protobuf/upb/handlers.h

/*
** upb::Handlers (upb_handlers)
**
** A upb_handlers is like a virtual table for a upb_msgdef.  Each field of the
** message can have associated functions that will be called when we are
** parsing or visiting a stream of data.  This is similar to how handlers work
** in SAX (the Simple API for XML).
**
** The handlers have no idea where the data is coming from, so a single set of
** handlers could be used with two completely different data sources (for
** example, a parser and a visitor over in-memory objects).  This decoupling is
** the most important feature of upb, because it allows parsers and serializers
** to be highly reusable.
**
** This is a mixed C/C++ interface that offers a full API to both languages.
** See the top-level README for more information.
*/

#ifndef UPB_HANDLERS_H
#define UPB_HANDLERS_H

#include "upb/def.h"
#include "upb/table.int.h"

#ifdef __cplusplus
namespace upb {
class BufferHandle;
class BytesHandler;
class HandlerAttributes;
class Handlers;
template <class T> class Handler;
template <class T> struct CanonicalType;
}  /* namespace upb */
#endif

UPB_DECLARE_TYPE(upb::BufferHandle, upb_bufhandle)
UPB_DECLARE_TYPE(upb::BytesHandler, upb_byteshandler)
UPB_DECLARE_TYPE(upb::HandlerAttributes, upb_handlerattr)
UPB_DECLARE_DERIVED_TYPE(upb::Handlers, upb::RefCounted,
                         upb_handlers, upb_refcounted)

/* The maximum depth that the handler graph can have.  This is a resource limit
 * for the C stack since we sometimes need to recursively traverse the graph.
 * Cycles are ok; the traversal will stop when it detects a cycle, but we must
 * hit the cycle before the maximum depth is reached.
 *
 * If having a single static limit is too inflexible, we can add another variant
 * of Handlers::Freeze that allows specifying this as a parameter. */
#define UPB_MAX_HANDLER_DEPTH 64

/* All the different types of handlers that can be registered.
 * Only needed for the advanced functions in upb::Handlers. */
typedef enum {
  UPB_HANDLER_INT32,
  UPB_HANDLER_INT64,
  UPB_HANDLER_UINT32,
  UPB_HANDLER_UINT64,
  UPB_HANDLER_FLOAT,
  UPB_HANDLER_DOUBLE,
  UPB_HANDLER_BOOL,
  UPB_HANDLER_STARTSTR,
  UPB_HANDLER_STRING,
  UPB_HANDLER_ENDSTR,
  UPB_HANDLER_STARTSUBMSG,
  UPB_HANDLER_ENDSUBMSG,
  UPB_HANDLER_STARTSEQ,
  UPB_HANDLER_ENDSEQ
} upb_handlertype_t;

#define UPB_HANDLER_MAX (UPB_HANDLER_ENDSEQ+1)

#define UPB_BREAK NULL

/* A convenient definition for when no closure is needed. */
extern char _upb_noclosure;
#define UPB_NO_CLOSURE &_upb_noclosure

/* A selector refers to a specific field handler in the Handlers object
 * (for example: the STARTSUBMSG handler for field "field15"). */
typedef int32_t upb_selector_t;

UPB_BEGIN_EXTERN_C

/* Forward-declares for C inline accessors.  We need to declare these here
 * so we can "friend" them in the class declarations in C++. */
UPB_INLINE upb_func *upb_handlers_gethandler(const upb_handlers *h,
                                             upb_selector_t s);
UPB_INLINE const void *upb_handlerattr_handlerdata(const upb_handlerattr *attr);
UPB_INLINE const void *upb_handlers_gethandlerdata(const upb_handlers *h,
                                                   upb_selector_t s);

UPB_INLINE void upb_bufhandle_init(upb_bufhandle *h);
UPB_INLINE void upb_bufhandle_setobj(upb_bufhandle *h, const void *obj,
                                     const void *type);
UPB_INLINE void upb_bufhandle_setbuf(upb_bufhandle *h, const char *buf,
                                     size_t ofs);
UPB_INLINE const void *upb_bufhandle_obj(const upb_bufhandle *h);
UPB_INLINE const void *upb_bufhandle_objtype(const upb_bufhandle *h);
UPB_INLINE const char *upb_bufhandle_buf(const upb_bufhandle *h);

UPB_END_EXTERN_C


/* Static selectors for upb::Handlers. */
#define UPB_STARTMSG_SELECTOR 0
#define UPB_ENDMSG_SELECTOR 1
#define UPB_UNKNOWN_SELECTOR 2
#define UPB_STATIC_SELECTOR_COUNT 3

/* Static selectors for upb::BytesHandler. */
#define UPB_STARTSTR_SELECTOR 0
#define UPB_STRING_SELECTOR 1
#define UPB_ENDSTR_SELECTOR 2

typedef void upb_handlerfree(void *d);

#ifdef __cplusplus

/* A set of attributes that accompanies a handler's function pointer. */
class upb::HandlerAttributes {
 public:
  HandlerAttributes();
  ~HandlerAttributes();

  /* Sets the handler data that will be passed as the second parameter of the
   * handler.  To free this pointer when the handlers are freed, call
   * Handlers::AddCleanup(). */
  bool SetHandlerData(const void *handler_data);
  const void* handler_data() const;

  /* Use this to specify the type of the closure.  This will be checked against
   * all other closure types for handler that use the same closure.
   * Registration will fail if this does not match all other non-NULL closure
   * types. */
  bool SetClosureType(const void *closure_type);
  const void* closure_type() const;

  /* Use this to specify the type of the returned closure.  Only used for
   * Start*{String,SubMessage,Sequence} handlers.  This must match the closure
   * type of any handlers that use it (for example, the StringBuf handler must
   * match the closure returned from StartString). */
  bool SetReturnClosureType(const void *return_closure_type);
  const void* return_closure_type() const;

  /* Set to indicate that the handler always returns "ok" (either "true" or a
   * non-NULL closure).  This is a hint that can allow code generators to
   * generate more efficient code. */
  bool SetAlwaysOk(bool always_ok);
  bool always_ok() const;

 private:
  friend UPB_INLINE const void * ::upb_handlerattr_handlerdata(
      const upb_handlerattr *attr);
#else
struct upb_handlerattr {
#endif
  const void *handler_data_;
  const void *closure_type_;
  const void *return_closure_type_;
  bool alwaysok_;
};

#define UPB_HANDLERATTR_INITIALIZER {NULL, NULL, NULL, false}

typedef struct {
  upb_func *func;

  /* It is wasteful to include the entire attributes here:
   *
   * * Some of the information is redundant (like storing the closure type
   *   separately for each handler that must match).
   * * Some of the info is only needed prior to freeze() (like closure types).
   * * alignment padding wastes a lot of space for alwaysok_.
   *
   * If/when the size and locality of handlers is an issue, we can optimize this
   * not to store the entire attr like this.  We do not expose the table's
   * layout to allow this optimization in the future. */
  upb_handlerattr attr;
} upb_handlers_tabent;

#ifdef __cplusplus

/* Extra information about a buffer that is passed to a StringBuf handler.
 * TODO(haberman): allow the handle to be pinned so that it will outlive
 * the handler invocation. */
class upb::BufferHandle {
 public:
  BufferHandle();
  ~BufferHandle();

  /* The beginning of the buffer.  This may be different than the pointer
   * passed to a StringBuf handler because the handler may receive data
   * that is from the middle or end of a larger buffer. */
  const char* buffer() const;

  /* The offset within the attached object where this buffer begins.  Only
   * meaningful if there is an attached object. */
  size_t object_offset() const;

  /* Note that object_offset is the offset of "buf" within the attached
   * object. */
  void SetBuffer(const char* buf, size_t object_offset);

  /* The BufferHandle can have an "attached object", which can be used to
   * tunnel through a pointer to the buffer's underlying representation. */
  template <class T>
  void SetAttachedObject(const T* obj);

  /* Returns NULL if the attached object is not of this type. */
  template <class T>
  const T* GetAttachedObject() const;

 private:
  friend UPB_INLINE void ::upb_bufhandle_init(upb_bufhandle *h);
  friend UPB_INLINE void ::upb_bufhandle_setobj(upb_bufhandle *h,
                                                const void *obj,
                                                const void *type);
  friend UPB_INLINE void ::upb_bufhandle_setbuf(upb_bufhandle *h,
                                                const char *buf, size_t ofs);
  friend UPB_INLINE const void* ::upb_bufhandle_obj(const upb_bufhandle *h);
  friend UPB_INLINE const void* ::upb_bufhandle_objtype(
      const upb_bufhandle *h);
  friend UPB_INLINE const char* ::upb_bufhandle_buf(const upb_bufhandle *h);
#else
struct upb_bufhandle {
#endif
  const char *buf_;
  const void *obj_;
  const void *objtype_;
  size_t objofs_;
};

#ifdef __cplusplus

/* A upb::Handlers object represents the set of handlers associated with a
 * message in the graph of messages.  You can think of it as a big virtual
 * table with functions corresponding to all the events that can fire while
 * parsing or visiting a message of a specific type.
 *
 * Any handlers that are not set behave as if they had successfully consumed
 * the value.  Any unset Start* handlers will propagate their closure to the
 * inner frame.
 *
 * The easiest way to create the *Handler objects needed by the Set* methods is
 * with the UpbBind() and UpbMakeHandler() macros; see below. */
class upb::Handlers {
 public:
  typedef upb_selector_t Selector;
  typedef upb_handlertype_t Type;

  typedef Handler<void *(*)(void *, const void *)> StartFieldHandler;
  typedef Handler<bool (*)(void *, const void *)> EndFieldHandler;
  typedef Handler<bool (*)(void *, const void *)> StartMessageHandler;
  typedef Handler<bool (*)(void *, const void *, Status*)> EndMessageHandler;
  typedef Handler<void *(*)(void *, const void *, size_t)> StartStringHandler;
  typedef Handler<size_t (*)(void *, const void *, const char *, size_t,
                             const BufferHandle *)> StringHandler;

  template <class T> struct ValueHandler {
    typedef Handler<bool(*)(void *, const void *, T)> H;
  };

  typedef ValueHandler<int32_t>::H     Int32Handler;
  typedef ValueHandler<int64_t>::H     Int64Handler;
  typedef ValueHandler<uint32_t>::H    UInt32Handler;
  typedef ValueHandler<uint64_t>::H    UInt64Handler;
  typedef ValueHandler<float>::H       FloatHandler;
  typedef ValueHandler<double>::H      DoubleHandler;
  typedef ValueHandler<bool>::H        BoolHandler;

  /* Any function pointer can be converted to this and converted back to its
   * correct type. */
  typedef void GenericFunction();

  typedef void HandlersCallback(const void *closure, upb_handlers *h);

  /* Returns a new handlers object for the given frozen msgdef.
   * Returns NULL if memory allocation failed. */
  static reffed_ptr<Handlers> New(const MessageDef *m);

  /* Convenience function for registering a graph of handlers that mirrors the
   * graph of msgdefs for some message.  For "m" and all its children a new set
   * of handlers will be created and the given callback will be invoked,
   * allowing the client to register handlers for this message.  Note that any
   * subhandlers set by the callback will be overwritten. */
  static reffed_ptr<const Handlers> NewFrozen(const MessageDef *m,
                                              HandlersCallback *callback,
                                              const void *closure);

  /* Functionality from upb::RefCounted. */
  UPB_REFCOUNTED_CPPMETHODS

  /* All handler registration functions return bool to indicate success or
   * failure; details about failures are stored in this status object.  If a
   * failure does occur, it must be cleared before the Handlers are frozen,
   * otherwise the freeze() operation will fail.  The functions may *only* be
   * used while the Handlers are mutable. */
  const Status* status();
  void ClearError();

  /* Call to freeze these Handlers.  Requires that any SubHandlers are already
   * frozen.  For cycles, you must use the static version below and freeze the
   * whole graph at once. */
  bool Freeze(Status* s);

  /* Freezes the given set of handlers.  You may not freeze a handler without
   * also freezing any handlers they point to. */
  static bool Freeze(Handlers*const* handlers, int n, Status* s);
  static bool Freeze(const std::vector<Handlers*>& handlers, Status* s);

  /* Returns the msgdef associated with this handlers object. */
  const MessageDef* message_def() const;

  /* Adds the given pointer and function to the list of cleanup functions that
   * will be run when these handlers are freed.  If this pointer has previously
   * been registered, the function returns false and does nothing. */
  bool AddCleanup(void *ptr, upb_handlerfree *cleanup);

  /* Sets the startmsg handler for the message, which is defined as follows:
   *
   *   bool startmsg(MyType* closure) {
   *     // Called when the message begins.  Returns true if processing should
   *     // continue.
   *     return true;
   *   }
   */
  bool SetStartMessageHandler(const StartMessageHandler& handler);

  /* Sets the endmsg handler for the message, which is defined as follows:
   *
   *   bool endmsg(MyType* closure, upb_status *status) {
   *     // Called when processing of this message ends, whether in success or
   *     // failure.  "status" indicates the final status of processing, and
   *     // can also be modified in-place to update the final status.
   *   }
   */
  bool SetEndMessageHandler(const EndMessageHandler& handler);

  /* Sets the value handler for the given field, which is defined as follows
   * (this is for an int32 field; other field types will pass their native
   * C/C++ type for "val"):
   *
   *   bool OnValue(MyClosure* c, const MyHandlerData* d, int32_t val) {
   *     // Called when the field's value is encountered.  "d" contains
   *     // whatever data was bound to this field when it was registered.
   *     // Returns true if processing should continue.
   *     return true;
   *   }
   *
   *   handers->SetInt32Handler(f, UpbBind(OnValue, new MyHandlerData(...)));
   *
   * The value type must exactly match f->type().
   * For example, a handler that takes an int32_t parameter may only be used for
   * fields of type UPB_TYPE_INT32 and UPB_TYPE_ENUM.
   *
   * Returns false if the handler failed to register; in this case the cleanup
   * handler (if any) will be called immediately.
   */
  bool SetInt32Handler (const FieldDef* f,  const Int32Handler& h);
  bool SetInt64Handler (const FieldDef* f,  const Int64Handler& h);
  bool SetUInt32Handler(const FieldDef* f, const UInt32Handler& h);
  bool SetUInt64Handler(const FieldDef* f, const UInt64Handler& h);
  bool SetFloatHandler (const FieldDef* f,  const FloatHandler& h);
  bool SetDoubleHandler(const FieldDef* f, const DoubleHandler& h);
  bool SetBoolHandler  (const FieldDef* f,   const BoolHandler& h);

  /* Like the previous, but templated on the type on the value (ie. int32).
   * This is mostly useful to call from other templates.  To call this you must
   * specify the template parameter explicitly, ie:
   *   h->SetValueHandler<T>(f, UpbBind(MyHandler<T>, MyData)); */
  template <class T>
  bool SetValueHandler(
      const FieldDef *f,
      const typename ValueHandler<typename CanonicalType<T>::Type>::H& handler);

  /* Sets handlers for a string field, which are defined as follows:
   *
   *   MySubClosure* startstr(MyClosure* c, const MyHandlerData* d,
   *                          size_t size_hint) {
   *     // Called when a string value begins.  The return value indicates the
   *     // closure for the string.  "size_hint" indicates the size of the
   *     // string if it is known, however if the string is length-delimited
   *     // and the end-of-string is not available size_hint will be zero.
   *     // This case is indistinguishable from the case where the size is
   *     // known to be zero.
   *     //
   *     // TODO(haberman): is it important to distinguish these cases?
   *     // If we had ssize_t as a type we could make -1 "unknown", but
   *     // ssize_t is POSIX (not ANSI) and therefore less portable.
   *     // In practice I suspect it won't be important to distinguish.
   *     return closure;
   *   }
   *
   *   size_t str(MyClosure* closure, const MyHandlerData* d,
   *              const char *str, size_t len) {
   *     // Called for each buffer of string data; the multiple physical buffers
   *     // are all part of the same logical string.  The return value indicates
   *     // how many bytes were consumed.  If this number is less than "len",
   *     // this will also indicate that processing should be halted for now,
   *     // like returning false or UPB_BREAK from any other callback.  If
   *     // number is greater than "len", the excess bytes will be skipped over
   *     // and not passed to the callback.
   *     return len;
   *   }
   *
   *   bool endstr(MyClosure* c, const MyHandlerData* d) {
   *     // Called when a string value ends.  Return value indicates whether
   *     // processing should continue.
   *     return true;
   *   }
   */
  bool SetStartStringHandler(const FieldDef* f, const StartStringHandler& h);
  bool SetStringHandler(const FieldDef* f, const StringHandler& h);
  bool SetEndStringHandler(const FieldDef* f, const EndFieldHandler& h);

  /* Sets the startseq handler, which is defined as follows:
   *
   *   MySubClosure *startseq(MyClosure* c, const MyHandlerData* d) {
   *     // Called when a sequence (repeated field) begins.  The returned
   *     // pointer indicates the closure for the sequence (or UPB_BREAK
   *     // to interrupt processing).
   *     return closure;
   *   }
   *
   *   h->SetStartSequenceHandler(f, UpbBind(startseq, new MyHandlerData(...)));
   *
   * Returns "false" if "f" does not belong to this message or is not a
   * repeated field.
   */
  bool SetStartSequenceHandler(const FieldDef* f, const StartFieldHandler& h);

  /* Sets the startsubmsg handler for the given field, which is defined as
   * follows:
   *
   *   MySubClosure* startsubmsg(MyClosure* c, const MyHandlerData* d) {
   *     // Called when a submessage begins.  The returned pointer indicates the
   *     // closure for the sequence (or UPB_BREAK to interrupt processing).
   *     return closure;
   *   }
   *
   *   h->SetStartSubMessageHandler(f, UpbBind(startsubmsg,
   *                                           new MyHandlerData(...)));
   *
   * Returns "false" if "f" does not belong to this message or is not a
   * submessage/group field.
   */
  bool SetStartSubMessageHandler(const FieldDef* f, const StartFieldHandler& h);

  /* Sets the endsubmsg handler for the given field, which is defined as
   * follows:
   *
   *   bool endsubmsg(MyClosure* c, const MyHandlerData* d) {
   *     // Called when a submessage ends.  Returns true to continue processing.
   *     return true;
   *   }
   *
   * Returns "false" if "f" does not belong to this message or is not a
   * submessage/group field.
   */
  bool SetEndSubMessageHandler(const FieldDef *f, const EndFieldHandler &h);

  /* Starts the endsubseq handler for the given field, which is defined as
   * follows:
   *
   *   bool endseq(MyClosure* c, const MyHandlerData* d) {
   *     // Called when a sequence ends.  Returns true continue processing.
   *     return true;
   *   }
   *
   * Returns "false" if "f" does not belong to this message or is not a
   * repeated field.
   */
  bool SetEndSequenceHandler(const FieldDef* f, const EndFieldHandler& h);

  /* Sets or gets the object that specifies handlers for the given field, which
   * must be a submessage or group.  Returns NULL if no handlers are set. */
  bool SetSubHandlers(const FieldDef* f, const Handlers* sub);
  const Handlers* GetSubHandlers(const FieldDef* f) const;

  /* Equivalent to GetSubHandlers, but takes the STARTSUBMSG selector for the
   * field. */
  const Handlers* GetSubHandlers(Selector startsubmsg) const;

  /* A selector refers to a specific field handler in the Handlers object
   * (for example: the STARTSUBMSG handler for field "field15").
   * On success, returns true and stores the selector in "s".
   * If the FieldDef or Type are invalid, returns false.
   * The returned selector is ONLY valid for Handlers whose MessageDef
   * contains this FieldDef. */
  static bool GetSelector(const FieldDef* f, Type type, Selector* s);

  /* Given a START selector of any kind, returns the corresponding END selector. */
  static Selector GetEndSelector(Selector start_selector);

  /* Returns the function pointer for this handler.  It is the client's
   * responsibility to cast to the correct function type before calling it. */
  GenericFunction* GetHandler(Selector selector);

  /* Sets the given attributes to the attributes for this selector. */
  bool GetAttributes(Selector selector, HandlerAttributes* attr);

  /* Returns the handler data that was registered with this handler. */
  const void* GetHandlerData(Selector selector);

  /* Could add any of the following functions as-needed, with some minor
   * implementation changes:
   *
   * const FieldDef* GetFieldDef(Selector selector);
   * static bool IsSequence(Selector selector); */

 private:
  UPB_DISALLOW_POD_OPS(Handlers, upb::Handlers)

  friend UPB_INLINE GenericFunction *::upb_handlers_gethandler(
      const upb_handlers *h, upb_selector_t s);
  friend UPB_INLINE const void *::upb_handlers_gethandlerdata(
      const upb_handlers *h, upb_selector_t s);
#else
struct upb_handlers {
#endif
  upb_refcounted base;

  const upb_msgdef *msg;
  const upb_handlers **sub;
  const void *top_closure_type;
  upb_inttable cleanup_;
  upb_status status_;  /* Used only when mutable. */
  upb_handlers_tabent table[1];  /* Dynamically-sized field handler array. */
};

#ifdef __cplusplus

namespace upb {

/* Convenience macros for creating a Handler object that is wrapped with a
 * type-safe wrapper function that converts the "void*" parameters/returns
 * of the underlying C API into nice C++ function.
 *
 * Sample usage:
 *   void OnValue1(MyClosure* c, const MyHandlerData* d, int32_t val) {
 *     // do stuff ...
 *   }
 *
 *   // Handler that doesn't need any data bound to it.
 *   void OnValue2(MyClosure* c, int32_t val) {
 *     // do stuff ...
 *   }
 *
 *   // Handler that returns bool so it can return failure if necessary.
 *   bool OnValue3(MyClosure* c, int32_t val) {
 *     // do stuff ...
 *     return ok;
 *   }
 *
 *   // Member function handler.
 *   class MyClosure {
 *    public:
 *     void OnValue(int32_t val) {
 *       // do stuff ...
 *     }
 *   };
 *
 *   // Takes ownership of the MyHandlerData.
 *   handlers->SetInt32Handler(f1, UpbBind(OnValue1, new MyHandlerData(...)));
 *   handlers->SetInt32Handler(f2, UpbMakeHandler(OnValue2));
 *   handlers->SetInt32Handler(f1, UpbMakeHandler(OnValue3));
 *   handlers->SetInt32Handler(f2, UpbMakeHandler(&MyClosure::OnValue));
 */

#ifdef UPB_CXX11

/* In C++11, the "template" disambiguator can appear even outside templates,
 * so all calls can safely use this pair of macros. */

#define UpbMakeHandler(f) upb::MatchFunc(f).template GetFunc<f>()

/* We have to be careful to only evaluate "d" once. */
#define UpbBind(f, d) upb::MatchFunc(f).template GetFunc<f>((d))

#else

/* Prior to C++11, the "template" disambiguator may only appear inside a
 * template, so the regular macro must not use "template" */

#define UpbMakeHandler(f) upb::MatchFunc(f).GetFunc<f>()

#define UpbBind(f, d) upb::MatchFunc(f).GetFunc<f>((d))

#endif  /* UPB_CXX11 */

/* This macro must be used in C++98 for calls from inside a template.  But we
 * define this variant in all cases; code that wants to be compatible with both
 * C++98 and C++11 should always use this macro when calling from a template. */
#define UpbMakeHandlerT(f) upb::MatchFunc(f).template GetFunc<f>()

/* We have to be careful to only evaluate "d" once. */
#define UpbBindT(f, d) upb::MatchFunc(f).template GetFunc<f>((d))

/* Handler: a struct that contains the (handler, data, deleter) tuple that is
 * used to register all handlers.  Users can Make() these directly but it's
 * more convenient to use the UpbMakeHandler/UpbBind macros above. */
template <class T> class Handler {
 public:
  /* The underlying, handler function signature that upb uses internally. */
  typedef T FuncPtr;

  /* Intentionally implicit. */
  template <class F> Handler(F func);
  ~Handler();

 private:
  void AddCleanup(Handlers* h) const {
    if (cleanup_func_) {
      bool ok = h->AddCleanup(cleanup_data_, cleanup_func_);
      UPB_ASSERT(ok);
    }
  }

  UPB_DISALLOW_COPY_AND_ASSIGN(Handler)
  friend class Handlers;
  FuncPtr handler_;
  mutable HandlerAttributes attr_;
  mutable bool registered_;
  void *cleanup_data_;
  upb_handlerfree *cleanup_func_;
};

}  /* namespace upb */

#endif  /* __cplusplus */

UPB_BEGIN_EXTERN_C

/* Native C API. */

/* Handler function typedefs. */
typedef bool upb_unknown_handlerfunc(void *c, const void *hd, const char *buf,
                                     size_t n);
typedef bool upb_startmsg_handlerfunc(void *c, const void*);
typedef bool upb_endmsg_handlerfunc(void *c, const void *, upb_status *status);
typedef void* upb_startfield_handlerfunc(void *c, const void *hd);
typedef bool upb_endfield_handlerfunc(void *c, const void *hd);
typedef bool upb_int32_handlerfunc(void *c, const void *hd, int32_t val);
typedef bool upb_int64_handlerfunc(void *c, const void *hd, int64_t val);
typedef bool upb_uint32_handlerfunc(void *c, const void *hd, uint32_t val);
typedef bool upb_uint64_handlerfunc(void *c, const void *hd, uint64_t val);
typedef bool upb_float_handlerfunc(void *c, const void *hd, float val);
typedef bool upb_double_handlerfunc(void *c, const void *hd, double val);
typedef bool upb_bool_handlerfunc(void *c, const void *hd, bool val);
typedef void *upb_startstr_handlerfunc(void *c, const void *hd,
                                       size_t size_hint);
typedef size_t upb_string_handlerfunc(void *c, const void *hd, const char *buf,
                                      size_t n, const upb_bufhandle* handle);

/* upb_bufhandle */
size_t upb_bufhandle_objofs(const upb_bufhandle *h);

/* upb_handlerattr */
void upb_handlerattr_init(upb_handlerattr *attr);
void upb_handlerattr_uninit(upb_handlerattr *attr);

bool upb_handlerattr_sethandlerdata(upb_handlerattr *attr, const void *hd);
bool upb_handlerattr_setclosuretype(upb_handlerattr *attr, const void *type);
const void *upb_handlerattr_closuretype(const upb_handlerattr *attr);
bool upb_handlerattr_setreturnclosuretype(upb_handlerattr *attr,
                                          const void *type);
const void *upb_handlerattr_returnclosuretype(const upb_handlerattr *attr);
bool upb_handlerattr_setalwaysok(upb_handlerattr *attr, bool alwaysok);
bool upb_handlerattr_alwaysok(const upb_handlerattr *attr);

UPB_INLINE const void *upb_handlerattr_handlerdata(
    const upb_handlerattr *attr) {
  return attr->handler_data_;
}

/* upb_handlers */
typedef void upb_handlers_callback(const void *closure, upb_handlers *h);
upb_handlers *upb_handlers_new(const upb_msgdef *m,
                               const void *owner);
const upb_handlers *upb_handlers_newfrozen(const upb_msgdef *m,
                                           const void *owner,
                                           upb_handlers_callback *callback,
                                           const void *closure);

/* Include refcounted methods like upb_handlers_ref(). */
UPB_REFCOUNTED_CMETHODS(upb_handlers, upb_handlers_upcast)

const upb_status *upb_handlers_status(upb_handlers *h);
void upb_handlers_clearerr(upb_handlers *h);
const upb_msgdef *upb_handlers_msgdef(const upb_handlers *h);
bool upb_handlers_addcleanup(upb_handlers *h, void *p, upb_handlerfree *hfree);
bool upb_handlers_setunknown(upb_handlers *h, upb_unknown_handlerfunc *func,
                             upb_handlerattr *attr);

bool upb_handlers_setstartmsg(upb_handlers *h, upb_startmsg_handlerfunc *func,
                              upb_handlerattr *attr);
bool upb_handlers_setendmsg(upb_handlers *h, upb_endmsg_handlerfunc *func,
                            upb_handlerattr *attr);
bool upb_handlers_setint32(upb_handlers *h, const upb_fielddef *f,
                           upb_int32_handlerfunc *func, upb_handlerattr *attr);
bool upb_handlers_setint64(upb_handlers *h, const upb_fielddef *f,
                           upb_int64_handlerfunc *func, upb_handlerattr *attr);
bool upb_handlers_setuint32(upb_handlers *h, const upb_fielddef *f,
                            upb_uint32_handlerfunc *func,
                            upb_handlerattr *attr);
bool upb_handlers_setuint64(upb_handlers *h, const upb_fielddef *f,
                            upb_uint64_handlerfunc *func,
                            upb_handlerattr *attr);
bool upb_handlers_setfloat(upb_handlers *h, const upb_fielddef *f,
                           upb_float_handlerfunc *func, upb_handlerattr *attr);
bool upb_handlers_setdouble(upb_handlers *h, const upb_fielddef *f,
                            upb_double_handlerfunc *func,
                            upb_handlerattr *attr);
bool upb_handlers_setbool(upb_handlers *h, const upb_fielddef *f,
                          upb_bool_handlerfunc *func,
                          upb_handlerattr *attr);
bool upb_handlers_setstartstr(upb_handlers *h, const upb_fielddef *f,
                              upb_startstr_handlerfunc *func,
                              upb_handlerattr *attr);
bool upb_handlers_setstring(upb_handlers *h, const upb_fielddef *f,
                            upb_string_handlerfunc *func,
                            upb_handlerattr *attr);
bool upb_handlers_setendstr(upb_handlers *h, const upb_fielddef *f,
                            upb_endfield_handlerfunc *func,
                            upb_handlerattr *attr);
bool upb_handlers_setstartseq(upb_handlers *h, const upb_fielddef *f,
                              upb_startfield_handlerfunc *func,
                              upb_handlerattr *attr);
bool upb_handlers_setstartsubmsg(upb_handlers *h, const upb_fielddef *f,
                                 upb_startfield_handlerfunc *func,
                                 upb_handlerattr *attr);
bool upb_handlers_setendsubmsg(upb_handlers *h, const upb_fielddef *f,
                               upb_endfield_handlerfunc *func,
                               upb_handlerattr *attr);
bool upb_handlers_setendseq(upb_handlers *h, const upb_fielddef *f,
                            upb_endfield_handlerfunc *func,
                            upb_handlerattr *attr);

bool upb_handlers_setsubhandlers(upb_handlers *h, const upb_fielddef *f,
                                 const upb_handlers *sub);
const upb_handlers *upb_handlers_getsubhandlers(const upb_handlers *h,
                                                const upb_fielddef *f);
const upb_handlers *upb_handlers_getsubhandlers_sel(const upb_handlers *h,
                                                    upb_selector_t sel);

UPB_INLINE upb_func *upb_handlers_gethandler(const upb_handlers *h,
                                             upb_selector_t s) {
  return (upb_func *)h->table[s].func;
}

bool upb_handlers_getattr(const upb_handlers *h, upb_selector_t s,
                          upb_handlerattr *attr);

UPB_INLINE const void *upb_handlers_gethandlerdata(const upb_handlers *h,
                                                   upb_selector_t s) {
  return upb_handlerattr_handlerdata(&h->table[s].attr);
}

#ifdef __cplusplus

/* Handler types for single fields.
 * Right now we only have one for TYPE_BYTES but ones for other types
 * should follow.
 *
 * These follow the same handlers protocol for fields of a message. */
class upb::BytesHandler {
 public:
  BytesHandler();
  ~BytesHandler();
#else
struct upb_byteshandler {
#endif
  upb_handlers_tabent table[3];
};

void upb_byteshandler_init(upb_byteshandler *h);

/* Caller must ensure that "d" outlives the handlers.
 * TODO(haberman): should this have a "freeze" operation?  It's not necessary
 * for memory management, but could be useful to force immutability and provide
 * a convenient moment to verify that all registration succeeded. */
bool upb_byteshandler_setstartstr(upb_byteshandler *h,
                                  upb_startstr_handlerfunc *func, void *d);
bool upb_byteshandler_setstring(upb_byteshandler *h,
                                upb_string_handlerfunc *func, void *d);
bool upb_byteshandler_setendstr(upb_byteshandler *h,
                                upb_endfield_handlerfunc *func, void *d);

/* "Static" methods */
bool upb_handlers_freeze(upb_handlers *const *handlers, int n, upb_status *s);
upb_handlertype_t upb_handlers_getprimitivehandlertype(const upb_fielddef *f);
bool upb_handlers_getselector(const upb_fielddef *f, upb_handlertype_t type,
                              upb_selector_t *s);
UPB_INLINE upb_selector_t upb_handlers_getendselector(upb_selector_t start) {
  return start + 1;
}

/* Internal-only. */
uint32_t upb_handlers_selectorbaseoffset(const upb_fielddef *f);
uint32_t upb_handlers_selectorcount(const upb_fielddef *f);

UPB_END_EXTERN_C

#include "upb/handlers-inl.h"

#endif  /* UPB_HANDLERS_H */