harfbuzz/src/hb-dispatch.hh

/*
 * Copyright © 2007,2008,2009,2010  Red Hat, Inc.
 * Copyright © 2012,2018  Google, Inc.
 *
 *  This is part of HarfBuzz, a text shaping library.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and its documentation for any purpose, provided that the
 * above copyright notice and the following two paragraphs appear in
 * all copies of this software.
 *
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 * Red Hat Author(s): Behdad Esfahbod
 * Google Author(s): Behdad Esfahbod
 */

#ifndef HB_DISPATCH_HH
#define HB_DISPATCH_HH

#include "hb.hh"

/*
 * Dispatch
 */

template <typename Context, typename Return, unsigned int MaxDebugDepth>
struct hb_dispatch_context_t
{
  private:
  /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
  const Context* thiz () const { return static_cast<const Context *> (this); }
        Context* thiz ()       { return static_cast<      Context *> (this); }
  public:
  static constexpr unsigned max_debug_depth = MaxDebugDepth;
  typedef Return return_t;
  template <typename T, typename F>
  bool may_dispatch (const T *obj HB_UNUSED, const F *format HB_UNUSED) { return true; }
  template <typename T, typename ...Ts>
  return_t dispatch (const T &obj, Ts &&...ds)
  { return _dispatch_impl (obj, hb_prioritize, hb_forward<Ts> (ds)...); }
  static return_t no_dispatch_return_value () { return Context::default_return_value (); }
  static bool stop_sublookup_iteration (const return_t r HB_UNUSED) { return false; }

  private:
  template <typename T, typename ...Ts>
  auto _dispatch_impl (const T &obj, hb_priority<1>, Ts &&...ds) HB_AUTO_RETURN
  (obj.dispatch (thiz (), hb_forward<Ts> (ds)...))
  template <typename T, typename ...Ts>
  Return _dispatch_impl (const T &obj, hb_priority<0>, Ts &&...ds)
  { return thiz()->_dispatch (obj, hb_forward<Ts> (ds)...); }
};


#endif /* HB_DISPATCH_HH */