File Sniffer

Story

The story of this exercise uses the premise of comparing the file extension to the binary file format to explore the ideas of binary data, pattern matching, string encoding. The student is tasked with writing some functions to compare the expected media type to the file's encoded media type.

Tasks

The story facilitates defining functions:

  • Returning the media type from a string extension.
  • Returning the media type from a binary file format.
  • Comparing the expected media type from the string extension to the actual type from the binary file.

Exercise Reference

File type Common extension Media type binary 'signature' from the first bytes
ELF none or "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

Implementations