// LzmaBase.cs

namespace NewLife.Compression.LZMA
{
    static class LzmaBase
    {
        public const uint kNumRepDistances = 4;
        public const uint kNumStates = 12;

        public static byte[] kDictionary = { };
        public static byte[] kLiteralNextStates = { 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 4, 5 };
        public static byte[] kMatchNextStates = { 7, 7, 7, 7, 7, 7, 7, 10, 10, 10, 10, 10 };
        public static byte[] kRepNextStates = { 8, 8, 8, 8, 8, 8, 8, 11, 11, 11, 11, 11 };
        public static byte[] kShortRepNextStates = { 9, 9, 9, 9, 9, 9, 9, 11, 11, 11, 11, 11 };

        public struct State
        {
            public uint Index;
            public void Init() { Index = 0; }
            public void UpdateChar()
            {
                if (Index < 4) Index = 0;
                else if (Index < 10) Index -= 3;
                else Index -= 6;
            }
            public void UpdateMatch() { Index = (uint)(Index < 7 ? 7 : 10); }
            public void UpdateRep() { Index = (uint)(Index < 7 ? 8 : 11); }
            public void UpdateShortRep() { Index = (uint)(Index < 7 ? 9 : 11); }
            public bool IsCharState() { return Index < 7; }
        }

        public const int kNumPosSlotBits = 6;
        public const int kDicLogSizeMin = 0;
        // public const int kDicLogSizeMax = 30;
        // public const uint kDistTableSizeMax = kDicLogSizeMax * 2;

        public const int kNumLenToPosStatesBits = 2; // it's for speed optimization
        public const uint kNumLenToPosStates = 1 << kNumLenToPosStatesBits;

        public const uint kMatchMinLen = 2;

        public static uint GetLenToPosState(uint len)
        {
            len -= kMatchMinLen;
            if (len < kNumLenToPosStates)
                return len;
            return (uint)(kNumLenToPosStates - 1);
        }

        public const int kNumAlignBits = 4;
        public const uint kAlignTableSize = 1 << kNumAlignBits;
        public const uint kAlignMask = (kAlignTableSize - 1);

        public const uint kStartPosModelIndex = 4;
        public const uint kEndPosModelIndex = 14;
        public const uint kNumPosModels = kEndPosModelIndex - kStartPosModelIndex;

        public const uint kNumFullDistances = 1 << ((int)kEndPosModelIndex / 2);

        public const uint kNumLitPosStatesBitsEncodingMax = 4;
        public const uint kNumLitContextBitsMax = 8;

        public const int kNumPosStatesBitsMax = 4;
        public const uint kNumPosStatesMax = (1 << kNumPosStatesBitsMax);
        public const int kNumPosStatesBitsEncodingMax = 4;
        public const uint kNumPosStatesEncodingMax = (1 << kNumPosStatesBitsEncodingMax);

        public const int kNumLowLenBits = 3;
        public const int kNumMidLenBits = 3;
        public const int kNumHighLenBits = 8;
        public const uint kNumLowLenSymbols = 1 << kNumLowLenBits;
        public const uint kNumMidLenSymbols = 1 << kNumMidLenBits;
        public const uint kNumLenSymbols = kNumLowLenSymbols + kNumMidLenSymbols + (1 << kNumHighLenBits);
        public const uint kMatchMaxLen = kMatchMinLen + kNumLenSymbols - 1;
    }
}