class Archive::Tar::PosixHeader
Archive::Tar::PosixHeader
¶ ↑
Implements the POSIX tar header as a Ruby class. The structure of the POSIX tar header is:
struct tarfile_entry_posix { // pack/unpack char name[100]; // ASCII (+ Z unless filled) a100/Z100 char mode[8]; // 0 padded, octal, null a8 /A8 char uid[8]; // ditto a8 /A8 char gid[8]; // ditto a8 /A8 char size[12]; // 0 padded, octal, null a12 /A12 char mtime[12]; // 0 padded, octal, null a12 /A12 char checksum[8]; // 0 padded, octal, null, space a8 /A8 char typeflag[1]; // see below a /a char linkname[100]; // ASCII + (Z unless filled) a100/Z100 char magic[6]; // "ustar\0" a6 /A6 char version[2]; // "00" a2 /A2 char uname[32]; // ASCIIZ a32 /Z32 char gname[32]; // ASCIIZ a32 /Z32 char devmajor[8]; // 0 padded, octal, null a8 /A8 char devminor[8]; // 0 padded, octal, null a8 /A8 char prefix[155]; // ASCII (+ Z unless filled) a155/Z155 };
The typeflag
may be one of the following known values:
"0"
-
Regular file. NULL should be treated as a synonym, for compatibility purposes.
"1"
-
Hard link.
"2"
-
Symbolic link.
"3"
-
Character device node.
"4"
-
Block device node.
"5"
-
Directory.
"6"
-
FIFO node.
"7"
-
Reserved.
POSIX indicates that “A POSIX-compliant implementation must treat any unrecognized typeflag value as a regular file.”
Constants
- FIELDS
- HEADER_PACK_FORMAT
- HEADER_UNPACK_FORMAT
Public Class Methods
new(vals)
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Creates a new PosixHeader
. A PosixHeader
cannot be created unless the name, size, prefix, and mode are provided.
# File lib/archive/tar/minitar.rb 97 def initialize(vals) 98 unless vals[:name] && vals[:size] && vals[:prefix] && vals[:mode] 99 raise ArgumentError 100 end 101 102 vals[:mtime] ||= 0 103 vals[:checksum] ||= "" 104 vals[:typeflag] ||= "0" 105 vals[:magic] ||= "ustar" 106 vals[:version] ||= "00" 107 108 FIELDS.each do |field| 109 instance_variable_set("@#{field}", vals[field.intern]) 110 end 111 @empty = vals[:empty] 112 end
new_from_stream(stream)
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Creates a new PosixHeader
from a data stream.
# File lib/archive/tar/minitar.rb 66 def self.new_from_stream(stream) 67 data = stream.read(512) 68 fields = data.unpack(HEADER_UNPACK_FORMAT) 69 name = fields.shift 70 mode = fields.shift.oct 71 uid = fields.shift.oct 72 gid = fields.shift.oct 73 size = fields.shift.oct 74 mtime = fields.shift.oct 75 checksum = fields.shift.oct 76 typeflag = fields.shift 77 linkname = fields.shift 78 magic = fields.shift 79 version = fields.shift.oct 80 uname = fields.shift 81 gname = fields.shift 82 devmajor = fields.shift.oct 83 devminor = fields.shift.oct 84 prefix = fields.shift 85 86 empty = (data == "\0" * 512) 87 88 new(:name => name, :mode => mode, :uid => uid, :gid => gid, 89 :size => size, :mtime => mtime, :checksum => checksum, 90 :typeflag => typeflag, :magic => magic, :version => version, 91 :uname => uname, :gname => gname, :devmajor => devmajor, 92 :devminor => devminor, :prefix => prefix, :empty => empty) 93 end
Public Instance Methods
empty?()
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# File lib/archive/tar/minitar.rb 114 def empty? 115 @empty 116 end
to_s()
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# File lib/archive/tar/minitar.rb 118 def to_s 119 update_checksum 120 header(@checksum) 121 end
update_checksum()
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Update the checksum field.
# File lib/archive/tar/minitar.rb 124 def update_checksum 125 hh = header(" " * 8) 126 @checksum = oct(calculate_checksum(hh), 6) 127 end
Private Instance Methods
calculate_checksum(hdr)
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# File lib/archive/tar/minitar.rb 138 def calculate_checksum(hdr) 139 hdr.unpack("C*").inject { |aa, bb| aa + bb } 140 end
header(chksum)
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# File lib/archive/tar/minitar.rb 142 def header(chksum) 143 arr = [name, oct(mode, 7), oct(uid, 7), oct(gid, 7), oct(size, 11), 144 oct(mtime, 11), chksum, " ", typeflag, linkname, magic, version, 145 uname, gname, oct(devmajor, 7), oct(devminor, 7), prefix] 146 str = arr.pack(HEADER_PACK_FORMAT) 147 str + "\0" * ((512 - str.size) % 512) 148 end
oct(num, len)
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# File lib/archive/tar/minitar.rb 130 def oct(num, len) 131 if num.nil? 132 "\0" * (len + 1) 133 else 134 "%0#{len}o" % num 135 end 136 end