Class: RPM::File::Header

Inherits:
Object
  • Object
show all
Includes:
Cabin::Inspectable
Defined in:
lib/arr-pm/file/header.rb

Constant Summary collapse

HEADER_SIGNED_TYPE = 
5
HEADER_MAGIC =

Ruby 2 forces all strings to be UTF-8, so “x01” becomes “u0001” which is two bytes 00 01 which is not what we want. I can’t find a sane way to create a string without this madness in Ruby 2, so let’s just pack two 4-byte integers and go about our day.

"\x8e\xad\xe8\x01\x00\x00\x00\x00"
HEADER_HEADER_LENGTH =

magic + index_count + data_length

HEADER_MAGIC.length + 4 + 4
TAG_ENTRY_SIZE =

tag id, type, offset, count == 16 bytes

16

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(file) ⇒ Header

Returns a new instance of Header.



29
30
31
32
33
34
 
# File 'lib/arr-pm/file/header.rb', line 29

def initialize(file)
  @file = file

  @inspectables = [:@length, :@index_count, :@data_length]
  @tags = []
end

Instance Attribute Details

#data_length ⇒ Object

rpmlib calls this field ‘dl’ unhelpfully



12
13
14
 
# File 'lib/arr-pm/file/header.rb', line 12

def data_length
  @data_length
end

#index_count ⇒ Object

rpmlib calls this field ‘il’ unhelpfully



11
12
13
 
# File 'lib/arr-pm/file/header.rb', line 11

def index_count
  @index_count
end

#length ⇒ Object (readonly)

Returns the value of attribute length.



8
9
10
 
# File 'lib/arr-pm/file/header.rb', line 8

def length
  @length
end

#magic ⇒ Object

8-byte string magic



10
11
12
 
# File 'lib/arr-pm/file/header.rb', line 10

def magic
  @magic
end

#tags ⇒ Object (readonly)

Returns the value of attribute tags.



7
8
9
 
# File 'lib/arr-pm/file/header.rb', line 7

def tags
  @tags
end

Instance Method Details

#read ⇒ Object 



36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
 
# File 'lib/arr-pm/file/header.rb', line 36

def read
  # TODO(sissel): update the comments here to reflect learnings about rpm
  # internals
  # At this point assume we've read and consumed the lead and signature.
  #len = @rpm.signature.index_length + @rpm.signature
  #
  # header size is
  #     ( @rpm.signature.index_length * size of a header entry )
  #     + @rpm.signature.data_length
  #
  # header 'entries' are an
  #   int32 (tag id), int32 (tag type), int32  (offset), uint32 (count)
  #
  #       len = sizeof(il) + sizeof(dl) + (il * sizeof(struct entryInfo_s)) + dl;
  # See rpm's header.c, the headerLoad method function for reference.

  # Header always starts with HEADER_MAGIC + index_count(2bytes) +
  # data_length(2bytes)
  data = @file.read(HEADER_HEADER_LENGTH).unpack("a8NN")
  # TODO(sissel): @index_count is really a count, rename?
  @magic, @index_count, @data_length = data
  validate
  
  @index_size = @index_count * TAG_ENTRY_SIZE
  tag_data = @file.read(@index_size)
  data = @file.read(@data_length)

  (0 ... @index_count).each do |i|
    offset = i * TAG_ENTRY_SIZE
    entry_data = tag_data[i * TAG_ENTRY_SIZE, TAG_ENTRY_SIZE]
    entry = entry_data.unpack("NNNN")
    entry << data
    tag = ::RPM::File::Tag.new(*entry)
    @tags << tag
  end # each index

  @length = HEADER_HEADER_LENGTH + @index_size + @data_length
end

#validate ⇒ Object

def write



82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
 
# File 'lib/arr-pm/file/header.rb', line 82

def validate
  # TODO(sissel): raise real exceptions
  if @magic != ::RPM::File::Header::HEADER_MAGIC
    raise "Header magic did not match; got #{@magic.inspect}, " \
          "expected #{::RPM::File::Header::HEADER_MAGIC.inspect}"
  end

  #if !(0..32).include?(@index_count)
    #raise "Invalid 'index_count' value #{@index_count}, expected to be in range [0..32]"
  #end

  #if !(0..8192).include?(@data_length)
    #raise "Invalid 'data_length' value #{@data_length}, expected to be in range [0..8192]"
  #end
end

#write ⇒ Object

def read



75
76
77
78
79
80
 
# File 'lib/arr-pm/file/header.rb', line 75

def write
  raise "not implemented yet"
  # Sort tags by type (integer value)
  # emit all tags in order
  # then emit all data segments in same order
end