protobuf/upb/msg.c

#include "upb/msg.h"

static bool is_power_of_two(size_t val) {
  return (val & (val - 1)) == 0;
}

/* Align up to the given power of 2. */
static size_t align_up(size_t val, size_t align) {
  UPB_ASSERT(is_power_of_two(align));
  return (val + align - 1) & ~(align - 1);
}

static size_t div_round_up(size_t n, size_t d) {
  return (n + d - 1) / d;
}

bool upb_fieldtype_mapkeyok(upb_fieldtype_t type) {
  return type == UPB_TYPE_BOOL || type == UPB_TYPE_INT32 ||
         type == UPB_TYPE_UINT32 || type == UPB_TYPE_INT64 ||
         type == UPB_TYPE_UINT64 || type == UPB_TYPE_STRING;
}

void *upb_array_pack(const upb_array *arr, void *p, size_t *ofs, size_t size);
void *upb_map_pack(const upb_map *map, void *p, size_t *ofs, size_t size);


/** upb_msgval ****************************************************************/

#define upb_alignof(t) offsetof(struct { char c; t x; }, x)

/* These functions will generate real memcpy() calls on ARM sadly, because
 * the compiler assumes they might not be aligned. */

static upb_msgval upb_msgval_read(const void *p, size_t ofs,
                                  uint8_t size) {
  upb_msgval val;
  p = (char*)p + ofs;
  memcpy(&val, p, size);
  return val;
}

static void upb_msgval_write(void *p, size_t ofs, upb_msgval val,
                             uint8_t size) {
  p = (char*)p + ofs;
  memcpy(p, &val, size);
}

static size_t upb_msgval_sizeof(upb_fieldtype_t type) {
  switch (type) {
    case UPB_TYPE_DOUBLE:
    case UPB_TYPE_INT64:
    case UPB_TYPE_UINT64:
      return 8;
    case UPB_TYPE_ENUM:
    case UPB_TYPE_INT32:
    case UPB_TYPE_UINT32:
    case UPB_TYPE_FLOAT:
      return 4;
    case UPB_TYPE_BOOL:
      return 1;
    case UPB_TYPE_BYTES:
    case UPB_TYPE_MESSAGE:
      return sizeof(void*);
    case UPB_TYPE_STRING:
      return sizeof(char*) + sizeof(size_t);
  }
  UPB_UNREACHABLE();
}

static uint8_t upb_msg_fieldsize(const upb_fielddef *f) {
  if (upb_fielddef_isseq(f)) {
    return sizeof(void*);
  } else {
    return upb_msgval_sizeof(upb_fielddef_type(f));
  }
}

/* TODO(haberman): this is broken right now because upb_msgval can contain
 * a char* / size_t pair, which is too big for a upb_value.  To fix this
 * we'll probably need to dynamically allocate a upb_msgval and store a
 * pointer to that in the tables for extensions/maps. */
static upb_value upb_toval(upb_msgval val) {
  upb_value ret;
  UPB_UNUSED(val);
  memset(&ret, 0, sizeof(upb_value));  /* XXX */
  return ret;
}

static upb_msgval upb_msgval_fromval(upb_value val) {
  upb_msgval ret;
  UPB_UNUSED(val);
  memset(&ret, 0, sizeof(upb_msgval));  /* XXX */
  return ret;
}

static upb_ctype_t upb_fieldtotabtype(upb_fieldtype_t type) {
  switch (type) {
    case UPB_TYPE_FLOAT: return UPB_CTYPE_FLOAT;
    case UPB_TYPE_DOUBLE: return UPB_CTYPE_DOUBLE;
    case UPB_TYPE_BOOL: return UPB_CTYPE_BOOL;
    case UPB_TYPE_BYTES:
    case UPB_TYPE_MESSAGE:
    case UPB_TYPE_STRING: return UPB_CTYPE_CONSTPTR;
    case UPB_TYPE_ENUM:
    case UPB_TYPE_INT32: return UPB_CTYPE_INT32;
    case UPB_TYPE_UINT32: return UPB_CTYPE_UINT32;
    case UPB_TYPE_INT64: return UPB_CTYPE_INT64;
    case UPB_TYPE_UINT64: return UPB_CTYPE_UINT64;
    default: UPB_ASSERT(false); return 0;
  }
}

static upb_msgval upb_msgval_fromdefault(const upb_fielddef *f) {
  /* TODO(haberman): improve/optimize this (maybe use upb_msgval in fielddef) */
  switch (upb_fielddef_type(f)) {
      case UPB_TYPE_FLOAT:
        return upb_msgval_float(upb_fielddef_defaultfloat(f));
      case UPB_TYPE_DOUBLE:
        return upb_msgval_double(upb_fielddef_defaultdouble(f));
      case UPB_TYPE_BOOL:
        return upb_msgval_bool(upb_fielddef_defaultbool(f));
      case UPB_TYPE_STRING:
      case UPB_TYPE_BYTES: {
        size_t len;
        const char *ptr = upb_fielddef_defaultstr(f, &len);
        return upb_msgval_str(ptr, len);
      }
      case UPB_TYPE_MESSAGE:
        return upb_msgval_msg(NULL);
      case UPB_TYPE_ENUM:
      case UPB_TYPE_INT32:
        return upb_msgval_int32(upb_fielddef_defaultint32(f));
      case UPB_TYPE_UINT32:
        return upb_msgval_uint32(upb_fielddef_defaultuint32(f));
      case UPB_TYPE_INT64:
        return upb_msgval_int64(upb_fielddef_defaultint64(f));
      case UPB_TYPE_UINT64:
        return upb_msgval_uint64(upb_fielddef_defaultuint64(f));
      default:
        UPB_ASSERT(false);
        return upb_msgval_msg(NULL);
  }
}


/** upb_msglayout *************************************************************/

struct upb_msglayout {
  const upb_msgdef *msgdef;
  size_t size;
  size_t extdict_offset;
  void *default_msg;
  uint32_t *offsets;
  uint32_t *case_offsets;
  uint32_t *hasbits;
  bool has_extdict;
  uint8_t align;
};

static void upb_msg_check(const upb_msglayout *l, const upb_fielddef *f) {
  UPB_ASSERT(l->msgdef == upb_fielddef_containingtype(f));
}

static void upb_msglayout_free(upb_msglayout *l) {
  upb_gfree(l->offsets);
  upb_gfree(l->hasbits);
  upb_gfree(l->default_msg);
  upb_gfree(l);
}

const upb_msgdef *upb_msglayout_msgdef(const upb_msglayout *l) {
  return l->msgdef;
}

static size_t upb_msglayout_place(upb_msglayout *l, size_t size) {
  size_t ret;

  l->size = align_up(l->size, size);
  l->align = align_up(l->align, size);
  ret = l->size;
  l->size += size;
  return ret;
}

static uint32_t upb_msglayout_offset(const upb_msglayout *l,
                                     const upb_fielddef *f) {
  return l->offsets[upb_fielddef_index(f)];
}

static uint32_t upb_msglayout_hasbit(const upb_msglayout *l,
                                     const upb_fielddef *f) {
  return l->hasbits[upb_fielddef_index(f)];
}

static upb_msglayout *upb_msglayout_new(const upb_msgdef *m) {
  upb_msg_field_iter it;
  upb_msg_oneof_iter oit;
  upb_msglayout *l;
  size_t hasbit;

  l = upb_gmalloc(sizeof(*l));
  if (!l) return NULL;

  memset(l, 0, sizeof(*l));

  l->msgdef = m;

  if (upb_msgdef_syntax(m) == UPB_SYNTAX_PROTO2) {
    l->hasbits = upb_gmalloc(sizeof(*l->hasbits) * upb_msgdef_numfields(m));
  }

  l->offsets = upb_gmalloc(sizeof(*l->offsets) * upb_msgdef_numfields(m));
  l->case_offsets =
      upb_gmalloc(sizeof(*l->case_offsets) * upb_msgdef_numoneofs(m));
  l->align = 1;

  /* Allocate data offsets in three stages:
   *
   * 1. hasbits.
   * 2. regular fields.
   * 3. oneof fields.
   *
   * OPT: There is a lot of room for optimization here to minimize the size.
   */

  /* Allocate hasbits.  Start at sizeof(void*) for upb_alloc*. */
  for (upb_msg_field_begin(&it, m), hasbit = sizeof(void*) * 8;
       !upb_msg_field_done(&it);
       upb_msg_field_next(&it)) {
    const upb_fielddef* f = upb_msg_iter_field(&it);

    if (upb_fielddef_haspresence(f) && !upb_fielddef_containingoneof(f)) {
      l->hasbits[upb_fielddef_index(f)] = hasbit++;
    }
  }

  /* Account for space used by hasbits. */
  l->size = div_round_up(hasbit, 8);

  /* Allocate non-oneof fields. */
  for (upb_msg_field_begin(&it, m); !upb_msg_field_done(&it);
       upb_msg_field_next(&it)) {
    const upb_fielddef* f = upb_msg_iter_field(&it);
    size_t field_size = upb_msg_fieldsize(f);

    if (upb_fielddef_containingoneof(f)) {
      /* Oneofs are handled separately below. */
      continue;
    }

    l->offsets[upb_fielddef_index(f)] = upb_msglayout_place(l, field_size);
  }

  /* Allocate oneof fields.  Each oneof field consists of a uint32 for the case
   * and space for the actual data. */
  for (upb_msg_oneof_begin(&oit, m); !upb_msg_oneof_done(&oit);
       upb_msg_oneof_next(&oit)) {
    const upb_oneofdef* oneof = upb_msg_iter_oneof(&oit);
    upb_oneof_iter fit;
    size_t case_size = sizeof(uint32_t);  /* Could potentially optimize this. */
    size_t field_size = 0;
    size_t case_offset;
    size_t val_offset;

    /* Calculate field size: the max of all field sizes. */
    for (upb_oneof_begin(&fit, oneof);
         !upb_oneof_done(&fit);
         upb_oneof_next(&fit)) {
      const upb_fielddef* f = upb_oneof_iter_field(&fit);
      field_size = UPB_MAX(field_size, upb_msg_fieldsize(f));
    }

    /* Align and allocate case offset. */
    case_offset = upb_msglayout_place(l, case_size);
    val_offset = upb_msglayout_place(l, field_size);

    l->case_offsets[upb_oneofdef_index(oneof)] = case_offset;

    /* Assign all fields in the oneof this same offset. */
    for (upb_oneof_begin(&fit, oneof); !upb_oneof_done(&fit);
         upb_oneof_next(&fit)) {
      const upb_fielddef* f = upb_oneof_iter_field(&fit);
      l->offsets[upb_fielddef_index(f)] = val_offset;
    }
  }

  /* Size of the entire structure should be a multiple of its greatest
   * alignment. */
  l->size = align_up(l->size, l->align);

  if (upb_msgdef_syntax(m) == UPB_SYNTAX_PROTO2 && l->size) {
    /* Allocate default message and set default values in it. */
    l->default_msg = upb_gmalloc(l->size);
    if (!l->default_msg) {
      goto err;
    }

    memset(l->default_msg, 0, l->size);

    for (upb_msg_field_begin(&it, m), hasbit = 0; !upb_msg_field_done(&it);
         upb_msg_field_next(&it)) {
      const upb_fielddef* f = upb_msg_iter_field(&it);

      if (upb_fielddef_containingoneof(f)) {
        continue;
      }

      if (!upb_fielddef_isstring(f) &&
          !upb_fielddef_issubmsg(f) &&
          !upb_fielddef_isseq(f)) {
        upb_msg_set(l->default_msg, f, upb_msgval_fromdefault(f), l);
      }
    }
  }

  return l;

 err:
  upb_msglayout_free(l);
  return NULL;
}


/** upb_msgfactory ************************************************************/

struct upb_msgfactory {
  const upb_symtab *symtab;  /* We own a ref. */
  upb_inttable layouts;
  upb_inttable mergehandlers;
};

upb_msgfactory *upb_msgfactory_new(const upb_symtab *symtab) {
  upb_msgfactory *ret = upb_gmalloc(sizeof(*ret));

  ret->symtab = symtab;
  upb_symtab_ref(ret->symtab, &ret->symtab);
  upb_inttable_init(&ret->layouts, UPB_CTYPE_PTR);
  upb_inttable_init(&ret->mergehandlers, UPB_CTYPE_CONSTPTR);

  return ret;
}

void upb_msgfactory_free(upb_msgfactory *f) {
  upb_inttable_iter i;
  upb_inttable_begin(&i, &f->layouts);
  for(; !upb_inttable_done(&i); upb_inttable_next(&i)) {
    upb_msglayout *l = upb_value_getptr(upb_inttable_iter_value(&i));
    upb_msglayout_free(l);
  }

  upb_inttable_begin(&i, &f->mergehandlers);
  for(; !upb_inttable_done(&i); upb_inttable_next(&i)) {
    const upb_handlers *h = upb_value_getconstptr(upb_inttable_iter_value(&i));
    upb_handlers_unref(h, f);
  }

  upb_inttable_uninit(&f->layouts);
  upb_inttable_uninit(&f->mergehandlers);
  upb_symtab_unref(f->symtab, &f->symtab);
  upb_gfree(f);
}

/* Requires:
 * - m is in upb_msgfactory_symtab(f)
 * - upb_msgdef_mapentry(m) == false (since map messages can't have layouts).
 *
 * The returned layout will live for as long as the msgfactory does.
 */
const upb_msglayout *upb_msgfactory_getlayout(const upb_msgfactory *f,
                                              const upb_msgdef *m) {
  upb_value v;
  UPB_ASSERT(upb_symtab_lookupmsg(f->symtab, upb_msgdef_fullname(m)) == m);
  UPB_ASSERT(!upb_msgdef_mapentry(m));

  if (upb_inttable_lookupptr(&f->layouts, m, &v)) {
    UPB_ASSERT(upb_value_getptr(v));
    return upb_value_getptr(v);
  } else {
    /* This method should be made thread-safe so the "const" is accurate. */
    upb_msgfactory *mutable_f = (void*)f;
    upb_msglayout *l = upb_msglayout_new(m);
    upb_inttable_insertptr(&mutable_f->layouts, m, upb_value_ptr(l));
    UPB_ASSERT(l);
    return l;
  }
}

/* Our handlers that we don't expose externally. */

void *upb_msg_startstr(void *msg, const void *hd, size_t size_hint) {
  uint32_t ofs = (uintptr_t)hd;
  /* We pass NULL here because we know we can get away with it. */
  upb_alloc *alloc = upb_msg_alloc(msg, NULL);
  upb_msgval val;
  UPB_UNUSED(size_hint);

  val = upb_msgval_read(msg, ofs, upb_msgval_sizeof(UPB_TYPE_STRING));

  upb_free(alloc, (void*)val.str.ptr);
  val.str.ptr = NULL;
  val.str.len = 0;

  upb_msgval_write(msg, ofs, val, upb_msgval_sizeof(UPB_TYPE_STRING));
  return msg;
}

size_t upb_msg_str(void *msg, const void *hd, const char *ptr, size_t size,
                 const upb_bufhandle *handle) {
  uint32_t ofs = (uintptr_t)hd;
  /* We pass NULL here because we know we can get away with it. */
  upb_alloc *alloc = upb_msg_alloc(msg, NULL);
  upb_msgval val;
  size_t newsize;
  UPB_UNUSED(handle);

  val = upb_msgval_read(msg, ofs, upb_msgval_sizeof(UPB_TYPE_STRING));

  newsize = val.str.len + size;
  val.str.ptr = upb_realloc(alloc, (void*)val.str.ptr, val.str.len, newsize);

  if (!val.str.ptr) {
    return false;
  }

  memcpy((char*)val.str.ptr + val.str.len, ptr, size);
  val.str.len = newsize;
  upb_msgval_write(msg, ofs, val, upb_msgval_sizeof(UPB_TYPE_STRING));
  return size;
}

static void callback(const void *closure, upb_handlers *h) {
  const upb_msgfactory *factory = closure;
  const upb_msgdef *md = upb_handlers_msgdef(h);
  const upb_msglayout* layout = upb_msgfactory_getlayout(factory, md);
  upb_msg_field_iter i;
  UPB_UNUSED(factory);

  for(upb_msg_field_begin(&i, md);
      !upb_msg_field_done(&i);
      upb_msg_field_next(&i)) {
    const upb_fielddef *f = upb_msg_iter_field(&i);
    size_t offset = upb_msglayout_offset(layout, f);
    upb_handlerattr attr = UPB_HANDLERATTR_INITIALIZER;
    upb_handlerattr_sethandlerdata(&attr, (void*)offset);

    if (upb_fielddef_isseq(f)) {
    } else if (upb_fielddef_isstring(f)) {
      upb_handlers_setstartstr(h, f, upb_msg_startstr, &attr);
      upb_handlers_setstring(h, f, upb_msg_str, &attr);
    } else {
      upb_msg_setscalarhandler(
          h, f, offset, upb_msglayout_hasbit(layout, f));
    }
  }
}

const upb_handlers *upb_msgfactory_getmergehandlers(const upb_msgfactory *f,
                                                    const upb_msgdef *m) {
  /* This method should be made thread-safe so the "const" is accurate. */
  upb_msgfactory *mutable_f = (void*)f;

  /* TODO(haberman): properly cache these. */
  const upb_handlers *ret = upb_handlers_newfrozen(m, f, callback, f);
  upb_inttable_push(&mutable_f->mergehandlers, upb_value_constptr(ret));

  return ret;
}


/** upb_msg *******************************************************************/

/* If we always read/write as a consistent type to each address, this shouldn't
 * violate aliasing.
 */
#define CHARPTR_AT(msg, ofs) ((char*)msg + ofs)
#define DEREF(msg, ofs, type) *(type*)CHARPTR_AT(msg, ofs)

static upb_inttable *upb_msg_trygetextdict(const upb_msg *msg,
                                           const upb_msglayout *l) {
  return l->has_extdict ? DEREF(msg, l->extdict_offset, upb_inttable*) : NULL;
}

static upb_inttable *upb_msg_getextdict(upb_msg *msg,
                                        const upb_msglayout *l,
                                        upb_alloc *a) {
  upb_inttable *ext_dict;
  UPB_ASSERT(l->has_extdict);

  ext_dict = upb_msg_trygetextdict(msg, l);

  if (!ext_dict) {
    ext_dict = upb_malloc(a, sizeof(upb_inttable));

    if (!ext_dict) {
      return NULL;
    }

    /* Use an 8-byte type to ensure all bytes are copied. */
    if (!upb_inttable_init2(ext_dict, UPB_CTYPE_INT64, a)) {
      upb_free(a, ext_dict);
      return NULL;
    }

    DEREF(msg, l->extdict_offset, upb_inttable*) = ext_dict;
  }

  return ext_dict;
}

static uint32_t upb_msg_getoneofint(const upb_msg *msg,
                                    const upb_oneofdef *o,
                                    const upb_msglayout *l) {
  size_t oneof_ofs = l->case_offsets[upb_oneofdef_index(o)];
  return DEREF(msg, oneof_ofs, uint8_t);
}

static void upb_msg_setoneofcase(const upb_msg *msg,
                                 const upb_oneofdef *o,
                                 const upb_msglayout *l,
                                 uint32_t val) {
  size_t oneof_ofs = l->case_offsets[upb_oneofdef_index(o)];
  DEREF(msg, oneof_ofs, uint8_t) = val;
}


static bool upb_msg_oneofis(const upb_msg *msg, const upb_msglayout *l,
                            const upb_oneofdef *o, const upb_fielddef *f) {
  return upb_msg_getoneofint(msg, o, l) == upb_fielddef_number(f);
}

size_t upb_msg_sizeof(const upb_msglayout *l) { return l->size; }

void upb_msg_init(upb_msg *msg, const upb_msglayout *l, upb_alloc *a) {
  if (l->default_msg) {
    memcpy(msg, l->default_msg, l->size);
  } else {
    memset(msg, 0, l->size);
  }

  /* Set arena pointer. */
  memcpy(msg, &a, sizeof(a));
}

void upb_msg_uninit(upb_msg *msg, const upb_msglayout *l) {
  upb_inttable *ext_dict = upb_msg_trygetextdict(msg, l);
  if (ext_dict) {
    upb_inttable_uninit2(ext_dict, upb_msg_alloc(msg, l));
  }
}

upb_msg *upb_msg_new(const upb_msglayout *l, upb_alloc *a) {
  upb_msg *msg = upb_malloc(a, upb_msg_sizeof(l));

  if (msg) {
    upb_msg_init(msg, l, a);
  }

  return msg;
}

void upb_msg_free(upb_msg *msg, const upb_msglayout *l) {
  upb_msg_uninit(msg, l);
  upb_free(upb_msg_alloc(msg, l), msg);
}

upb_alloc *upb_msg_alloc(const upb_msg *msg, const upb_msglayout *l) {
  upb_alloc *alloc;
  UPB_UNUSED(l);
  memcpy(&alloc, msg, sizeof(alloc));
  return alloc;
}

bool upb_msg_has(const upb_msg *msg,
                 const upb_fielddef *f,
                 const upb_msglayout *l) {
  const upb_oneofdef *o;
  upb_msg_check(l, f);
  UPB_ASSERT(upb_fielddef_haspresence(f));

  if (upb_fielddef_isextension(f)) {
    /* Extensions are set when they are present in the extension dict. */
    upb_inttable *ext_dict = upb_msg_trygetextdict(msg, l);
    upb_value v;
    return ext_dict != NULL &&
           upb_inttable_lookup32(ext_dict, upb_fielddef_number(f), &v);
  } else if ((o = upb_fielddef_containingoneof(f)) != NULL) {
    /* Oneofs are set when the oneof number is set to this field. */
    return upb_msg_getoneofint(msg, o, l) == upb_fielddef_number(f);
  } else {
    /* Other fields are set when their hasbit is set. */
    uint32_t hasbit = l->hasbits[upb_fielddef_index(f)];
    return DEREF(msg, hasbit / 8, char) | (1 << (hasbit % 8));
  }
}

upb_msgval upb_msg_get(const upb_msg *msg, const upb_fielddef *f,
                       const upb_msglayout *l) {
  upb_msg_check(l, f);

  if (upb_fielddef_isextension(f)) {
    upb_inttable *ext_dict = upb_msg_trygetextdict(msg, l);
    upb_value val;
    if (upb_inttable_lookup32(ext_dict, upb_fielddef_number(f), &val)) {
      return upb_msgval_fromval(val);
    } else {
      return upb_msgval_fromdefault(f);
    }
  } else {
    size_t ofs = l->offsets[upb_fielddef_index(f)];
    const upb_oneofdef *o = upb_fielddef_containingoneof(f);
    upb_msgval ret;

    if (o && !upb_msg_oneofis(msg, l, o, f)) {
      /* Oneof defaults can't come from the message because the memory is reused
       * by all types in the oneof. */
      return upb_msgval_fromdefault(f);
    }

    ret = upb_msgval_read(msg, ofs, upb_msg_fieldsize(f));
    return ret;
  }
}

bool upb_msg_set(upb_msg *msg,
                 const upb_fielddef *f,
                 upb_msgval val,
                 const upb_msglayout *l) {
  upb_alloc *a = upb_msg_alloc(msg, l);
  upb_msg_check(l, f);

  if (upb_fielddef_isextension(f)) {
    /* TODO(haberman): introduce table API that can do this in one call. */
    upb_inttable *ext = upb_msg_getextdict(msg, l, a);
    upb_value val2 = upb_toval(val);
    if (!upb_inttable_replace(ext, upb_fielddef_number(f), val2) &&
        !upb_inttable_insert2(ext, upb_fielddef_number(f), val2, a)) {
      return false;
    }
  } else {
    size_t ofs = l->offsets[upb_fielddef_index(f)];
    const upb_oneofdef *o = upb_fielddef_containingoneof(f);

    if (o) {
      upb_msg_setoneofcase(msg, o, l, upb_fielddef_number(f));
    }

    upb_msgval_write(msg, ofs, val, upb_msg_fieldsize(f));
  }
  return true;
}


/** upb_array *****************************************************************/

struct upb_array {
  upb_fieldtype_t type;
  uint8_t element_size;
  void *data;   /* Each element is element_size. */
  size_t len;   /* Measured in elements. */
  size_t size;  /* Measured in elements. */
  upb_alloc *alloc;
};

#define DEREF_ARR(arr, i, type) ((type*)arr->data)[i]

size_t upb_array_sizeof(upb_fieldtype_t type) {
  UPB_UNUSED(type);
  return sizeof(upb_array);
}

void upb_array_init(upb_array *arr, upb_fieldtype_t type, upb_alloc *alloc) {
  arr->type = type;
  arr->data = NULL;
  arr->len = 0;
  arr->size = 0;
  arr->element_size = upb_msgval_sizeof(type);
  arr->alloc = alloc;
}

void upb_array_uninit(upb_array *arr) {
  upb_free(arr->alloc, arr->data);
}

upb_array *upb_array_new(upb_fieldtype_t type, upb_alloc *a) {
  upb_array *ret = upb_malloc(a, upb_array_sizeof(type));

  if (ret) {
    upb_array_init(ret, type, a);
  }

  return ret;
}

void upb_array_free(upb_array *arr) {
  upb_array_uninit(arr);
  upb_free(arr->alloc, arr);
}

size_t upb_array_size(const upb_array *arr) {
  return arr->len;
}

upb_fieldtype_t upb_array_type(const upb_array *arr) {
  return arr->type;
}

upb_msgval upb_array_get(const upb_array *arr, size_t i) {
  UPB_ASSERT(i < arr->len);
  return upb_msgval_read(arr->data, i * arr->element_size, arr->element_size);
}

bool upb_array_set(upb_array *arr, size_t i, upb_msgval val) {
  UPB_ASSERT(i <= arr->len);

  if (i == arr->len) {
    /* Extending the array. */

    if (i == arr->size) {
      /* Need to reallocate. */
      size_t new_size = UPB_MAX(arr->size * 2, 8);
      size_t new_bytes = new_size * arr->element_size;
      size_t old_bytes = arr->size * arr->element_size;
      upb_msgval *new_data =
          upb_realloc(arr->alloc, arr->data, old_bytes, new_bytes);

      if (!new_data) {
        return false;
      }

      arr->data = new_data;
      arr->size = new_size;
    }

    arr->len = i + 1;
  }

  upb_msgval_write(arr->data, i * arr->element_size, val, arr->element_size);
  return true;
}


/** upb_map *******************************************************************/

struct upb_map {
  upb_fieldtype_t key_type;
  upb_fieldtype_t val_type;
  /* We may want to optimize this to use inttable where possible, for greater
   * efficiency and lower memory footprint. */
  upb_strtable strtab;
  upb_alloc *alloc;
};

static void upb_map_tokey(upb_fieldtype_t type, upb_msgval *key,
                          const char **out_key, size_t *out_len) {
  switch (type) {
    case UPB_TYPE_STRING:
      /* Point to string data of the input key. */
      *out_key = key->str.ptr;
      *out_len = key->str.len;
      return;
    case UPB_TYPE_BOOL:
    case UPB_TYPE_INT32:
    case UPB_TYPE_UINT32:
    case UPB_TYPE_INT64:
    case UPB_TYPE_UINT64:
      /* Point to the key itself.  XXX: big-endian. */
      *out_key = (const char*)key;
      *out_len = upb_msgval_sizeof(type);
      return;
    case UPB_TYPE_BYTES:
    case UPB_TYPE_DOUBLE:
    case UPB_TYPE_ENUM:
    case UPB_TYPE_FLOAT:
    case UPB_TYPE_MESSAGE:
      break;  /* Cannot be a map key. */
  }
  UPB_UNREACHABLE();
}

static upb_msgval upb_map_fromkey(upb_fieldtype_t type, const char *key,
                                  size_t len) {
  switch (type) {
    case UPB_TYPE_STRING:
      return upb_msgval_str(key, len);
    case UPB_TYPE_BOOL:
    case UPB_TYPE_INT32:
    case UPB_TYPE_UINT32:
    case UPB_TYPE_INT64:
    case UPB_TYPE_UINT64:
      return upb_msgval_read(key, 0, upb_msgval_sizeof(type));
    case UPB_TYPE_BYTES:
    case UPB_TYPE_DOUBLE:
    case UPB_TYPE_ENUM:
    case UPB_TYPE_FLOAT:
    case UPB_TYPE_MESSAGE:
      break;  /* Cannot be a map key. */
  }
  UPB_UNREACHABLE();
}

size_t upb_map_sizeof(upb_fieldtype_t ktype, upb_fieldtype_t vtype) {
  /* Size does not currently depend on key/value type. */
  UPB_UNUSED(ktype);
  UPB_UNUSED(vtype);
  return sizeof(upb_map);
}

bool upb_map_init(upb_map *map, upb_fieldtype_t ktype, upb_fieldtype_t vtype,
                  upb_alloc *a) {
  upb_ctype_t vtabtype = upb_fieldtotabtype(vtype);
  UPB_ASSERT(upb_fieldtype_mapkeyok(ktype));
  map->key_type = ktype;
  map->val_type = vtype;
  map->alloc = a;

  if (!upb_strtable_init2(&map->strtab, vtabtype, a)) {
    return false;
  }

  return true;
}

void upb_map_uninit(upb_map *map) {
  upb_strtable_uninit2(&map->strtab, map->alloc);
}

upb_map *upb_map_new(upb_fieldtype_t ktype, upb_fieldtype_t vtype,
                     upb_alloc *a) {
  upb_map *map = upb_malloc(a, upb_map_sizeof(ktype, vtype));

  if (!map) {
    return NULL;
  }

  if (!upb_map_init(map, ktype, vtype, a)) {
    return NULL;
  }

  return map;
}

void upb_map_free(upb_map *map) {
  upb_map_uninit(map);
  upb_free(map->alloc, map);
}

size_t upb_map_size(const upb_map *map) {
  return upb_strtable_count(&map->strtab);
}

upb_fieldtype_t upb_map_keytype(const upb_map *map) {
  return map->key_type;
}

upb_fieldtype_t upb_map_valuetype(const upb_map *map) {
  return map->val_type;
}

bool upb_map_get(const upb_map *map, upb_msgval key, upb_msgval *val) {
  upb_value tabval;
  const char *key_str;
  size_t key_len;
  bool ret;

  upb_map_tokey(map->key_type, &key, &key_str, &key_len);
  ret = upb_strtable_lookup2(&map->strtab, key_str, key_len, &tabval);
  if (ret) {
    memcpy(val, &tabval, sizeof(tabval));
  }

  return ret;
}

bool upb_map_set(upb_map *map, upb_msgval key, upb_msgval val,
                 upb_msgval *removed) {
  const char *key_str;
  size_t key_len;
  upb_value tabval = upb_toval(val);
  upb_value removedtabval;
  upb_alloc *a = map->alloc;

  upb_map_tokey(map->key_type, &key, &key_str, &key_len);

  if (upb_strtable_lookup2(&map->strtab, key_str, key_len, NULL)) {
    upb_strtable_remove3(&map->strtab, key_str, key_len, &removedtabval, a);
    memcpy(&removed, &removedtabval, sizeof(removed));
  }

  return upb_strtable_insert3(&map->strtab, key_str, key_len, tabval, a);
}

bool upb_map_del(upb_map *map, upb_msgval key) {
  const char *key_str;
  size_t key_len;
  upb_alloc *a = map->alloc;

  upb_map_tokey(map->key_type, &key, &key_str, &key_len);
  return upb_strtable_remove3(&map->strtab, key_str, key_len, NULL, a);
}


/** upb_mapiter ***************************************************************/

struct upb_mapiter {
  upb_strtable_iter iter;
  upb_fieldtype_t key_type;
};

size_t upb_mapiter_sizeof() {
  return sizeof(upb_mapiter);
}

void upb_mapiter_begin(upb_mapiter *i, const upb_map *map) {
  upb_strtable_begin(&i->iter, &map->strtab);
  i->key_type = map->key_type;
}

upb_mapiter *upb_mapiter_new(const upb_map *t, upb_alloc *a) {
  upb_mapiter *ret = upb_malloc(a, upb_mapiter_sizeof());

  if (!ret) {
    return NULL;
  }

  upb_mapiter_begin(ret, t);
  return ret;
}

void upb_mapiter_free(upb_mapiter *i, upb_alloc *a) {
  upb_free(a, i);
}

void upb_mapiter_next(upb_mapiter *i) {
  upb_strtable_next(&i->iter);
}

bool upb_mapiter_done(const upb_mapiter *i) {
  return upb_strtable_done(&i->iter);
}

upb_msgval upb_mapiter_key(const upb_mapiter *i) {
  return upb_map_fromkey(i->key_type, upb_strtable_iter_key(&i->iter),
                         upb_strtable_iter_keylength(&i->iter));
}

upb_msgval upb_mapiter_value(const upb_mapiter *i) {
  return upb_msgval_fromval(upb_strtable_iter_value(&i->iter));
}

void upb_mapiter_setdone(upb_mapiter *i) {
  upb_strtable_iter_setdone(&i->iter);
}

bool upb_mapiter_isequal(const upb_mapiter *i1, const upb_mapiter *i2) {
  return upb_strtable_iter_isequal(&i1->iter, &i2->iter);
}


/** 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;
}