Class: Archive::Tar::Format

Inherits:
Object
  • Object
show all
Defined in:
lib/archive/tar/format.rb

Constant Summary collapse

DEC_TYPES = 
{
  "\0" => :normal,
  "0" => :normal,
  "1" => :link,
  "2" => :symbolic,
  "3" => :character,
  "4" => :block,
  "5" => :directory,
  "6" => :fifo,
  "7" => :reserved,
  "I" => :index,
  "g" => :pax_global_header
}
ENC_TYPES = 
DEC_TYPES.invert

Class Method Summary collapse

Class Method Details

.blocks_for_bytes(bytes) ⇒ Object

Calculate quantity of blocks



143
144
145
 
# File 'lib/archive/tar/format.rb', line 143

def blocks_for_bytes(bytes)
  bytes % 512 == 0 ? bytes / 512 : (bytes + 512 - bytes % 512) / 512
end

.calculate_checksum(header) ⇒ Object

Generate checksum with header



91
92
93
94
95
96
97
98
99
 
# File 'lib/archive/tar/format.rb', line 91

def calculate_checksum(header)
  checksum = 0
  
  header.each_byte do |byte|
    checksum += byte
  end
  
  checksum.to_s(8).rjust(6, " ") + "\0 "
end

.detect_type(header) ⇒ Object

Detect type of tar file by header



83
84
85
86
87
88
 
# File 'lib/archive/tar/format.rb', line 83

def detect_type(header)
  return :ustar if header[257, 6] == "ustar0"
  return :gnu if header[257, 6] == "ustar "
  
  :other
end

.pack_header(header) ⇒ Object

Pack header from Stat



102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
 
# File 'lib/archive/tar/format.rb', line 102

def pack_header(header)
  blob = ""
  
  blob += header.path.ljust(100, "\0")
  blob += header.mode.to_s(8).rjust(8, "0")
  blob += header.uid.to_s(8).rjust(8, "0")
  blob += header.gid.to_s(8).rjust(8, "0")
  blob += header.size.to_s(8).rjust(12, "0")
  blob += header.mtime.to_i.to_s(8).rjust(12, "0")
  blob += " " * 8
  blob += ENC_TYPES[header.type]
  blob += header.dest.ljust(100, "\0")
  
  case header.format
  when :ustar
    blob += "ustar\000"
  when :gnu
    blob += "ustar  \0"
  end
  
  if header.gnu? || header.ustar?
    blob += header.user.ljust(32, "\0")
    blob += header.group.ljust(32, "\0")
    blob += header.major.to_s(8).rjust(8, "0")
    blob += header.minor.to_s(8).rjust(8, "0")
    
    if header.gnu?
      blob += header.atime.to_i.to_s(8).rjust(12, "0")
      blob += header.ctime.to_i.to_s(8).rjust(12, "0")
    end
  end
  
  pad_length = 512 - blob.bytesize
  blob += "\0" * pad_length
  
  blob[148, 8] = calculate_checksum(blob)
  
  blob
end

.strip_nuls(string) ⇒ Object

Remove all NUL bytes at the end of a string



44
45
46
47
48
49
50
 
# File 'lib/archive/tar/format.rb', line 44

def strip_nuls(string)
  until string[-1] != "\0"
    string = string[0..-2]
  end
  
  string
end

.unpack_header(header) ⇒ Object

Transform tar header to Stat



53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
 
# File 'lib/archive/tar/format.rb', line 53

def unpack_header(header)
  new_obj = Archive::Tar::Stat.new

  new_obj.path = strip_nuls(header[0, 100])
  new_obj.mode = header[100, 8].oct
  new_obj.uid = header[108, 8].oct
  new_obj.gid = header[116, 8].oct
  new_obj.size = header[124, 12].oct
  new_obj.mtime = Time.at(header[136, 12].oct)
  new_obj.checksum = header[148, 8].oct
  new_obj.type = DEC_TYPES[header[156]]
  new_obj.dest = strip_nuls(header[157, 100])
  new_obj.format = header[257, 5] == "ustar" ?
    ( header[257, 6] == "ustar " ? :gnu : :ustar ) : :other
  new_obj.user = strip_nuls(header[265, 32])
  new_obj.group = strip_nuls(header[297, 32])
  new_obj.major = header[329, 8].oct
  new_obj.minor = header[337, 8].oct
  
  new_obj.path = header[345, 155].strip + new_obj.path if new_obj.ustar?
  
  if new_obj.gnu?
    new_obj.atime = Time.at(header[345, 12].oct)
    new_obj.ctime = Time.at(header[357, 12].oct)
  end
  
  new_obj
end