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Class: Rack::ETag

Relationships & Source Files
Inherits: Object
Defined in: lib/rack/etag.rb

Overview

Automatically sets the etag header on all String bodies.

The etag header is skipped if etag or last-modified headers are sent or if a sendfile body (body.responds_to :to_path) is given (since such cases should be handled by apache/nginx).

On initialization, you can pass two parameters: a cache-control directive used when etag is absent and a directive when it is present. The first defaults to nil, while the second defaults to “max-age=0, private, must-revalidate”

Constant Summary

Class Method Summary

Instance Method Summary

Constructor Details

.new(app, no_cache_control = nil, cache_control = DEFAULT_CACHE_CONTROL) ⇒ ETag

[ GitHub ] 

  


# File 'lib/rack/etag.rb', line 22



def initialize(app, no_cache_control = nil, cache_control = DEFAULT_CACHE_CONTROL)
  @app = app
  @cache_control = cache_control
  @no_cache_control = no_cache_control
end


  







Instance Method Details



  

    #call(env)  
  

  [ GitHub ]


  

  


# File 'lib/rack/etag.rb', line 28



def call(env)
  status, headers, body = response = @app.call(env)

  if etag_status?(status) && body.respond_to?(:to_ary) && !skip_caching?(headers)
    body = body.to_ary
    digest = digest_body(body)
    headers[ETAG_STRING] = %(W/"#{digest}") if digest
  end

  unless headers[CACHE_CONTROL]
    if digest
      headers[CACHE_CONTROL] = @cache_control if @cache_control
    else
      headers[CACHE_CONTROL] = @no_cache_control if @no_cache_control
    end
  end

  response
end


  








  

    #digest_body(body)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rack/etag.rb', line 58



def digest_body(body)
  digest = nil

  body.each do |part|
    (digest ||= Digest::SHA256.new) << part unless part.empty?
  end

  digest && digest.hexdigest.byteslice(0,32)
end


  








  

    #etag_status?(status)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rack/etag.rb', line 50



def etag_status?(status)
  status == 200 || status == 201
end


  








  

    #skip_caching?(headers)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rack/etag.rb', line 54



def skip_caching?(headers)
  headers.key?(ETAG_STRING) || headers.key?('last-modified')
end