module Nokogiri::LibXML

def self.pointer_offset(n)
  n * FFI.type_size(:pointer) # byte offset of nth pointer in an array of pointers
end

def self.xmlFree(pointer)
  # xmlFree is a C preprocessor macro, not an actual function
  self.free(pointer)
end

def xmlXPathReturnFalse(ctx)
  valuePush(ctx, xmlXPathNewBoolean(0))
end

def xmlXPathReturnNodeSet(ctx, ns)
  valuePush(ctx, xmlXPathWrapNodeSet(ns))
end

def xmlXPathReturnNumber(ctx, val)
  valuePush(ctx, xmlXPathNewFloat(val))
end

def xmlXPathReturnString(ctx, str)
  valuePush(ctx, xmlXPathWrapString(str))
end

def xmlXPathReturnTrue(ctx)
  valuePush(ctx, xmlXPathNewBoolean(1))
end