HashMap.h

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/*
  ==============================================================================
 
   This file is part of the Water library.
   Copyright (c) 2016 ROLI Ltd.
   Copyright (C) 2018-2022 Filipe Coelho <falktx@falktx.com>
 
   Permission is granted to use this software under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license/
 
   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.
 
   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.
 
  ==============================================================================
*/
 
#ifndef WATER_HASHMAP_H_INCLUDED
#define WATER_HASHMAP_H_INCLUDED
 
#include "Array.h"
#include "../text/String.h"
 
#include "CarlaScopeUtils.hpp"
 
namespace water {
 
//==============================================================================
struct DefaultHashFunctions
{
    int generateHash (const int key, const int upperLimit) const noexcept        { return std::abs (key) % upperLimit; }
    int generateHash (const int64 key, const int upperLimit) const noexcept      { return std::abs ((int) key) % upperLimit; }
    int generateHash (const String& key, const int upperLimit) const noexcept    { return (int) (((uint32) key.hashCode()) % (uint32) upperLimit); }
    int generateHash (const void* key, const int upperLimit) const noexcept      { return (int)(((pointer_sized_uint) key) % ((pointer_sized_uint) upperLimit)); }
};
 
 
//==============================================================================
template <typename KeyType,
          typename ValueType,
          class HashFunctionType = DefaultHashFunctions>
class HashMap
{
private:
    typedef PARAMETER_TYPE (KeyType)   KeyTypeParameter;
    typedef PARAMETER_TYPE (ValueType) ValueTypeParameter;
 
public:
    //==============================================================================
    explicit HashMap (int numberOfSlots = defaultHashTableSize,
                      HashFunctionType hashFunction = HashFunctionType())
       : hashFunctionToUse (hashFunction), totalNumItems (0)
    {
        hashSlots.insertMultiple (0, nullptr, numberOfSlots);
    }

    ~HashMap()
    {
        clear();
    }
 
    //==============================================================================
    void clear()
    {
        for (int i = hashSlots.size(); --i >= 0;)
        {
            HashEntry* h = hashSlots.getUnchecked(i);
 
            while (h != nullptr)
            {
                const CarlaScopedPointer<HashEntry> deleter (h);
                h = h->nextEntry;
            }
 
            hashSlots.set (i, nullptr);
        }
 
        totalNumItems = 0;
    }
 
    //==============================================================================
    inline int size() const noexcept
    {
        return totalNumItems;
    }

    inline ValueType operator[] (KeyTypeParameter keyToLookFor) const
    {
        for (const HashEntry* entry = hashSlots.getUnchecked (generateHashFor (keyToLookFor)); entry != nullptr; entry = entry->nextEntry)
            if (entry->key == keyToLookFor)
                return entry->value;
 
        return ValueType();
    }
 
    //==============================================================================
    bool contains (KeyTypeParameter keyToLookFor) const
    {
        for (const HashEntry* entry = hashSlots.getUnchecked (generateHashFor (keyToLookFor)); entry != nullptr; entry = entry->nextEntry)
            if (entry->key == keyToLookFor)
                return true;
 
        return false;
    }

    bool containsValue (ValueTypeParameter valueToLookFor) const
    {
        for (int i = getNumSlots(); --i >= 0;)
            for (const HashEntry* entry = hashSlots.getUnchecked(i); entry != nullptr; entry = entry->nextEntry)
                if (entry->value == valueToLookFor)
                    return true;
 
        return false;
    }
 
    //==============================================================================
    void set (KeyTypeParameter newKey, ValueTypeParameter newValue)
    {
        const int hashIndex = generateHashFor (newKey);
 
        HashEntry* const firstEntry = hashSlots.getUnchecked (hashIndex);
 
        for (HashEntry* entry = firstEntry; entry != nullptr; entry = entry->nextEntry)
        {
            if (entry->key == newKey)
            {
                entry->value = newValue;
                return;
            }
        }
 
        hashSlots.set (hashIndex, new HashEntry (newKey, newValue, firstEntry));
        ++totalNumItems;
 
        if (totalNumItems > (getNumSlots() * 3) / 2)
            remapTable (getNumSlots() * 2);
    }

    void remove (KeyTypeParameter keyToRemove)
    {
        const int hashIndex = generateHashFor (keyToRemove);
        HashEntry* entry = hashSlots.getUnchecked (hashIndex);
        HashEntry* previous = nullptr;
 
        while (entry != nullptr)
        {
            if (entry->key == keyToRemove)
            {
                const CarlaScopedPointer<HashEntry> deleter (entry);
 
                entry = entry->nextEntry;
 
                if (previous != nullptr)
                    previous->nextEntry = entry;
                else
                    hashSlots.set (hashIndex, entry);
 
                --totalNumItems;
            }
            else
            {
                previous = entry;
                entry = entry->nextEntry;
            }
        }
    }

    void removeValue (ValueTypeParameter valueToRemove)
    {
        for (int i = getNumSlots(); --i >= 0;)
        {
            HashEntry* entry = hashSlots.getUnchecked(i);
            HashEntry* previous = nullptr;
 
            while (entry != nullptr)
            {
                if (entry->value == valueToRemove)
                {
                    const CarlaScopedPointer<HashEntry> deleter (entry);
 
                    entry = entry->nextEntry;
 
                    if (previous != nullptr)
                        previous->nextEntry = entry;
                    else
                        hashSlots.set (i, entry);
 
                    --totalNumItems;
                }
                else
                {
                    previous = entry;
                    entry = entry->nextEntry;
                }
            }
        }
    }

    void remapTable (int newNumberOfSlots)
    {
        HashMap newTable (newNumberOfSlots);
 
        for (int i = getNumSlots(); --i >= 0;)
            for (const HashEntry* entry = hashSlots.getUnchecked(i); entry != nullptr; entry = entry->nextEntry)
                newTable.set (entry->key, entry->value);
 
        swapWith (newTable);
    }

    inline int getNumSlots() const noexcept
    {
        return hashSlots.size();
    }
 
    //==============================================================================
    template <class OtherHashMapType>
    void swapWith (OtherHashMapType& otherHashMap) noexcept
    {
        hashSlots.swapWith (otherHashMap.hashSlots);
        std::swap (totalNumItems, otherHashMap.totalNumItems);
    }
 
private:
    //==============================================================================
    class HashEntry
    {
    public:
        HashEntry (KeyTypeParameter k, ValueTypeParameter val, HashEntry* const next)
            : key (k), value (val), nextEntry (next)
        {}
 
        const KeyType key;
        ValueType value;
        HashEntry* nextEntry;
 
        CARLA_DECLARE_NON_COPYABLE (HashEntry)
    };
 
public:
    //==============================================================================
    struct Iterator
    {
        Iterator (const HashMap& hashMapToIterate) noexcept
            : hashMap (hashMapToIterate), entry (nullptr), index (0)
        {}
 
        Iterator (const Iterator& other) noexcept
            : hashMap (other.hashMap), entry (other.entry), index (other.index)
        {}

        bool next() noexcept
        {
            if (entry != nullptr)
                entry = entry->nextEntry;
 
            while (entry == nullptr)
            {
                if (index >= hashMap.getNumSlots())
                    return false;
 
                entry = hashMap.hashSlots.getUnchecked (index++);
            }
 
            return true;
        }

        KeyType getKey() const
        {
            return entry != nullptr ? entry->key : KeyType();
        }

        ValueType getValue() const
        {
            return entry != nullptr ? entry->value : ValueType();
        }

        void reset() noexcept
        {
            entry = nullptr;
            index = 0;
        }
 
        Iterator& operator++() noexcept                         { next(); return *this; }
        ValueType operator*() const                             { return getValue(); }
        bool operator!= (const Iterator& other) const noexcept  { return entry != other.entry || index != other.index; }
        void resetToEnd() noexcept                              { index = hashMap.getNumSlots(); }
 
    private:
        //==============================================================================
        const HashMap& hashMap;
        HashEntry* entry;
        int index;
 
        CARLA_LEAK_DETECTOR (Iterator)
    };

    Iterator begin() const noexcept             { Iterator i (*this); i.next(); return i; }

    Iterator end() const noexcept               { Iterator i (*this); i.resetToEnd(); return i; }
 
private:
    //==============================================================================
    enum { defaultHashTableSize = 101 };
    friend struct Iterator;
 
    HashFunctionType hashFunctionToUse;
    Array<HashEntry*> hashSlots;
    int totalNumItems;
 
    int generateHashFor (KeyTypeParameter key) const
    {
        const int hash = hashFunctionToUse.generateHash (key, getNumSlots());
        wassert (isPositiveAndBelow (hash, getNumSlots())); // your hash function is generating out-of-range numbers!
        return hash;
    }
 
    CARLA_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (HashMap)
};
 
}
 
#endif   // WATER_HASHMAP_H_INCLUDED