Module: Leptris::XML::CStringArray

Defined in:
lib/leptris/xml/c_string_array.rb

Overview

Adapter for libleptris's NULL-terminated char** wire format. Both directions of the conversion live here so the pointer arithmetic has one home (previously c14n built the array by hand and SAX walked it by hand).

Class Method Summary collapse

Class Method Details

.to_c(strings) ⇒ Object

Ruby strings -> NULL-terminated char**. Returns [buffer, anchors]; the caller must keep both referenced for the duration of the FFI call (e.g. via local variables).



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# File 'lib/leptris/xml/c_string_array.rb', line 11

def self.to_c(strings)
  strs = Array(strings).map(&:to_s)
  return [nil, nil] if strs.empty?

  ptr_size = ::FFI::type_size(:pointer)
  buffer = ::FFI::MemoryPointer.new(:pointer, strs.size + 1)
  anchors = strs.map { |s| ::FFI::MemoryPointer.from_string(s) }
  anchors.each_with_index { |p, i| buffer.put_pointer(i * ptr_size, p) }
  buffer.put_pointer(strs.size * ptr_size, nil)
  [buffer, anchors]
end

.to_ruby(ptr) ⇒ Object

NULL-terminated char** -> Ruby strings. Stops at the first NULL entry. Returns [] for a NULL pointer.



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# File 'lib/leptris/xml/c_string_array.rb', line 25

def self.to_ruby(ptr)
  return [] if ptr.nil? || ptr.null?

  ptr_size = ::FFI::type_size(:pointer)
  result = []
  offset = 0
  while (entry = ptr.get_pointer(offset)) && !entry.null?
    result << entry.read_string.force_encoding(Encoding::UTF_8)
    offset += ptr_size
  end
  result
end