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C# structs, byte swapping for conversion from big to little endian using reflection to enumerate members

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<p>This example uses a Swap member to enumerate the struct&#8217;s fields and swap multi-byte fields. It doesn&#8217;t traverse nested structs.</p>

<p>It would be nice if dot.net has something equivalent to &#8216;#pragma endian big&#8217; as seen in some compilers. There might be a way to leverage marshaling to automatically endianize multi-byte values.</p>

<p>This example uses:
* System.Net.IPAddress.NetworkToHostOrder for byte swapping
* unchecked() to convert a value of, say, 0&#8201;&#215;&#8201;87654321 to a Int32 without a runtime error
* foreach (System.Reflection.FieldInfo field in typeof(MyStruct).GetFields()) to enumerate structure members
* TypeCode typeCode = Type.GetTypeCode(fieldValue.GetType()); to get the underlying type enumeration (typeof of verbose).
* SetValue and GetValue to access struct members.
* Boxed object of struct - this was necessary only because SetValue didn&#8217;t work on structs. It failed quietly.</p>

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  1. public struct MyStruct
  2. {
  3.     public UInt32 u4;
  4.     public int  s4;
  5.     public UInt16 u2;
  6.     public short  s2;
  7.     public UInt64 u8;
  8.     public Int64  s8;
  9.  
  10.     // byte-swap members of this struct.
  11.     public MyStruct Swap()
  12.     {
  13.         // The copy is made becuase SetValue won't work on a struct.
  14.         // Boxing was used because SetValue works on classes/objects.
  15.         // Unfortunately, it results in 2 copy operations.
  16.         object thisBoxed = this; // Why make a copy?
  17.  
  18.         // System.Net.IPAddress.NetworkToHostOrder is used to perform byte swapping.
  19.         // To convert unsigned to signed, 'unchecked()' was used.
  20.         // See http://stackoverflow.com/questions/1131843/how-do-i-convert-uint-to-int-in-c
  21.  
  22.         // Enumerate each structure field using reflection.
  23.         foreach (var field in typeof(MyStruct).GetFields())
  24.         {
  25.             // field.Name has the field's name.
  26.  
  27.             object fieldValue = field.GetValue(thisBoxed); // Get value
  28.  
  29.             // Get the TypeCode enumeration. Multiple types get mapped to a common typecode.
  30.             TypeCode typeCode = Type.GetTypeCode(fieldValue.GetType());
  31.  
  32.             switch (typeCode)
  33.             {
  34.                 case TypeCode.Int32:
  35.                 {
  36.                     Int32 i = System.Net.IPAddress.NetworkToHostOrder((Int32)fieldValue);
  37.                     field.SetValue(thisBoxed, (Int32)i);
  38.                     break;
  39.                 }
  40.                 case TypeCode.UInt32:
  41.                 {
  42.                     Int32 i = System.Net.IPAddress.NetworkToHostOrder(unchecked((Int32)(UInt32)fieldValue));
  43.                     field.SetValue(thisBoxed, (UInt32)i);
  44.                     break;
  45.                 }
  46.                 case TypeCode.Int16:
  47.                 {
  48.                     Int16 i = System.Net.IPAddress.NetworkToHostOrder((Int16)fieldValue);
  49.                     field.SetValue(thisBoxed, (Int16)i);
  50.                     break;
  51.                 }
  52.                 case TypeCode.UInt16:
  53.                 {
  54.                     Int16 i = System.Net.IPAddress.NetworkToHostOrder(unchecked((Int16)(UInt16)fieldValue));
  55.                     field.SetValue(thisBoxed, (UInt16)i);
  56.                     break;
  57.                 }
  58.                 case TypeCode.Int64:
  59.                 {
  60.                     Int64 i = System.Net.IPAddress.NetworkToHostOrder((Int64)fieldValue);
  61.                     field.SetValue(thisBoxed, i);
  62.                     break;
  63.                 }
  64.                 case TypeCode.UInt64:
  65.                 {
  66.                     Int64 i = System.Net.IPAddress.NetworkToHostOrder(unchecked((Int64)(UInt64)fieldValue));
  67.                     field.SetValue(thisBoxed, (UInt64)i);
  68.                     break;
  69.                 }
  70.                 default:
  71.                 {
  72.                     System.Diagnostics.Debug.Fail("No conversion provided for this type");
  73.                     break;
  74.                 }
  75.             }; // switch
  76.  
  77.         } // foreach
  78.         return (MyStruct)thisBoxed;
  79.     } // Swap
  80. }; // MyStruct
  81.  
  82.  
  83. // Usage example:
  84.     MyStruct s = new MyStruct();
  85.  
  86.     s.u4 = 0x78563412; 
  87.     s.s4 = 0x21436587;
  88.     s.u2 = 0x2143;
  89.     s.s2 = 0x3412;
  90.     s.u8 = 0xFF007856341200FF;
  91.     s.s8 = 0x7700785634120077;
  92.  
  93.     s = s.Swap();

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