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﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.ExceptionServices;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace Medallion.Threading
    internal static class DistributedLockHelpers
        public static int ToInt32Timeout(this TimeSpan timeout, string paramName = null)
            // based on http://referencesource.microsoft.com/#mscorlib/system/threading/Tasks/Task.cs,959427ac16fa52fa
            var totalMilliseconds = (long)timeout.TotalMilliseconds;
            if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
                throw new ArgumentOutOfRangeException(paramName ?? "timeout");
            return (int)totalMilliseconds;
        public static Task<IDisposable> AcquireAsync(IDistributedLock @lock, TimeSpan? timeout, CancellationToken cancellationToken)
            var tryAcquireTask = @lock.TryAcquireAsync(timeout ?? Timeout.InfiniteTimeSpan, cancellationToken);
            return ValidateTryAcquireResultAsync(tryAcquireTask, timeout);
        public static IDisposable Acquire(IDistributedLock @lock, TimeSpan? timeout, CancellationToken cancellationToken)
            var handle = @lock.TryAcquire(timeout ?? Timeout.InfiniteTimeSpan, cancellationToken);
            ValidateTryAcquireResult(handle, timeout);
            return handle;
        public static async Task<THandle> ValidateTryAcquireResultAsync<THandle>(Task<THandle> tryAcquireTask, TimeSpan? timeout)
            where THandle : class, IDisposable
            var handle = await tryAcquireTask.ConfigureAwait(false);
            ValidateTryAcquireResult(handle, timeout);
            return handle;
        public static void ValidateTryAcquireResult(IDisposable handle, TimeSpan? timeout) =>
            ValidateTryAcquireResult(succeeded: handle != null, timeout: timeout);
        public static void ValidateTryAcquireResult(bool succeeded, TimeSpan? timeout)
            if (!succeeded)
                if (timeout.HasValue && timeout >= TimeSpan.Zero)
                    throw new TimeoutException("Timeout exceeded when trying to acquire the lock");
                // should never get here
                throw new InvalidOperationException("Failed to acquire the lock");
        public static IDisposable TryAcquireWithAsyncCancellation(IDistributedLock @lock, TimeSpan timeout, CancellationToken cancellationToken)
            var tryAcquireTask = @lock.TryAcquireAsync(timeout, cancellationToken);
                return tryAcquireTask.Result;
            catch (AggregateException ex)
                // attempt to prevent the throwing of aggregate exceptions
                if (ex.InnerExceptions.Count == 1)
                    // rethrow the inner exception without losing stack trace
                    ExceptionDispatchInfo.Capture(ex.InnerException).Throw();
                throw; // otherwise just rethrow
        public static string ToSafeLockName(string baseLockName, int maxNameLength, Func<string, string> convertToValidName)
            if (baseLockName == null)
                throw new ArgumentNullException("baseLockName");
            var validBaseLockName = convertToValidName(baseLockName);
            if (validBaseLockName == baseLockName && validBaseLockName.Length <= maxNameLength)
                return baseLockName;
            using (var sha = SHA512.Create())
                var hash = Convert.ToBase64String(sha.ComputeHash(Encoding.UTF8.GetBytes(baseLockName)));
                if (hash.Length >= maxNameLength)
                    return hash.Substring(0, length: maxNameLength);
                var prefix = validBaseLockName.Substring(0, Math.Min(validBaseLockName.Length, maxNameLength - hash.Length));
                return prefix + hash;
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