protobuf/upb/handlers.c

/*
** TODO(haberman): it's unclear whether a lot of the consistency checks should
** UPB_ASSERT() or return false.
*/

#include "upb/handlers.h"
#include "upb/structdefs.int.h"

#include <string.h>

#include "upb/sink.h"

static void *upb_calloc(size_t size) {
  void *mem = upb_gmalloc(size);
  if (mem) {
    memset(mem, 0, size);
  }
  return mem;
}

/* Defined for the sole purpose of having a unique pointer value for
 * UPB_NO_CLOSURE. */
char _upb_noclosure;

static void freehandlers(upb_refcounted *r) {
  upb_handlers *h = (upb_handlers*)r;

  upb_inttable_iter i;
  upb_inttable_begin(&i, &h->cleanup_);
  for(; !upb_inttable_done(&i); upb_inttable_next(&i)) {
    void *val = (void*)upb_inttable_iter_key(&i);
    upb_value func_val = upb_inttable_iter_value(&i);
    upb_handlerfree *func = upb_value_getfptr(func_val);
    func(val);
  }

  upb_inttable_uninit(&h->cleanup_);
  upb_msgdef_unref(h->msg, h);
  upb_gfree(h->sub);
  upb_gfree(h);
}

static void visithandlers(const upb_refcounted *r, upb_refcounted_visit *visit,
                          void *closure) {
  const upb_handlers *h = (const upb_handlers*)r;
  upb_msg_field_iter i;
  for(upb_msg_field_begin(&i, h->msg);
      !upb_msg_field_done(&i);
      upb_msg_field_next(&i)) {
    upb_fielddef *f = upb_msg_iter_field(&i);
    const upb_handlers *sub;
    if (!upb_fielddef_issubmsg(f)) continue;
    sub = upb_handlers_getsubhandlers(h, f);
    if (sub) visit(r, upb_handlers_upcast(sub), closure);
  }
}

static const struct upb_refcounted_vtbl vtbl = {visithandlers, freehandlers};

typedef struct {
  upb_inttable tab;  /* maps upb_msgdef* -> upb_handlers*. */
  upb_handlers_callback *callback;
  const void *closure;
} dfs_state;

/* TODO(haberman): discard upb_handlers* objects that do not actually have any
 * handlers set and cannot reach any upb_handlers* object that does.  This is
 * slightly tricky to do correctly. */
static upb_handlers *newformsg(const upb_msgdef *m, const void *owner,
                               dfs_state *s) {
  upb_msg_field_iter i;
  upb_handlers *h = upb_handlers_new(m, owner);
  if (!h) return NULL;
  if (!upb_inttable_insertptr(&s->tab, m, upb_value_ptr(h))) goto oom;

  s->callback(s->closure, h);

  /* For each submessage field, get or create a handlers object and set it as
   * the subhandlers. */
  for(upb_msg_field_begin(&i, m);
      !upb_msg_field_done(&i);
      upb_msg_field_next(&i)) {
    upb_fielddef *f = upb_msg_iter_field(&i);
    const upb_msgdef *subdef;
    upb_value subm_ent;

    if (!upb_fielddef_issubmsg(f)) continue;

    subdef = upb_downcast_msgdef(upb_fielddef_subdef(f));
    if (upb_inttable_lookupptr(&s->tab, subdef, &subm_ent)) {
      upb_handlers_setsubhandlers(h, f, upb_value_getptr(subm_ent));
    } else {
      upb_handlers *sub_mh = newformsg(subdef, &sub_mh, s);
      if (!sub_mh) goto oom;
      upb_handlers_setsubhandlers(h, f, sub_mh);
      upb_handlers_unref(sub_mh, &sub_mh);
    }
  }
  return h;

oom:
  upb_handlers_unref(h, owner);
  return NULL;
}

/* Given a selector for a STARTSUBMSG handler, resolves to a pointer to the
 * subhandlers for this submessage field. */
#define SUBH(h, selector) (h->sub[selector])

/* The selector for a submessage field is the field index. */
#define SUBH_F(h, f) SUBH(h, f->index_)

static int32_t trygetsel(upb_handlers *h, const upb_fielddef *f,
                         upb_handlertype_t type) {
  upb_selector_t sel;
  UPB_ASSERT(!upb_handlers_isfrozen(h));
  if (upb_handlers_msgdef(h) != upb_fielddef_containingtype(f)) {
    upb_status_seterrf(
        &h->status_, "type mismatch: field %s does not belong to message %s",
        upb_fielddef_name(f), upb_msgdef_fullname(upb_handlers_msgdef(h)));
    return -1;
  }
  if (!upb_handlers_getselector(f, type, &sel)) {
    upb_status_seterrf(
        &h->status_,
        "type mismatch: cannot register handler type %d for field %s",
        type, upb_fielddef_name(f));
    return -1;
  }
  return sel;
}

static upb_selector_t handlers_getsel(upb_handlers *h, const upb_fielddef *f,
                             upb_handlertype_t type) {
  int32_t sel = trygetsel(h, f, type);
  UPB_ASSERT(sel >= 0);
  return sel;
}

static const void **returntype(upb_handlers *h, const upb_fielddef *f,
                               upb_handlertype_t type) {
  return &h->table[handlers_getsel(h, f, type)].attr.return_closure_type_;
}

static bool doset(upb_handlers *h, int32_t sel, const upb_fielddef *f,
                  upb_handlertype_t type, upb_func *func,
                  upb_handlerattr *attr) {
  upb_handlerattr set_attr = UPB_HANDLERATTR_INITIALIZER;
  const void *closure_type;
  const void **context_closure_type;

  UPB_ASSERT(!upb_handlers_isfrozen(h));

  if (sel < 0) {
    upb_status_seterrmsg(&h->status_,
                         "incorrect handler type for this field.");
    return false;
  }

  if (h->table[sel].func) {
    upb_status_seterrmsg(&h->status_,
                         "cannot change handler once it has been set.");
    return false;
  }

  if (attr) {
    set_attr = *attr;
  }

  /* Check that the given closure type matches the closure type that has been
   * established for this context (if any). */
  closure_type = upb_handlerattr_closuretype(&set_attr);

  if (type == UPB_HANDLER_STRING) {
    context_closure_type = returntype(h, f, UPB_HANDLER_STARTSTR);
  } else if (f && upb_fielddef_isseq(f) &&
             type != UPB_HANDLER_STARTSEQ &&
             type != UPB_HANDLER_ENDSEQ) {
    context_closure_type = returntype(h, f, UPB_HANDLER_STARTSEQ);
  } else {
    context_closure_type = &h->top_closure_type;
  }

  if (closure_type && *context_closure_type &&
      closure_type != *context_closure_type) {
    /* TODO(haberman): better message for debugging. */
    if (f) {
      upb_status_seterrf(&h->status_,
                         "closure type does not match for field %s",
                         upb_fielddef_name(f));
    } else {
      upb_status_seterrmsg(
          &h->status_, "closure type does not match for message-level handler");
    }
    return false;
  }

  if (closure_type)
    *context_closure_type = closure_type;

  /* If this is a STARTSEQ or STARTSTR handler, check that the returned pointer
   * matches any pre-existing expectations about what type is expected. */
  if (type == UPB_HANDLER_STARTSEQ || type == UPB_HANDLER_STARTSTR) {
    const void *return_type = upb_handlerattr_returnclosuretype(&set_attr);
    const void *table_return_type =
        upb_handlerattr_returnclosuretype(&h->table[sel].attr);
    if (return_type && table_return_type && return_type != table_return_type) {
      upb_status_seterrmsg(&h->status_, "closure return type does not match");
      return false;
    }

    if (table_return_type && !return_type)
      upb_handlerattr_setreturnclosuretype(&set_attr, table_return_type);
  }

  h->table[sel].func = (upb_func*)func;
  h->table[sel].attr = set_attr;
  return true;
}

/* Returns the effective closure type for this handler (which will propagate
 * from outer frames if this frame has no START* handler).  Not implemented for
 * UPB_HANDLER_STRING at the moment since this is not needed.  Returns NULL is
 * the effective closure type is unspecified (either no handler was registered
 * to specify it or the handler that was registered did not specify the closure
 * type). */
const void *effective_closure_type(upb_handlers *h, const upb_fielddef *f,
                                   upb_handlertype_t type) {
  const void *ret;
  upb_selector_t sel;

  UPB_ASSERT(type != UPB_HANDLER_STRING);
  ret = h->top_closure_type;

  if (upb_fielddef_isseq(f) &&
      type != UPB_HANDLER_STARTSEQ &&
      type != UPB_HANDLER_ENDSEQ &&
      h->table[sel = handlers_getsel(h, f, UPB_HANDLER_STARTSEQ)].func) {
    ret = upb_handlerattr_returnclosuretype(&h->table[sel].attr);
  }

  if (type == UPB_HANDLER_STRING &&
      h->table[sel = handlers_getsel(h, f, UPB_HANDLER_STARTSTR)].func) {
    ret = upb_handlerattr_returnclosuretype(&h->table[sel].attr);
  }

  /* The effective type of the submessage; not used yet.
   * if (type == SUBMESSAGE &&
   *     h->table[sel = handlers_getsel(h, f, UPB_HANDLER_STARTSUBMSG)].func) {
   *   ret = upb_handlerattr_returnclosuretype(&h->table[sel].attr);
   * } */

  return ret;
}

/* Checks whether the START* handler specified by f & type is missing even
 * though it is required to convert the established type of an outer frame
 * ("closure_type") into the established type of an inner frame (represented in
 * the return closure type of this handler's attr. */
bool checkstart(upb_handlers *h, const upb_fielddef *f, upb_handlertype_t type,
                upb_status *status) {
  const void *closure_type;
  const upb_handlerattr *attr;
  const void *return_closure_type;

  upb_selector_t sel = handlers_getsel(h, f, type);
  if (h->table[sel].func) return true;
  closure_type = effective_closure_type(h, f, type);
  attr = &h->table[sel].attr;
  return_closure_type = upb_handlerattr_returnclosuretype(attr);
  if (closure_type && return_closure_type &&
      closure_type != return_closure_type) {
    upb_status_seterrf(status,
                       "expected start handler to return sub type for field %f",
                       upb_fielddef_name(f));
    return false;
  }
  return true;
}

/* Public interface ***********************************************************/

upb_handlers *upb_handlers_new(const upb_msgdef *md, const void *owner) {
  int extra;
  upb_handlers *h;

  UPB_ASSERT(upb_msgdef_isfrozen(md));

  extra = sizeof(upb_handlers_tabent) * (md->selector_count - 1);
  h = upb_calloc(sizeof(*h) + extra);
  if (!h) return NULL;

  h->msg = md;
  upb_msgdef_ref(h->msg, h);
  upb_status_clear(&h->status_);

  if (md->submsg_field_count > 0) {
    h->sub = upb_calloc(md->submsg_field_count * sizeof(*h->sub));
    if (!h->sub) goto oom;
  } else {
    h->sub = 0;
  }

  if (!upb_refcounted_init(upb_handlers_upcast_mutable(h), &vtbl, owner))
    goto oom;
  if (!upb_inttable_init(&h->cleanup_, UPB_CTYPE_FPTR)) goto oom;

  /* calloc() above initialized all handlers to NULL. */
  return h;

oom:
  freehandlers(upb_handlers_upcast_mutable(h));
  return NULL;
}

const upb_handlers *upb_handlers_newfrozen(const upb_msgdef *m,
                                           const void *owner,
                                           upb_handlers_callback *callback,
                                           const void *closure) {
  dfs_state state;
  upb_handlers *ret;
  bool ok;
  upb_refcounted *r;

  state.callback = callback;
  state.closure = closure;
  if (!upb_inttable_init(&state.tab, UPB_CTYPE_PTR)) return NULL;

  ret = newformsg(m, owner, &state);

  upb_inttable_uninit(&state.tab);
  if (!ret) return NULL;

  r = upb_handlers_upcast_mutable(ret);
  ok = upb_refcounted_freeze(&r, 1, NULL, UPB_MAX_HANDLER_DEPTH);
  UPB_ASSERT(ok);

  return ret;
}

const upb_status *upb_handlers_status(upb_handlers *h) {
  UPB_ASSERT(!upb_handlers_isfrozen(h));
  return &h->status_;
}

void upb_handlers_clearerr(upb_handlers *h) {
  UPB_ASSERT(!upb_handlers_isfrozen(h));
  upb_status_clear(&h->status_);
}

#define SETTER(name, handlerctype, handlertype) \
  bool upb_handlers_set ## name(upb_handlers *h, const upb_fielddef *f, \
                                handlerctype func, upb_handlerattr *attr) { \
    int32_t sel = trygetsel(h, f, handlertype); \
    return doset(h, sel, f, handlertype, (upb_func*)func, attr); \
  }

SETTER(int32,       upb_int32_handlerfunc*,       UPB_HANDLER_INT32)
SETTER(int64,       upb_int64_handlerfunc*,       UPB_HANDLER_INT64)
SETTER(uint32,      upb_uint32_handlerfunc*,      UPB_HANDLER_UINT32)
SETTER(uint64,      upb_uint64_handlerfunc*,      UPB_HANDLER_UINT64)
SETTER(float,       upb_float_handlerfunc*,       UPB_HANDLER_FLOAT)
SETTER(double,      upb_double_handlerfunc*,      UPB_HANDLER_DOUBLE)
SETTER(bool,        upb_bool_handlerfunc*,        UPB_HANDLER_BOOL)
SETTER(startstr,    upb_startstr_handlerfunc*,    UPB_HANDLER_STARTSTR)
SETTER(string,      upb_string_handlerfunc*,      UPB_HANDLER_STRING)
SETTER(endstr,      upb_endfield_handlerfunc*,    UPB_HANDLER_ENDSTR)
SETTER(startseq,    upb_startfield_handlerfunc*,  UPB_HANDLER_STARTSEQ)
SETTER(startsubmsg, upb_startfield_handlerfunc*,  UPB_HANDLER_STARTSUBMSG)
SETTER(endsubmsg,   upb_endfield_handlerfunc*,    UPB_HANDLER_ENDSUBMSG)
SETTER(endseq,      upb_endfield_handlerfunc*,    UPB_HANDLER_ENDSEQ)

#undef SETTER

bool upb_handlers_setunknown(upb_handlers *h, upb_unknown_handlerfunc *func,
                             upb_handlerattr *attr) {
  return doset(h, UPB_UNKNOWN_SELECTOR, NULL, UPB_HANDLER_INT32,
               (upb_func *)func, attr);
}

bool upb_handlers_setstartmsg(upb_handlers *h, upb_startmsg_handlerfunc *func,
                              upb_handlerattr *attr) {
  return doset(h, UPB_STARTMSG_SELECTOR, NULL, UPB_HANDLER_INT32,
               (upb_func *)func, attr);
}

bool upb_handlers_setendmsg(upb_handlers *h, upb_endmsg_handlerfunc *func,
                            upb_handlerattr *attr) {
  UPB_ASSERT(!upb_handlers_isfrozen(h));
  return doset(h, UPB_ENDMSG_SELECTOR, NULL, UPB_HANDLER_INT32,
               (upb_func *)func, attr);
}

bool upb_handlers_setsubhandlers(upb_handlers *h, const upb_fielddef *f,
                                 const upb_handlers *sub) {
  UPB_ASSERT(sub);
  UPB_ASSERT(!upb_handlers_isfrozen(h));
  UPB_ASSERT(upb_fielddef_issubmsg(f));
  if (SUBH_F(h, f)) return false;  /* Can't reset. */
  if (upb_msgdef_upcast(upb_handlers_msgdef(sub)) != upb_fielddef_subdef(f)) {
    return false;
  }
  SUBH_F(h, f) = sub;
  upb_ref2(sub, h);
  return true;
}

const upb_handlers *upb_handlers_getsubhandlers(const upb_handlers *h,
                                                const upb_fielddef *f) {
  UPB_ASSERT(upb_fielddef_issubmsg(f));
  return SUBH_F(h, f);
}

bool upb_handlers_getattr(const upb_handlers *h, upb_selector_t sel,
                          upb_handlerattr *attr) {
  if (!upb_handlers_gethandler(h, sel))
    return false;
  *attr = h->table[sel].attr;
  return true;
}

const upb_handlers *upb_handlers_getsubhandlers_sel(const upb_handlers *h,
                                                    upb_selector_t sel) {
  /* STARTSUBMSG selector in sel is the field's selector base. */
  return SUBH(h, sel - UPB_STATIC_SELECTOR_COUNT);
}

const upb_msgdef *upb_handlers_msgdef(const upb_handlers *h) { return h->msg; }

bool upb_handlers_addcleanup(upb_handlers *h, void *p, upb_handlerfree *func) {
  bool ok;
  if (upb_inttable_lookupptr(&h->cleanup_, p, NULL)) {
    return false;
  }
  ok = upb_inttable_insertptr(&h->cleanup_, p, upb_value_fptr(func));
  UPB_ASSERT(ok);
  return true;
}


/* "Static" methods ***********************************************************/

bool upb_handlers_freeze(upb_handlers *const*handlers, int n, upb_status *s) {
  /* TODO: verify we have a transitive closure. */
  int i;
  for (i = 0; i < n; i++) {
    upb_msg_field_iter j;
    upb_handlers *h = handlers[i];

    if (!upb_ok(&h->status_)) {
      upb_status_seterrf(s, "handlers for message %s had error status: %s",
                         upb_msgdef_fullname(upb_handlers_msgdef(h)),
                         upb_status_errmsg(&h->status_));
      return false;
    }

    /* Check that there are no closure mismatches due to missing Start* handlers
     * or subhandlers with different type-level types. */
    for(upb_msg_field_begin(&j, h->msg);
        !upb_msg_field_done(&j);
        upb_msg_field_next(&j)) {

      const upb_fielddef *f = upb_msg_iter_field(&j);
      if (upb_fielddef_isseq(f)) {
        if (!checkstart(h, f, UPB_HANDLER_STARTSEQ, s))
          return false;
      }

      if (upb_fielddef_isstring(f)) {
        if (!checkstart(h, f, UPB_HANDLER_STARTSTR, s))
          return false;
      }

      if (upb_fielddef_issubmsg(f)) {
        bool hashandler = false;
        if (upb_handlers_gethandler(
                h, handlers_getsel(h, f, UPB_HANDLER_STARTSUBMSG)) ||
            upb_handlers_gethandler(
                h, handlers_getsel(h, f, UPB_HANDLER_ENDSUBMSG))) {
          hashandler = true;
        }

        if (upb_fielddef_isseq(f) &&
            (upb_handlers_gethandler(
                 h, handlers_getsel(h, f, UPB_HANDLER_STARTSEQ)) ||
             upb_handlers_gethandler(
                 h, handlers_getsel(h, f, UPB_HANDLER_ENDSEQ)))) {
          hashandler = true;
        }

        if (hashandler && !upb_handlers_getsubhandlers(h, f)) {
          /* For now we add an empty subhandlers in this case.  It makes the
           * decoder code generator simpler, because it only has to handle two
           * cases (submessage has handlers or not) as opposed to three
           * (submessage has handlers in enclosing message but no subhandlers).
           *
           * This makes parsing less efficient in the case that we want to
           * notice a submessage but skip its contents (like if we're testing
           * for submessage presence or counting the number of repeated
           * submessages).  In this case we will end up parsing the submessage
           * field by field and throwing away the results for each, instead of
           * skipping the whole delimited thing at once.  If this is an issue we
           * can revisit it, but do remember that this only arises when you have
           * handlers (startseq/startsubmsg/endsubmsg/endseq) set for the
           * submessage but no subhandlers.  The uses cases for this are
           * limited. */
          upb_handlers *sub = upb_handlers_new(upb_fielddef_msgsubdef(f), &sub);
          upb_handlers_setsubhandlers(h, f, sub);
          upb_handlers_unref(sub, &sub);
        }

        /* TODO(haberman): check type of submessage.
         * This is slightly tricky; also consider whether we should check that
         * they match at setsubhandlers time. */
      }
    }
  }

  if (!upb_refcounted_freeze((upb_refcounted*const*)handlers, n, s,
                             UPB_MAX_HANDLER_DEPTH)) {
    return false;
  }

  return true;
}

upb_handlertype_t upb_handlers_getprimitivehandlertype(const upb_fielddef *f) {
  switch (upb_fielddef_type(f)) {
    case UPB_TYPE_INT32:
    case UPB_TYPE_ENUM: return UPB_HANDLER_INT32;
    case UPB_TYPE_INT64: return UPB_HANDLER_INT64;
    case UPB_TYPE_UINT32: return UPB_HANDLER_UINT32;
    case UPB_TYPE_UINT64: return UPB_HANDLER_UINT64;
    case UPB_TYPE_FLOAT: return UPB_HANDLER_FLOAT;
    case UPB_TYPE_DOUBLE: return UPB_HANDLER_DOUBLE;
    case UPB_TYPE_BOOL: return UPB_HANDLER_BOOL;
    default: UPB_ASSERT(false); return -1;  /* Invalid input. */
  }
}

bool upb_handlers_getselector(const upb_fielddef *f, upb_handlertype_t type,
                              upb_selector_t *s) {
  switch (type) {
    case UPB_HANDLER_INT32:
    case UPB_HANDLER_INT64:
    case UPB_HANDLER_UINT32:
    case UPB_HANDLER_UINT64:
    case UPB_HANDLER_FLOAT:
    case UPB_HANDLER_DOUBLE:
    case UPB_HANDLER_BOOL:
      if (!upb_fielddef_isprimitive(f) ||
          upb_handlers_getprimitivehandlertype(f) != type)
        return false;
      *s = f->selector_base;
      break;
    case UPB_HANDLER_STRING:
      if (upb_fielddef_isstring(f)) {
        *s = f->selector_base;
      } else if (upb_fielddef_lazy(f)) {
        *s = f->selector_base + 3;
      } else {
        return false;
      }
      break;
    case UPB_HANDLER_STARTSTR:
      if (upb_fielddef_isstring(f) || upb_fielddef_lazy(f)) {
        *s = f->selector_base + 1;
      } else {
        return false;
      }
      break;
    case UPB_HANDLER_ENDSTR:
      if (upb_fielddef_isstring(f) || upb_fielddef_lazy(f)) {
        *s = f->selector_base + 2;
      } else {
        return false;
      }
      break;
    case UPB_HANDLER_STARTSEQ:
      if (!upb_fielddef_isseq(f)) return false;
      *s = f->selector_base - 2;
      break;
    case UPB_HANDLER_ENDSEQ:
      if (!upb_fielddef_isseq(f)) return false;
      *s = f->selector_base - 1;
      break;
    case UPB_HANDLER_STARTSUBMSG:
      if (!upb_fielddef_issubmsg(f)) return false;
      /* Selectors for STARTSUBMSG are at the beginning of the table so that the
       * selector can also be used as an index into the "sub" array of
       * subhandlers.  The indexes for the two into these two tables are the
       * same, except that in the handler table the static selectors come first. */
      *s = f->index_ + UPB_STATIC_SELECTOR_COUNT;
      break;
    case UPB_HANDLER_ENDSUBMSG:
      if (!upb_fielddef_issubmsg(f)) return false;
      *s = f->selector_base;
      break;
  }
  UPB_ASSERT((size_t)*s < upb_fielddef_containingtype(f)->selector_count);
  return true;
}

uint32_t upb_handlers_selectorbaseoffset(const upb_fielddef *f) {
  return upb_fielddef_isseq(f) ? 2 : 0;
}

uint32_t upb_handlers_selectorcount(const upb_fielddef *f) {
  uint32_t ret = 1;
  if (upb_fielddef_isseq(f)) ret += 2;    /* STARTSEQ/ENDSEQ */
  if (upb_fielddef_isstring(f)) ret += 2; /* [STRING]/STARTSTR/ENDSTR */
  if (upb_fielddef_issubmsg(f)) {
    /* ENDSUBMSG (STARTSUBMSG is at table beginning) */
    ret += 0;
    if (upb_fielddef_lazy(f)) {
      /* STARTSTR/ENDSTR/STRING (for lazy) */
      ret += 3;
    }
  }
  return ret;
}


/* upb_handlerattr ************************************************************/

void upb_handlerattr_init(upb_handlerattr *attr) {
  upb_handlerattr from = UPB_HANDLERATTR_INITIALIZER;
  memcpy(attr, &from, sizeof(*attr));
}

void upb_handlerattr_uninit(upb_handlerattr *attr) {
  UPB_UNUSED(attr);
}

bool upb_handlerattr_sethandlerdata(upb_handlerattr *attr, const void *hd) {
  attr->handler_data_ = hd;
  return true;
}

bool upb_handlerattr_setclosuretype(upb_handlerattr *attr, const void *type) {
  attr->closure_type_ = type;
  return true;
}

const void *upb_handlerattr_closuretype(const upb_handlerattr *attr) {
  return attr->closure_type_;
}

bool upb_handlerattr_setreturnclosuretype(upb_handlerattr *attr,
                                          const void *type) {
  attr->return_closure_type_ = type;
  return true;
}

const void *upb_handlerattr_returnclosuretype(const upb_handlerattr *attr) {
  return attr->return_closure_type_;
}

bool upb_handlerattr_setalwaysok(upb_handlerattr *attr, bool alwaysok) {
  attr->alwaysok_ = alwaysok;
  return true;
}

bool upb_handlerattr_alwaysok(const upb_handlerattr *attr) {
  return attr->alwaysok_;
}

/* upb_bufhandle **************************************************************/

size_t upb_bufhandle_objofs(const upb_bufhandle *h) {
  return h->objofs_;
}

/* upb_byteshandler ***********************************************************/

void upb_byteshandler_init(upb_byteshandler* h) {
  memset(h, 0, sizeof(*h));
}

/* For when we support handlerfree callbacks. */
void upb_byteshandler_uninit(upb_byteshandler* h) {
  UPB_UNUSED(h);
}

bool upb_byteshandler_setstartstr(upb_byteshandler *h,
                                  upb_startstr_handlerfunc *func, void *d) {
  h->table[UPB_STARTSTR_SELECTOR].func = (upb_func*)func;
  h->table[UPB_STARTSTR_SELECTOR].attr.handler_data_ = d;
  return true;
}

bool upb_byteshandler_setstring(upb_byteshandler *h,
                                upb_string_handlerfunc *func, void *d) {
  h->table[UPB_STRING_SELECTOR].func = (upb_func*)func;
  h->table[UPB_STRING_SELECTOR].attr.handler_data_ = d;
  return true;
}

bool upb_byteshandler_setendstr(upb_byteshandler *h,
                                upb_endfield_handlerfunc *func, void *d) {
  h->table[UPB_ENDSTR_SELECTOR].func = (upb_func*)func;
  h->table[UPB_ENDSTR_SELECTOR].attr.handler_data_ = d;
  return true;
}


/** Handlers for upb_msg ******************************************************/

typedef struct {
  size_t offset;
  int32_t hasbit;
} upb_msg_handlerdata;

/* Fallback implementation if the handler is not specialized by the producer. */
#define MSG_WRITER(type, ctype)                                               \
  bool upb_msg_set ## type (void *c, const void *hd, ctype val) {             \
    uint8_t *m = c;                                                           \
    const upb_msg_handlerdata *d = hd;                                        \
    if (d->hasbit > 0)                                                        \
      *(uint8_t*)&m[d->hasbit / 8] |= 1 << (d->hasbit % 8);                   \
    *(ctype*)&m[d->offset] = val;                                             \
    return true;                                                              \
  }                                                                           \

MSG_WRITER(double, double)
MSG_WRITER(float,  float)
MSG_WRITER(int32,  int32_t)
MSG_WRITER(int64,  int64_t)
MSG_WRITER(uint32, uint32_t)
MSG_WRITER(uint64, uint64_t)
MSG_WRITER(bool,   bool)

bool upb_msg_setscalarhandler(upb_handlers *h, const upb_fielddef *f,
                              size_t offset, int32_t hasbit) {
  upb_handlerattr attr = UPB_HANDLERATTR_INITIALIZER;
  bool ok;

  upb_msg_handlerdata *d = upb_gmalloc(sizeof(*d));
  if (!d) return false;
  d->offset = offset;
  d->hasbit = hasbit;

  upb_handlerattr_sethandlerdata(&attr, d);
  upb_handlerattr_setalwaysok(&attr, true);
  upb_handlers_addcleanup(h, d, upb_gfree);

#define TYPE(u, l) \
  case UPB_TYPE_##u: \
    ok = upb_handlers_set##l(h, f, upb_msg_set##l, &attr); break;

  ok = false;

  switch (upb_fielddef_type(f)) {
    TYPE(INT64,  int64);
    TYPE(INT32,  int32);
    TYPE(ENUM,   int32);
    TYPE(UINT64, uint64);
    TYPE(UINT32, uint32);
    TYPE(DOUBLE, double);
    TYPE(FLOAT,  float);
    TYPE(BOOL,   bool);
    default: UPB_ASSERT(false); break;
  }
#undef TYPE

  upb_handlerattr_uninit(&attr);
  return ok;
}

bool upb_msg_getscalarhandlerdata(const upb_handlers *h,
                                  upb_selector_t s,
                                  upb_fieldtype_t *type,
                                  size_t *offset,
                                  int32_t *hasbit) {
  const upb_msg_handlerdata *d;
  upb_func *f = upb_handlers_gethandler(h, s);

  if ((upb_int64_handlerfunc*)f == upb_msg_setint64) {
    *type = UPB_TYPE_INT64;
  } else if ((upb_int32_handlerfunc*)f == upb_msg_setint32) {
    *type = UPB_TYPE_INT32;
  } else if ((upb_uint64_handlerfunc*)f == upb_msg_setuint64) {
    *type = UPB_TYPE_UINT64;
  } else if ((upb_uint32_handlerfunc*)f == upb_msg_setuint32) {
    *type = UPB_TYPE_UINT32;
  } else if ((upb_double_handlerfunc*)f == upb_msg_setdouble) {
    *type = UPB_TYPE_DOUBLE;
  } else if ((upb_float_handlerfunc*)f == upb_msg_setfloat) {
    *type = UPB_TYPE_FLOAT;
  } else if ((upb_bool_handlerfunc*)f == upb_msg_setbool) {
    *type = UPB_TYPE_BOOL;
  } else {
    return false;
  }

  d = upb_handlers_gethandlerdata(h, s);
  *offset = d->offset;
  *hasbit = d->hasbit;
  return true;
}