Allow custom db paths

README.md

@@ -34,6 +34,17 @@ MiniMime.lookup_by_content_type("text/plain").binary?
 
 ```
 
+## Configuration
+
+If you'd like to add your own mime types, try using custom database files:
+
+```
+MiniMime::Configuration.ext_db_path = "path_to_file_extension_db"
+MiniMime::Configuration.content_type_db_path = "path_to_content_type_db"
+```
+
+Check out the [default databases](lib/db) for proper formatting and structure hints.
+
 ## Performance
 
 MiniMime is optimised to minimize memory usage. It keeps a cache of 100 mime type lookups (and 100 misses). There are benchmarks in the [bench directory](https://github.com/discourse/mini_mime/blob/master/bench/bench.rb)

lib/mini_mime.rb

@@ -14,6 +14,16 @@ module MiniMime
     Db.lookup_by_content_type(mime)
   end
 
+  module Configuration
+    class << self
+      attr_accessor :ext_db_path
+      attr_accessor :content_type_db_path
+    end
+
+    self.ext_db_path = File.expand_path("../db/ext_mime.db", __FILE__)
+    self.content_type_db_path = File.expand_path("../db/content_type_mime.db", __FILE__)
+  end
+
   class Info
     BINARY_ENCODINGS = %w(base64 8bit)
 
@@ -83,8 +93,8 @@ module MiniMime
     class RandomAccessDb
       MAX_CACHED = 100
 
-      def initialize(name, sort_order)
-        @path = File.expand_path("../db/#{name}", __FILE__)
+      def initialize(path, sort_order)
+        @path = path
         @file = File.open(@path)
 
         @row_length = @file.readline.length
@@ -141,8 +151,8 @@ module MiniMime
     end
 
     def initialize
-      @ext_db = RandomAccessDb.new("ext_mime.db", 0)
-      @content_type_db = RandomAccessDb.new("content_type_mime.db", 1)
+      @ext_db = RandomAccessDb.new(Configuration.ext_db_path, 0)
+      @content_type_db = RandomAccessDb.new(Configuration.content_type_db_path, 1)
     end
 
     def lookup_by_extension(extension)

test/fixtures/custom_content_type_mime.db

@@ -0,0 +1,2 @@
+liquid      application/x-liquid                                                      8bit
+mp4         video/vnd.objectvideo                                                     quoted-printable

test/fixtures/custom_ext_mime.db

@@ -0,0 +1,2 @@
+lua         application/x-lua                                                         8bit
+m4v         video/vnd.objectvideo                                                     quoted-printable

test/mini_mime/configuration_test.rb

@@ -0,0 +1,32 @@
+require 'test_helper'
+
+class MiniMime::ConfigurationTest < Minitest::Test
+  CUSTOM_EXT_MIME_DB_PATH = File.expand_path("../../fixtures/custom_ext_mime.db", __FILE__)
+  CUSTOM_CONTENT_TYPE_MIME_DB_PATH = File.expand_path("../../fixtures/custom_content_type_mime.db", __FILE__)
+
+  def setup
+    MiniMime::Db.instance_variable_set(:@db, nil)
+    @old_ext_db_path = MiniMime::Configuration.ext_db_path
+    @old_content_type_db_path = MiniMime::Configuration.content_type_db_path
+  end
+
+  def teardown
+    MiniMime::Db.instance_variable_set(:@db, nil)
+    MiniMime::Configuration.ext_db_path = @old_ext_db_path
+    MiniMime::Configuration.content_type_db_path = @old_content_type_db_path
+  end
+
+  def test_using_custom_ext_mime_db
+    MiniMime::Configuration.ext_db_path = CUSTOM_EXT_MIME_DB_PATH
+
+    assert_equal "application/x-lua", MiniMime.lookup_by_extension("lua").content_type
+    assert_equal "quoted-printable", MiniMime.lookup_by_extension("m4v").encoding
+  end
+
+  def test_using_custom_content_type_mime_db
+    MiniMime::Configuration.content_type_db_path = CUSTOM_CONTENT_TYPE_MIME_DB_PATH
+
+    assert_equal "liquid", MiniMime.lookup_by_content_type("application/x-liquid").extension
+    assert_equal "quoted-printable", MiniMime.lookup_by_content_type("video/vnd.objectvideo").encoding
+  end
+end