DecompressedContent.cs

using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;

namespace CompatApiClient.Compression;

public class DecompressedContent : HttpContent
{
    private readonly HttpContent content;
    private readonly ICompressor compressor;

    public DecompressedContent(HttpContent content, ICompressor compressor)
    {
        this.content = content;
        this.compressor = compressor;
        RemoveHeaders();
    }

    protected override bool TryComputeLength(out long length)
    {
        length = -1;
        return false;
    }

    protected override async Task SerializeToStreamAsync(Stream stream, TransportContext? context)
    {
        var contentStream = await content.ReadAsStreamAsync().ConfigureAwait(false);
        var decompressedLength = await compressor.DecompressAsync(contentStream, stream).ConfigureAwait(false);
        Headers.ContentLength = decompressedLength;
    }

    private void RemoveHeaders()
    {
        foreach (var (key, value) in content.Headers)
            Headers.TryAddWithoutValidation(key, value);
        Headers.ContentEncoding.Clear();
        Headers.ContentLength = null;
    }
}