Make the tests work.

lib/moviehash.rb

@@ -0,0 +1,95 @@
+# frozen_string_literal: true
+
+require_relative "moviehash/version"
+require "net/http"
+require "uri"
+
+module Moviehash
+  class Error < StandardError; end
+  class FileNotFoundError < Error; end
+  class NetworkError < Error; end
+
+  CHUNK_SIZE = 64 * 1024 # in bytes
+
+  def self.compute_hash(url)
+    data = url.start_with?("http") ? data_from_url(url) : data_from_file(url)
+
+    hash = data[:filesize]
+
+    hash = process_chunk(data.dig(:chunks, 0), hash)
+    hash = process_chunk(data.dig(:chunks, 1), hash)
+
+    format("%016x", hash)
+  end
+
+  def self.data_from_file(path)
+    filesize = File.size(path)
+
+    data = { filesize: filesize, chunks: [] }
+
+    File.open(path, "rb") do |f|
+      data[:chunks] << f.read(CHUNK_SIZE)
+      f.seek([0, filesize - CHUNK_SIZE].max, IO::SEEK_SET)
+      data[:chunks] << f.read(CHUNK_SIZE)
+    end
+
+    data
+  end
+
+  def self.data_from_url(url)
+    uri = URI(url)
+    http = Net::HTTP.new(uri.host, uri.port)
+    http.use_ssl = (uri.scheme == "https")
+
+    # Get the file size
+    response = http.request_head(uri.path)
+    filesize = response["content-length"].to_i
+
+    data = { filesize: filesize, chunks: [] }
+
+    # Process the beginning of the file
+    response = http.get(uri.path, { "Range" => "bytes=0-#{CHUNK_SIZE - 1}" })
+    data[:chunks] << response.body
+
+    # Process the end of the file
+    start_byte = [0, filesize - CHUNK_SIZE].max
+    response = http.get(uri.path, { "Range" => "bytes=#{start_byte}-#{filesize - 1}" })
+    data[:chunks] << response.body
+
+    data
+  end
+
+  def self.process_chunk(chunk, hash)
+    chunk.unpack("Q*").each do |n|
+      hash = hash + n & 0xffffffffffffffff
+    end
+
+    hash
+  end
+end
+
+def self.old_compute_hash(path)
+  filesize = File.size(path)
+  hash = filesize
+
+  format("%016x", hash)
+
+  # Read 64 kbytes, divide up into 64 bits and add each
+  # to hash. Do for beginning and end of file.
+  File.open(path, "rb") do |f|
+    # Q = unsigned long long = 64 bit
+    f.read(CHUNK_SIZE).unpack("Q*").each do |n|
+      hash = hash + n & 0xffffffffffffffff # to remain as 64 bit number
+    end
+    format("%016x", hash)
+    f.seek([0, filesize - CHUNK_SIZE].max, IO::SEEK_SET)
+
+    # And again for the end of the file
+    f.read(CHUNK_SIZE).unpack("Q*").each do |n|
+      hash = hash + n & 0xffffffffffffffff
+    end
+    format("%016x", hash)
+  end
+
+  format("%016x", hash)
+end