Class: RPM::File::Header

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

Constant Summary collapse

HEADER_SIGNED_TYPE = 
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HEADER_MAGIC = 
"\x8e\xad\xe8\x01\x00\x00\x00\x00".force_encoding("BINARY")
HEADER_HEADER_LENGTH =

magic + index_count + data_length

HEADER_MAGIC.length + 4 + 4
TAG_ENTRY_SIZE =

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

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Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(file) ⇒ Header

Returns a new instance of Header.



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# File 'lib/arr-pm/file/header.rb', line 19

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



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

def data_length
  @data_length
end

#index_count ⇒ Object

rpmlib calls this field ‘il’ unhelpfully



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

def index_count
  @index_count
end

#length ⇒ Object (readonly)

Returns the value of attribute length.



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# File 'lib/arr-pm/file/header.rb', line 6

def length
  @length
end

#magic ⇒ Object

8-byte string magic



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

def magic
  @magic
end

#tags ⇒ Object (readonly)

Returns the value of attribute tags.



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# File 'lib/arr-pm/file/header.rb', line 5

def tags
  @tags
end

Instance Method Details

#read ⇒ Object 



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# File 'lib/arr-pm/file/header.rb', line 26

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



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# File 'lib/arr-pm/file/header.rb', line 72

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



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# File 'lib/arr-pm/file/header.rb', line 65

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