LimitedStreamResultExecutor.cs

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using System;
using System.IO;
using System.Threading.Tasks;
 
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using Microsoft.Extensions.Logging;
 
namespace Tgstation.Server.Host.Controllers
{
    public class LimitedStreamResultExecutor : FileResultExecutorBase, IActionResultExecutor<LimitedStreamResult>
    {
        public LimitedStreamResultExecutor(ILogger<LimitedStreamResultExecutor> logger)
            : base(logger)
        {
        }
 
        public async Task ExecuteAsync(ActionContext context, LimitedStreamResult result)
        {
            ArgumentNullException.ThrowIfNull(context);
 
            ArgumentNullException.ThrowIfNull(result);
 
            await using (result)
            {
                var cancellationToken = context.HttpContext.RequestAborted;
                var stream = await result.GetResult(cancellationToken);
                var contentLength = stream.Length;
                var (range, rangeLength, serveBody) = SetHeadersAndLog(context, result, contentLength, result.EnableRangeProcessing);
                if (!serveBody)
                    return;
 
                try
                {
                    var outputStream = context.HttpContext.Response.Body;
                    if (range == null)
                    {
                        await StreamCopyOperation.CopyToAsync(
                            stream,
                            outputStream,
                            contentLength,
                            BufferSize,
                            cancellationToken);
                    }
                    else
                    {
                        stream.Seek(range.From.Value, SeekOrigin.Begin);
                        await StreamCopyOperation.CopyToAsync(
                            stream,
                            outputStream,
                            rangeLength,
                            BufferSize,
                            cancellationToken);
                    }
                }
                catch (OperationCanceledException)
                {
                    // Don't throw this exception, it's most likely caused by the client disconnecting.
                    // However, if it was cancelled for any other reason we need to prevent empty responses.
                    context.HttpContext.Abort();
                }
            }
        }
    }
}