87 lines
3.9 KiB
C#
87 lines
3.9 KiB
C#
// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
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using System;
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using System.Buffers;
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using System.Diagnostics;
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using System.IO;
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using System.Threading;
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using System.Threading.Tasks;
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namespace Microsoft.AspNetCore.Http.Extensions
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{
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// FYI: In most cases the source will be a FileStream and the destination will be to the network.
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public static class StreamCopyOperation
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{
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private const int DefaultBufferSize = 4096;
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/// <summary>Asynchronously reads the bytes from the source stream and writes them to another stream.</summary>
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/// <returns>A task that represents the asynchronous copy operation.</returns>
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/// <param name="source">The stream from which the contents will be copied.</param>
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/// <param name="destination">The stream to which the contents of the current stream will be copied.</param>
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/// <param name="count">The count of bytes to be copied.</param>
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/// <param name="cancel">The token to monitor for cancellation requests. The default value is <see cref="P:System.Threading.CancellationToken.None" />.</param>
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public static Task CopyToAsync(Stream source, Stream destination, long? count, CancellationToken cancel)
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{
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return CopyToAsync(source, destination, count, DefaultBufferSize, cancel);
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}
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/// <summary>Asynchronously reads the bytes from the source stream and writes them to another stream, using a specified buffer size.</summary>
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/// <returns>A task that represents the asynchronous copy operation.</returns>
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/// <param name="source">The stream from which the contents will be copied.</param>
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/// <param name="destination">The stream to which the contents of the current stream will be copied.</param>
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/// <param name="count">The count of bytes to be copied.</param>
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/// <param name="bufferSize">The size, in bytes, of the buffer. This value must be greater than zero. The default size is 4096.</param>
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/// <param name="cancel">The token to monitor for cancellation requests. The default value is <see cref="P:System.Threading.CancellationToken.None" />.</param>
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public static async Task CopyToAsync(Stream source, Stream destination, long? count, int bufferSize, CancellationToken cancel)
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{
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long? bytesRemaining = count;
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var buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
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try
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{
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Debug.Assert(source != null);
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Debug.Assert(destination != null);
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Debug.Assert(!bytesRemaining.HasValue || bytesRemaining.Value >= 0);
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Debug.Assert(buffer != null);
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while (true)
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{
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// The natural end of the range.
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if (bytesRemaining.HasValue && bytesRemaining.Value <= 0)
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{
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return;
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}
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cancel.ThrowIfCancellationRequested();
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int readLength = buffer.Length;
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if (bytesRemaining.HasValue)
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{
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readLength = (int)Math.Min(bytesRemaining.Value, (long)readLength);
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}
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int read = await source.ReadAsync(buffer, 0, readLength, cancel);
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if (bytesRemaining.HasValue)
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{
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bytesRemaining -= read;
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}
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// End of the source stream.
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if (read == 0)
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{
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return;
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}
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cancel.ThrowIfCancellationRequested();
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await destination.WriteAsync(buffer, 0, read, cancel);
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}
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}
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finally
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{
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ArrayPool<byte>.Shared.Return(buffer);
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}
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}
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}
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} |