attachment_adapter.rb

module Paperclip
  class AttachmentAdapter < AbstractAdapter
    def initialize(target)
      @target, @style = case target
      when Paperclip::Attachment
        [target, :original]
      when Paperclip::Style
        [target.attachment, target.name]
      end

      cache_current_values
    end

    def original_filename
      @original_filename
    end

    def content_type
      @content_type
    end

    def size
      @size
    end

    def nil?
      false
    end

    def fingerprint
      @fingerprint ||= Digest::MD5.file(path).to_s
    end

    def read(length = nil, buffer = nil)
      @tempfile.read(length, buffer)
    end

    # We don't use this directly, but aws/sdk does.
    def rewind
      @tempfile.rewind
    end

    def eof?
      @tempfile.eof?
    end

    def path
      @tempfile.path
    end

    private

    def cache_current_values
      @original_filename = @target.original_filename
      @content_type = @target.content_type
      @tempfile = copy_to_tempfile(@target)
      @size = @tempfile.size || @target.size
    end

    def copy_to_tempfile(src)
      if src.respond_to? :copy_to_local_file
        src.copy_to_local_file(@style, destination.path)
      else
        FileUtils.cp(src.path(@style), destination.path)
      end
      destination
    end
  end
end

Paperclip.io_adapters.register Paperclip::AttachmentAdapter do |target|
  Paperclip::Attachment === target || Paperclip::Style === target
end