The format class knows the guts of the RubyGem .gem file format and provides the capability to read gem files

Methods
F
N
R
S
Attributes
[RW] file_entries
[RW] gem_path
[RW] spec
Class Public methods
from_file_by_path(file_path)

Reads the named gem file and returns a Format object, representing the data from the gem file

file_path
String

Path to the gem file

Source: show | on GitHub 

# File ../ruby/lib/rubygems/old_format.rb, line 37
def self.from_file_by_path(file_path)
  unless File.exist?(file_path)
    raise Gem::Exception, "Cannot load gem file [#{file_path}]"
  end

  File.open(file_path, 'rb') do |file|
    from_io(file, file_path)
  end
end
from_io(io, gem_path="(io)")

Reads a gem from an io stream and returns a Format object, representing the data from the gem file

io
IO

Stream from which to read the gem

Source: show | on GitHub 

# File ../ruby/lib/rubygems/old_format.rb, line 53
def self.from_io(io, gem_path="(io)")
  format = self.new(gem_path)
  skip_ruby(io)
  format.spec = read_spec(io)
  format.file_entries = []
  read_files_from_gem(io) do |entry, file_data|
    format.file_entries << [entry, file_data]
  end
  format
end
new(gem_path)

Constructs an instance of a Format object, representing the gem's data structure.

gem
String

The file name of the gem

Source: show | on GitHub 

# File ../ruby/lib/rubygems/old_format.rb, line 23
def initialize(gem_path)
  require 'fileutils'
  require 'zlib'
  Gem.load_yaml

  @gem_path = gem_path
end
Class Private methods
read_files_from_gem(gem_file)

Reads the embedded file data from a gem file, yielding an entry containing metadata about the file and the file contents themselves for each file that's archived in the gem. NOTE: Many of these methods should be extracted into some kind of Gem file read/writer

gem_file
IO

The IO to process

Source: show | on GitHub 

# File ../ruby/lib/rubygems/old_format.rb, line 130
def self.read_files_from_gem(gem_file)
  errstr = "Error reading files from gem"
  header_yaml = ''
  begin
    self.read_until_dashes(gem_file) do |line|
      header_yaml << line
    end
    header = YAML.load(header_yaml)
    raise Gem::Exception, errstr unless header

    header.each do |entry|
      file_data = ''
      self.read_until_dashes(gem_file) do |line|
        file_data << line
      end
      yield [entry, Zlib::Inflate.inflate(file_data.strip.unpack("m")[0])]
    end
  rescue Zlib::DataError
    raise Gem::Exception, errstr
  end
end
read_spec(file)

Reads the specification YAML from the supplied IO and constructs a Gem::Specification from it. After calling this method, the IO index will be set after the specification header.

file
IO

The IO to process

Source: show | on GitHub 

# File ../ruby/lib/rubygems/old_format.rb, line 94
def self.read_spec(file)
  yaml = ''

  read_until_dashes file do |line|
    yaml << line
  end

  Gem::Specification.from_yaml yaml
rescue YAML::Error => e
  raise Gem::Exception, "Failed to parse gem specification out of gem file"
rescue ArgumentError => e
  raise Gem::Exception, "Failed to parse gem specification out of gem file"
end
read_until_dashes(file)

Reads lines from the supplied IO until a end-of-yaml (—) is reached

file
IO

The IO to process

block
String

The read line

Source: show | on GitHub 

# File ../ruby/lib/rubygems/old_format.rb, line 115
def self.read_until_dashes(file)
  while((line = file.gets) && line.chomp.strip != "---") do
    yield line
  end
end
skip_ruby(file)

Skips the Ruby self-install header. After calling this method, the IO index will be set after the Ruby code.

file
IO

The IO to process (skip the Ruby code)

Source: show | on GitHub 

# File ../ruby/lib/rubygems/old_format.rb, line 72
def self.skip_ruby(file)
  end_seen = false
  loop {
    line = file.gets
    if(line == nil || line.chomp == "__END__") then
      end_seen = true
      break
    end
  }

  if end_seen == false then
    raise Gem::Exception.new("Failed to find end of ruby script while reading gem")
  end
end