You have been working on a project which allows users to upload files to the server to be shared with other users. You have been tasked with writing a function to verify that an upload matches its media type. You do some research and discover that the first few bytes of a file are generally unique to that filetype, giving it a sort of signature.
Use the following table for reference:
| File type | Common extension | Media type | binary 'signature' |
|---|---|---|---|
| ELF | "exe" |
"application/octet-stream" |
0x7F, 0x45, 0x4C, 0x46 |
| BMP | "bmp" |
"image/bmp" |
0x42, 0x4D |
| PNG | "png" |
"image/png" |
0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A |
| JPG | "jpg" |
"image/jpg" |
0xFF, 0xD8, 0xFF |
| GIF | "gif" |
"image/gif" |
0x47, 0x49, 0x46 |
Implement the type_from_extension/1 function. It should take a file extension (string) and return the media type (string).
FileSniffer.type_from_extension("exe")
# => "application/octet-stream"Implement the type_from_binary/1 function. It should take a file (binary) and return the media type (string).
file = File.read!("application.exe")
FileSniffer.type_from_binary(file)
# => "application/octet-stream"Don't worry about reading the file as a binary, assume that has been done for you and will provided for the tests as an argument.
Implement the verify/2 function. It should take a file (binary) and extension (string) then an :ok or :error tuple.
file = File.read!("application.exe")
FileSniffer.verify(file, "exe")
# => {:ok, "application/octet-stream"}
FileSniffer.verify(file, "png")
# => {:error, "Warning, file format and file extension do not match."}