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# frozen_string_literal: true
#--
# Copyright (C) 2004 Mauricio Julio Fernández Pradier
# See LICENSE.txt for additional licensing information.
#++
##
#--
# struct tarfile_entry_posix {
# char name[100]; # ASCII + (Z unless filled)
# char mode[8]; # 0 padded, octal, null
# char uid[8]; # ditto
# char gid[8]; # ditto
# char size[12]; # 0 padded, octal, null
# char mtime[12]; # 0 padded, octal, null
# char checksum[8]; # 0 padded, octal, null, space
# char typeflag[1]; # file: "0" dir: "5"
# char linkname[100]; # ASCII + (Z unless filled)
# char magic[6]; # "ustar\0"
# char version[2]; # "00"
# char uname[32]; # ASCIIZ
# char gname[32]; # ASCIIZ
# char devmajor[8]; # 0 padded, octal, null
# char devminor[8]; # o padded, octal, null
# char prefix[155]; # ASCII + (Z unless filled)
# };
#++
# A header for a tar file
class Gem::Package::TarHeader
##
# Fields in the tar header
FIELDS = [
:checksum,
:devmajor,
:devminor,
:gid,
:gname,
:linkname,
:magic,
:mode,
:mtime,
:name,
:prefix,
:size,
:typeflag,
:uid,
:uname,
:version,
].freeze
##
# Pack format for a tar header
PACK_FORMAT = 'a100' + # name
'a8' + # mode
'a8' + # uid
'a8' + # gid
'a12' + # size
'a12' + # mtime
'a7a' + # chksum
'a' + # typeflag
'a100' + # linkname
'a6' + # magic
'a2' + # version
'a32' + # uname
'a32' + # gname
'a8' + # devmajor
'a8' + # devminor
'a155' # prefix
##
# Unpack format for a tar header
UNPACK_FORMAT = 'A100' + # name
'A8' + # mode
'A8' + # uid
'A8' + # gid
'A12' + # size
'A12' + # mtime
'A8' + # checksum
'A' + # typeflag
'A100' + # linkname
'A6' + # magic
'A2' + # version
'A32' + # uname
'A32' + # gname
'A8' + # devmajor
'A8' + # devminor
'A155' # prefix
attr_reader(*FIELDS)
EMPTY_HEADER = ("\0" * 512).freeze # :nodoc:
##
# Creates a tar header from IO +stream+
def self.from(stream)
header = stream.read 512
empty = (EMPTY_HEADER == header)
fields = header.unpack UNPACK_FORMAT
new :name => fields.shift,
:mode => strict_oct(fields.shift),
:uid => oct_or_256based(fields.shift),
:gid => oct_or_256based(fields.shift),
:size => strict_oct(fields.shift),
:mtime => strict_oct(fields.shift),
:checksum => strict_oct(fields.shift),
:typeflag => fields.shift,
:linkname => fields.shift,
:magic => fields.shift,
:version => strict_oct(fields.shift),
:uname => fields.shift,
:gname => fields.shift,
:devmajor => strict_oct(fields.shift),
:devminor => strict_oct(fields.shift),
:prefix => fields.shift,
:empty => empty
end
def self.strict_oct(str)
return str.strip.oct if str.strip =~ /\A[0-7]*\z/
raise ArgumentError, "#{str.inspect} is not an octal string"
end
def self.oct_or_256based(str)
# \x80 flags a positive 256-based number
# \ff flags a negative 256-based number
# In case we have a match, parse it as a signed binary value
# in big-endian order, except that the high-order bit is ignored.
return str.unpack('N2').last if str =~ /\A[\x80\xff]/n
strict_oct(str)
end
##
# Creates a new TarHeader using +vals+
def initialize(vals)
unless vals[:name] && vals[:size] && vals[:prefix] && vals[:mode]
raise ArgumentError, ":name, :size, :prefix and :mode required"
end
vals[:uid] ||= 0
vals[:gid] ||= 0
vals[:mtime] ||= 0
vals[:checksum] ||= ""
vals[:typeflag] = "0" if vals[:typeflag].nil? || vals[:typeflag].empty?
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
##
# Is the tar entry empty?
def empty?
@empty
end
def ==(other) # :nodoc:
self.class === other and
@checksum == other.checksum and
@devmajor == other.devmajor and
@devminor == other.devminor and
@gid == other.gid and
@gname == other.gname and
@linkname == other.linkname and
@magic == other.magic and
@mode == other.mode and
@mtime == other.mtime and
@name == other.name and
@prefix == other.prefix and
@size == other.size and
@typeflag == other.typeflag and
@uid == other.uid and
@uname == other.uname and
@version == other.version
end
def to_s # :nodoc:
update_checksum
header
end
##
# Updates the TarHeader's checksum
def update_checksum
header = header " " * 8
@checksum = oct calculate_checksum(header), 6
end
private
def calculate_checksum(header)
header.unpack("C*").inject {|a, b| a + b }
end
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
def oct(num, len)
"%0#{len}o" % num
end
end
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