mcs/class/referencesource/System.Runtime.Serialization/System/Runtime/Serialization/BitFlagsGenerator.cs

   1 //-----------------------------------------------------------------------------
   2 // Copyright (c) Microsoft Corporation.  All rights reserved.
   3 //-----------------------------------------------------------------------------
   4
   5 namespace System.Runtime.Serialization
   6 {
   7     using System;
   8     using System.Reflection;
   9     using System.Reflection.Emit;
  10     using System.Security;
  11
  12 #if !NO_DYNAMIC_CODEGEN
  13     [Fx.Tag.SecurityNote(Miscellaneous = "RequiresReview (Critical) - works on CodeGenerator objects, which require Critical access.")]
  14     class BitFlagsGenerator
  15     {
  16         int bitCount;
  17         CodeGenerator ilg;
  18         LocalBuilder[] locals;
  19
  20         public BitFlagsGenerator(int bitCount, CodeGenerator ilg, string localName)
  21         {
  22             this.ilg = ilg;
  23             this.bitCount = bitCount;
  24             int localCount = (bitCount + 7) / 8;
  25             locals = new LocalBuilder[localCount];
  26             for (int i = 0; i < locals.Length; i++)
  27             {
  28                 locals[i] = ilg.DeclareLocal(typeof(byte), localName + i, (byte) 0);
  29             }
  30         }
  31
  32         public static bool IsBitSet(byte[] bytes, int bitIndex)
  33         {
  34             int byteIndex = GetByteIndex(bitIndex);
  35             byte bitValue = GetBitValue(bitIndex);
  36             return (bytes[byteIndex] & bitValue) == bitValue;
  37         }
  38
  39         public static void SetBit(byte[] bytes, int bitIndex)
  40         {
  41             int byteIndex = GetByteIndex(bitIndex);
  42             byte bitValue = GetBitValue(bitIndex);
  43             bytes[byteIndex] |= bitValue;
  44         }
  45
  46         public int GetBitCount()
  47         {
  48             return bitCount;
  49         }
  50
  51         public LocalBuilder GetLocal(int i)
  52         {
  53             return locals[i];
  54         }
  55
  56         public int GetLocalCount()
  57         {
  58             return locals.Length;
  59         }
  60
  61         public void Load(int bitIndex)
  62         {
  63             LocalBuilder local = locals[GetByteIndex(bitIndex)];
  64             byte bitValue = GetBitValue(bitIndex);
  65             ilg.Load(local);
  66             ilg.Load(bitValue);
  67             ilg.And();
  68             ilg.Load(bitValue);
  69             ilg.Ceq();
  70         }
  71
  72         public void LoadArray()
  73         {
  74             LocalBuilder localArray = ilg.DeclareLocal(Globals.TypeOfByteArray, "localArray");
  75             ilg.NewArray(typeof(byte), locals.Length);
  76             ilg.Store(localArray);
  77             for (int i = 0; i < locals.Length; i++)
  78             {
  79                 ilg.StoreArrayElement(localArray, i, locals[i]);
  80             }
  81             ilg.Load(localArray);
  82         }
  83
  84         public void Store(int bitIndex, bool value)
  85         {
  86             LocalBuilder local = locals[GetByteIndex(bitIndex)];
  87             byte bitValue = GetBitValue(bitIndex);
  88             if (value)
  89             {
  90                 ilg.Load(local);
  91                 ilg.Load(bitValue);
  92                 ilg.Or();
  93                 ilg.Stloc(local);
  94             }
  95             else
  96             {
  97                 ilg.Load(local);
  98                 ilg.Load(bitValue);
  99                 ilg.Not();
 100                 ilg.And();
 101                 ilg.Stloc(local);
 102             }
 103         }
 104
 105         static byte GetBitValue(int bitIndex)
 106         {
 107             return (byte)(1 << (bitIndex & 7));
 108         }
 109
 110         static int GetByteIndex(int bitIndex)
 111         {
 112             return bitIndex >> 3;
 113         }
 114
 115     }
 116 #endif
 117 }
 118