diff options
author | mtklein <mtklein@chromium.org> | 2015-04-21 06:53:56 -0700 |
---|---|---|
committer | Commit bot <commit-bot@chromium.org> | 2015-04-21 06:53:56 -0700 |
commit | 33d73c39dd3cca7594b3ad4304143872d5f7f570 (patch) | |
tree | 7b5cd5a03661a34c120fe4bd10f0ae26ae78d1db | |
parent | bc227140ffea6eb15e2e8b147eb6d8ec6228d95a (diff) |
SkTHash: remove()
BUG=skia:
Review URL: https://codereview.chromium.org/1057043003
-rw-r--r-- | src/core/SkTHash.h | 62 | ||||
-rw-r--r-- | tests/HashTest.cpp | 13 |
2 files changed, 63 insertions, 12 deletions
diff --git a/src/core/SkTHash.h b/src/core/SkTHash.h index 3637c53c46..ffcdea5329 100644 --- a/src/core/SkTHash.h +++ b/src/core/SkTHash.h @@ -24,7 +24,7 @@ template <typename T, typename K, typename Traits = T> class SkTHashTable : SkNoncopyable { public: - SkTHashTable() : fCount(0), fCapacity(0) {} + SkTHashTable() : fCount(0), fRemoved(0), fCapacity(0) {} // Clear the table. void reset() { @@ -48,7 +48,7 @@ public: // Copy val into the hash table, returning a pointer to the copy now in the table. // If there already is an entry in the table with the same key, we overwrite it. T* set(const T& val) { - if (4 * fCount >= 3 * fCapacity) { + if (4 * (fCount+fRemoved) >= 3 * fCapacity) { this->resize(fCapacity > 0 ? fCapacity * 2 : 4); } return this->uncheckedSet(val); @@ -63,7 +63,7 @@ public: if (s.empty()) { return NULL; } - if (hash == s.hash && key == Traits::GetKey(s.val)) { + if (!s.removed() && hash == s.hash && key == Traits::GetKey(s.val)) { return &s.val; } index = this->next(index, n); @@ -72,11 +72,31 @@ public: return NULL; } + // Remove the value with this key from the hash table. + void remove(const K& key) { + SkASSERT(this->find(key)); + + uint32_t hash = Hash(key); + int index = hash & (fCapacity-1); + for (int n = 0; n < fCapacity; n++) { + Slot& s = fSlots[index]; + SkASSERT(!s.empty()); + if (!s.removed() && hash == s.hash && key == Traits::GetKey(s.val)) { + fRemoved++; + fCount--; + s.markRemoved(); + return; + } + index = this->next(index, n); + } + SkASSERT(fCapacity == 0); + } + // Call fn on every entry in the table. You may mutate the entries, but be very careful. template <typename Fn> // f(T*) void foreach(Fn&& fn) { for (int i = 0; i < fCapacity; i++) { - if (!fSlots[i].empty()) { + if (!fSlots[i].empty() && !fSlots[i].removed()) { fn(&fSlots[i].val); } } @@ -86,7 +106,7 @@ public: template <typename Fn> // f(T) or f(const T&) void foreach(Fn&& fn) const { for (int i = 0; i < fCapacity; i++) { - if (!fSlots[i].empty()) { + if (!fSlots[i].empty() && !fSlots[i].removed()) { fn(fSlots[i].val); } } @@ -99,8 +119,11 @@ private: int index = hash & (fCapacity-1); for (int n = 0; n < fCapacity; n++) { Slot& s = fSlots[index]; - if (s.empty()) { + if (s.empty() || s.removed()) { // New entry. + if (s.removed()) { + fRemoved--; + } s.val = val; s.hash = hash; fCount++; @@ -122,14 +145,14 @@ private: int oldCapacity = fCapacity; SkDEBUGCODE(int oldCount = fCount); - fCount = 0; + fCount = fRemoved = 0; fCapacity = capacity; SkAutoTArray<Slot> oldSlots(capacity); oldSlots.swap(fSlots); for (int i = 0; i < oldCapacity; i++) { const Slot& s = oldSlots[i]; - if (!s.empty()) { + if (!s.empty() && !s.removed()) { this->uncheckedSet(s.val); } } @@ -145,18 +168,21 @@ private: static uint32_t Hash(const K& key) { uint32_t hash = Traits::Hash(key); - return hash == 0 ? 1 : hash; // We reserve hash == 0 to mark empty slots. + return hash < 2 ? hash+2 : hash; // We reserve hash 0 and 1 to mark empty or removed slots. } struct Slot { Slot() : hash(0) {} - bool empty() const { return hash == 0; } + bool empty() const { return this->hash == 0; } + bool removed() const { return this->hash == 1; } + + void markRemoved() { this->hash = 1; } T val; uint32_t hash; }; - int fCount, fCapacity; + int fCount, fRemoved, fCapacity; SkAutoTArray<Slot> fSlots; }; @@ -192,6 +218,12 @@ public: return NULL; } + // Remove the key/value entry in the table with this key. + void remove(const K& key) { + SkASSERT(this->find(key)); + fTable.remove(key); + } + // Call fn on every key/value pair in the table. You may mutate the value but not the key. template <typename Fn> // f(K, V*) or f(const K&, V*) void foreach(Fn&& fn) { @@ -237,10 +269,16 @@ public: // This pointer remains valid until the next call to add(). const T* find(const T& item) const { return fTable.find(item); } + // Remove the item in the set equal to this. + void remove(const T& item) { + SkASSERT(this->contains(item)); + fTable.remove(item); + } + // Call fn on every item in the set. You may not mutate anything. template <typename Fn> // f(T), f(const T&) void foreach (Fn&& fn) const { - fTable.foreach (fn); + fTable.foreach(fn); } private: diff --git a/tests/HashTest.cpp b/tests/HashTest.cpp index d2acafe08b..c1bdf884d8 100644 --- a/tests/HashTest.cpp +++ b/tests/HashTest.cpp @@ -52,6 +52,15 @@ DEF_TEST(HashMap, r) { REPORTER_ASSERT(r, map.count() == N); + for (int i = 0; i < N/2; i++) { + map.remove(i); + } + for (int i = 0; i < N; i++) { + double* found = map.find(i); + REPORTER_ASSERT(r, (found == nullptr) == (i < N/2)); + } + REPORTER_ASSERT(r, map.count() == N/2); + map.reset(); REPORTER_ASSERT(r, map.count() == 0); } @@ -71,6 +80,10 @@ DEF_TEST(HashSet, r) { REPORTER_ASSERT(r, set.find(SkString("Hello"))); REPORTER_ASSERT(r, *set.find(SkString("Hello")) == SkString("Hello")); + set.remove(SkString("Hello")); + REPORTER_ASSERT(r, !set.contains(SkString("Hello"))); + REPORTER_ASSERT(r, set.count() == 1); + set.reset(); REPORTER_ASSERT(r, set.count() == 0); } |