class Gem::Package::TarHeader

# File lib/rubygems/package/tar_header.rb, line 98
def self.from(stream)
  header = stream.read 512
  empty = (header == "\0" * 512)

  fields = header.unpack UNPACK_FORMAT

  new :name     => fields.shift,
      :mode     => fields.shift.oct,
      :uid      => fields.shift.oct,
      :gid      => fields.shift.oct,
      :size     => fields.shift.oct,
      :mtime    => fields.shift.oct,
      :checksum => fields.shift.oct,
      :typeflag => fields.shift,
      :linkname => fields.shift,
      :magic    => fields.shift,
      :version  => fields.shift.oct,
      :uname    => fields.shift,
      :gname    => fields.shift,
      :devmajor => fields.shift.oct,
      :devminor => fields.shift.oct,
      :prefix   => fields.shift,

      :empty => empty
end

# File lib/rubygems/package/tar_header.rb, line 127
def initialize(vals)
  unless vals[:name] && vals[:size] && vals[:prefix] && vals[:mode] then
    raise ArgumentError, ":name, :size, :prefix and :mode required"
  end

  vals[:uid] ||= 0
  vals[:gid] ||= 0
  vals[:mtime] ||= 0
  vals[:checksum] ||= ""
  vals[:typeflag] ||= "0"
  vals[:magic] ||= "ustar"
  vals[:version] ||= "00"
  vals[:uname] ||= "wheel"
  vals[:gname] ||= "wheel"
  vals[:devmajor] ||= 0
  vals[:devminor] ||= 0

  FIELDS.each do |name|
    instance_variable_set "@#{name}", vals[name]
  end

  @empty = vals[:empty]
end

# File lib/rubygems/package/tar_header.rb, line 154
def empty?
  @empty
end

# File lib/rubygems/package/tar_header.rb, line 186
def update_checksum
  header = header " " * 8
  @checksum = oct calculate_checksum(header), 6
end

# File lib/rubygems/package/tar_header.rb, line 193
def calculate_checksum(header)
  header.unpack("C*").inject { |a, b| a + b }
end

# File lib/rubygems/package/tar_header.rb, line 197
def header(checksum = @checksum)
  header = [
    name,
    oct(mode, 7),
    oct(uid, 7),
    oct(gid, 7),
    oct(size, 11),
    oct(mtime, 11),
    checksum,
    " ",
    typeflag,
    linkname,
    magic,
    oct(version, 2),
    uname,
    gname,
    oct(devmajor, 7),
    oct(devminor, 7),
    prefix
  ]

  header = header.pack PACK_FORMAT

  header << ("\0" * ((512 - header.size) % 512))
end

# File lib/rubygems/package/tar_header.rb, line 223
def oct(num, len)
  "%0#{len}o" % num
end