Merged core/ and stream/ -> src/. The split wasn't worth it.

1 files changed, 0 insertions, 1349 deletions

diff --git a/core/upb_def.c b/core/upb_def.c
deleted file mode 100644
index 651afc1..0000000
--- a/core/upb_def.c
+++ /dev/null
@@ -1,1349 +0,0 @@
-/*
- * upb - a minimalist implementation of protocol buffers.
- *
- * Copyright (c) 2008-2009 Joshua Haberman.  See LICENSE for details.
- */
-
-#include <stdlib.h>
-#include <stddef.h>
-#include "descriptor_const.h"
-#include "descriptor.h"
-#include "upb_def.h"
-
-#define alignof(t) offsetof(struct { char c; t x; }, x)
-
-/* Rounds p up to the next multiple of t. */
-static size_t upb_align_up(size_t val, size_t align) {
-  return val % align == 0 ? val : val + align - (val % align);
-}
-
-static int upb_div_round_up(int numerator, int denominator) {
-  /* cf. http://stackoverflow.com/questions/17944/how-to-round-up-the-result-of-integer-division */
-  return numerator > 0 ? (numerator - 1) / denominator + 1 : 0;
-}
-
-/* Joins strings together, for example:
- *   join("Foo.Bar", "Baz") -> "Foo.Bar.Baz"
- *   join("", "Baz") -> "Baz"
- * Caller owns a ref on the returned string. */
-static upb_string *upb_join(upb_string *base, upb_string *name) {
-  if (!base || upb_string_len(base) == 0) {
-    return upb_string_getref(name);
-  } else {
-    return upb_string_asprintf(UPB_STRFMT "." UPB_STRFMT,
-                               UPB_STRARG(base), UPB_STRARG(name));
-  }
-}
-
-/* Search for a character in a string, in reverse. */
-static int my_memrchr(char *data, char c, size_t len)
-{
-  int off = len-1;
-  while(off > 0 && data[off] != c) --off;
-  return off;
-}
-
-/* upb_def ********************************************************************/
-
-// Defs are reference counted, but can have cycles when types are
-// self-recursive or mutually recursive, so we need to be capable of collecting
-// the cycles.  In our situation defs are immutable (so cycles cannot be
-// created or destroyed post-initialization).  We need to be thread-safe but
-// want to avoid locks if at all possible and rely only on atomic operations.
-//
-// Our scheme is as follows.  First we give each def a flag indicating whether
-// it is part of a cycle or not.  Because defs are immutable, this flag will
-// never change.  For acyclic defs, we can use a naive algorithm and avoid the
-// overhead of dealing with cycles.  Most defs will be acyclic, and most cycles
-// will be very short.
-//
-// For defs that participate in cycles we keep two reference counts.  One
-// tracks references that come from outside the cycle (we call these external
-// references), and is incremented and decremented like a regular refcount.
-// The other is a cycle refcount, and works as follows.  Every cycle is
-// considered distinct, even if two cycles share members.  For example, this
-// graph has two distinct cycles:
-//
-//   A-->B-->C
-//   ^   |   |
-//   +---+---+
-//
-// The cycles in this graph are AB and ABC.  When A's external refcount
-// transitions from 0->1, we say that A takes "cycle references" on both
-// cycles.  Taking a cycle reference means incrementing the cycle refcount of
-// all defs in the cycle.  Since A and B are common to both cycles, A and B's
-// cycle refcounts will be incremented by two, and C's will be incremented by
-// one.  Likewise, when A's external refcount transitions from 1->0, we
-// decrement A and B's cycle refcounts by two and C's by one.  We collect a
-// cyclic type when its cycle refcount drops to zero.  A precondition for this
-// is that the external refcount has dropped to zero also.
-//
-// This algorithm is relatively cheap, since it only requires extra work when
-// the external refcount on a cyclic type transitions from 0->1 or 1->0.
-
-static void upb_msgdef_free(upb_msgdef *m);
-static void upb_enumdef_free(upb_enumdef *e);
-static void upb_unresolveddef_free(struct _upb_unresolveddef *u);
-
-static void upb_def_free(upb_def *def)
-{
-  switch(def->type) {
-    case UPB_DEF_MSG:
-      upb_msgdef_free(upb_downcast_msgdef(def));
-      break;
-    case UPB_DEF_ENUM:
-      upb_enumdef_free(upb_downcast_enumdef(def));
-      break;
-    case UPB_DEF_SVC:
-      assert(false);  /* Unimplemented. */
-      break;
-    case UPB_DEF_UNRESOLVED:
-      upb_unresolveddef_free(upb_downcast_unresolveddef(def));
-      break;
-    default:
-      assert(false);
-  }
-}
-
-// Depth-first search for all cycles that include cycle_base.  Returns the
-// number of paths from def that lead to cycle_base, which is equivalent to the
-// number of cycles def is in that include cycle_base.
-//
-// open_defs tracks the set of nodes that are currently being visited in the
-// search so we can stop the search if we detect a cycles that do not involve
-// cycle_base.  We can't color the nodes as we go by writing to a member of the
-// def, because another thread could be performing the search concurrently.
-static int upb_cycle_ref_or_unref(upb_msgdef *m, upb_msgdef *cycle_base,
-                                  upb_msgdef **open_defs, int num_open_defs,
-                                  bool ref) {
-  bool found = false;
-  for(int i = 0; i < num_open_defs; i++) {
-    if(open_defs[i] == m) {
-      // We encountered a cycle that did not involve cycle_base.
-      found = true;
-      break;
-    }
-  }
-
-  if(found || num_open_defs == UPB_MAX_TYPE_CYCLE_LEN) {
-    return 0;
-  } else if(m == cycle_base) {
-    return 1;
-  } else {
-    int path_count = 0;
-    if(cycle_base == NULL) {
-      cycle_base = m;
-    } else {
-      open_defs[num_open_defs++] = m;
-    }
-    upb_msg_iter iter = upb_msg_begin(m);
-    for(; !upb_msg_done(iter); iter = upb_msg_next(m, iter)) {
-      upb_fielddef *f = upb_msg_iter_field(iter);
-      upb_def *def = f->def;
-      if(upb_issubmsg(f) && def->is_cyclic) {
-        upb_msgdef *sub_m = upb_downcast_msgdef(def);
-        path_count += upb_cycle_ref_or_unref(sub_m, cycle_base, open_defs,
-                                         num_open_defs, ref);
-      }
-    }
-    if(ref) {
-      upb_atomic_add(&m->cycle_refcount, path_count);
-    } else {
-      if(upb_atomic_add(&m->cycle_refcount, -path_count))
-        upb_def_free(UPB_UPCAST(m));
-    }
-    return path_count;
-  }
-}
-
-void _upb_def_reftozero(upb_def *def) {
-  if(def->is_cyclic) {
-    upb_msgdef *m = upb_downcast_msgdef(def);
-    upb_msgdef *open_defs[UPB_MAX_TYPE_CYCLE_LEN];
-    upb_cycle_ref_or_unref(m, NULL, open_defs, 0, false);
-  } else {
-    upb_def_free(def);
-  }
-}
-
-void _upb_def_cyclic_ref(upb_def *def) {
-  upb_msgdef *open_defs[UPB_MAX_TYPE_CYCLE_LEN];
-  upb_cycle_ref_or_unref(upb_downcast_msgdef(def), NULL, open_defs, 0, true);
-}
-
-static void upb_def_init(upb_def *def, upb_deftype type) {
-  def->type = type;
-  def->is_cyclic = 0;  // We detect this later, after resolving refs.
-  def->search_depth = 0;
-  def->fqname = NULL;
-  upb_atomic_refcount_init(&def->refcount, 1);
-}
-
-static void upb_def_uninit(upb_def *def) {
-  upb_string_unref(def->fqname);
-}
-
-
-/* upb_defbuilder  ************************************************************/
-
-// A upb_defbuilder builds a list of defs by handling a parse of a protobuf in
-// the format defined in descriptor.proto.  The output of a upb_defbuilder is
-// a list of upb_def* that possibly contain unresolved references.
-//
-// We use a separate object (upb_defbuilder) instead of having the defs handle
-// the parse themselves because we need to store state that is only necessary
-// during the building process itself.
-
-// When we are bootstrapping descriptor.proto, we must help the bare decoder out
-// by telling it when to descend into a submessage, because with the wire format
-// alone we cannot tell the difference between a submessage and a string.
-//
-// TODO: In the long-term, we should bootstrap from a serialization format that
-// contains this information, so we can remove this special-case code.  This
-// would involve defining a serialization format very similar to the existing
-// protobuf format, but that contains more information about the wire type.
-#define BEGIN_SUBMSG 100
-
-// upb_deflist: A little dynamic array for storing a growing list of upb_defs.
-typedef struct {
-  upb_def **defs;
-  uint32_t len;
-  uint32_t size;
-} upb_deflist;
-
-static void upb_deflist_init(upb_deflist *l) {
-  l->size = 8;
-  l->defs = malloc(l->size * sizeof(void*));
-  l->len = 0;
-}
-
-static void upb_deflist_uninit(upb_deflist *l) {
-  for(uint32_t i = 0; i < l->len; i++)
-    if(l->defs[i]) upb_def_unref(l->defs[i]);
-  free(l->defs);
-}
-
-static void upb_deflist_push(upb_deflist *l, upb_def *d) {
-  if(l->len == l->size) {
-    l->size *= 2;
-    l->defs = realloc(l->defs, l->size * sizeof(void*));
-  }
-  l->defs[l->len++] = d;
-}
-
-static upb_def *upb_deflist_last(upb_deflist *l) {
-  return l->defs[l->len-1];
-}
-
-// Qualify the defname for all defs starting with offset "start" with "str".
-static void upb_deflist_qualify(upb_deflist *l, upb_string *str, int32_t start) {
-  for(uint32_t i = start; i < l->len; i++) {
-    upb_def *def = l->defs[i];
-    upb_string *name = def->fqname;
-    def->fqname = upb_join(str, name);
-    upb_string_unref(name);
-  }
-}
-
-// We keep a stack of all the messages scopes we are currently in, as well as
-// the top-level file scope.  This is necessary to correctly qualify the
-// definitions that are contained inside.  "name" tracks the name of the
-// message or package (a bare name -- not qualified by any enclosing scopes).
-typedef struct {
-  upb_string *name;
-  // Index of the first def that is under this scope.  For msgdefs, the
-  // msgdef itself is at start-1.
-  int start;
-} upb_defbuilder_frame;
-
-struct _upb_defbuilder {
-  upb_deflist defs;
-  upb_defbuilder_frame stack[UPB_MAX_TYPE_DEPTH];
-  int stack_len;
-  upb_status status;
-
-  uint32_t number;
-  upb_string *name;
-  bool saw_number;
-  bool saw_name;
-
-  upb_fielddef *f;
-};
-typedef struct _upb_defbuilder upb_defbuilder;
-
-// Forward declares for top-level file descriptors.
-static void upb_msgdef_register_DescriptorProto(upb_defbuilder *b, upb_handlers *h);
-static void upb_enumdef_register_EnumDescriptorProto(upb_defbuilder *b,
-                                                     upb_handlers *h);
-
-
-static void upb_defbuilder_init(upb_defbuilder *b) {
-  upb_deflist_init(&b->defs);
-  upb_status_init(&b->status);
-  b->stack_len = 0;
-  b->name = NULL;
-}
-
-static void upb_defbuilder_uninit(upb_defbuilder *b) {
-  upb_string_unref(b->name);
-  upb_status_uninit(&b->status);
-  upb_deflist_uninit(&b->defs);
-}
-
-static upb_msgdef *upb_defbuilder_top(upb_defbuilder *b) {
-  if (b->stack_len <= 1) return NULL;
-  int index = b->stack[b->stack_len-1].start - 1;
-  assert(index >= 0);
-  return upb_downcast_msgdef(b->defs.defs[index]);
-}
-
-static upb_def *upb_defbuilder_last(upb_defbuilder *b) {
-  return upb_deflist_last(&b->defs);
-}
-
-// Start/end handlers for FileDescriptorProto and DescriptorProto (the two
-// entities that have names and can contain sub-definitions.
-void upb_defbuilder_startcontainer(upb_defbuilder *b) {
-  upb_defbuilder_frame *f = &b->stack[b->stack_len++];
-  f->start = b->defs.len;
-  f->name = NULL;
-}
-
-void upb_defbuilder_endcontainer(upb_defbuilder *b) {
-  upb_defbuilder_frame *f = &b->stack[--b->stack_len];
-  upb_deflist_qualify(&b->defs, f->name, f->start);
-  upb_string_unref(f->name);
-}
-
-void upb_defbuilder_setscopename(upb_defbuilder *b, upb_string *str) {
-  upb_defbuilder_frame *f = &b->stack[b->stack_len-1];
-  upb_string_unref(f->name);
-  f->name = upb_string_getref(str);
-}
-
-// Handlers for google.protobuf.FileDescriptorProto.
-static upb_flow_t upb_defbuilder_FileDescriptorProto_startmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  upb_defbuilder_startcontainer(b);
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_defbuilder_FileDescriptorProto_endmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  upb_defbuilder_endcontainer(b);
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_defbuilder_FileDescriptorProto_value(void *_b,
-                                                           upb_fielddef *f,
-                                                           upb_value val) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_PACKAGE_FIELDNUM:
-      upb_defbuilder_setscopename(b, upb_value_getstr(val));
-      break;
-    case GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_MESSAGE_TYPE_FIELDNUM:
-    case GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_ENUM_TYPE_FIELDNUM:
-      return BEGIN_SUBMSG;
-  }
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_defbuilder_FileDescriptorProto_startsubmsg(
-    void *_b, upb_fielddef *f, upb_handlers *h) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_MESSAGE_TYPE_FIELDNUM:
-      upb_msgdef_register_DescriptorProto(b, h);
-      return UPB_DELEGATE;
-    case GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_ENUM_TYPE_FIELDNUM:
-      upb_enumdef_register_EnumDescriptorProto(b, h);
-      return UPB_DELEGATE;
-    default:
-      // TODO: services and extensions.
-      return UPB_SKIPSUBMSG;
-  }
-}
-
-static void upb_defbuilder_register_FileDescriptorProto(upb_defbuilder *b,
-                                                        upb_handlers *h) {
-  static upb_handlerset handlers = {
-    &upb_defbuilder_FileDescriptorProto_startmsg,
-    &upb_defbuilder_FileDescriptorProto_endmsg,
-    &upb_defbuilder_FileDescriptorProto_value,
-    &upb_defbuilder_FileDescriptorProto_startsubmsg,
-  };
-  upb_register_handlerset(h, &handlers);
-  upb_set_handler_closure(h, b, &b->status);
-}
-
-// Handlers for google.protobuf.FileDescriptorSet.
-static upb_flow_t upb_defbuilder_FileDescriptorSet_value(void *b,
-                                                         upb_fielddef *f,
-                                                         upb_value val) {
-  (void)b;
-  (void)val;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_FILEDESCRIPTORSET_FILE_FIELDNUM:
-      return BEGIN_SUBMSG;
-  }
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_defbuilder_FileDescriptorSet_startsubmsg(
-    void *_b, upb_fielddef *f, upb_handlers *h) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_FILEDESCRIPTORSET_FILE_FIELDNUM:
-      upb_defbuilder_register_FileDescriptorProto(b, h);
-      return UPB_DELEGATE;
-  }
-  return UPB_SKIPSUBMSG;
-}
-
-static void upb_defbuilder_register_FileDescriptorSet(
-    upb_defbuilder *b, upb_handlers *h) {
-  static upb_handlerset handlers = {
-    NULL,  // startmsg
-    NULL,  // endmsg
-    &upb_defbuilder_FileDescriptorSet_value,
-    &upb_defbuilder_FileDescriptorSet_startsubmsg,
-  };
-  upb_register_handlerset(h, &handlers);
-  upb_set_handler_closure(h, b, &b->status);
-}
-
-
-/* upb_unresolveddef **********************************************************/
-
-// Unresolved defs are used as temporary placeholders for a def whose name has
-// not been resolved yet.  During the name resolution step, all unresolved defs
-// are replaced with pointers to the actual def being referenced.
-typedef struct _upb_unresolveddef {
-  upb_def base;
-
-  // The target type name.  This may or may not be fully qualified.  It is
-  // tempting to want to use base.fqname for this, but that will be qualified
-  // which is inappropriate for a name we still have to resolve.
-  upb_string *name;
-} upb_unresolveddef;
-
-// Is passed a ref on the string.
-static upb_unresolveddef *upb_unresolveddef_new(upb_string *str) {
-  upb_unresolveddef *def = malloc(sizeof(*def));
-  upb_def_init(&def->base, UPB_DEF_UNRESOLVED);
-  def->name = upb_string_getref(str);
-  return def;
-}
-
-static void upb_unresolveddef_free(struct _upb_unresolveddef *def) {
-  upb_string_unref(def->name);
-  upb_def_uninit(&def->base);
-  free(def);
-}
-
-
-/* upb_enumdef ****************************************************************/
-
-static void upb_enumdef_free(upb_enumdef *e) {
-  upb_enum_iter i;
-  for(i = upb_enum_begin(e); !upb_enum_done(i); i = upb_enum_next(e, i)) {
-    // Frees the ref taken when the string was parsed.
-    upb_string_unref(upb_enum_iter_name(i));
-  }
-  upb_strtable_free(&e->ntoi);
-  upb_inttable_free(&e->iton);
-  upb_def_uninit(&e->base);
-  free(e);
-}
-
-// google.protobuf.EnumValueDescriptorProto.
-static upb_flow_t upb_enumdef_EnumValueDescriptorProto_startmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  b->saw_number = false;
-  b->saw_name = false;
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_enumdef_EnumValueDescriptorProto_value(void *_b,
-                                                             upb_fielddef *f,
-                                                             upb_value val) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_NAME_FIELDNUM:
-      upb_string_unref(b->name);
-      b->name = upb_string_getref(upb_value_getstr(val));
-      b->saw_name = true;
-      break;
-    case GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_NUMBER_FIELDNUM:
-      b->number = upb_value_getint32(val);
-      b->saw_number = true;
-      break;
-    default:
-      break;
-  }
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_enumdef_EnumValueDescriptorProto_endmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  if(!b->saw_number || !b->saw_name) {
-    upb_seterr(&b->status, UPB_ERROR, "Enum value missing name or number.");
-    return UPB_BREAK;
-  }
-  upb_ntoi_ent ntoi_ent = {{b->name, 0}, b->number};
-  upb_iton_ent iton_ent = {{b->number, 0}, b->name};
-  upb_enumdef *e = upb_downcast_enumdef(upb_defbuilder_last(b));
-  upb_strtable_insert(&e->ntoi, &ntoi_ent.e);
-  upb_inttable_insert(&e->iton, &iton_ent.e);
-  // We don't unref "name" because we pass our ref to the iton entry of the
-  // table.  strtables can ref their keys, but the inttable doesn't know that
-  // the value is a string.
-  b->name = NULL;
-  return UPB_CONTINUE;
-}
-
-static void upb_enumdef_register_EnumValueDescriptorProto(upb_defbuilder *b,
-                                                          upb_handlers *h) {
-  static upb_handlerset handlers = {
-    &upb_enumdef_EnumValueDescriptorProto_startmsg,
-    &upb_enumdef_EnumValueDescriptorProto_endmsg,
-    &upb_enumdef_EnumValueDescriptorProto_value,
-  };
-  upb_register_handlerset(h, &handlers);
-  upb_set_handler_closure(h, b, &b->status);
-}
-
-// google.protobuf.EnumDescriptorProto.
-static upb_flow_t upb_enumdef_EnumDescriptorProto_startmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  upb_enumdef *e = malloc(sizeof(*e));
-  upb_def_init(&e->base, UPB_DEF_ENUM);
-  upb_strtable_init(&e->ntoi, 0, sizeof(upb_ntoi_ent));
-  upb_inttable_init(&e->iton, 0, sizeof(upb_iton_ent));
-  upb_deflist_push(&b->defs, UPB_UPCAST(e));
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_enumdef_EnumDescriptorProto_endmsg(void *_b) {
-  (void)_b;
-  assert(upb_defbuilder_last((upb_defbuilder*)_b)->fqname != NULL);
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_enumdef_EnumDescriptorProto_value(void *_b,
-                                                        upb_fielddef *f,
-                                                        upb_value val) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_NAME_FIELDNUM: {
-      upb_enumdef *e = upb_downcast_enumdef(upb_defbuilder_last(b));
-      upb_string_unref(e->base.fqname);
-      e->base.fqname = upb_string_getref(upb_value_getstr(val));
-      return UPB_CONTINUE;
-    }
-    case GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_VALUE_FIELDNUM:
-      return BEGIN_SUBMSG;
-    default:
-      return UPB_CONTINUE;
-  }
-}
-
-static upb_flow_t upb_enumdef_EnumDescriptorProto_startsubmsg(void *_b,
-                                                              upb_fielddef *f,
-                                                              upb_handlers *h) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_VALUE_FIELDNUM:
-      upb_enumdef_register_EnumValueDescriptorProto(b, h);
-      return UPB_DELEGATE;
-    default:
-      return UPB_SKIPSUBMSG;
-  }
-}
-
-static void upb_enumdef_register_EnumDescriptorProto(upb_defbuilder *b,
-                                                     upb_handlers *h) {
-  static upb_handlerset handlers = {
-    &upb_enumdef_EnumDescriptorProto_startmsg,
-    &upb_enumdef_EnumDescriptorProto_endmsg,
-    &upb_enumdef_EnumDescriptorProto_value,
-    &upb_enumdef_EnumDescriptorProto_startsubmsg,
-  };
-  upb_register_handlerset(h, &handlers);
-  upb_set_handler_closure(h, b, &b->status);
-}
-
-upb_enum_iter upb_enum_begin(upb_enumdef *e) {
-  // We could iterate over either table here; the choice is arbitrary.
-  return upb_inttable_begin(&e->iton);
-}
-
-upb_enum_iter upb_enum_next(upb_enumdef *e, upb_enum_iter iter) {
-  assert(iter);
-  return upb_inttable_next(&e->iton, &iter->e);
-}
-
-upb_string *upb_enumdef_iton(upb_enumdef *def, upb_enumval_t num) {
-  upb_iton_ent *e =
-      (upb_iton_ent*)upb_inttable_fastlookup(&def->iton, num, sizeof(*e));
-  return e ? e->string : NULL;
-}
-
-
-/* upb_fielddef ***************************************************************/
-
-static void upb_fielddef_free(upb_fielddef *f) {
-  upb_string_unref(f->name);
-  if(f->owned) {
-    upb_def_unref(f->def);
-  }
-  free(f);
-}
-
-static upb_flow_t upb_fielddef_startmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  upb_fielddef *f = malloc(sizeof(*f));
-  f->number = -1;
-  f->name = NULL;
-  f->def = NULL;
-  f->owned = false;
-  f->msgdef = upb_defbuilder_top(b);
-  b->f = f;
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_fielddef_endmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  upb_fielddef *f = b->f;
-  // TODO: verify that all required fields were present.
-  assert(f->number != -1 && f->name != NULL);
-  assert((f->def != NULL) == upb_hasdef(f));
-
-  // Field was successfully read, add it as a field of the msgdef.
-  upb_msgdef *m = upb_defbuilder_top(b);
-  upb_itof_ent itof_ent = {{f->number, 0}, f};
-  upb_ntof_ent ntof_ent = {{f->name, 0}, f};
-  upb_inttable_insert(&m->itof, &itof_ent.e);
-  upb_strtable_insert(&m->ntof, &ntof_ent.e);
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_fielddef_value(void *_b, upb_fielddef *f, upb_value val) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_FIELDNUM:
-      b->f->type = upb_value_getenumval(val);
-      break;
-    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_FIELDNUM:
-      b->f->label = upb_value_getenumval(val);
-      break;
-    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_NUMBER_FIELDNUM:
-      b->f->number = upb_value_getint32(val);
-      break;
-    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_NAME_FIELDNUM:
-      upb_string_unref(b->f->name);
-      b->f->name = upb_string_getref(upb_value_getstr(val));
-      break;
-    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_NAME_FIELDNUM: {
-      upb_def_unref(b->f->def);
-      b->f->def = UPB_UPCAST(upb_unresolveddef_new(upb_value_getstr(val)));
-      b->f->owned = true;
-      break;
-    }
-  }
-  return UPB_CONTINUE;
-}
-
-static void upb_fielddef_register_FieldDescriptorProto(upb_defbuilder *b,
-                                                       upb_handlers *h) {
-  static upb_handlerset handlers = {
-    &upb_fielddef_startmsg,
-    &upb_fielddef_endmsg,
-    &upb_fielddef_value,
-  };
-  upb_register_handlerset(h, &handlers);
-  upb_set_handler_closure(h, b, &b->status);
-}
-
-
-/* upb_msgdef *****************************************************************/
-
-static int upb_compare_typed_fields(upb_fielddef *f1, upb_fielddef *f2) {
-  // Sort by data size (ascending) to reduce padding.
-  size_t size1 = upb_types[f1->type].size;
-  size_t size2 = upb_types[f2->type].size;
-  if (size1 != size2) return size1 - size2;
-  // Otherwise return in number order (just so we get a reproduceable order.
-  return f1->number - f2->number;
-}
-
-static int upb_compare_fields(const void *f1, const void *f2) {
-  return upb_compare_typed_fields(*(void**)f1, *(void**)f2);
-}
-
-// google.protobuf.DescriptorProto.
-static upb_flow_t upb_msgdef_startmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  upb_msgdef *m = malloc(sizeof(*m));
-  upb_def_init(&m->base, UPB_DEF_MSG);
-  upb_atomic_refcount_init(&m->cycle_refcount, 0);
-  upb_inttable_init(&m->itof, 4, sizeof(upb_itof_ent));
-  upb_strtable_init(&m->ntof, 4, sizeof(upb_ntof_ent));
-  upb_deflist_push(&b->defs, UPB_UPCAST(m));
-  upb_defbuilder_startcontainer(b);
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_msgdef_endmsg(void *_b) {
-  upb_defbuilder *b = _b;
-  upb_msgdef *m = upb_defbuilder_top(b);
-  if(!m->base.fqname) {
-    upb_seterr(&b->status, UPB_ERROR, "Encountered message with no name.");
-    return UPB_BREAK;
-  }
-
-  // Create an ordering over the fields.
-  upb_field_count_t n = upb_msgdef_numfields(m);
-  upb_fielddef **sorted_fields = malloc(sizeof(upb_fielddef*) * n);
-  upb_field_count_t field = 0;
-  upb_msg_iter i;
-  for (i = upb_msg_begin(m); !upb_msg_done(i); i = upb_msg_next(m, i)) {
-    sorted_fields[field++]= upb_msg_iter_field(i);
-  }
-  qsort(sorted_fields, n, sizeof(*sorted_fields), upb_compare_fields);
-
-  // Assign offsets in the msg.
-  m->set_flags_bytes = upb_div_round_up(n, 8);
-  m->size = sizeof(upb_atomic_refcount_t) + m->set_flags_bytes;
-
-  size_t max_align = 0;
-  for (int i = 0; i < n; i++) {
-    upb_fielddef *f = sorted_fields[i];
-    const upb_type_info *type_info = &upb_types[f->type];
-
-    // This identifies the set bit.  When we implement is_initialized (a
-    // general check about whether all required bits are set) we will probably
-    // want to use a different ordering that puts all the required bits
-    // together.
-    f->field_index = i;
-    f->set_bit_mask = 1 << (i % 8);
-    f->set_bit_offset = i / 8;
-
-    size_t size, align;
-    if (upb_isarray(f)) {
-      size = sizeof(void*);
-      align = alignof(void*);
-    } else {
-      size = type_info->size;
-      align = type_info->align;
-    }
-    // General alignment rules are: each member must be at an address that is a
-    // multiple of that type's alignment.  Also, the size of the structure as a
-    // whole must be a multiple of the greatest alignment of any member.
-    size_t offset = upb_align_up(m->size, align);
-    // Offsets are relative to the end of the refcount.
-    f->byte_offset = offset - sizeof(upb_atomic_refcount_t);
-    m->size = offset + size;
-    max_align = UPB_MAX(max_align, align);
-  }
-  free(sorted_fields);
-
-  if (max_align > 0) m->size = upb_align_up(m->size, max_align);
-
-  upb_defbuilder_endcontainer(b);
-  return UPB_CONTINUE;
-}
-
-static upb_flow_t upb_msgdef_value(void *_b, upb_fielddef *f, upb_value val) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_DESCRIPTORPROTO_NAME_FIELDNUM: {
-      upb_msgdef *m = upb_defbuilder_top(b);
-      upb_string_unref(m->base.fqname);
-      m->base.fqname = upb_string_getref(upb_value_getstr(val));
-      upb_defbuilder_setscopename(b, upb_value_getstr(val));
-      return UPB_CONTINUE;
-    }
-    case GOOGLE_PROTOBUF_DESCRIPTORPROTO_FIELD_FIELDNUM:
-    case GOOGLE_PROTOBUF_DESCRIPTORPROTO_NESTED_TYPE_FIELDNUM:
-    case GOOGLE_PROTOBUF_DESCRIPTORPROTO_ENUM_TYPE_FIELDNUM:
-      return BEGIN_SUBMSG;
-    default:
-      // TODO: extensions.
-      return UPB_CONTINUE;
-  }
-}
-
-static upb_flow_t upb_msgdef_startsubmsg(void *_b, upb_fielddef *f,
-                                         upb_handlers *h) {
-  upb_defbuilder *b = _b;
-  switch(f->number) {
-    case GOOGLE_PROTOBUF_DESCRIPTORPROTO_FIELD_FIELDNUM:
-      upb_fielddef_register_FieldDescriptorProto(b, h);
-      return UPB_DELEGATE;
-    case GOOGLE_PROTOBUF_DESCRIPTORPROTO_NESTED_TYPE_FIELDNUM:
-      upb_msgdef_register_DescriptorProto(b, h);
-      return UPB_DELEGATE;
-    case GOOGLE_PROTOBUF_DESCRIPTORPROTO_ENUM_TYPE_FIELDNUM:
-      upb_enumdef_register_EnumDescriptorProto(b, h);
-      return UPB_DELEGATE;
-      break;
-    default:
-      return UPB_SKIPSUBMSG;
-  }
-}
-
-static void upb_msgdef_register_DescriptorProto(upb_defbuilder *b,
-                                                upb_handlers *h) {
-  static upb_handlerset handlers = {
-    &upb_msgdef_startmsg,
-    &upb_msgdef_endmsg,
-    &upb_msgdef_value,
-    &upb_msgdef_startsubmsg,
-  };
-  upb_register_handlerset(h, &handlers);
-  upb_set_handler_closure(h, b, &b->status);
-}
-
-static void upb_msgdef_free(upb_msgdef *m)
-{
-  upb_msg_iter i;
-  for(i = upb_msg_begin(m); !upb_msg_done(i); i = upb_msg_next(m, i))
-    upb_fielddef_free(upb_msg_iter_field(i));
-  upb_strtable_free(&m->ntof);
-  upb_inttable_free(&m->itof);
-  upb_def_uninit(&m->base);
-  free(m);
-}
-
-static void upb_msgdef_resolve(upb_msgdef *m, upb_fielddef *f, upb_def *def) {
-  (void)m;
-  if(f->owned) upb_def_unref(f->def);
-  f->def = def;
-  // We will later make the ref unowned if it is a part of a cycle.
-  f->owned = true;
-  upb_def_ref(def);
-}
-
-upb_msg_iter upb_msg_begin(upb_msgdef *m) {
-  return upb_inttable_begin(&m->itof);
-}
-
-upb_msg_iter upb_msg_next(upb_msgdef *m, upb_msg_iter iter) {
-  return upb_inttable_next(&m->itof, &iter->e);
-}
-
-/* upb_symtab adding defs *****************************************************/
-
-// This is a self-contained group of functions that, given a list of upb_defs
-// whose references are not yet resolved, resolves references and adds them
-// atomically to a upb_symtab.
-
-typedef struct {
-  upb_strtable_entry e;
-  upb_def *def;
-} upb_symtab_ent;
-
-// Given a symbol and the base symbol inside which it is defined, find the
-// symbol's definition in t.
-static upb_symtab_ent *upb_resolve(upb_strtable *t,
-                                   upb_string *base, upb_string *sym)
-{
-  if(upb_string_len(base) + upb_string_len(sym) + 1 >= UPB_SYMBOL_MAXLEN ||
-     upb_string_len(sym) == 0) return NULL;
-
-  if(upb_string_getrobuf(sym)[0] == UPB_SYMBOL_SEPARATOR) {
-    // Symbols starting with '.' are absolute, so we do a single lookup.
-    // Slice to omit the leading '.'
-    upb_string *sym_str = upb_strslice(sym, 1, upb_string_len(sym) - 1);
-    upb_symtab_ent *e = upb_strtable_lookup(t, sym_str);
-    upb_string_unref(sym_str);
-    return e;
-  } else {
-    // Remove components from base until we find an entry or run out.
-    // TODO: This branch is totally broken, but currently not used.
-    upb_string *sym_str = upb_string_new();
-    int baselen = upb_string_len(base);
-    while(1) {
-      // sym_str = base[0...base_len] + UPB_SYMBOL_SEPARATOR + sym
-      upb_strlen_t len = baselen + upb_string_len(sym) + 1;
-      char *buf = upb_string_getrwbuf(sym_str, len);
-      memcpy(buf, upb_string_getrobuf(base), baselen);
-      buf[baselen] = UPB_SYMBOL_SEPARATOR;
-      memcpy(buf + baselen + 1, upb_string_getrobuf(sym), upb_string_len(sym));
-
-      upb_symtab_ent *e = upb_strtable_lookup(t, sym_str);
-      if (e) return e;
-      else if(baselen == 0) return NULL;  // No more scopes to try.
-
-      baselen = my_memrchr(buf, UPB_SYMBOL_SEPARATOR, baselen);
-    }
-  }
-}
-
-// Performs a pass over the type graph to find all cycles that include m.
-static bool upb_symtab_findcycles(upb_msgdef *m, int depth, upb_status *status)
-{
-  if(depth > UPB_MAX_TYPE_DEPTH) {
-    // We have found a non-cyclic path from the base of the type tree that
-    // exceeds the maximum allowed depth.  There are many situations in upb
-    // where we recurse over the type tree (like for example, right now) and an
-    // absurdly deep tree could cause us to stack overflow on systems with very
-    // limited stacks.
-    upb_seterr(status, UPB_ERROR, "Type " UPB_STRFMT " was found at "
-               "depth %d in the type graph, which exceeds the maximum type "
-               "depth of %d.", UPB_UPCAST(m)->fqname, depth,
-               UPB_MAX_TYPE_DEPTH);
-    return false;
-  } else if(UPB_UPCAST(m)->search_depth == 1) {
-    // Cycle!
-    int cycle_len = depth - 1;
-    if(cycle_len > UPB_MAX_TYPE_CYCLE_LEN) {
-      upb_seterr(status, UPB_ERROR, "Type " UPB_STRFMT " was involved "
-                 "in a cycle of length %d, which exceeds the maximum type "
-                 "cycle length of %d.", UPB_UPCAST(m)->fqname, cycle_len,
-                 UPB_MAX_TYPE_CYCLE_LEN);
-      return false;
-    }
-    return true;
-  } else if(UPB_UPCAST(m)->search_depth > 0) {
-    // This was a cycle, but did not originate from the base of our search tree.
-    // We'll find it when we call find_cycles() on this node directly.
-    return false;
-  } else {
-    UPB_UPCAST(m)->search_depth = ++depth;
-    bool cycle_found = false;
-    upb_msg_iter i;
-    for(i = upb_msg_begin(m); !upb_msg_done(i); i = upb_msg_next(m, i)) {
-      upb_fielddef *f = upb_msg_iter_field(i);
-      if(!upb_issubmsg(f)) continue;
-      upb_def *sub_def = f->def;
-      upb_msgdef *sub_m = upb_downcast_msgdef(sub_def);
-      if(upb_symtab_findcycles(sub_m, depth, status)) {
-        cycle_found = true;
-        UPB_UPCAST(m)->is_cyclic = true;
-        if(f->owned) {
-          upb_atomic_unref(&sub_def->refcount);
-          f->owned = false;
-        }
-      }
-    }
-    UPB_UPCAST(m)->search_depth = 0;
-    return cycle_found;
-  }
-}
-
-// Given a table of pending defs "tmptab" and a table of existing defs "symtab",
-// resolves all of the unresolved refs for the defs in tmptab.
-bool upb_resolverefs(upb_strtable *tmptab, upb_strtable *symtab,
-                     upb_status *status)
-{
-  upb_symtab_ent *e;
-  for(e = upb_strtable_begin(tmptab); e; e = upb_strtable_next(tmptab, &e->e)) {
-    upb_msgdef *m = upb_dyncast_msgdef(e->def);
-    if(!m) continue;
-    // Type names are resolved relative to the message in which they appear.
-    upb_string *base = e->e.key;
-
-    upb_msg_iter i;
-    for(i = upb_msg_begin(m); !upb_msg_done(i); i = upb_msg_next(m, i)) {
-      upb_fielddef *f = upb_msg_iter_field(i);
-      if(!upb_hasdef(f)) continue;  // No resolving necessary.
-      upb_string *name = upb_downcast_unresolveddef(f->def)->name;
-
-      // Resolve from either the tmptab (pending adds) or symtab (existing
-      // defs).  If both exist, prefer the pending add, because it will be
-      // overwriting the existing def.
-      upb_symtab_ent *found;
-      if(!(found = upb_resolve(tmptab, base, name)) &&
-         !(found = upb_resolve(symtab, base, name))) {
-        upb_seterr(status, UPB_ERROR,
-                   "could not resolve symbol '" UPB_STRFMT "'"
-                   " in context '" UPB_STRFMT "'",
-                   UPB_STRARG(name), UPB_STRARG(base));
-        return false;
-      }
-
-      // Check the type of the found def.
-      upb_fieldtype_t expected = upb_issubmsg(f) ? UPB_DEF_MSG : UPB_DEF_ENUM;
-      if(found->def->type != expected) {
-        upb_seterr(status, UPB_ERROR, "Unexpected type");
-        return false;
-      }
-      upb_msgdef_resolve(m, f, found->def);
-    }
-  }
-
-  // Deal with type cycles.
-  for(e = upb_strtable_begin(tmptab); e; e = upb_strtable_next(tmptab, &e->e)) {
-    upb_msgdef *m = upb_dyncast_msgdef(e->def);
-    if(!m) continue;
-    // The findcycles() call will decrement the external refcount of the
-    upb_symtab_findcycles(m, 0, status);
-    upb_msgdef *open_defs[UPB_MAX_TYPE_CYCLE_LEN];
-    upb_cycle_ref_or_unref(m, NULL, open_defs, 0, true);
-  }
-
-  return true;
-}
-
-// Given a list of defs, a list of extensions (in the future), and a flag
-// indicating whether the new defs can overwrite existing defs in the symtab,
-// attempts to add the given defs to the symtab.  The whole operation either
-// succeeds or fails.  Ownership of "defs" and "exts" is taken.
-bool upb_symtab_add_defs(upb_symtab *s, upb_def **defs, int num_defs,
-                         bool allow_redef, upb_status *status)
-{
-  upb_rwlock_wrlock(&s->lock);
-
-  // Build a table of the defs we mean to add, for duplicate detection and name
-  // resolution.
-  upb_strtable tmptab;
-  upb_strtable_init(&tmptab, num_defs, sizeof(upb_symtab_ent));
-  for (int i = 0; i < num_defs; i++) {
-    upb_def *def = defs[i];
-    upb_symtab_ent e = {{def->fqname, 0}, def};
-
-    // Redefinition is never allowed within a single FileDescriptorSet.
-    // Additionally, we only allow overwriting of an existing definition if
-    // allow_redef is set.
-    if (upb_strtable_lookup(&tmptab, def->fqname) ||
-        (!allow_redef && upb_strtable_lookup(&s->symtab, def->fqname))) {
-      upb_seterr(status, UPB_ERROR, "Redefinition of symbol " UPB_STRFMT,
-                 UPB_STRARG(def->fqname));
-      goto err;
-    }
-
-    // Pass ownership from the deflist to the strtable.
-    upb_strtable_insert(&tmptab, &e.e);
-    defs[i] = NULL;
-  }
-
-  // TODO: process the list of extensions by modifying entries from
-  // tmptab in-place (copying them from the symtab first if necessary).
-
-  if (!upb_resolverefs(&tmptab, &s->symtab, status)) goto err;
-
-  // The defs in tmptab have been vetted, and can be added to the symtab
-  // without causing errors.  Now add all tmptab defs to the symtab,
-  // overwriting (and releasing a ref on) any existing defs with the same
-  // names.  Ownership for tmptab defs passes from the tmptab to the symtab.
-  upb_symtab_ent *tmptab_e;
-  for(tmptab_e = upb_strtable_begin(&tmptab); tmptab_e;
-      tmptab_e = upb_strtable_next(&tmptab, &tmptab_e->e)) {
-    upb_symtab_ent *symtab_e =
-        upb_strtable_lookup(&s->symtab, tmptab_e->def->fqname);
-    if(symtab_e) {
-      upb_def_unref(symtab_e->def);
-      symtab_e->def = tmptab_e->def;
-    } else {
-      upb_strtable_insert(&s->symtab, &tmptab_e->e);
-    }
-  }
-
-  upb_rwlock_unlock(&s->lock);
-  upb_strtable_free(&tmptab);
-  return true;
-
-err:
-  // We need to free all defs from "tmptab."
-  upb_rwlock_unlock(&s->lock);
-  for(upb_symtab_ent *e = upb_strtable_begin(&tmptab); e;
-      e = upb_strtable_next(&tmptab, &e->e)) {
-    upb_def_unref(e->def);
-  }
-  upb_strtable_free(&tmptab);
-  for (int i = 0; i < num_defs; i++) upb_def_unref(defs[i]);
-  return false;
-}
-
-
-/* upb_symtab public interface ************************************************/
-
-upb_symtab *upb_symtab_new()
-{
-  upb_symtab *s = malloc(sizeof(*s));
-  upb_atomic_refcount_init(&s->refcount, 1);
-  upb_rwlock_init(&s->lock);
-  upb_strtable_init(&s->symtab, 16, sizeof(upb_symtab_ent));
-  s->fds_msgdef = NULL;
-  return s;
-}
-
-static void upb_free_symtab(upb_strtable *t)
-{
-  upb_symtab_ent *e;
-  for(e = upb_strtable_begin(t); e; e = upb_strtable_next(t, &e->e))
-    upb_def_unref(e->def);
-  upb_strtable_free(t);
-}
-
-void _upb_symtab_free(upb_symtab *s)
-{
-  upb_free_symtab(&s->symtab);
-  upb_rwlock_destroy(&s->lock);
-  free(s);
-}
-
-upb_def **upb_symtab_getdefs(upb_symtab *s, int *count, upb_deftype_t type)
-{
-  upb_rwlock_rdlock(&s->lock);
-  int total = upb_strtable_count(&s->symtab);
-  // We may only use part of this, depending on how many symbols are of the
-  // correct type.
-  upb_def **defs = malloc(sizeof(*defs) * total);
-  upb_symtab_ent *e = upb_strtable_begin(&s->symtab);
-  int i = 0;
-  for(; e; e = upb_strtable_next(&s->symtab, &e->e)) {
-    upb_def *def = e->def;
-    assert(def);
-    if(type == UPB_DEF_ANY || def->type == type)
-      defs[i++] = def;
-  }
-  upb_rwlock_unlock(&s->lock);
-  *count = i;
-  for(i = 0; i < *count; i++)
-    upb_def_ref(defs[i]);
-  return defs;
-}
-
-upb_def *upb_symtab_lookup(upb_symtab *s, upb_string *sym)
-{
-  upb_rwlock_rdlock(&s->lock);
-  upb_symtab_ent *e = upb_strtable_lookup(&s->symtab, sym);
-  upb_def *ret = NULL;
-  if(e) {
-    ret = e->def;
-    upb_def_ref(ret);
-  }
-  upb_rwlock_unlock(&s->lock);
-  return ret;
-}
-
-
-upb_def *upb_symtab_resolve(upb_symtab *s, upb_string *base, upb_string *symbol) {
-  upb_rwlock_rdlock(&s->lock);
-  upb_symtab_ent *e = upb_resolve(&s->symtab, base, symbol);
-  upb_def *ret = NULL;
-  if(e) {
-    ret = e->def;
-    upb_def_ref(ret);
-  }
-  upb_rwlock_unlock(&s->lock);
-  return ret;
-}
-
-void upb_symtab_addfds(upb_symtab *s, upb_src *src, upb_status *status)
-{
-  upb_defbuilder b;
-  upb_defbuilder_init(&b);
-  upb_handlers handlers;
-  upb_handlers_init(&handlers);
-  upb_defbuilder_register_FileDescriptorSet(&b, &handlers);
-  upb_src_sethandlers(src, &handlers);
-  upb_src_run(src, status);
-  if (upb_ok(status))
-    upb_symtab_add_defs(s, b.defs.defs, b.defs.len, false, status);
-  upb_defbuilder_uninit(&b);
-  upb_handlers_uninit(&handlers);
-}
-
-
-/* upb_baredecoder ************************************************************/
-
-// upb_baredecoder is a upb_src that can parse a subset of the protocol buffer
-// binary format.  It is only used for bootstrapping.  It can parse without
-// having a upb_msgdef, which is why it is useful for bootstrapping the first
-// msgdef.  On the downside, it does not support:
-//
-// * having its input span multiple upb_strings.
-// * reading any field of the returned upb_fielddef's except f->number.
-// * keeping a pointer to the upb_fielddef* and reading it later (the same
-//   upb_fielddef is reused over and over).
-// * detecting errors in the input (we trust that our input is known-good).
-// * skipping the rest of the submessage (UPB_SKIPSUBMSG).
-//
-// It also does not support any of the follow protobuf features:
-// * packed fields.
-// * groups.
-// * zig-zag-encoded types like sint32 and sint64.
-//
-// Since it cannot tell the difference between submessages and strings, it
-// always reports them as strings first, but if the value callback returns
-// UPB_TREAT_AS_SUBMSG this signals to the baredecoder that it should be
-// treated like a submessage instead.
-//
-// TODO: for bootstrapping we should define a slightly different wire format
-// that includes enough information to know the precise integer types and
-// that distinguishes between strings and submessages.  This will allow
-// us to get rid of the UPB_TREAT_AS_SUBMSG hack.  It will also allow us
-// to get rid of the upb_value_setraw() scheme, which would be more
-// complicated to support on big-endian machines.
-
-typedef struct {
-  upb_src src;
-  upb_string *input;
-  upb_strlen_t offset;
-  upb_dispatcher dispatcher;
-} upb_baredecoder;
-
-static uint64_t upb_baredecoder_readv64(upb_baredecoder *d)
-{
-  const uint8_t *start = (uint8_t*)upb_string_getrobuf(d->input) + d->offset;
-  const uint8_t *buf = start;
-  uint8_t last = 0x80;
-  uint64_t val = 0;
-  for(int bitpos = 0; (last & 0x80); buf++, bitpos += 7)
-    val |= ((uint64_t)((last = *buf) & 0x7F)) << bitpos;
-  d->offset += buf - start;
-  return val;
-}
-
-static uint32_t upb_baredecoder_readv32(upb_baredecoder *d)
-{
-  return (uint32_t)upb_baredecoder_readv64(d); // Truncate.
-}
-
-static uint64_t upb_baredecoder_readf64(upb_baredecoder *d)
-{
-  uint64_t val;
-  memcpy(&val, upb_string_getrobuf(d->input) + d->offset, 8);
-  d->offset += 8;
-  return val;
-}
-
-static uint32_t upb_baredecoder_readf32(upb_baredecoder *d)
-{
-  uint32_t val;
-  memcpy(&val, upb_string_getrobuf(d->input) + d->offset, 4);
-  d->offset += 4;
-  return val;
-}
-
-static void upb_baredecoder_sethandlers(upb_src *src, upb_handlers *handlers) {
-  upb_baredecoder *d = (upb_baredecoder*)src;
-  upb_dispatcher_reset(&d->dispatcher, handlers, false);
-}
-
-static void upb_baredecoder_run(upb_src *src, upb_status *status) {
-  upb_baredecoder *d = (upb_baredecoder*)src;
-  assert(!upb_handlers_isempty(&d->dispatcher.top->handlers));
-  upb_string *str = NULL;
-  upb_strlen_t stack[UPB_MAX_NESTING] = {UPB_STRLEN_MAX};
-  upb_strlen_t *top = &stack[0];
-  d->offset = 0;
-
-#define CHECK(x) if (x != UPB_CONTINUE && x != BEGIN_SUBMSG) goto err;
-
-  CHECK(upb_dispatch_startmsg(&d->dispatcher));
-  while(d->offset < upb_string_len(d->input)) {
-    uint32_t key = upb_baredecoder_readv64(d);
-    upb_fielddef f;
-    f.number = key >> 3;
-    upb_wire_type_t wt = key & 0x7;
-    if(wt == UPB_WIRE_TYPE_DELIMITED) {
-      uint32_t delim_len = upb_baredecoder_readv32(d);
-      // We don't know if it's a string or a submessage; deliver first as
-      // string.
-      upb_string_recycle(&str);
-      upb_string_substr(str, d->input, d->offset, delim_len);
-      upb_value v;
-      upb_value_setstr(&v, str);
-      upb_flow_t ret = upb_dispatch_value(&d->dispatcher, &f, v);
-      CHECK(ret);
-      if(ret == BEGIN_SUBMSG) {
-        // Should deliver as a submessage instead.
-        CHECK(upb_dispatch_startsubmsg(&d->dispatcher, &f));
-        *(++top) = d->offset + delim_len;
-      } else {
-        d->offset += delim_len;
-      }
-    } else {
-      upb_value v;
-      switch(wt) {
-        case UPB_WIRE_TYPE_VARINT:
-          upb_value_setraw(&v, upb_baredecoder_readv64(d));
-          break;
-        case UPB_WIRE_TYPE_64BIT:
-          upb_value_setraw(&v, upb_baredecoder_readf64(d));
-          break;
-        case UPB_WIRE_TYPE_32BIT:
-          upb_value_setraw(&v, upb_baredecoder_readf32(d));
-          break;
-        default:
-          assert(false);
-          abort();
-      }
-      CHECK(upb_dispatch_value(&d->dispatcher, &f, v));
-    }
-    // Detect end-of-submessage.
-    while(d->offset >= *top) {
-      CHECK(upb_dispatch_endsubmsg(&d->dispatcher));
-      d->offset = *(top--);
-    }
-  }
-  CHECK(upb_dispatch_endmsg(&d->dispatcher));
-  upb_string_unref(str);
-  return;
-
-err:
-  upb_copyerr(status, d->dispatcher.top->handlers.status);
-  upb_string_unref(str);
-}
-
-static upb_baredecoder *upb_baredecoder_new(upb_string *str) {
-  static upb_src_vtbl vtbl = {
-    &upb_baredecoder_sethandlers,
-    &upb_baredecoder_run,
-  };
-  upb_baredecoder *d = malloc(sizeof(*d));
-  upb_src_init(&d->src, &vtbl);
-  d->input = upb_string_getref(str);
-  d->offset = 0;
-  upb_dispatcher_init(&d->dispatcher);
-  return d;
-}
-
-static void upb_baredecoder_free(upb_baredecoder *d) {
-  upb_string_unref(d->input);
-  free(d);
-}
-
-static upb_src *upb_baredecoder_src(upb_baredecoder *d) {
-  return &d->src;
-}
-
-void upb_symtab_add_descriptorproto(upb_symtab *symtab) {
-  // For the moment we silently decline to perform the operation if the symbols
-  // already exist in the symtab.  Revisit this when we have a better story
-  // about whether syms in a table can be replaced.
-  if(symtab->fds_msgdef) upb_def_unref(UPB_UPCAST(symtab->fds_msgdef));
-
-  upb_baredecoder *decoder = upb_baredecoder_new(&descriptor_str);
-  upb_status status = UPB_STATUS_INIT;
-  upb_symtab_addfds(symtab, upb_baredecoder_src(decoder), &status);
-  upb_baredecoder_free(decoder);
-
-  if(!upb_ok(&status)) {
-    // upb itself is corrupt.
-    upb_printerr(&status);
-    upb_clearerr(&status);
-    upb_symtab_unref(symtab);
-    abort();
-  }
-  upb_def *def = upb_symtab_lookup(
-      symtab, UPB_STRLIT("google.protobuf.FileDescriptorSet"));
-  if (!def || (symtab->fds_msgdef = upb_dyncast_msgdef(def)) == NULL) {
-    // upb itself is corrupt.
-    abort();
-  }
-  upb_def_unref(def);  // The symtab already holds a ref on it.
-  upb_status_uninit(&status);
-}
-
-upb_msgdef *upb_symtab_fds_def(upb_symtab *s) {
-  assert(s->fds_msgdef != NULL);
-  upb_def_ref(UPB_UPCAST(s->fds_msgdef));
-  return s->fds_msgdef;
-}