An extension for Data to get the file extension

Data+File.swift

extension Data {
    private static let mimeTypeSignatures: [UInt8 : String] = [
        0xFF : "image/jpeg",
        0x89 : "image/png",
        0x47 : "image/gif",
        0x49 : "image/tiff",
        0x4D : "image/tiff",
        0x25 : "application/pdf",
        0xD0 : "application/vnd",
        0x46 : "text/plain",
        ]
    
    var mimeType: String {
        var c: UInt8 = 0
        copyBytes(to: &c, count: 1)
        return Data.mimeTypeSignatures[c] ?? "application/octet-stream"
    }
    
    var fileExtension: String {
        switch mimeType {
        case "image/jpeg":
            return "jpeg"
        case "image/png":
            return "png"
        case "image/gif":
            return "gif"
        case "image/tiff":
            return "tiff"
        case "application/pdf":
            return "pdf"
        case "application/vnd":
            return "vnd"
        case "text/plain":
            return "txt"
        default:
            return "uknown"
        }
    }
}

👍 what is the mimeTypeSignatures for video, audio, svg other can you please update?

Have you ever encountered an error like this? I have the same code as above.

Crashed: com.apple.main-thread
0  libswiftFoundation.dylib       0x118b10 Data.copyBytes(to:count:) + 340
1  My Apps                        0x42432c Data.mimeType.getter + 13 (Data.swift:13)