video_file.cr

module MediaManager
  class VideoFile

    CHUNK_SIZE = 64 * 1024
    def self.compute_hash(file_path : String)
      filesize = File.size(file_path)
      hash = filesize

      # Read 64 kbytes, divide up into 64 bits and add each
      # to hash. Do for beginning and end of file.
      File.open(file_path,  "rb") do |f|
        (CHUNK_SIZE / sizeof(UInt64)).times do
          hash += f.read_bytes(UInt64, IO::ByteOrder::LittleEndian)
        end

        f.seek([0, filesize - CHUNK_SIZE].max)

        # And again for the end of the file
        (CHUNK_SIZE / sizeof(UInt64)).times do
          hash += f.read_bytes(UInt64, IO::ByteOrder::LittleEndian)
        end
      end

      sprintf("%016x", hash)
    end
  end
end