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SkTHash: remove()

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BUG=skia:

Review URL: https://codereview.chromium.org/1057043003
This commit is contained in:
mtklein 2015-04-21 06:53:56 -07:00 committed by Commit bot
parent bc227140ff
commit 33d73c39dd
2 changed files with 63 additions and 12 deletions
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62
src/core/SkTHash.h
View File

@ -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:

13
tests/HashTest.cpp
View File

@ -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);
}