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-rw-r--r--src/leveldb/util/cache.cc123
1 files changed, 59 insertions, 64 deletions
diff --git a/src/leveldb/util/cache.cc b/src/leveldb/util/cache.cc
index ce46886171..12de306cad 100644
--- a/src/leveldb/util/cache.cc
+++ b/src/leveldb/util/cache.cc
@@ -8,13 +8,13 @@
#include "leveldb/cache.h"
#include "port/port.h"
+#include "port/thread_annotations.h"
#include "util/hash.h"
#include "util/mutexlock.h"
namespace leveldb {
-Cache::~Cache() {
-}
+Cache::~Cache() {}
namespace {
@@ -45,21 +45,19 @@ struct LRUHandle {
LRUHandle* next_hash;
LRUHandle* next;
LRUHandle* prev;
- size_t charge; // TODO(opt): Only allow uint32_t?
+ size_t charge; // TODO(opt): Only allow uint32_t?
size_t key_length;
- bool in_cache; // Whether entry is in the cache.
- uint32_t refs; // References, including cache reference, if present.
- uint32_t hash; // Hash of key(); used for fast sharding and comparisons
- char key_data[1]; // Beginning of key
+ bool in_cache; // Whether entry is in the cache.
+ uint32_t refs; // References, including cache reference, if present.
+ uint32_t hash; // Hash of key(); used for fast sharding and comparisons
+ char key_data[1]; // Beginning of key
Slice key() const {
- // For cheaper lookups, we allow a temporary Handle object
- // to store a pointer to a key in "value".
- if (next == this) {
- return *(reinterpret_cast<Slice*>(value));
- } else {
- return Slice(key_data, key_length);
- }
+ // next_ is only equal to this if the LRU handle is the list head of an
+ // empty list. List heads never have meaningful keys.
+ assert(next != this);
+
+ return Slice(key_data, key_length);
}
};
@@ -70,7 +68,7 @@ struct LRUHandle {
// 4.4.3's builtin hashtable.
class HandleTable {
public:
- HandleTable() : length_(0), elems_(0), list_(NULL) { Resize(); }
+ HandleTable() : length_(0), elems_(0), list_(nullptr) { Resize(); }
~HandleTable() { delete[] list_; }
LRUHandle* Lookup(const Slice& key, uint32_t hash) {
@@ -80,9 +78,9 @@ class HandleTable {
LRUHandle* Insert(LRUHandle* h) {
LRUHandle** ptr = FindPointer(h->key(), h->hash);
LRUHandle* old = *ptr;
- h->next_hash = (old == NULL ? NULL : old->next_hash);
+ h->next_hash = (old == nullptr ? nullptr : old->next_hash);
*ptr = h;
- if (old == NULL) {
+ if (old == nullptr) {
++elems_;
if (elems_ > length_) {
// Since each cache entry is fairly large, we aim for a small
@@ -96,7 +94,7 @@ class HandleTable {
LRUHandle* Remove(const Slice& key, uint32_t hash) {
LRUHandle** ptr = FindPointer(key, hash);
LRUHandle* result = *ptr;
- if (result != NULL) {
+ if (result != nullptr) {
*ptr = result->next_hash;
--elems_;
}
@@ -115,8 +113,7 @@ class HandleTable {
// pointer to the trailing slot in the corresponding linked list.
LRUHandle** FindPointer(const Slice& key, uint32_t hash) {
LRUHandle** ptr = &list_[hash & (length_ - 1)];
- while (*ptr != NULL &&
- ((*ptr)->hash != hash || key != (*ptr)->key())) {
+ while (*ptr != nullptr && ((*ptr)->hash != hash || key != (*ptr)->key())) {
ptr = &(*ptr)->next_hash;
}
return ptr;
@@ -132,7 +129,7 @@ class HandleTable {
uint32_t count = 0;
for (uint32_t i = 0; i < length_; i++) {
LRUHandle* h = list_[i];
- while (h != NULL) {
+ while (h != nullptr) {
LRUHandle* next = h->next_hash;
uint32_t hash = h->hash;
LRUHandle** ptr = &new_list[hash & (new_length - 1)];
@@ -159,8 +156,8 @@ class LRUCache {
void SetCapacity(size_t capacity) { capacity_ = capacity; }
// Like Cache methods, but with an extra "hash" parameter.
- Cache::Handle* Insert(const Slice& key, uint32_t hash,
- void* value, size_t charge,
+ Cache::Handle* Insert(const Slice& key, uint32_t hash, void* value,
+ size_t charge,
void (*deleter)(const Slice& key, void* value));
Cache::Handle* Lookup(const Slice& key, uint32_t hash);
void Release(Cache::Handle* handle);
@@ -173,32 +170,31 @@ class LRUCache {
private:
void LRU_Remove(LRUHandle* e);
- void LRU_Append(LRUHandle*list, LRUHandle* e);
+ void LRU_Append(LRUHandle* list, LRUHandle* e);
void Ref(LRUHandle* e);
void Unref(LRUHandle* e);
- bool FinishErase(LRUHandle* e);
+ bool FinishErase(LRUHandle* e) EXCLUSIVE_LOCKS_REQUIRED(mutex_);
// Initialized before use.
size_t capacity_;
// mutex_ protects the following state.
mutable port::Mutex mutex_;
- size_t usage_;
+ size_t usage_ GUARDED_BY(mutex_);
// Dummy head of LRU list.
// lru.prev is newest entry, lru.next is oldest entry.
// Entries have refs==1 and in_cache==true.
- LRUHandle lru_;
+ LRUHandle lru_ GUARDED_BY(mutex_);
// Dummy head of in-use list.
// Entries are in use by clients, and have refs >= 2 and in_cache==true.
- LRUHandle in_use_;
+ LRUHandle in_use_ GUARDED_BY(mutex_);
- HandleTable table_;
+ HandleTable table_ GUARDED_BY(mutex_);
};
-LRUCache::LRUCache()
- : usage_(0) {
+LRUCache::LRUCache() : capacity_(0), usage_(0) {
// Make empty circular linked lists.
lru_.next = &lru_;
lru_.prev = &lru_;
@@ -208,7 +204,7 @@ LRUCache::LRUCache()
LRUCache::~LRUCache() {
assert(in_use_.next == &in_use_); // Error if caller has an unreleased handle
- for (LRUHandle* e = lru_.next; e != &lru_; ) {
+ for (LRUHandle* e = lru_.next; e != &lru_;) {
LRUHandle* next = e->next;
assert(e->in_cache);
e->in_cache = false;
@@ -229,11 +225,12 @@ void LRUCache::Ref(LRUHandle* e) {
void LRUCache::Unref(LRUHandle* e) {
assert(e->refs > 0);
e->refs--;
- if (e->refs == 0) { // Deallocate.
+ if (e->refs == 0) { // Deallocate.
assert(!e->in_cache);
(*e->deleter)(e->key(), e->value);
free(e);
- } else if (e->in_cache && e->refs == 1) { // No longer in use; move to lru_ list.
+ } else if (e->in_cache && e->refs == 1) {
+ // No longer in use; move to lru_ list.
LRU_Remove(e);
LRU_Append(&lru_, e);
}
@@ -255,7 +252,7 @@ void LRUCache::LRU_Append(LRUHandle* list, LRUHandle* e) {
Cache::Handle* LRUCache::Lookup(const Slice& key, uint32_t hash) {
MutexLock l(&mutex_);
LRUHandle* e = table_.Lookup(key, hash);
- if (e != NULL) {
+ if (e != nullptr) {
Ref(e);
}
return reinterpret_cast<Cache::Handle*>(e);
@@ -266,13 +263,14 @@ void LRUCache::Release(Cache::Handle* handle) {
Unref(reinterpret_cast<LRUHandle*>(handle));
}
-Cache::Handle* LRUCache::Insert(
- const Slice& key, uint32_t hash, void* value, size_t charge,
- void (*deleter)(const Slice& key, void* value)) {
+Cache::Handle* LRUCache::Insert(const Slice& key, uint32_t hash, void* value,
+ size_t charge,
+ void (*deleter)(const Slice& key,
+ void* value)) {
MutexLock l(&mutex_);
- LRUHandle* e = reinterpret_cast<LRUHandle*>(
- malloc(sizeof(LRUHandle)-1 + key.size()));
+ LRUHandle* e =
+ reinterpret_cast<LRUHandle*>(malloc(sizeof(LRUHandle) - 1 + key.size()));
e->value = value;
e->deleter = deleter;
e->charge = charge;
@@ -288,8 +286,10 @@ Cache::Handle* LRUCache::Insert(
LRU_Append(&in_use_, e);
usage_ += charge;
FinishErase(table_.Insert(e));
- } // else don't cache. (Tests use capacity_==0 to turn off caching.)
-
+ } else { // don't cache. (capacity_==0 is supported and turns off caching.)
+ // next is read by key() in an assert, so it must be initialized
+ e->next = nullptr;
+ }
while (usage_ > capacity_ && lru_.next != &lru_) {
LRUHandle* old = lru_.next;
assert(old->refs == 1);
@@ -302,17 +302,17 @@ Cache::Handle* LRUCache::Insert(
return reinterpret_cast<Cache::Handle*>(e);
}
-// If e != NULL, finish removing *e from the cache; it has already been removed
-// from the hash table. Return whether e != NULL. Requires mutex_ held.
+// If e != nullptr, finish removing *e from the cache; it has already been
+// removed from the hash table. Return whether e != nullptr.
bool LRUCache::FinishErase(LRUHandle* e) {
- if (e != NULL) {
+ if (e != nullptr) {
assert(e->in_cache);
LRU_Remove(e);
e->in_cache = false;
usage_ -= e->charge;
Unref(e);
}
- return e != NULL;
+ return e != nullptr;
}
void LRUCache::Erase(const Slice& key, uint32_t hash) {
@@ -345,49 +345,46 @@ class ShardedLRUCache : public Cache {
return Hash(s.data(), s.size(), 0);
}
- static uint32_t Shard(uint32_t hash) {
- return hash >> (32 - kNumShardBits);
- }
+ static uint32_t Shard(uint32_t hash) { return hash >> (32 - kNumShardBits); }
public:
- explicit ShardedLRUCache(size_t capacity)
- : last_id_(0) {
+ explicit ShardedLRUCache(size_t capacity) : last_id_(0) {
const size_t per_shard = (capacity + (kNumShards - 1)) / kNumShards;
for (int s = 0; s < kNumShards; s++) {
shard_[s].SetCapacity(per_shard);
}
}
- virtual ~ShardedLRUCache() { }
- virtual Handle* Insert(const Slice& key, void* value, size_t charge,
- void (*deleter)(const Slice& key, void* value)) {
+ ~ShardedLRUCache() override {}
+ Handle* Insert(const Slice& key, void* value, size_t charge,
+ void (*deleter)(const Slice& key, void* value)) override {
const uint32_t hash = HashSlice(key);
return shard_[Shard(hash)].Insert(key, hash, value, charge, deleter);
}
- virtual Handle* Lookup(const Slice& key) {
+ Handle* Lookup(const Slice& key) override {
const uint32_t hash = HashSlice(key);
return shard_[Shard(hash)].Lookup(key, hash);
}
- virtual void Release(Handle* handle) {
+ void Release(Handle* handle) override {
LRUHandle* h = reinterpret_cast<LRUHandle*>(handle);
shard_[Shard(h->hash)].Release(handle);
}
- virtual void Erase(const Slice& key) {
+ void Erase(const Slice& key) override {
const uint32_t hash = HashSlice(key);
shard_[Shard(hash)].Erase(key, hash);
}
- virtual void* Value(Handle* handle) {
+ void* Value(Handle* handle) override {
return reinterpret_cast<LRUHandle*>(handle)->value;
}
- virtual uint64_t NewId() {
+ uint64_t NewId() override {
MutexLock l(&id_mutex_);
return ++(last_id_);
}
- virtual void Prune() {
+ void Prune() override {
for (int s = 0; s < kNumShards; s++) {
shard_[s].Prune();
}
}
- virtual size_t TotalCharge() const {
+ size_t TotalCharge() const override {
size_t total = 0;
for (int s = 0; s < kNumShards; s++) {
total += shard_[s].TotalCharge();
@@ -398,8 +395,6 @@ class ShardedLRUCache : public Cache {
} // end anonymous namespace
-Cache* NewLRUCache(size_t capacity) {
- return new ShardedLRUCache(capacity);
-}
+Cache* NewLRUCache(size_t capacity) { return new ShardedLRUCache(capacity); }
} // namespace leveldb
generated by cgit v1.2.3 (git 2.26.2) at 2024-07-08 15:30:14 +0000