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#pragma once
#include "defs.h"
namespace NActors {
// wait-free one writer multi reader hash-tree for service mapping purposes
// on fast updates on same key - could lead to false-negatives, we don't care as such cases are broken from service-map app logic
template <typename TKey, typename TValue, typename THash, ui64 BaseSize = 256 * 1024, ui64 ExtCount = 4, ui64 ExtBranching = 4>
class TServiceMap : TNonCopyable {
struct TEntry : TNonCopyable {
ui32 CounterIn;
ui32 CounterOut;
TKey Key;
TValue Value;
TEntry()
: CounterIn(0)
, CounterOut(0)
, Key()
, Value()
{
}
};
struct TBranch : TNonCopyable {
TEntry Entries[ExtCount];
TBranch* Branches[ExtBranching];
TBranch() {
Fill(Branches, Branches + ExtBranching, (TBranch*)nullptr);
}
};
ui32 Counter;
TBranch* Line[BaseSize];
bool ScanBranch(TBranch* branch, const TKey& key, ui64 hash, TValue& ret) {
for (ui32 i = 0; i != ExtCount; ++i) {
const TEntry& entry = branch->Entries[i];
const ui32 counterIn = AtomicLoad(&entry.CounterIn);
if (counterIn != 0 && entry.Key == key) {
ret = entry.Value;
const ui32 counterOut = AtomicLoad(&entry.CounterOut);
if (counterOut == counterIn)
return true;
}
}
const ui64 hash0 = hash % ExtBranching;
if (TBranch* next = AtomicLoad(branch->Branches + hash0))
return ScanBranch(next, key, hash / ExtBranching, ret);
return false;
}
void ScanZeroOld(TBranch* branch, const TKey& key, ui64 hash, TEntry** zeroEntry, TEntry*& oldEntry) {
for (ui32 i = 0; i != ExtCount; ++i) {
TEntry& entry = branch->Entries[i];
if (entry.CounterIn == 0) {
if (zeroEntry && !*zeroEntry) {
*zeroEntry = &entry;
if (oldEntry != nullptr)
return;
}
} else {
if (entry.Key == key) {
oldEntry = &entry;
if (!zeroEntry || *zeroEntry)
return;
}
}
}
const ui64 hash0 = hash % ExtBranching;
if (TBranch* next = branch->Branches[hash0]) {
ScanZeroOld(next, key, hash / ExtBranching, zeroEntry, oldEntry);
} else { // found tail, if zeroEntry requested, but not yet found - insert one
if (zeroEntry && !*zeroEntry) {
TBranch* next = new TBranch();
*zeroEntry = next->Entries;
AtomicStore(branch->Branches + hash0, next);
}
}
}
public:
TServiceMap()
: Counter(0)
{
Fill(Line, Line + BaseSize, (TBranch*)nullptr);
}
~TServiceMap() {
for (ui64 i = 0; i < BaseSize; ++i) {
delete Line[i];
}
}
TValue Find(const TKey& key) {
THash hashOp;
const ui64 hash = hashOp(key);
const ui64 hash0 = hash % BaseSize;
if (TBranch* branch = AtomicLoad(Line + hash0)) {
TValue ret;
if (ScanBranch(branch, key, hash / BaseSize, ret))
return ret;
}
return TValue();
}
// returns true on update, false on insert
TValue Update(const TKey& key, const TValue& value) {
THash hashOp;
const ui64 hash = hashOp(key);
const ui64 hash0 = hash % BaseSize;
TEntry* zeroEntry = nullptr;
TEntry* oldEntry = nullptr;
if (TBranch* branch = Line[hash0]) {
ScanZeroOld(branch, key, hash / BaseSize, &zeroEntry, oldEntry);
} else {
TBranch* next = new TBranch();
zeroEntry = next->Entries;
AtomicStore(Line + hash0, next);
}
// now we got both entries, first - push new one
const ui32 counter = AtomicUi32Increment(&Counter);
AtomicStore(&zeroEntry->CounterOut, counter);
zeroEntry->Key = key;
zeroEntry->Value = value;
AtomicStore(&zeroEntry->CounterIn, counter);
if (oldEntry != nullptr) {
const TValue ret = oldEntry->Value;
AtomicStore<ui32>(&oldEntry->CounterOut, 0);
AtomicStore<ui32>(&oldEntry->CounterIn, 0);
return ret;
} else {
return TValue();
}
}
bool Erase(const TKey& key) {
THash hashOp;
const ui64 hash = hashOp(key);
const ui64 hash0 = hash % BaseSize;
TEntry* oldEntry = 0;
if (TBranch* branch = Line[hash0]) {
ScanZeroOld(branch, key, hash / BaseSize, 0, oldEntry);
}
if (oldEntry != 0) {
AtomicStore<ui32>(&oldEntry->CounterOut, 0);
AtomicStore<ui32>(&oldEntry->CounterIn, 0);
return true;
} else {
return false;
}
}
};
}
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