Large memory allocated when handling relatively small MSG file

[mathy-plutoflume]

Describe the bug I was trying to extract BodyText and BodyHtml from MSG file and noticed that the memory usage was very high.

To Reproduce I used the EmailWith2Attachments.msg from the sample test files for my analysis

Code i used to benchmark

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using MsgReader.Outlook;
using System.Text;

public class Program
{
    public static void Main(string[] args)
    {
        BenchmarkRunner.Run<ExtractMsg>();
    }
}

[MemoryDiagnoser]
public class ExtractMsg
{
    [Params(@"C:\EmailWith2Attachments.msg")]
    public string FileName { get; set; }

    public ExtractMsg() => Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);

    [Benchmark]
    public void Extract()
    {
        using (var msg = new Storage.Message(FileName))
        {
            //var txtBody = msg.BodyText;
            var htmlBody = msg.BodyHtml;
        }
    }
}

Expected behavior

• Lesser memory allocated for such a small file

Actual behavior Input msg file size is 267 KB and memory allocated for that is around 55 MB

Method	FileName	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
ExtractMsg	C:\EmailWith2Attachments.msg [74]	9,315.1 us	184.83 us	417.19 us	6078.1250	15.6250	-	55879.93 KB

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Windows 11 (10.0.22621.1702/22H2/2022Update/SunValley2)
• Browser: NA
• Version: 5.2.2
• 12th Gen Intel Core i7-1260P, 1 CPU, 16 logical and 12 physical cores
  • .NET SDK=7.0.203 [Host] : .NET 6.0.16 (6.0.1623.17311), X64 RyuJIT AVX2 .NET 6.0 : .NET 6.0.16 (6.0.1623.17311), X64 RyuJIT AVX2
  • BenchmarkDotNet=v0.13.5

Additional context

• I tried loading other test msg files with large text in body (400,000 words). The msg file size was 548 KB whereas the Memory allocated for that was around 43 MB. Benchmark report below,

Method	FileName	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
Extract	C:\LargeHtmlbody.msg [22]	6.161 ms	0.1224 ms	0.2581 ms	4781.2500	250.0000	234.3750	43.8 MB

[Sicos1977]

Did you find out what part is consuming the memory?

[dhilmathy]

Did you find out what part is consuming the memory?

@Sicos1977 Not exactly. I tried removing some of the parts (specially the Attachment part) inside LoadStorage to see whether that may be cause. But could find the exact place.