liulanghe / myrmec

This library is used to detect real file format type via file hex head.

What is Myrmec

Myrmec is a library that used to identifie real file format type by detecting the file binary head with out file extention like xxxxx.png.

How to use

That was very easy.

Install from nuget

Install-Package Myrmec

Or DotNet cli

dotnet add package Myrmec

Write code

// create a sniffer instance.
Sniffer sniffer = new Sniffer();

// populate with mata data.
sniffer.Populate(FileTypes.CommonFileTypes);

// get file head byte, may be 20 bytes enough.
byte[] fileHead = ReadFileHead();

// start match.
List<string> results = sniffer.Match(fileHead);

Many times the results has more than one value, because some file format has multiple extentions, such as jpeg,jpg. or some extentions that point to same file format like apk,zip,pptx they are all zip archive.

Find one result vs multiple result

// this will match one result that sniffer first matched.
// default is false
List<string> results = sniffer.Match(fileHead,false);

// this will match all result that sniffer matched.
List<string> results = sniffer.Match(fileHead,true);

Add your own file format head into metadata

May be you make some file format,or the FileTypes.CommonFileTypes not contains the file format that you need, then you can add it in :

var data = new byte[]
{
    0x11,
    0x22,
    0x33
};
sniffer.Add(data, new[] { "what", "file", "type" });

The variable data is file hex head that you want to add, new[] { "what", "file", "type" } mean that this file type has three extention that named what,file,type. When you match this head will return three result at least*(may be some other file type has same hex head or it's head contains above head(but only on match multiple))*.

Get the MIME type

Suprise! this library also offer the function is get Mime type:

List<string> result = sniffer.Match(head);
string mimeType = MimeTypes.GetMimeType(result.First());

But, some thing that you need to know is this function relay on file extention name, you can write like this:

string mimeType = MimeTypes.GetMimeType("png");

The result is

image/png

Matedate source

the metadata information from wiki pedia List of file signatures.

Not support

The file type matedate only suport that file hex head has no offset and byte value continuous, for example, the following examples do not support:

Jpg file

jpg file head not support: FF D8 FF E0 ?? ?? 4A 46 49 46 00 01

this format middle part allows an arbitrary value, but another jpg format is supported:

Jpg file

jpg file head supported: FF D8 FF DB 

PDB file

PDB file head not support: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

this format has offset 11,so not support.

Road Map

1. Next major vertion I will add the support of file format that contains offset or contains arbitrary value.