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  1. using System;
  2. using System.Diagnostics;
  3. using System.Text;
  4.  
  5. namespace VarIntTest
  6. {
  7. 	class Program
  8. 	{
  9. 		public static void Main (string[] args)
  10. 		{
  11. 			Console.WriteLine ("Test VarInt encoding");
  12.  
  13. 			Console.WriteLine ("{0,6} | = | {1,6} | {2,33}", "Value", "VarInt", "Bits");
  14. 			Console.WriteLine (new String ('-', 3 * 3 + 6 * 2 + 33 + 1));
  15. 			for (int n = -12; n < 4; n++) {
  16. 				uint v = IntToVarInt (n);
  17. 				Console.WriteLine ("{0,6} | {1} | {2,6} | {3,33}", n, (n == VarIntToInt (v)) ? '=' : '/', v, ShowBits (v));
  18. 			}
  19.  
  20. 			Console.WriteLine ("\n{0,6} | = | {1,6} | {2,33}", "Value", "Base-2", "Bits");
  21. 			Console.WriteLine (new String ('-', 3 * 3 + 6 * 2 + 33 + 1));
  22. 			for (int n = -12; n < 4; n++) {
  23. 				uint v = IntToNeg2 (n);
  24. 				Console.WriteLine ("{0,6} | {1} | {2,6} | {3,33}", n, (n == Neg2ToInt (v)) ? '=' : '/', v, ShowBits (v));
  25. 			}
  26.  
  27. 			var sw = new Stopwatch ();
  28.  
  29. 			for (int n = -100000; n < 100000; n++) {
  30. 				uint v = IntToVarInt (n);
  31. 				int i = VarIntToInt (v);
  32. 			}
  33. 			sw.Restart ();
  34. 			for (int n = -100000; n < 100000; n++) {
  35. 				uint v = IntToVarInt (n);
  36. 				int i = VarIntToInt (v);
  37. 			}
  38. 			sw.Stop ();
  39. 			Console.WriteLine ("\nInt To VarInt conversion took: {0}", sw.Elapsed);
  40.  
  41. 			for (int n = -100000; n < 100000; n++) {
  42. 				uint v = IntToNeg2 (n);
  43. 				int i = Neg2ToInt (v);
  44. 			}
  45. 			sw.Restart ();
  46. 			for (int n = -100000; n < 100000; n++) {
  47. 				uint v = IntToNeg2 (n);
  48. 				int i = Neg2ToInt (v);
  49. 			}
  50. 			sw.Stop ();
  51. 			Console.WriteLine ("Int To Base-2 conversion took: {0}", sw.Elapsed);
  52.  
  53. 			Console.Write ("Press any key to continue . . . ");
  54. 			Console.ReadKey (true);
  55. 		}
  56.  
  57. 		static StringBuilder sb = new StringBuilder ();
  58.  
  59. 		public static string ShowBits (int value)
  60. 		{
  61. 			return ShowBits ((uint)value);
  62. 		}
  63.  
  64. 		public static string ShowBits (uint value)
  65. 		{
  66. 			sb.Length = 0;
  67. 			do {
  68. 				sb.Append ((value & 1) > 0 ? '1' : '0');
  69. 				unchecked {
  70. 					value >>= 1;
  71. 				}
  72. 			} while (value != 0);
  73. 			int j = sb.Length - 1, i = 0;
  74. 			while (i < j) {
  75. 				var c = sb[i];
  76. 				sb[i] = sb[j];
  77. 				sb[j] = c;
  78. 				i++;
  79. 				j--;
  80. 			}
  81. 			return sb.ToString ();
  82. 		}
  83.  
  84. 		public static uint IntToVarInt (int n)
  85. 		{
  86. 			unchecked {
  87. 				return (uint)((n << 1) ^ (n >> 31));
  88. 			}
  89. 		}
  90.  
  91. 		public static int VarIntToInt (uint v)
  92. 		{
  93. 			unchecked {
  94. 				var n = (int)v;
  95. 				return (n >> 1) ^ (-(n & 1));
  96. 			}
  97. 		}
  98.  
  99. 		public static uint IntToNeg2 (int n)
  100. 		{
  101. 			uint val = 0;
  102. 			uint shift = 1;
  103. 			while (n != 0) {
  104. 				int rem;
  105. 				n = Math.DivRem (n, -2, out rem);
  106. 				if (rem < 0) {
  107. 					++n;
  108. 				}
  109. 				if (rem != 0) {
  110. 					val |= shift;
  111. 				}
  112. 				shift <<= 1;
  113. 			}
  114. 			return val;
  115. 		}
  116.  
  117. 		public static int Neg2ToInt (uint v)
  118. 		{
  119. 			int n = 0;
  120. 			int shift = 0;
  121. 			int neg = 1;
  122. 			while (v > 0) {
  123. 				int rem = (int)(v & 1);
  124. 				v >>= 1;
  125. 				n += (rem << shift) * neg;
  126. 				++shift;
  127. 				neg *= -1;
  128. 			}
  129. 			return n;
  130. 		}
  131. 	}
  132. }
Success #stdin #stdout 0.1s 29800KB
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stdin
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Standard input is empty
stdout
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Test VarInt encoding
 Value | = | VarInt |                              Bits
-------------------------------------------------------
   -12 | = |     23 |                             10111
   -11 | = |     21 |                             10101
   -10 | = |     19 |                             10011
    -9 | = |     17 |                             10001
    -8 | = |     15 |                              1111
    -7 | = |     13 |                              1101
    -6 | = |     11 |                              1011
    -5 | = |      9 |                              1001
    -4 | = |      7 |                               111
    -3 | = |      5 |                               101
    -2 | = |      3 |                                11
    -1 | = |      1 |                                 1
     0 | = |      0 |                                 0
     1 | = |      2 |                                10
     2 | = |      4 |                               100
     3 | = |      6 |                               110

 Value | = | Base-2 |                              Bits
-------------------------------------------------------
   -12 | = |     52 |                            110100
   -11 | = |     53 |                            110101
   -10 | = |     10 |                              1010
    -9 | = |     11 |                              1011
    -8 | = |      8 |                              1000
    -7 | = |      9 |                              1001
    -6 | = |     14 |                              1110
    -5 | = |     15 |                              1111
    -4 | = |     12 |                              1100
    -3 | = |     13 |                              1101
    -2 | = |      2 |                                10
    -1 | = |      3 |                                11
     0 | = |      0 |                                 0
     1 | = |      1 |                                 1
     2 | = |      6 |                               110
     3 | = |      7 |                               111

Int To VarInt conversion took: 00:00:00.0010748
Int To Base-2 conversion took: 00:00:00.0452521
Press any key to continue . . .
https://ideone.com/Iih5z2
language:
C# (gmcs 5.20.1)
created:
7 years ago
visibility:
public

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