ClickHouse/src/Common/HashTable/StringHashMap.h

#pragma once

#include <Common/HashTable/HashMap.h>
#include <Common/HashTable/HashTableAllocator.h>
#include <Common/HashTable/StringHashTable.h>

template <typename Key, typename TMapped>
struct StringHashMapCell : public HashMapCell<Key, TMapped, StringHashTableHash, HashTableNoState>
{
    using Base = HashMapCell<Key, TMapped, StringHashTableHash, HashTableNoState>;
    using value_type = typename Base::value_type;
    using Base::Base;
    static constexpr bool need_zero_value_storage = false;
    // external
    const StringRef getKey() const { return toStringRef(this->value.first); }
    // internal
    static const Key & getKey(const value_type & value_) { return value_.first; }
};

template <typename TMapped>
struct StringHashMapCell<StringKey16, TMapped> : public HashMapCell<StringKey16, TMapped, StringHashTableHash, HashTableNoState>
{
    using Base = HashMapCell<StringKey16, TMapped, StringHashTableHash, HashTableNoState>;
    using value_type = typename Base::value_type;
    using Base::Base;
    static constexpr bool need_zero_value_storage = false;
    bool isZero(const HashTableNoState & state) const { return isZero(this->value.first, state); }

    // Zero means unoccupied cells in hash table. Use key with last word = 0 as
    // zero keys, because such keys are unrepresentable (no way to encode length).
    static bool isZero(const StringKey16 & key, const HashTableNoState &)
    { return key.high == 0; }
    void setZero() { this->value.first.high = 0; }

    // external
    const StringRef getKey() const { return toStringRef(this->value.first); }
    // internal
    static const StringKey16 & getKey(const value_type & value_) { return value_.first; }
};

template <typename TMapped>
struct StringHashMapCell<StringKey24, TMapped> : public HashMapCell<StringKey24, TMapped, StringHashTableHash, HashTableNoState>
{
    using Base = HashMapCell<StringKey24, TMapped, StringHashTableHash, HashTableNoState>;
    using value_type = typename Base::value_type;
    using Base::Base;
    static constexpr bool need_zero_value_storage = false;
    bool isZero(const HashTableNoState & state) const { return isZero(this->value.first, state); }

    // Zero means unoccupied cells in hash table. Use key with last word = 0 as
    // zero keys, because such keys are unrepresentable (no way to encode length).
    static bool isZero(const StringKey24 & key, const HashTableNoState &)
    { return key.c == 0; }
    void setZero() { this->value.first.c = 0; }

    // external
    const StringRef getKey() const { return toStringRef(this->value.first); }
    // internal
    static const StringKey24 & getKey(const value_type & value_) { return value_.first; }
};

template <typename TMapped>
struct StringHashMapCell<StringRef, TMapped> : public HashMapCellWithSavedHash<StringRef, TMapped, StringHashTableHash, HashTableNoState>
{
    using Base = HashMapCellWithSavedHash<StringRef, TMapped, StringHashTableHash, HashTableNoState>;
    using value_type = typename Base::value_type;
    using Base::Base;
    static constexpr bool need_zero_value_storage = false;
    // external
    using Base::getKey;
    // internal
    static const StringRef & getKey(const value_type & value_) { return value_.first; }
};

template <typename TMapped, typename Allocator>
struct StringHashMapSubMaps
{
    using T0 = StringHashTableEmpty<StringHashMapCell<StringRef, TMapped>>;
    using T1 = HashMapTable<StringKey8, StringHashMapCell<StringKey8, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
    using T2 = HashMapTable<StringKey16, StringHashMapCell<StringKey16, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
    using T3 = HashMapTable<StringKey24, StringHashMapCell<StringKey24, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
    using Ts = HashMapTable<StringRef, StringHashMapCell<StringRef, TMapped>, StringHashTableHash, StringHashTableGrower<>, Allocator>;
};

template <typename TMapped, typename Allocator = HashTableAllocator>
class StringHashMap : public StringHashTable<StringHashMapSubMaps<TMapped, Allocator>>
{
public:
    using Key = StringRef;
    using Base = StringHashTable<StringHashMapSubMaps<TMapped, Allocator>>;
    using Self = StringHashMap;
    using LookupResult = typename Base::LookupResult;

    using Base::Base;

    /// Merge every cell's value of current map into the destination map.
    ///  Func should have signature void(Mapped & dst, Mapped & src, bool emplaced).
    ///  Each filled cell in current map will invoke func once. If that map doesn't
    ///  have a key equals to the given cell, a new cell gets emplaced into that map,
    ///  and func is invoked with the third argument emplaced set to true. Otherwise
    ///  emplaced is set to false.
    template <typename Func>
    void ALWAYS_INLINE mergeToViaEmplace(Self & that, Func && func)
    {
        if (this->m0.hasZero() && that.m0.hasZero())
            func(that.m0.zeroValue()->getMapped(), this->m0.zeroValue()->getMapped(), false);
        else if (this->m0.hasZero())
        {
            that.m0.setHasZero();
            func(that.m0.zeroValue()->getMapped(), this->m0.zeroValue()->getMapped(), true);
        }
        this->m1.mergeToViaEmplace(that.m1, func);
        this->m2.mergeToViaEmplace(that.m2, func);
        this->m3.mergeToViaEmplace(that.m3, func);
        this->ms.mergeToViaEmplace(that.ms, func);
    }

    /// Merge every cell's value of current map into the destination map via find.
    ///  Func should have signature void(Mapped & dst, Mapped & src, bool exist).
    ///  Each filled cell in current map will invoke func once. If that map doesn't
    ///  have a key equals to the given cell, func is invoked with the third argument
    ///  exist set to false. Otherwise exist is set to true.
    template <typename Func>
    void ALWAYS_INLINE mergeToViaFind(Self & that, Func && func)
    {
        if (this->m0.size() && that.m0.size())
            func(that.m0.zeroValue()->getMapped(), this->m0.zeroValue()->getMapped(), true);
        else if (this->m0.size())
            func(this->m0.zeroValue()->getMapped(), this->m0.zeroValue()->getMapped(), false);
        this->m1.mergeToViaFind(that.m1, func);
        this->m2.mergeToViaFind(that.m2, func);
        this->m3.mergeToViaFind(that.m3, func);
        this->ms.mergeToViaFind(that.ms, func);
    }

    TMapped & ALWAYS_INLINE operator[](const Key & x)
    {
        LookupResult it;
        bool inserted;
        this->emplace(x, it, inserted);
        if (inserted)
            new (&it->getMapped()) TMapped();

        return it->getMapped();
    }

    template <typename Func>
    void ALWAYS_INLINE forEachValue(Func && func)
    {
        if (this->m0.size())
        {
            func(StringRef{}, this->m0.zeroValue()->getMapped());
        }

        for (auto & v : this->m1)
        {
            func(v.getKey(), v.getMapped());
        }

        for (auto & v : this->m2)
        {
            func(v.getKey(), v.getMapped());
        }

        for (auto & v : this->m3)
        {
            func(v.getKey(), v.getMapped());
        }

        for (auto & v : this->ms)
        {
            func(v.getKey(), v.getMapped());
        }
    }

    template <typename Func>
    void ALWAYS_INLINE forEachMapped(Func && func)
    {
        if (this->m0.size())
            func(this->m0.zeroValue()->getMapped());
        for (auto & v : this->m1)
            func(v.getMapped());
        for (auto & v : this->m2)
            func(v.getMapped());
        for (auto & v : this->m3)
            func(v.getMapped());
        for (auto & v : this->ms)
            func(v.getMapped());
    }
};