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BatchTransformingAsyncCursor.cs
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BatchTransformingAsyncCursor.cs
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/* Copyright 2010-present MongoDB Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using MongoDB.Driver.Core.Misc;
namespace MongoDB.Driver
{
/// <summary>
/// Represents a cursor that wraps another cursor with a transformation function on the documents.
/// </summary>
/// <typeparam name="TFromDocument">The type of from document.</typeparam>
/// <typeparam name="TToDocument">The type of to document.</typeparam>
/// <seealso cref="MongoDB.Driver.IAsyncCursor{TToDocument}" />
public sealed class BatchTransformingAsyncCursor<TFromDocument, TToDocument> : IAsyncCursor<TToDocument>
{
private bool _disposed;
private readonly Func<IEnumerable<TFromDocument>, IEnumerable<TToDocument>> _transformer;
private readonly IAsyncCursor<TFromDocument> _wrapped;
private List<TToDocument> _current;
/// <summary>
/// Initializes a new instance of the <see cref="BatchTransformingAsyncCursor{TFromDocument, TToDocument}"/> class.
/// </summary>
/// <param name="wrapped">The wrapped.</param>
/// <param name="transformer">The transformer.</param>
public BatchTransformingAsyncCursor(IAsyncCursor<TFromDocument> wrapped, Func<IEnumerable<TFromDocument>, IEnumerable<TToDocument>> transformer)
{
_wrapped = Ensure.IsNotNull(wrapped, nameof(wrapped));
_transformer = Ensure.IsNotNull(transformer, nameof(transformer));
}
/// <inheritdoc/>
public IEnumerable<TToDocument> Current
{
get
{
ThrowIfDisposed();
if (_current == null)
{
throw new InvalidOperationException("Must call MoveNextAsync first.");
}
return _current;
}
}
// methods
/// <inheritdoc/>
public bool MoveNext(CancellationToken cancellationToken)
{
ThrowIfDisposed();
while (_wrapped.MoveNext(cancellationToken))
{
_current = _transformer(_wrapped.Current).ToList();
if (_current.Count > 0)
{
return true;
}
}
return false;
}
/// <inheritdoc/>
public async Task<bool> MoveNextAsync(CancellationToken cancellationToken)
{
ThrowIfDisposed();
while (await _wrapped.MoveNextAsync(cancellationToken).ConfigureAwait(false))
{
_current = _transformer(_wrapped.Current).ToList();
if (_current.Count > 0)
{
return true;
}
}
return false;
}
/// <inheritdoc/>
public void Dispose()
{
_disposed = true;
_current = null;
_wrapped.Dispose();
}
private void ThrowIfDisposed()
{
if (_disposed)
{
throw new ObjectDisposedException(GetType().Name);
}
}
}
}