class Minitar::PaxHeader

Implements the PAX Extended Header as a Ruby class. The header consists of following format:

<decimal-length><space><ascii-keyword>=<value><newline>

Where:

decimal-length is the total number of bytes for the PaxHeader record using ASCII decimal values; this includes the terminal newline (0x10).
space is a single literal ASCII space (0x20).
ascii-keyword is a PAX Extended Header keyword, which may be any ASCII character except newline (0x10) or equal sign (0x3D).
+=+ is the literal ASCII equal sign (0x3D).
value is any series of bytes except newline (0x10).
newline is the literal ASCII newline (0x10).

There are several keywords defined in the POSIX standard; some of them are supported in this class, but may not be supported by Minitar as a whole.

Primary support for PAX extended headers is for extracting size information for large file support. Other features may be added in the future.

Constants

BLOCK_SIZE

Attributes

attributes [R]

Public Class Methods

from_data (content)

Source

# File lib/minitar/pax_header.rb, line 47
  def from_data(content) = new(parse_content(content))

  private

  def parse_content(content)
    attributes = {}
    offset = 0

    while offset < content.bytesize
      space_pos = content.index(" ", offset)
      break unless space_pos

      length_str = content[offset, space_pos - offset]

      unless length_str.match?(/\A\d+\z/)
        raise ArgumentError, "Invalid length format in PAX header: '#{length_str}'"
      end

      length = length_str.to_i
      if offset + length > content.bytesize
        raise ArgumentError, "Length beyond PAX header: '#{content[offset..]}'"
      end
      record = content[offset, length]

      keyword_value = record[(space_pos - offset + 1)..-2]
      if keyword_value.include?("=")
        keyword, value = keyword_value.split("=", 2)
        attributes[keyword] = value
      end

      offset += length
    end
    attributes
  end
end

Creates a new PaxHeader from PAX content data.

from_stream (stream, posix_header)

Source

# File lib/minitar/pax_header.rb, line 33
def from_stream(stream, posix_header)
  raise ArgumentError, "Header must be a PAX header" unless posix_header.pax_header?

  pax_block = (posix_header.size / BLOCK_SIZE.to_f).ceil * BLOCK_SIZE
  pax_content = stream.read(pax_block)

  raise Minitar::InvalidTarStream if pax_content.nil? || pax_content.bytesize < posix_header.size

  actual_content = pax_content[0, posix_header.size]

  from_data(actual_content)
end

Creates a new PaxHeader from a data stream and posix header. Reads the PAX content based on the size specified in the posix header.

initialize (attributes = {})

Source

# File lib/minitar/pax_header.rb, line 84
def initialize(attributes = {})
  @attributes = attributes.transform_keys(&:to_s)
end

Creates a new PaxHeader from attributes hash.

mtime (= @attributes["mtime"]&.to_f)

Source

# File lib/minitar/pax_header.rb, line 95
  def mtime = @attributes["mtime"]&.to_f

  # Returns a string representation of the PAX header content.
  def to_s
    @attributes.map do |keyword, value|
      keyword_value = " #{keyword}=#{value}\n"
      record = keyword_value
      begin
        length = record.bytesize
        length_str = length.to_s
        record = "#{length_str}#{keyword_value}"
      end while record.size != length # standard:disable Lint/Loop
      record
    end.join
  end
end

The mtime value from PAX attributes

parse_content (content)

Source

# File lib/minitar/pax_header.rb, line 51
def parse_content(content)
  attributes = {}
  offset = 0

  while offset < content.bytesize
    space_pos = content.index(" ", offset)
    break unless space_pos

    length_str = content[offset, space_pos - offset]

    unless length_str.match?(/\A\d+\z/)
      raise ArgumentError, "Invalid length format in PAX header: '#{length_str}'"
    end

    length = length_str.to_i
    if offset + length > content.bytesize
      raise ArgumentError, "Length beyond PAX header: '#{content[offset..]}'"
    end
    record = content[offset, length]

    keyword_value = record[(space_pos - offset + 1)..-2]
    if keyword_value.include?("=")
      keyword, value = keyword_value.split("=", 2)
      attributes[keyword] = value
    end

    offset += length
  end
  attributes
end

path (= @attributes["path"])

Source

# File lib/minitar/pax_header.rb, line 92
    def path = @attributes["path"]

    # The mtime value from PAX attributes
    def mtime = @attributes["mtime"]&.to_f

    # Returns a string representation of the PAX header content.
    def to_s
      @attributes.map do |keyword, value|
        keyword_value = " #{keyword}=#{value}\n"
        record = keyword_value
        begin
          length = record.bytesize
          length_str = length.to_s
          record = "#{length_str}#{keyword_value}"
        end while record.size != length # standard:disable Lint/Loop
        record
      end.join
    end
  end
end

The path value from PAX attributes

size (= @attributes["size"]&.to_i)

Source

# File lib/minitar/pax_header.rb, line 89
  def size = @attributes["size"]&.to_i

  # The path value from PAX attributes
  def path = @attributes["path"]

  # The mtime value from PAX attributes
  def mtime = @attributes["mtime"]&.to_f

  # Returns a string representation of the PAX header content.
  def to_s
    @attributes.map do |keyword, value|
      keyword_value = " #{keyword}=#{value}\n"
      record = keyword_value
      begin
        length = record.bytesize
        length_str = length.to_s
        record = "#{length_str}#{keyword_value}"
      end while record.size != length # standard:disable Lint/Loop
      record
    end.join
  end
end

The size value from PAX attributes

to_s ()

Source

# File lib/minitar/pax_header.rb, line 98
def to_s
  @attributes.map do |keyword, value|
    keyword_value = " #{keyword}=#{value}\n"
    record = keyword_value
    begin
      length = record.bytesize
      length_str = length.to_s
      record = "#{length_str}#{keyword_value}"
    end while record.size != length # standard:disable Lint/Loop
    record
  end.join
end

Returns a string representation of the PAX header content.