require 'rubygems'
require 'inline'
 
class Module
  inline do |builder| 
    builder.c %{
      static VALUE 
      disable_mixin(VALUE super)
      {
        VALUE p, kid;
        VALUE module = self;
 
        Check_Type(super, T_MODULE);
        for (kid = module, p = RCLASS(module)->super; p; kid = p, p = RCLASS(p)->super) {
          if (BUILTIN_TYPE(p) == T_ICLASS) {
            if (RBASIC(p)->klass == super) {
              RCLASS(kid)->super = RCLASS(p)->super;
              rb_clear_cache_by_class(module);
              return p;
            }
          }
        }
 
        return Qnil;
      }
    }
 
    builder.c %{
      static VALUE 
      enable_mixin(VALUE mixin)
      {
        VALUE p;
        VALUE module = self;
 
        Check_Type(mixin, T_ICLASS);
        Check_Type(RBASIC(mixin)->klass, T_MODULE);
        for (p = module; p; p = RCLASS(p)->super) {
          if (RCLASS(p)->super == RCLASS(mixin)->super) {
            RCLASS(p)->super = mixin;
            rb_clear_cache_by_class(module);
            return RBASIC(mixin)->klass;
          }
        }
 
        return Qnil;
      }
    }
  end
end
 
class Object
  inline do |builder|
    builder.prefix %{
      #define KLASS_OF(o) RCLASS(RBASIC(o)->klass)
    }
 
    builder.c %{
      void redirect_tbls(VALUE obj) {
        unsigned long orig_iv_tbl, orig_m_tbl;
        orig_iv_tbl = (unsigned long)ROBJECT(self)->iv_tbl;
        orig_m_tbl = (unsigned long)KLASS_OF(self)->m_tbl;
        ROBJECT(self)->iv_tbl = ROBJECT(obj)->iv_tbl;
        KLASS_OF(self)->m_tbl = KLASS_OF(obj)->m_tbl;
        rb_iv_set(self, "__orig_m_tbl__", orig_m_tbl);
        rb_iv_set(self, "__orig_iv_tbl__", orig_iv_tbl);
      }
    }
 
    # restore needed, or else GC will crash
    builder.c %{
      void restore_tbls() {
        KLASS_OF(self)->m_tbl = (struct st_table *)rb_iv_get(self, "__orig_m_tbl__");
        ROBJECT(self)->iv_tbl = (struct st_table *)rb_iv_get(self, "__orig_iv_tbl__");
      }
    }
  end
end
 
class Class
  inline do |builder|
    builder.c %{
      void redirect_tbls(VALUE class) {
        unsigned long orig_iv_tbl, orig_m_tbl;
        orig_iv_tbl = (unsigned long)RCLASS(self)->iv_tbl;
        orig_m_tbl = (unsigned long)RCLASS(self)->m_tbl;
        RCLASS(self)->iv_tbl = RCLASS(class)->iv_tbl;
        RCLASS(self)->m_tbl = RCLASS(class)->m_tbl;
        rb_iv_set(self, "__orig_iv_tbl__", orig_iv_tbl);
        rb_iv_set(self, "__orig_m_tbl__", orig_m_tbl);
      }
    }
 
    # restore needed, or else GC will crash
    builder.c %{
      void restore_tbls() {
        RCLASS(self)->m_tbl = rb_iv_get(self, "__orig_m_tbl__");
        RCLASS(self)->iv_tbl = rb_iv_get(self, "__orig_iv_tbl__");
      }
    }
  end
end
 
class Proc
  def mixin mod
    context.extend mod
  end
 
  def mixout mod
    (class << context; self end).disable_mixin mod
  end
  
  def context
    eval('self', self)
  end
end
 
class Module
  def mix_eval mod, *args, &blk
    blk.mixin mod
    begin
      yield *args
    ensure
      blk.mixout mod
    end
  end
  
  def safe_mix_eval mod, &blk
    duped_context = blk.context.dup
    # make sure the singleton class is in existence
    class << duped_context; self; end
 
    duped_context.redirect_tbls(blk.context)
 
    duped_context.extend mod
    begin
      m = duped_context.is_a?(Module) ? :class_eval : :instance_eval
      duped_context.send(m, &blk)
    ensure
      duped_context.restore_tbls
      (class << duped_context; self; end).disable_mixin mod
    end
  end
 
  alias_method :mix_exec, :mix_eval
end