Class: Archive::Gem

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/archive/gem.rb

Overview

Archive::Gem is a slice-and-dice toolkit for Ruby Gems packages.

It contains exposed functionality not included in the standard Ruby Gems system:

  • It can work with a Gem completely in memory, allowing you to avoid potential pitfalls using FileUtils and other toolkits to navigate the extracted gem

  • It can get at the specification of the file with very little effort.

  • It provides iterators for each file of the package

  • Most importantly: Ruby Gems does not need to be installed on the system for this toolkit to work.

The largest drawback is that Archive::Gem is currently read-only.

At this point you may be wondering why this was written, as Ruby Gems obviously has to have this functionality. This is true - but it’s buried in twisted, barely documented code that is not easy to access without extracting the gem.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(io_or_filename = $stdin) ⇒ Gem

Creates a new Archive::Gem object from a filename or IO object. Defaults to using the standard input.



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# File 'lib/archive/gem.rb', line 41

def initialize(io_or_filename = $stdin)
    if io_or_filename.respond_to? :read
        @io = io_or_filename
    else
        @io = File.open(io_or_filename)
    end

    Archive::Tar::Minitar::Reader.open(@io) do |r|
        r.each do |entry|
            if entry.name == "metadata.gz"
                gz = Zlib::GzipReader.new(entry)
                @metadata = gz.read
                gz.close
            elsif entry.name == "data.tar.gz"
                gz = Zlib::GzipReader.new(entry)
                @data = StringIO.new(gz.read)
                gz.close
            end
        end
    end
end

Instance Attribute Details

#data ⇒ Object (readonly)

Returns the value of attribute data.



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# File 'lib/archive/gem.rb', line 35

def data
  @data
end

#io ⇒ Object (readonly)

Returns the value of attribute io.



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# File 'lib/archive/gem.rb', line 37

def io
  @io
end

#metadata ⇒ Object (readonly)

Returns the value of attribute metadata.



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# File 'lib/archive/gem.rb', line 36

def metadata
  @metadata
end

Instance Method Details

#each ⇒ Object

Iterates over each file in the tarball. Yields IO objects for each of them.



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# File 'lib/archive/gem.rb', line 90

def each
    Archive::Tar::Minitar::Reader.open(@data) do |r|
        r.each do |entry|
            yield StringIO.new(entry.read || '')
        end
    end
    @data.rewind
end

#files_as_tar ⇒ Object

Returns an IO object of the tarball of the actual files in the gem.



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# File 'lib/archive/gem.rb', line 82

def files_as_tar
    @data
end

#specification ⇒ Object Also known as: spec

Extracts the YAML specification from the Gem and parses it. Returns the YAML data if that was possible, otherwise returns nil.



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# File 'lib/archive/gem.rb', line 67

def specification
    spec = nil

    if @metadata
        spec = Gem::Specification.from_yaml metadata
    end

    return spec 
end