FixedSizeBuffer.hpp

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#pragma once 
#include <vector>
#include <fishnet/FunctionalConcepts.hpp>
 
namespace fishnet::util {
template<typename T, typename C> requires std::totally_ordered<C>
class FixedSizeBuffer{
private:
    std::vector<T> collection;
    std::vector<C> cache;
    size_t capacity;
    std::function<C(const T &)> mapper;
public:
    FixedSizeBuffer(size_t capacity,UnaryFunction<T,C> auto mapper):capacity(capacity),mapper(mapper){
        collection.reserve(capacity);
        cache.reserve(capacity);
    }
 
    bool empty() const noexcept {
        return collection.empty();
    }
 
    template<typename U>
    void push(U && value){
        static_assert(std::is_same_v<std::decay_t<U>, T>, "Type of value must be T");
        auto mappedValue = mapper(value);
        if(collection.size() < capacity){
            cache.push_back(mappedValue);
            collection.push_back(std::forward<U>(value));
        }else{
            int swapIndex=0;
            auto max = cache[0];
            for(int i=1; i < int(capacity);i++){
                auto val = cache[i];
                if(val> max){
                    max = val;
                    swapIndex = i;
                }
            }
            if(mappedValue < max){
                cache[swapIndex] = mappedValue;
                collection[swapIndex] = std::forward<U>(value);
            }
        }
    }
 
    auto begin(){
        return collection.begin();
    }
 
    auto end(){
        return collection.end();
    }
};
}