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#pragma once

#include <library/cpp/deprecated/accessors/accessors.h>

#include <util/stream/output.h> 
#include <util/system/yassert.h> 
#include <util/generic/bitops.h>
#include <util/generic/vector.h>
#include <util/generic/yexception.h>

namespace NBitIO {
    // Based on junk/solar/codecs/bitstream.h 

    // Almost all code is hard tuned for sequential write performance. 
    // Use tools/bursttrie/benchmarks/bitstreams_benchmark to check your changes. 

    inline constexpr ui64 BytesUp(ui64 bits) {
        return (bits + 7ULL) >> 3ULL;
    }

    template <typename TStorage> 
    class TBitOutputBase { 
    protected: 
        TStorage* Storage; 
        ui64 FreeBits; 
        ui64 Active; 
        ui64 Offset; 

    public: 
        TBitOutputBase(TStorage* storage) 
            : Storage(storage) 
            , FreeBits(64) 
            , Active() 
            , Offset() 
        { 
        } 

        ui64 GetOffset() const { 
            return Offset + BytesUp(64ULL - FreeBits);
        } 

        ui64 GetBitOffset() const { 
            return (64ULL - FreeBits) & 7ULL; 
        } 

        ui64 GetByteReminder() const { 
            return FreeBits & 7ULL; 
        } 

    public: 
        // interface 

        // Write "bits" lower bits. 
        Y_FORCE_INLINE void Write(ui64 data, ui64 bits) {
            if (FreeBits < bits) { 
                if (FreeBits) { 
                    bits -= FreeBits; 

                    Active |= (data & MaskLowerBits(FreeBits)) << (64ULL - FreeBits); 
                    data >>= FreeBits; 

                    FreeBits = 0ULL; 
                } 
 
                Flush(); 
            } 
 
            Active |= bits ? ((data & MaskLowerBits(bits)) << (64ULL - FreeBits)) : 0;
            FreeBits -= bits; 
        }

        // Write "bits" lower bits starting from "skipbits" bit. 
        Y_FORCE_INLINE void Write(ui64 data, ui64 bits, ui64 skipbits) {
            Write(data >> skipbits, bits); 
        } 

        // Unsigned wordwise write. Underlying data is splitted in "words" of "bits(data) + 1(flag)" bits. 
        // Like this: (unsigned char)0x2E<3> (0000 0010 1110) <=> 1110 0101 
        //                                                        fddd fddd 
        template <ui64 bits> 
        Y_FORCE_INLINE void WriteWords(ui64 data) {
            do { 
                ui64 part = data; 

                data >>= bits; 
                part |= FastZeroIfFalse(data, NthBit64(bits));
                Write(part, bits + 1ULL); 
            } while (data); 
        } 

        Y_FORCE_INLINE ui64 /* padded bits */ Flush() {
            const ui64 ubytes = 8ULL - (FreeBits >> 3ULL); 

            if (ubytes) { 
                Active <<= FreeBits; 
                Active >>= FreeBits; 

                Storage->WriteData((const char*)&Active, (const char*)&Active + ubytes); 
                Offset += ubytes; 
            } 

            const ui64 padded = FreeBits & 7; 

            FreeBits = 64ULL; 
            Active = 0ULL; 

            return padded; 
        } 

        virtual ~TBitOutputBase() { 
            Flush(); 
        } 

    private:
        static Y_FORCE_INLINE ui64 FastZeroIfFalse(bool cond, ui64 iftrue) {
            return -i64(cond) & iftrue;
        }
    }; 

    template <typename TVec> 
    class TBitOutputVectorImpl { 
        TVec* Data; 

    public: 
        void WriteData(const char* begin, const char* end) { 
            NAccessors::Append(*Data, begin, end);
        } 

        TBitOutputVectorImpl(TVec* data) 
            : Data(data) 
        { 
        } 
    }; 

    template <typename TVec> 
    struct TBitOutputVector: public TBitOutputVectorImpl<TVec>, public TBitOutputBase<TBitOutputVectorImpl<TVec>> { 
        inline TBitOutputVector(TVec* data) 
            : TBitOutputVectorImpl<TVec>(data) 
            , TBitOutputBase<TBitOutputVectorImpl<TVec>>(this) 
        { 
        } 
    }; 
 
    class TBitOutputArrayImpl { 
        char* Data; 
        size_t Left; 

    public: 
        void WriteData(const char* begin, const char* end) { 
            size_t sz = end - begin; 
            Y_VERIFY(sz <= Left, " ");
            memcpy(Data, begin, sz); 
            Data += sz; 
            Left -= sz; 
        } 

        TBitOutputArrayImpl(char* begin, size_t len) 
            : Data(begin) 
            , Left(len) 
        { 
        } 
    }; 

    struct TBitOutputArray: public TBitOutputArrayImpl, public TBitOutputBase<TBitOutputArrayImpl> { 
        inline TBitOutputArray(char* begin, size_t len) 
            : TBitOutputArrayImpl(begin, len) 
            , TBitOutputBase<TBitOutputArrayImpl>(this) 
        { 
        } 
    }; 
 
    using TBitOutputYVector = TBitOutputVector<TVector<char>>;

    class TBitOutputStreamImpl { 
        IOutputStream* Out;

    public: 
        void WriteData(const char* begin, const char* end) { 
            Out->Write(begin, end - begin); 
        } 

        TBitOutputStreamImpl(IOutputStream* out)
            : Out(out) 
        { 
        } 
    }; 
 
    struct TBitOutputStream: public TBitOutputStreamImpl, public TBitOutputBase<TBitOutputStreamImpl> { 
        inline TBitOutputStream(IOutputStream* out)
            : TBitOutputStreamImpl(out) 
            , TBitOutputBase<TBitOutputStreamImpl>(this) 
        { 
        } 
    }; 
}