MicroStation Design File

import magic
# Libmagic may identify V8 DGN files simply as 'Composite Document File V2 Document' due to the OLE header
print(magic.from_file('architecture.dgn', mime=True))

const fs = require('fs');
// Sniffing for the Microsoft OLE signature used by V8 DGN files
const buffer = Buffer.alloc(8);
const fd = fs.openSync('architecture.dgn', 'r');
fs.readSync(fd, buffer, 0, 8, 0);
fs.closeSync(fd);
const isOLE = buffer[0] === 0xD0 && buffer[1] === 0xCF && buffer[2] === 0x11 && buffer[3] === 0xE0;
// Note: If isOLE is true, further parsing of the internal streams is required to confirm it's a DGN and not an old .doc file
console.log('Is OLE Container (Potential V8 DGN):', isOLE);

import (
    "bytes"
    "net/http"
    "strings"
)
// HTTP detection will likely return 'application/CDFV2' or 'application/octet-stream'
// Relying on the .dgn extension is often necessary for quick routing
// isDGN := strings.HasSuffix(strings.ToLower(filename), ".dgn")

$mime = mime_content_type('architecture.dgn');
echo $mime; // Standard PHP setups will often resolve V8 DGNs to 'application/vnd.ms-office' or 'application/CDFV2' because of the OLE header.