File Sniffer
10 Points
binaries
Instructions
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 file type, 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 |
1. Given an extension, return the expected media type
Implement the type_from_extension/1 function. It should take a file extension (string) and return the media type (string) or nil if the extension does not match with the expected ones.
FileSniffer.type_from_extension("exe")
# => "application/octet-stream"
FileSniffer.type_from_extension("txt")
# => nil2. Given a binary file, return the expected media type
Implement the type_from_binary/1 function. It should take a file (binary) and return the media type (string) or nil if the extension does not match with the expected ones.
file = File.read!("application.exe")
FileSniffer.type_from_binary(file)
# => "application/octet-stream"
file = File.read!("example.txt")
FileSniffer.type_from_binary(file)
# => nilDon't worry about reading the file as a binary. Assume that has been done for you and is provided by the tests as an argument.
3. Given an extension and a binary file, verify that the file matches the expected type
Implement the verify/2 function. It should take a file (binary) and extension (string) and return 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."}File Sniffer
10 Points
binaries
Instructions
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 file type, 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 |
1. Given an extension, return the expected media type
Implement the type_from_extension/1 function. It should take a file extension (string) and return the media type (string) or nil if the extension does not match with the expected ones.
FileSniffer.type_from_extension("exe")
# => "application/octet-stream"
FileSniffer.type_from_extension("txt")
# => nil2. Given a binary file, return the expected media type
Implement the type_from_binary/1 function. It should take a file (binary) and return the media type (string) or nil if the extension does not match with the expected ones.
file = File.read!("application.exe")
FileSniffer.type_from_binary(file)
# => "application/octet-stream"
file = File.read!("example.txt")
FileSniffer.type_from_binary(file)
# => nilDon't worry about reading the file as a binary. Assume that has been done for you and is provided by the tests as an argument.
3. Given an extension and a binary file, verify that the file matches the expected type
Implement the verify/2 function. It should take a file (binary) and extension (string) and return 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."}