protobuf/lang_ext/cpp/upb/handlers.hpp

/*
 * upb - a minimalist implementation of protocol buffers.
 *
 * Copyright (c) 2011 Google Inc.  See LICENSE for details.
 * Author: Josh Haberman <jhaberman@gmail.com>
 *
 * Note!  This file is a proof-of-concept for C++ wrappers and does not
 * yet build.
 *
 * upb::Handlers is a generic visitor-like interface for iterating over a
 * stream of protobuf data.  You can register function pointers that will be
 * called for each message and/or field as the data is being parsed or iterated
 * over, without having to know the source format that we are parsing from.
 * This decouples the parsing logic from the processing logic.
 */

#ifndef UPB_HANDLERS_HPP
#define UPB_HANDLERS_HPP

#include "upb_handlers.h"

namespace upb {

typedef upb_flow_t Flow;

class FieldHandlers : public upb_fhandlers {
 public:
  typedef upb_value_handler ValueHandler;
  typedef upb_startfield_handler StartFieldHandler;
  typedef upb_endfield_handler EndFieldHandler;

  // The FieldHandlers will live at least as long as the upb::Handlers to
  // which it belongs, but can be Ref'd/Unref'd to make it live longer (which
  // will prolong the life of the underlying upb::Handlers also).
  void Ref()   { upb_fhandlers_ref(this); }
  void Unref() { upb_fhandlers_unref(this); }

  // Functions to set this field's handlers.
  // These return "this" so they can be conveniently chained, eg.
  //   message_handlers->NewField(...)
  //       ->SetStartSequenceHandler(&StartSequence),
  //       ->SetEndSequenceHandler(&EndSequence),
  //       ->SetValueHandler(&Value);
  FieldHandlers* SetValueHandler(ValueHandler* h) {
    upb_fhandlers_setvalue(this, h); return this;
  }
  FieldHandlers* SetStartSequenceHandler(StartFieldHandler* h) {
    upb_fhandlers_setstartseq(this, h); return this;
  }
  FieldHandlers* SetEndSequenceHandler(EndFieldHandler* h) {
    upb_fhandlers_endseq(this, h); return this;
  }
  FieldHandlers* SetStartSubmessageHandler(StartFieldHandler* h) {
    upb_fhandlers_setstartsubmsg(this, h); return this;
  }
  FieldHandlers* SetEndSubmessageHandler(EndFieldHandler* h) {
    upb_fhandlers_endsubmsg(this, h); return this;
  }

  // Get/Set the field's bound value, which will be passed to its handlers.
  Value GetBoundValue() { return upb_fhandlers_getfval(this); }
  FieldHandlers* SetBoundValue(Value val) {
    upb_fhandlers_setfval(this, val); return this;
  }

 private:
  FieldHandlers();  // Only created by upb::Handlers.
  ~FieldHandlers(); // Only destroyed by refcounting.
};


class MessageHandlers : public upb_mhandlers {
 public:
  typedef upb_startmsg_handler StartMessageHandler;
  typedef upb_endmsg_handler EndMessageHandler;

  // The MessageHandlers will live at least as long as the upb::Handlers to
  // which it belongs, but can be Ref'd/Unref'd to make it live longer (which
  // will prolong the life of the underlying upb::Handlers also).
  void Ref()   { upb_mhandlers_ref(this); }
  void Unref() { upb_mhandlers_unref(this); }

  // Functions to set this message's handlers.
  // These return "this" so they can be conveniently chained, eg.
  //   handlers->NewMessage()
  //       ->SetStartMessageHandler(&StartMessage)
  //       ->SetEndMessageHandler(&EndMessage);
  MessageHandlers* SetStartMessageHandler(StartMessageHandler* h) {
    upb_mhandlers_setstartmsg(this, h); return this;
  }
  MessageHandlers* SetEndMessageHandler(EndMessageHandler* h) {
    upb_mhandlers_setendmsg(this, h); return this;
  }

  // Functions to create new FieldHandlers for this message.
  FieldHandlers* NewFieldHandlers(uint32_t fieldnum, upb_fieldtype_t type,
                                  bool repeated) {
    return upb_mhandlers_newfhandlers(this, fieldnum, type, repeated);
  }
  FieldHandlers* NewFieldHandlers(FieldDef* f) {
    return upb_mhandlers_newfhandlers_fordef(f);
  }

  // Like the previous but for MESSAGE or GROUP fields.  For GROUP fields, the
  // given submessage must not have any fields with this field number.
  FieldHandlers* NewFieldHandlersForSubmessage(uint32_t n, FieldType type,
                                               bool repeated,
                                               MessageHandlers* subm) {
    return upb_mhandlers_newsubmsgfhandlers(this, n, type, repeated, subm);
  }

  FieldHandlers* NewFieldHandlersForSubmessage(FieldDef* f,
                                               MessageHandlers* subm) {
    return upb_mhandlers_newsubmsgfhandlers_fordef(f);
  }


 private:
  MessageHandlers();  // Only created by upb::Handlers.
  ~MessageHandlers(); // Only destroyed by refcounting.
};

class Handlers : public upb_handlers {
 public:
  // Creates a new Handlers instance.
  Handlers* New() { return static_cast<Handlers*>(upb_handlers_new()); }

  void Ref()   { upb_handlers_ref(this); }
  void Unref() { upb_handlers_unref(this); }

  // Returns a new MessageHandlers object.  The first such message that is
  // obtained will be the top-level message for this Handlers object.
  MessageHandlers* NewMessageHandlers() { return upb_handlers_newmhandlers(); }

 private:
  FieldHandlers();  // Only created by Handlers::New().
  ~FieldHandlers(); // Only destroyed by refcounting.
};

}  // namespace upb

#endif