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Diffstat (limited to 'src/System.Data.SqlClient/tests/StressTests/System.Data.StressFramework/TrackedRandom.cs')
| -rw-r--r-- | src/System.Data.SqlClient/tests/StressTests/System.Data.StressFramework/TrackedRandom.cs | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/System.Data.SqlClient/tests/StressTests/System.Data.StressFramework/TrackedRandom.cs b/src/System.Data.SqlClient/tests/StressTests/System.Data.StressFramework/TrackedRandom.cs new file mode 100644 index 0000000000..b42128fff5 --- /dev/null +++ b/src/System.Data.SqlClient/tests/StressTests/System.Data.StressFramework/TrackedRandom.cs @@ -0,0 +1,184 @@ +// Licensed to the .NET Foundation under one or more agreements. +// The .NET Foundation licenses this file to you under the MIT license. +// See the LICENSE file in the project root for more information. + +using System; +using System.Collections.Generic; + +namespace Stress.Data +{ + /// <summary> + /// Random number generator that tracks information necessary to reproduce a sequence of random numbers. + /// </summary> + /// <remarks> + /// There are three items maintained by instances of this class + /// that are used to assist in the reproduction of a sequence of generated numbers: + /// + /// 1. The seed used for initialization. + /// 2. The count of numbers generated. + /// 3. Markers to indicate relevant points in the sequence. + /// + /// For tests that use random numbers to control execution, + /// these tracked items can be used to help determine the specific code path that was executed. + /// Here's an example: + /// + /// A test starts to execute, and retrieves an instance of this class. + /// If an instance of this class has not been created beforehand, it is constructed and the *seed* is stored. + /// The test inserts a *marker* to track the *count* of numbers generated before the test starts its work. + /// As the test executes, it asks for a sequence of random numbers. At some point, the test causes a crash. + /// Using the resulting dump (or live debugging session if available), it is possible to examine an instance + /// of this class to recreate the sequence of numbers used by the test. + /// You can create an instance of a Random offline using the tracked *seed*, + /// and generate numbers up to the *marked* count to determine the starting point for the sequence of numbers used by the test. + /// The length of the sequence is indicated by the last *count* of number generated. + /// So for a failed test, you can use the numbers from Mark+1 to Count to retrace the code path taken by the test. + /// + /// Instances of this class keep track of a finite number of multiple marks, + /// so it is possible to track the beginning and end of a series of tests, + /// assuming they all mark at least the start of their execution. + /// </remarks> + public class TrackedRandom : Random + { + private readonly int _seed; + + /// <summary> + /// Number of random numbers generated. + /// </summary> + private long _count; + + /// <summary> + /// Circular buffer to track the most recent marks that indicate the count at the time a given mark was created. + /// </summary> + private readonly long[] _marks = new long[16]; + + /// <summary> + /// Index of where to place next mark in buffer. + /// This index is incremented after each mark, and wraps around as necessary. + /// </summary> + private int _nextMark; + + private const int EmptyMark = -1; + + public TrackedRandom() + : this(Environment.TickCount) + { + } + + public TrackedRandom(int seed) + : base(seed) + { + _seed = seed; + + for (int i = 0; i < _marks.Length; i++) + { + _marks[i] = EmptyMark; + } + } + + public int Seed + { + get + { + return _seed; + } + } + + public long Count + { + get + { + return _count; + } + } + + public void Mark() + { + long mark = _count; + + // marking forward + _marks[_nextMark++] = mark; + + // wrap when necessary + if (_nextMark == _marks.Length) + { + _nextMark = 0; + } + } + + /// <summary> + /// Return an enumerable that can be used to iterate over the most recent marks, + /// starting from the most recent, and ending with the earliest mark still being tracked. + /// </summary> + public IEnumerable<long> Marks + { + get + { + // Iterate backwards through the mark array, + // starting just before the index of the next mark, + // and ending at the next mark. + // Iteration stops earlier if an empty mark is found. + int index; + long mark; + + for (int i = 1; i <= _marks.Length; i++) + { + // Index of current element determined by: + // ((L+n) - i) % L + // where + // L is the length of the array, + // n is the index of where to insert the next mark, 0 <= n < L, + // i is the current iteration variable value, 0 < i <= L. + index = (_marks.Length + _nextMark - i) % _marks.Length; + mark = _marks[index]; + + if (mark == EmptyMark) + { + break; + } + + yield return mark; + } + } + } + + private void IncrementCount() + { + if (_count == long.MaxValue) + { + _count = -1; + } + + ++_count; + } + + public override int Next() + { + IncrementCount(); + return base.Next(); + } + + public override int Next(int minValue, int maxValue) + { + IncrementCount(); + return base.Next(minValue, maxValue); + } + + public override int Next(int maxValue) + { + IncrementCount(); + return base.Next(maxValue); + } + + public override void NextBytes(byte[] buffer) + { + IncrementCount(); + base.NextBytes(buffer); + } + + public override double NextDouble() + { + IncrementCount(); + return base.NextDouble(); + } + } +}
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