Move hashmap into base/.

src/base/hashmap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// This file is ported from src/hashmap.h
-
-#ifndef V8_LIBSAMPLER_HASHMAP_H_
-#define V8_LIBSAMPLER_HASHMAP_H_
+#ifndef V8_BASE_HASHMAP_H_
+#define V8_BASE_HASHMAP_H_
 
 #include "src/base/bits.h"
 #include "src/base/logging.h"
-#include "src/libsampler/utils.h"
 
 namespace v8 {
-namespace sampler {
+namespace base {
 
 class HashMapImpl {

[Yang, 2016/05/30 09:19:04]

Imo this name is misleading. "Impl" stands for implementation. But this is not a
full implementation. Rather it has to be extended to be usable. Can we rename it
to HashMapBase or something along that line?

  public:
-  typedef bool (*MatchFun) (void* key1, void* key2);
+  typedef bool (*MatchFun)(void* key1, void* key2);
 
-  // The default capacity.
+  // The default capacity.  This is used by the call sites which want
+  // to pass in a non-default AllocationPolicy but want to use the
+  // default value of capacity specified by the implementation.
   static const uint32_t kDefaultHashMapCapacity = 8;
 
-  // initial_capacity is the size of the initial hash map;
-  // it must be a power of 2 (and thus must not be 0).
-  HashMapImpl(MatchFun match,
-              uint32_t capacity = kDefaultHashMapCapacity);
+  HashMapImpl() {}
 
-  ~HashMapImpl();
+  virtual ~HashMapImpl() {}
 
   // HashMap entries are (key, value, hash) triplets.
   // Some clients may not need to use the value slot
   // (e.g. implementers of sets, where the key is the value).
   struct Entry {
     void* key;
     void* value;
     uint32_t hash;  // The full hash value for key
-    int order;  // If you never remove entries this is the insertion order.
+    int order;      // If you never remove entries this is the insertion order.
   };
 
   // If an entry with matching key is found, returns that entry.
   // Otherwise, NULL is returned.
   Entry* Lookup(void* key, uint32_t hash) const;
 
   // If an entry with matching key is found, returns that entry.
   // If no matching entry is found, a new entry is inserted with
   // corresponding key, key hash, and NULL value.
   Entry* LookupOrInsert(void* key, uint32_t hash);
@@ skipping 19 matching lines @@
   // for (Entry* p = map.Start(); p != NULL; p = map.Next(p)) {
   //   ...
   // }
   //
   // If entries are inserted during iteration, the effect of
   // calling Next() is undefined.
   Entry* Start() const;
   Entry* Next(Entry* p) const;
 
   // Some match functions defined for convenience.
-  static bool PointersMatch(void* key1, void* key2) {
-    return key1 == key2;
-  }
+  static bool PointersMatch(void* key1, void* key2) { return key1 == key2; }
 
- private:
+ protected:
   MatchFun match_;
   Entry* map_;
   uint32_t capacity_;
   uint32_t occupancy_;
 
+  Entry* Probe(void* key, uint32_t hash) const;
+  virtual void Resize() = 0;
   Entry* map_end() const { return map_ + capacity_; }
-  Entry* Probe(void* key, uint32_t hash) const;
-  void Initialize(uint32_t capacity);
-  void Resize();
 };
 
-typedef HashMapImpl HashMap;
+class HashMap : public HashMapImpl {
+ public:
+  // initial_capacity is the size of the initial hash map;
+  // it must be a power of 2 (and thus must not be 0).
+  explicit HashMap(MatchFun match, uint32_t capacity = kDefaultHashMapCapacity);
 
-HashMapImpl::HashMapImpl(MatchFun match, uint32_t initial_capacity) {
-  match_ = match;
-  Initialize(initial_capacity);
-}
+  ~HashMap() override;
 
+ private:
+  void Initialize(uint32_t capacity);
+  void Resize() override;
+};
 
-HashMapImpl::~HashMapImpl() {
-  Malloced::Delete(map_);
-}
-
-
-HashMapImpl::Entry* HashMapImpl::Lookup(void* key, uint32_t hash) const {
-  Entry* p = Probe(key, hash);
-  return p->key != NULL ? p : NULL;
-}
-
-
-HashMapImpl::Entry* HashMapImpl::LookupOrInsert(void* key, uint32_t hash) {
-  // Find a matching entry.
-  Entry* p = Probe(key, hash);
-  if (p->key != NULL) {
-    return p;
-  }
-
-  // No entry found; insert one.
-  p->key = key;
-  p->value = NULL;
-  p->hash = hash;
-  p->order = occupancy_;
-  occupancy_++;
-
-  // Grow the map if we reached >= 80% occupancy.
-  if (occupancy_ + occupancy_ / 4 >= capacity_) {
-    Resize();
-    p = Probe(key, hash);
-  }
-
-  return p;
-}
-
-
-void* HashMapImpl::Remove(void* key, uint32_t hash) {
-  // Lookup the entry for the key to remove.
-  Entry* p = Probe(key, hash);
-  if (p->key == NULL) {
-    // Key not found nothing to remove.
-    return NULL;
-  }
-
-  void* value = p->value;
-  // To remove an entry we need to ensure that it does not create an empty
-  // entry that will cause the search for another entry to stop too soon. If all
-  // the entries between the entry to remove and the next empty slot have their
-  // initial position inside this interval, clearing the entry to remove will
-  // not break the search. If, while searching for the next empty entry, an
-  // entry is encountered which does not have its initial position between the
-  // entry to remove and the position looked at, then this entry can be moved to
-  // the place of the entry to remove without breaking the search for it. The
-  // entry made vacant by this move is now the entry to remove and the process
-  // starts over.
-  // Algorithm from http://en.wikipedia.org/wiki/Open_addressing.
-
-  // This guarantees loop termination as there is at least one empty entry so
-  // eventually the removed entry will have an empty entry after it.
-  DCHECK(occupancy_ < capacity_);
-
-  // p is the candidate entry to clear. q is used to scan forwards.
-  Entry* q = p;  // Start at the entry to remove.
-  while (true) {
-    // Move q to the next entry.
-    q = q + 1;
-    if (q == map_end()) {
-      q = map_;
-    }
-
-    // All entries between p and q have their initial position between p and q
-    // and the entry p can be cleared without breaking the search for these
-    // entries.
-    if (q->key == NULL) {
-      break;
-    }
-
-    // Find the initial position for the entry at position q.
-    Entry* r = map_ + (q->hash & (capacity_ - 1));
-
-    // If the entry at position q has its initial position outside the range
-    // between p and q it can be moved forward to position p and will still be
-    // found. There is now a new candidate entry for clearing.
-    if ((q > p && (r <= p || r > q)) ||
-        (q < p && (r <= p && r > q))) {
-      *p = *q;
-      p = q;
-    }
-  }
-
-  // Clear the entry which is allowed to en emptied.
-  p->key = NULL;
-  occupancy_--;
-  return value;
-}
-
-
-void HashMapImpl::Clear() {
-  // Mark all entries as empty.
-  const Entry* end = map_end();
-  for (Entry* p = map_; p < end; p++) {
-    p->key = NULL;
-  }
-  occupancy_ = 0;
-}
-
-
-HashMapImpl::Entry* HashMapImpl::Start() const {
-  return Next(map_ - 1);
-}
-
-
-HashMapImpl::Entry* HashMapImpl::Next(Entry* p) const {
-  const Entry* end = map_end();
-  DCHECK(map_ - 1 <= p && p < end);
-  for (p++; p < end; p++) {
-    if (p->key != NULL) {
-      return p;
-    }
-  }
-  return NULL;
-}
-
-
-HashMapImpl::Entry* HashMapImpl::Probe(void* key, uint32_t hash) const {
-  DCHECK(key != NULL);
-
-  DCHECK(base::bits::IsPowerOfTwo32(capacity_));
-  Entry* p = map_ + (hash & (capacity_ - 1));
-  const Entry* end = map_end();
-  DCHECK(map_ <= p && p < end);
-
-  DCHECK(occupancy_ < capacity_);  // Guarantees loop termination.
-  while (p->key != NULL && (hash != p->hash || !match_(key, p->key))) {
-    p++;
-    if (p >= end) {
-      p = map_;
-    }
-  }
-
-  return p;
-}
-
-
-void HashMapImpl::Initialize(uint32_t capacity) {
-  DCHECK(base::bits::IsPowerOfTwo32(capacity));
-  map_ = reinterpret_cast<Entry*>(Malloced::New(capacity * sizeof(Entry)));
-  CHECK(map_ != NULL);
-  capacity_ = capacity;
-  Clear();
-}
-
-
-void HashMapImpl::Resize() {
-  Entry* map = map_;
-  uint32_t n = occupancy_;
-
-  // Allocate larger map.
-  Initialize(capacity_ * 2);
-
-  // Rehash all current entries.
-  for (Entry* p = map; n > 0; p++) {
-    if (p->key != NULL) {
-      Entry* entry = LookupOrInsert(p->key, p->hash);
-      entry->value = p->value;
-      entry->order = p->order;
-      n--;
-    }
-  }
-
-  // Delete old map.
-  Malloced::Delete(map);
-}
-
-}  // namespace sampler
+}  // namespace base
 }  // namespace v8
 
-#endif  // V8_LIBSAMPLER_HASHMAP_H_
+#endif  // V8_BASE_HASHMAP_H_