1 // LzmaBase.cs

     2 

     3 namespace SevenZip.Compression.LZMA

     4 {

     5 	internal abstract class Base

     6 	{

     7 		public const uint kNumRepDistances = 4;

     8 		public const uint kNumStates = 12;

     9 

    10 		// static byte []kLiteralNextStates  = {0, 0, 0, 0, 1, 2, 3, 4,  5,  6,   4, 5};

    11 		// static byte []kMatchNextStates    = {7, 7, 7, 7, 7, 7, 7, 10, 10, 10, 10, 10};

    12 		// static byte []kRepNextStates      = {8, 8, 8, 8, 8, 8, 8, 11, 11, 11, 11, 11};

    13 		// static byte []kShortRepNextStates = {9, 9, 9, 9, 9, 9, 9, 11, 11, 11, 11, 11};

    14 

    15 		public struct State

    16 		{

    17 			public uint Index;

    18 			public void Init() { Index = 0; }

    19 			public void UpdateChar()

    20 			{

    21 				if (Index < 4) Index = 0;

    22 				else if (Index < 10) Index -= 3;

    23 				else Index -= 6;

    24 			}

    25 			public void UpdateMatch() { Index = (uint)(Index < 7 ? 7 : 10); }

    26 			public void UpdateRep() { Index = (uint)(Index < 7 ? 8 : 11); }

    27 			public void UpdateShortRep() { Index = (uint)(Index < 7 ? 9 : 11); }

    28 			public bool IsCharState() { return Index < 7; }

    29 		}

    30 

    31 		public const int kNumPosSlotBits = 6;

    32 		public const int kDicLogSizeMin = 0;

    33 		// public const int kDicLogSizeMax = 30;

    34 		// public const uint kDistTableSizeMax = kDicLogSizeMax * 2;

    35 

    36 		public const int kNumLenToPosStatesBits = 2; // it's for speed optimization

    37 		public const uint kNumLenToPosStates = 1 << kNumLenToPosStatesBits;

    38 

    39 		public const uint kMatchMinLen = 2;

    40 

    41 		public static uint GetLenToPosState(uint len)

    42 		{

    43 			len -= kMatchMinLen;

    44 			if (len < kNumLenToPosStates)

    45 				return len;

    46 			return (uint)(kNumLenToPosStates - 1);

    47 		}

    48 

    49 		public const int kNumAlignBits = 4;

    50 		public const uint kAlignTableSize = 1 << kNumAlignBits;

    51 		public const uint kAlignMask = (kAlignTableSize - 1);

    52 

    53 		public const uint kStartPosModelIndex = 4;

    54 		public const uint kEndPosModelIndex = 14;

    55 		public const uint kNumPosModels = kEndPosModelIndex - kStartPosModelIndex;

    56 

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

    58 

    59 		public const uint kNumLitPosStatesBitsEncodingMax = 4;

    60 		public const uint kNumLitContextBitsMax = 8;

    61 

    62 		public const int kNumPosStatesBitsMax = 4;

    63 		public const uint kNumPosStatesMax = (1 << kNumPosStatesBitsMax);

    64 		public const int kNumPosStatesBitsEncodingMax = 4;

    65 		public const uint kNumPosStatesEncodingMax = (1 << kNumPosStatesBitsEncodingMax);

    66 

    67 		public const int kNumLowLenBits = 3;

    68 		public const int kNumMidLenBits = 3;

    69 		public const int kNumHighLenBits = 8;

    70 		public const uint kNumLowLenSymbols = 1 << kNumLowLenBits;

    71 		public const uint kNumMidLenSymbols = 1 << kNumMidLenBits;

    72 		public const uint kNumLenSymbols = kNumLowLenSymbols + kNumMidLenSymbols +

    73 				(1 << kNumHighLenBits);

    74 		public const uint kMatchMaxLen = kMatchMinLen + kNumLenSymbols - 1;

    75 	}

    76 }