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Last active December 21, 2015 07:09
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Gzip Generation Plugin For Jekyll
#
# Gzip Generation Plugin For Jekyll
#
module Jekyll
#
# Polymorphic Monkey-Patching
#
# Page, Post, and StaticFile have very different interfaces, but this plugin
# needs to process all three. Here, I add methods to each class to create
# a common interface.
#
class StaticFile
# Expose two attributes that are visible on Page/Post.
attr_accessor :name, :site
# output_ext is defined in Convertible. It returns the file extension of
# the output file. Because StaticFile doesn't change the file type, the
# implementation is easy:
def output_ext
¦ File.extname(name)
end
# content_length is new for this plugin. It's necessary because, while Page
# and Post pull their contents into memory, StaticFile does not. We have
# to abstract this difference away.
def content_length
File.stat(path).size
end
end
module Convertible
# This causes content_length to appear on Page and Post, which inherit
# their @content variables from Convertible.
def content_length
@content.length
end
end
#
# Plugin Code
#
# This represents a gzipped derivative of a StaticFile. It's designed to
# act like a StaticFile, but isn't one.
class GzippedContent
# Derives from the given 'model', which can be a Page, Post, or StaticFile.
def initialize(model)
@source_path = model.destination(model.site.dest)
@dest_path = @source_path + '.gz'
end
# Returns the destination path for the gzipped output. The 'dest' parameter
# is ignored, because we captured the site's dest during initialization.
# This is a bit of a hack.
def destination(dest)
@dest_path
end
## Jekyll 2.x compatibility issue
# Returns source file path.
def path
File.join(*[@base, @dir, @name].compact)
end
# Returns the source file path relative to the site source
def relative_path
@relative_path ||= @source_path
end
## Jekyll 2.x compatibility issue
# Produces gzipped output.
def write(dest)
dest_path = destination(dest)
FileUtils.mkdir_p(File.dirname(dest_path))
system "gzip -9 -c #{@source_path} > #{dest_path}"
end
end
# The actual generator:
class GzipGenerator < Generator
safe true
priority :lowest
def generate(site)
everything = site.pages + site.posts + site.static_files
zipped = everything.select { |p| should_compress p }.collect { |p|
GzippedContent.new(p)
}
site.static_files.concat(zipped)
end
def should_compress(thing)
compressible_type(thing.output_ext) && large_enough(thing)
end
def compressible_type(ext)
[
'.html',
'.css',
'.js',
'.txt',
'.ttf',
'.atom',
'.stl',
'.xml',
'.svg',
'.eot',
'.woff',
].include?(ext)
end
def large_enough(thing)
thing.content_length > 200
end
end
@rbarriuso
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Very useful, thanks.
A couple of small details:

  • The source and destination paths should be between quotes, to avoid problems if any path contains white spaces. This works (at least on W7): system "gzip -9 -c \"#{@source_path}\" > \"#{dest_path}\""
  • I needed to remove the ¦ character in line 23, otherwise Jekyll 2.4 crashed (running on Windows, even if not officially supported).

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