject {
+ public:
+ // Constructor. A new set will be empty.
+ UniqueSet() : size_(0), capacity_(0), array_(NULL) { }
+
+ // Add a new element to this unique set. Mutates this set. O(|this|).
+ void Add(Unique<T> uniq, Zone* zone) {
+ // Keep the set sorted by the {raw_address} of the unique elements.
+ for (int i = 0; i < size_; i++) {
+ if (array_[i] == uniq) return;
+ if (array_[i].raw_address_ > uniq.raw_address_) {
+ // Insert in the middle.
+ Grow(size_ + 1, zone);
+ for (int j = size_ - 1; j >= i; j--) array_[j + 1] = array_[j];
+ array_[i] = uniq;
+ size_++;
+ return;
+ }
+ }
+ // Append the element to the the end.
+ Grow(size_ + 1, zone);
+ array_[size_++] = uniq;
+ }
+
+ // Compare this set against another set. O(|this|).
+ bool Equals(UniqueSet<T>* that) {
+ if (that->size_ != this->size_) return false;
+ for (int i = 0; i < this->size_; i++) {
+ if (this->array_[i] != that->array_[i]) return false;
+ }
+ return true;
+ }
+
+ // Check if this set is a subset of the given set. O(|this| + |that|).
+ bool IsSubset(UniqueSet<T>* that) {
+ if (that->size_ < this->size_) return false;
+ int j = 0;
+ for (int i = 0; i < this->size_; i++) {
+ Unique<T> sought = this->array_[i];
+ while (true) {
+ if (sought == that->array_[j++]) break;
+ // Fail whenever there are more elements in {this} than {that}.
+ if ((this->size_ - i) > (that->size_ - j)) return false;
+ }
+ }
+ return true;
+ }
+
+ // Returns a new set representing the intersection of this set and the other.
+ // O(|this| + |that|).
+ UniqueSet<T>* Intersect(UniqueSet<T>* that, Zone* zone) {
+ if (that->size_ == 0 || this->size_ == 0) return new(zone) UniqueSet<T>();
+
+ UniqueSet<T>* out = new(zone) UniqueSet<T>();
+ out->Grow(Min(this->size_, that->size_), zone);
+
+ int i = 0, j = 0, k = 0;
+ while (i < this->size_ && j < that->size_) {
+ Unique<T> a = this->array_[i];
+ Unique<T> b = that->array_[j];
+ if (a == b) {
+ out->array_[k++] = a;
+ i++;
+ j++;
+ } else if (a.raw_address_ < b.raw_address_) {
+ i++;
+ } else {
+ j++;
+ }
+ }
+
+ out->size_ = k;
+ return out;
+ }
+
+ // Returns a new set representing the union of this set and the other.
+ // O(|this| + |that|).
+ UniqueSet<T>* Union(UniqueSet<T>* that, Zone* zone) {
+ if (that->size_ == 0) return this->Copy(zone);
+ if (this->size_ == 0) return that->Copy(zone);
+
+ UniqueSet<T>* out = new(zone) UniqueSet<T>();
+ out->Grow(this->size_ + that->size_, zone);
+
+ int i = 0, j = 0, k = 0;
+ while (i < this->size_ && j < that->size_) {
+ Unique<T> a = this->array_[i];
+ Unique<T> b = that->array_[j];
+ if (a == b) {
+ out->array_[k++] = a;
+ i++;
+ j++;
+ } else if (a.raw_address_ < b.raw_address_) {
+ out->array_[k++] = a;
+ i++;
+ } else {
+ out->array_[k++] = b;
+ j++;
+ }
+ }
+
+ while (i < this->size_) out->array_[k++] = this->array_[i++];
+ while (j < that->size_) out->array_[k++] = that->array_[j++];
+
+ out->size_ = k;
+ return out;
+ }
+
+ // Makes an exact copy of this set. O(|this| + |that|).
+ UniqueSet<T>* Copy(Zone* zone) {
+ UniqueSet<T>* copy = new(zone) UniqueSet<T>();
+ copy->size_ = this->size_;
+ copy->capacity_ = this->size_;
+ copy->array_ = zone->NewArray<Unique<T> >(this->size_);
+ memcpy(copy->array_, this->array_, this->size_ * sizeof(Unique<T>));
+ return copy;
+ }
+
+ inline int size() {
+ return size_;
+ }
+
+ private:
+ // These sets should be small, since operations are implemented with simple
+ // linear algorithms. Enforce a maximum size.
+ static const int kMaxCapacity = 65535;
+
+ uint16_t size_;
+ uint16_t capacity_;
+ Unique<T>* array_;
+
+ // Grow the size of internal storage to be at least {size} elements.
+ void Grow(int size, Zone* zone) {
+ CHECK(size < kMaxCapacity); // Enforce maximum size.
+ if (capacity_ < size) {
+ int new_capacity = 2 * capacity_ + size;
+ if (new_capacity > kMaxCapacity) new_capacity = kMaxCapacity;
+ Unique<T>* new_array = zone->NewArray<Unique<T> >(new_capacity);
+ if (size_ > 0) {
+ memcpy(new_array, array_, size_ * sizeof(Unique<T>));
+ }
+ capacity_ = new_capacity;
+ array_ = new_array;
+ }
+ }
+};
+
+
+} } // namespace v8::internal
+
+#endif // V8_HYDROGEN_UNIQUE_H_
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