/// <summary>
/// Creates a new <see cref="IAsyncReadOnlyCollection{T}" /> that contains the sorted elements of the
/// <see cref="IAsyncEnumerable{T}" />.
/// </summary>
/// <param name="source">
/// The <see cref="IAsyncEnumerable{T}" /> to sort.
/// </param>
/// <param name="comparison">
/// The comparison to use while sorting.
/// </param>
/// <typeparam name="T">
/// The type of the items.
/// </typeparam>
/// <returns>
/// The sorted <see cref="IAsyncReadOnlyCollection{T}" />.
/// </returns>
public async Task <IAsyncReadOnlyCollection <T> > SortAsync <T>(IAsyncEnumerable <T> source, Comparison <T> comparison)
{
var chunks = new List <IAsyncReadOnlyCollection <T> >();
if (source.Policy != this)
{
source = await this.MaterializeAsync(source).ConfigureAwait(false);
}
await source.Batch(this.MaximumChunkSize).ForEachAsync(
async batch =>
{
var builder = await this.CreateBuilder <T>().AddAsync(await this.memPolicy.SortAsync(batch, comparison).ConfigureAwait(false));
chunks.Add(await builder.BuildAsync().ConfigureAwait(false));
});
var result = this.CreateBuilder <T>();
var enumerators = chunks.Select(c => c.GetAsyncEnumerator()).ToList();
foreach (var enumerator in enumerators.ToArray())
{
if (!enumerator.MoveNext() && !(await enumerator.NextBatchAsync().ConfigureAwait(false) && enumerator.MoveNext()))
{
enumerator.Dispose();
enumerators.Remove(enumerator);
}
}
enumerators.Sort((a, b) => comparison(a.Current, b.Current));
while (true)
{
await result.AddAsync(TemporaryFilePolicy.TakeItems(enumerators, comparison)).ConfigureAwait(false);
if (!(await enumerators[0].NextBatchAsync().ConfigureAwait(false) && enumerators[0].MoveNext()))
{
enumerators[0].Dispose();
enumerators.RemoveAt(0);
if (enumerators.Count == 0)
{
break;
}
}
else
{
TemporaryFilePolicy.SortEnumerators(enumerators, comparison);
}
}
foreach (var chunk in chunks)
{
chunk.Dispose();
}
return(await result.BuildAsync().ConfigureAwait(false));
}
/// <summary>
/// Initializes a new instance of the <see cref="Collection{T}"/> class.
/// </summary>
/// <param name="policy">
/// The policy.
/// </param>
/// <param name="fileId">
/// The file id.
/// </param>
/// <param name="count">
/// The count.
/// </param>
/// <param name="transform">
/// The transform.
/// </param>
/// <param name="context">
/// The context.
/// </param>
public Collection(TemporaryFilePolicy policy, int fileId, long count, ITransform <T> transform, IDisposable context)
{
this.policy = policy;
this.fileId = fileId;
this.Count = count;
this.transform = transform;
this.context = context;
}
/// <summary>
/// Takes sorted items from the enumerators while it can be done synchronously.
/// </summary>
/// <param name="enumerators">
/// The enumerators.
/// </param>
/// <param name="comparison">
/// The comparison.
/// </param>
/// <typeparam name="T">
/// The type of the items.
/// </typeparam>
/// <returns>
/// The items that were taken synchronously.
/// </returns>
private static IEnumerable <T> TakeItems <T>([NotNull] List <IAsyncEnumerator <T> > enumerators, Comparison <T> comparison)
{
while (true)
{
yield return(enumerators[0].Current);
if (!enumerators[0].MoveNext())
{
yield break;
}
TemporaryFilePolicy.SortEnumerators(enumerators, comparison);
}
}
public async Task <IAsyncReadOnlyCollection <T> > BuildAsync()
{
if (this.policy == null)
{
throw new InvalidOperationException("A builder can only be used once; collection was already built.");
}
if (this.addTask != null)
{
await this.addTask;
}
await this.file.FlushAsync();
this.file.Dispose();
this.file = null;
var result = new Collection <T>(this.policy, this.fileId, this.count, this.transform, this.context);
this.policy = null;
return(result);
}
/// <summary>
/// Initializes a new instance of the <see cref="Builder{T}" /> class.
/// </summary>
/// <param name="policy">
/// The policy.
/// </param>
public Builder(TemporaryFilePolicy policy)
{
this.policy = policy;
}