Path  Archive::Tar::PosixHeader

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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
(Not documented)
HEADER_PACK_FORMAT
(Not documented)
HEADER_UNPACK_FORMAT
(Not documented)

Public Class Methods

new(vals) click to toggle source

Creates a new PosixHeader. A PosixHeader cannot be created unless the name, size, prefix, and mode are provided. 

# File vendor/path/minitar.rb, line 97
  def initialize(vals)
    unless vals[:name] && vals[:size] && vals[:prefix] && vals[:mode]
      raise ArgumentError
    end

    vals[:mtime]    ||= 0
    vals[:checksum] ||= ""
    vals[:typeflag] ||= "0"
    vals[:magic]    ||= "ustar"
    vals[:version]  ||= "00"

    FIELDS.each do |field|
      instance_variable_set("@#{field}", vals[field.intern])
    end
    @empty = vals[:empty]
  end
new_from_stream(stream) click to toggle source

Creates a new PosixHeader from a data stream. 

# File vendor/path/minitar.rb, line 66
  def self.new_from_stream(stream)
    data = stream.read(512)
    fields    = data.unpack(HEADER_UNPACK_FORMAT)
    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 = (data == "\0" * 512)

    new(:name => name, :mode => mode, :uid => uid, :gid => gid,
        :size => size, :mtime => mtime, :checksum => checksum,
        :typeflag => typeflag, :magic => magic, :version => version,
        :uname => uname, :gname => gname, :devmajor => devmajor,
        :devminor => devminor, :prefix => prefix, :empty => empty)
  end

Public Instance Methods

empty?() click to toggle source

(Not documented)

# File vendor/path/minitar.rb, line 114
  def empty?
    @empty
  end
to_s() click to toggle source

(Not documented)

# File vendor/path/minitar.rb, line 118
  def to_s
    update_checksum
    header(@checksum)
  end
update_checksum() click to toggle source

Update the checksum field. 

# File vendor/path/minitar.rb, line 124
  def update_checksum
    hh = header(" " * 8)
    @checksum = oct(calculate_checksum(hh), 6)
  end

Private Instance Methods

calculate_checksum(hdr) click to toggle source

(Not documented)

# File vendor/path/minitar.rb, line 138
  def calculate_checksum(hdr)
    hdr.unpack("C*").inject { |aa, bb| aa + bb }
  end
header(chksum) click to toggle source

(Not documented)

# File vendor/path/minitar.rb, line 142
  def header(chksum)
    arr = [name, oct(mode, 7), oct(uid, 7), oct(gid, 7), oct(size, 11),
    oct(mtime, 11), chksum, " ", typeflag, linkname, magic, version,
    uname, gname, oct(devmajor, 7), oct(devminor, 7), prefix]
    str = arr.pack(HEADER_PACK_FORMAT)
    str + "\0" * ((512 - str.size) % 512)
  end
oct(num, len) click to toggle source

(Not documented)

# File vendor/path/minitar.rb, line 130
  def oct(num, len)
    if num.nil?
      "\0" * (len + 1)
    else
      "%0#{len}o" % num
    end
  end

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