Ruby MIME type registry library
The mime-types library provides a library and registry for information about
MIME content type definitions. It can be used to determine defined filename
extensions for MIME types, or to use filename extensions to look up the likely
MIME type definitions.
Version 3.0 is a major release that requires Ruby 2.0 compatibility and removes
deprecated functions. The columnar registry format introduced in 2.6 has been
made the primary format; the registry data has been extracted from this library
and put into mime-types-data. Additionally, mime-types is now licensed
exclusively under the MIT licence and there is a code of conduct in effect.
There are a number of other smaller changes described in the History file.
MIME content types are used in MIME-compliant communications, as in e-mail or
HTTP traffic, to indicate the type of content which is transmitted. The
mime-types library provides the ability for detailed information about MIME
entities (provided as an enumerable collection of MIME::Type objects) to be
determined and used. There are many types defined by RFCs and vendors, so the
list is long but by definition incomplete; don’t hesitate to add additional type
definitions. MIME type definitions found in mime-types are from RFCs, W3C
recommendations, the IANA Media Types registry, and user
contributions. It conforms to RFCs 2045 and 2231.
Users are encouraged to upgrade to mime-types 3.x as soon as is practical.
mime-types 3.x requires Ruby 2.0 compatibility and a simpler licensing scheme.
MIME types are used in MIME entities, as in email or HTTP traffic. It is useful
at times to have information available about MIME types (or, inversely, about
files). A MIME::Type stores the known information about one MIME type.
require 'mime/types'plaintext = MIME::Types['text/plain'] # => [ text/plain ]text = plaintext.firstputs text.media_type # => 'text'puts text.sub_type # => 'plain'puts text.extensions.join(' ') # => 'txt asc c cc h hh cpp hpp dat hlp'puts text.preferred_extension # => 'txt'puts text.friendly # => 'Text Document'puts text.i18n_key # => 'text.plain'puts text.encoding # => quoted-printableputs text.default_encoding # => quoted-printableputs text.binary? # => falseputs text.ascii? # => trueputs text.obsolete? # => falseputs text.registered? # => trueputs text.provisional? # => falseputs text.complete? # => trueputs text # => 'text/plain'puts text == 'text/plain' # => trueputs 'text/plain' == text # => trueputs text == 'text/x-plain' # => falseputs 'text/x-plain' == text # => falseputs MIME::Type.simplified('x-appl/x-zip') # => 'x-appl/x-zip'puts MIME::Type.i18n_key('x-appl/x-zip') # => 'x-appl.x-zip'puts text.like?('text/x-plain') # => trueputs text.like?(MIME::Type.new('x-text/x-plain')) # => trueputs text.xrefs.inspect # => { "rfc" => [ "rfc2046", "rfc3676", "rfc5147" ] }puts text.xref_urls # => [ "http://www.iana.org/go/rfc2046",# "http://www.iana.org/go/rfc3676",# "http://www.iana.org/go/rfc5147" ]xtext = MIME::Type.new('x-text/x-plain')puts xtext.media_type # => 'text'puts xtext.raw_media_type # => 'x-text'puts xtext.sub_type # => 'plain'puts xtext.raw_sub_type # => 'x-plain'puts xtext.complete? # => falseputs MIME::Types.any? { |type| type.content_type == 'text/plain' } # => trueputs MIME::Types.all?(&:registered?) # => false# Various string representations of MIME typesqcelp = MIME::Types['audio/QCELP'].first # => audio/QCELPputs qcelp.content_type # => 'audio/QCELP'puts qcelp.simplified # => 'audio/qcelp'xwingz = MIME::Types['application/x-Wingz'].first # => application/x-Wingzputs xwingz.content_type # => 'application/x-Wingz'puts xwingz.simplified # => 'application/x-wingz'
mime-types uses as its primary registry storage format a columnar storage format
reducing the default memory footprint. This is done by selectively loading the
data on a per-attribute basis. When the registry is first loaded from the
columnar store, only the canonical MIME content type and known extensions and
the MIME type will be connected to its loading registry. When other data about
the type is required (including preferred_extension, obsolete?, andregistered?) that data is loaded from its own column file for all types in the
registry.
The load of any column data is performed with a Mutex to ensure that types are
updated safely in a multithreaded environment. Benchmarks show that while
columnar data loading is slower than the JSON store, it cuts the memory use by a
third over the JSON store.
If you prefer to load all the data at once, this can be specified in your
application Gemfile as:
gem 'mime-types', require: 'mime/types/full'
Projects that do not use Bundler should require the same:
require 'mime/types/full'
Libraries that use mime-types are discouraged from choosing the JSON store.
For applications and clients that used mime-types 2.6 when the columnar store
was introduced, the require used previously will still work through at least
version 4 and possibly beyond; it is effectively an empty
operation. You are recommended to change your Gemfile as soon as is practical.
require 'mime/types/columnar'
Note that MIME:
:Columnar and MIME:
:Columnar are considered private
variant implementations of MIME::Type and MIME::Types and the specific
implementation should not be relied upon by consumers of the mime-types library.
Instead, depend on the public implementations (MIME::Type and MIME::Types) only.
mime-types supports a cache of MIME types using Marshal.dump. The cache is
invalidated for each version of the mime-types-data gem so that data version
3.2015.1201 will not be reused with data version 3.2016.0101. If the environment
variable RUBY_MIME_TYPES_CACHE is set to a cache file, mime-types will attempt
to load the MIME type registry from the cache file. If it cannot, it will load
the types normally and then saves the registry to the cache file.
The caching works with both full stores and columnar stores. Only the data that
has been loaded prior to saving the cache will be stored.
The mime-types library has one version number, but this single version number
tracks both API changes and registry data changes; this is not wholly compatible
with all aspects of Semantic Versioning; removing a MIME type from the
registry could be considered a breaking change under some interpretations of
semantic versioning (as lookups for that particular type would no longer work by
default).
mime-types itself uses a modified semantic versioning scheme. Given the versionMAJOR.MINOR:
If an incompatible API (code) change is made, the MAJOR version will be
incremented and both MINOR and PATCH will be set to zero. Major version
updates will also generally break Ruby version compatibility guarantees.
If an API (code) feature is added that does not break compatibility, theMINOR version will be incremented and PATCH will be set to zero.
If there is a bug fix to a feature added in the most recent MAJOR.MINOR
release, the PATCH value will be incremented.
In practical terms, there will be fewer releases of mime-types focussing on
features because of the existence of the mime-types-data gem, and if
features are marked deprecated in the course of mime-types 3.x, they will not be
removed until mime-types 4.x or possibly later.