static void test_create_many_persistant_metadata(void) {
  grpc_mdctx *ctx;
  char buffer[GPR_LTOA_MIN_BUFSIZE];
  long i;
  grpc_mdelem **created = gpr_malloc(sizeof(grpc_mdelem *) * MANY);
  grpc_mdelem *md;

  LOG_TEST("test_create_many_persistant_metadata");

  ctx = grpc_mdctx_create();
  /* add phase */
  for (i = 0; i < MANY; i++) {
    gpr_ltoa(i, buffer);
    created[i] = grpc_mdelem_from_strings(ctx, "a", buffer);
  }
  /* verify phase */
  for (i = 0; i < MANY; i++) {
    gpr_ltoa(i, buffer);
    md = grpc_mdelem_from_strings(ctx, "a", buffer);
    GPR_ASSERT(md == created[i]);
    GRPC_MDELEM_UNREF(md);
  }
  /* cleanup phase */
  for (i = 0; i < MANY; i++) {
    GRPC_MDELEM_UNREF(created[i]);
  }
  grpc_mdctx_unref(ctx);

  gpr_free(created);
}

static void on_initial_header(grpc_exec_ctx *exec_ctx, void *tp,
                              grpc_mdelem *md) {
  grpc_chttp2_transport *t = tp;
  grpc_chttp2_stream *s = t->incoming_stream;

  GPR_TIMER_BEGIN("on_initial_header", 0);

  GPR_ASSERT(s != NULL);

  GRPC_CHTTP2_IF_TRACING(gpr_log(
      GPR_INFO, "HTTP:%d:HDR:%s: %s: %s", s->id, t->is_client ? "CLI" : "SVR",
      grpc_mdstr_as_c_string(md->key), grpc_mdstr_as_c_string(md->value)));

  if (md->key == GRPC_MDSTR_GRPC_STATUS && md != GRPC_MDELEM_GRPC_STATUS_0) {
    /* TODO(ctiller): check for a status like " 0" */
    s->seen_error = true;
  }

  if (md->key == GRPC_MDSTR_GRPC_TIMEOUT) {
    gpr_timespec *cached_timeout = grpc_mdelem_get_user_data(md, free_timeout);
    if (!cached_timeout) {
      /* not already parsed: parse it now, and store the result away */
      cached_timeout = gpr_malloc(sizeof(gpr_timespec));
      if (!grpc_http2_decode_timeout(grpc_mdstr_as_c_string(md->value),
                                     cached_timeout)) {
        gpr_log(GPR_ERROR, "Ignoring bad timeout value '%s'",
                grpc_mdstr_as_c_string(md->value));
        *cached_timeout = gpr_inf_future(GPR_TIMESPAN);
      }
      grpc_mdelem_set_user_data(md, free_timeout, cached_timeout);
    }
    grpc_chttp2_incoming_metadata_buffer_set_deadline(
        &s->metadata_buffer[0],
        gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC), *cached_timeout));
    GRPC_MDELEM_UNREF(md);
  } else {
    const size_t new_size = s->metadata_buffer[0].size + GRPC_MDELEM_LENGTH(md);
    const size_t metadata_size_limit =
        t->settings[GRPC_ACKED_SETTINGS]
                   [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
    if (new_size > metadata_size_limit) {
      gpr_log(GPR_DEBUG,
              "received initial metadata size exceeds limit (%" PRIuPTR
              " vs. %" PRIuPTR ")",
              new_size, metadata_size_limit);
      grpc_chttp2_cancel_stream(
          exec_ctx, t, s,
          grpc_error_set_int(
              GRPC_ERROR_CREATE("received initial metadata size exceeds limit"),
              GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_RESOURCE_EXHAUSTED));
      grpc_chttp2_parsing_become_skip_parser(exec_ctx, t);
      s->seen_error = true;
      GRPC_MDELEM_UNREF(md);
    } else {
      grpc_chttp2_incoming_metadata_buffer_add(&s->metadata_buffer[0], md);
    }
  }

  GPR_TIMER_END("on_initial_header", 0);
}

static void destroy_channel(grpc_exec_ctx *exec_ctx, grpc_channel *channel) {
  size_t i;
  grpc_channel_stack_destroy(exec_ctx, CHANNEL_STACK_FROM_CHANNEL(channel));
  for (i = 0; i < NUM_CACHED_STATUS_ELEMS; i++) {
    GRPC_MDELEM_UNREF(channel->grpc_status_elem[i]);
  }
  GRPC_MDSTR_UNREF(channel->grpc_status_string);
  GRPC_MDSTR_UNREF(channel->grpc_compression_algorithm_string);
  GRPC_MDSTR_UNREF(channel->grpc_encodings_accepted_by_peer_string);
  GRPC_MDSTR_UNREF(channel->grpc_message_string);
  GRPC_MDSTR_UNREF(channel->path_string);
  GRPC_MDSTR_UNREF(channel->authority_string);
  while (channel->registered_calls) {
    registered_call *rc = channel->registered_calls;
    channel->registered_calls = rc->next;
    GRPC_MDELEM_UNREF(rc->path);
    if (rc->authority) {
      GRPC_MDELEM_UNREF(rc->authority);
    }
    gpr_free(rc);
  }
  if (channel->default_authority != NULL) {
    GRPC_MDELEM_UNREF(channel->default_authority);
  }
  grpc_mdctx_unref(channel->metadata_context);
  gpr_mu_destroy(&channel->registered_call_mu);
  gpr_free(channel->target);
  gpr_free(channel);
}

void grpc_metadata_batch_destroy(grpc_metadata_batch *batch) {
  grpc_linked_mdelem *l;
  for (l = batch->list.head; l; l = l->next) {
    GRPC_MDELEM_UNREF(l->md);
  }
  for (l = batch->garbage.head; l; l = l->next) {
    GRPC_MDELEM_UNREF(l->md);
  }
}

static void test_spin_creating_the_same_thing(void) {
  LOG_TEST("test_spin_creating_the_same_thing");

  grpc_init();
  GRPC_MDELEM_UNREF(grpc_mdelem_from_strings("a", "b"));
  GRPC_MDELEM_UNREF(grpc_mdelem_from_strings("a", "b"));
  GRPC_MDELEM_UNREF(grpc_mdelem_from_strings("a", "b"));
  grpc_shutdown();
}

static void on_trailing_header(grpc_exec_ctx *exec_ctx, void *tp,
                               grpc_mdelem md) {
  grpc_chttp2_transport *t = (grpc_chttp2_transport *)tp;
  grpc_chttp2_stream *s = t->incoming_stream;

  GPR_TIMER_BEGIN("on_trailing_header", 0);

  GPR_ASSERT(s != NULL);

  if (GRPC_TRACER_ON(grpc_http_trace)) {
    char *key = grpc_slice_to_c_string(GRPC_MDKEY(md));
    char *value =
        grpc_dump_slice(GRPC_MDVALUE(md), GPR_DUMP_HEX | GPR_DUMP_ASCII);
    gpr_log(GPR_INFO, "HTTP:%d:TRL:%s: %s: %s", s->id,
            t->is_client ? "CLI" : "SVR", key, value);
    gpr_free(key);
    gpr_free(value);
  }

  if (grpc_slice_eq(GRPC_MDKEY(md), GRPC_MDSTR_GRPC_STATUS) &&
      !grpc_mdelem_eq(md, GRPC_MDELEM_GRPC_STATUS_0)) {
    /* TODO(ctiller): check for a status like " 0" */
    s->seen_error = true;
  }

  const size_t new_size = s->metadata_buffer[1].size + GRPC_MDELEM_LENGTH(md);
  const size_t metadata_size_limit =
      t->settings[GRPC_ACKED_SETTINGS]
                 [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
  if (new_size > metadata_size_limit) {
    gpr_log(GPR_DEBUG,
            "received trailing metadata size exceeds limit (%" PRIuPTR
            " vs. %" PRIuPTR ")",
            new_size, metadata_size_limit);
    grpc_chttp2_cancel_stream(
        exec_ctx, t, s,
        grpc_error_set_int(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
                               "received trailing metadata size exceeds limit"),
                           GRPC_ERROR_INT_GRPC_STATUS,
                           GRPC_STATUS_RESOURCE_EXHAUSTED));
    grpc_chttp2_parsing_become_skip_parser(exec_ctx, t);
    s->seen_error = true;
    GRPC_MDELEM_UNREF(exec_ctx, md);
  } else {
    grpc_error *error = grpc_chttp2_incoming_metadata_buffer_add(
        exec_ctx, &s->metadata_buffer[1], md);
    if (error != GRPC_ERROR_NONE) {
      grpc_chttp2_cancel_stream(exec_ctx, t, s, error);
      grpc_chttp2_parsing_become_skip_parser(exec_ctx, t);
      s->seen_error = true;
      GRPC_MDELEM_UNREF(exec_ctx, md);
    }
  }

  GPR_TIMER_END("on_trailing_header", 0);
}

void grpc_chttp2_hptbl_destroy(grpc_chttp2_hptbl *tbl) {
  size_t i;
  for (i = 0; i < GRPC_CHTTP2_LAST_STATIC_ENTRY; i++) {
    GRPC_MDELEM_UNREF(tbl->static_ents[i]);
  }
  for (i = 0; i < tbl->num_ents; i++) {
    GRPC_MDELEM_UNREF(tbl->ents[(tbl->first_ent + i) % tbl->cap_entries]);
  }
  gpr_free(tbl->ents);
}

/* Destructor for channel data */
static void destroy_channel_elem(grpc_channel_element *elem) {
  channel_data *channeld = elem->channel_data;
  grpc_compression_algorithm algo_idx;

  GRPC_MDSTR_UNREF(channeld->mdstr_request_compression_algorithm_key);
  GRPC_MDSTR_UNREF(channeld->mdstr_outgoing_compression_algorithm_key);
  GRPC_MDSTR_UNREF(channeld->mdstr_compression_capabilities_key);
  for (algo_idx = 0; algo_idx < GRPC_COMPRESS_ALGORITHMS_COUNT; ++algo_idx) {
    GRPC_MDELEM_UNREF(channeld->mdelem_compression_algorithms[algo_idx]);
  }
  GRPC_MDELEM_UNREF(channeld->mdelem_accept_encoding);
}

static void test_many_additions(void) {
  grpc_chttp2_hptbl tbl;
  int i;
  char *key;
  char *value;

  LOG_TEST("test_many_additions");

  grpc_chttp2_hptbl_init(&tbl);

  for (i = 0; i < 1000000; i++) {
    grpc_mdelem *elem;
    gpr_asprintf(&key, "K:%d", i);
    gpr_asprintf(&value, "VALUE:%d", i);
    elem = grpc_mdelem_from_strings(key, value);
    GPR_ASSERT(grpc_chttp2_hptbl_add(&tbl, elem));
    GRPC_MDELEM_UNREF(elem);
    assert_index(&tbl, 1 + GRPC_CHTTP2_LAST_STATIC_ENTRY, key, value);
    gpr_free(key);
    gpr_free(value);
    if (i) {
      gpr_asprintf(&key, "K:%d", i - 1);
      gpr_asprintf(&value, "VALUE:%d", i - 1);
      assert_index(&tbl, 2 + GRPC_CHTTP2_LAST_STATIC_ENTRY, key, value);
      gpr_free(key);
      gpr_free(value);
    }
  }

  grpc_chttp2_hptbl_destroy(&tbl);
}

void grpc_credentials_mdelem_array_destroy(
    grpc_exec_ctx *exec_ctx, grpc_credentials_mdelem_array *list) {
  for (size_t i = 0; i < list->size; ++i) {
    GRPC_MDELEM_UNREF(exec_ctx, list->md[i]);
  }
  gpr_free(list->md);
}

static void destroy_call(grpc_exec_ctx *exec_ctx, void *call, int success) {
  size_t i;
  int ii;
  grpc_call *c = call;
  GPR_TIMER_BEGIN("destroy_call", 0);
  for (i = 0; i < 2; i++) {
    grpc_metadata_batch_destroy(
        &c->metadata_batch[1 /* is_receiving */][i /* is_initial */]);
  }
  if (c->receiving_stream != NULL) {
    grpc_byte_stream_destroy(c->receiving_stream);
  }
  grpc_call_stack_destroy(exec_ctx, CALL_STACK_FROM_CALL(c));
  GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, c->channel, "call");
  gpr_mu_destroy(&c->mu);
  for (i = 0; i < STATUS_SOURCE_COUNT; i++) {
    if (c->status[i].details) {
      GRPC_MDSTR_UNREF(c->status[i].details);
    }
  }
  for (ii = 0; ii < c->send_extra_metadata_count; ii++) {
    GRPC_MDELEM_UNREF(c->send_extra_metadata[ii].md);
  }
  for (i = 0; i < GRPC_CONTEXT_COUNT; i++) {
    if (c->context[i].destroy) {
      c->context[i].destroy(c->context[i].value);
    }
  }
  if (c->cq) {
    GRPC_CQ_INTERNAL_UNREF(c->cq, "bind");
  }
  gpr_free(c);
  GPR_TIMER_END("destroy_call", 0);
}

static void test_algorithm_mesh(void) {
  int i;

  gpr_log(GPR_DEBUG, "test_algorithm_mesh");

  for (i = 0; i < GRPC_COMPRESS_ALGORITHMS_COUNT; i++) {
    const char *name;
    grpc_compression_algorithm parsed;
    grpc_slice mdstr;
    grpc_mdelem mdelem;
    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
    GPR_ASSERT(
        grpc_compression_algorithm_name((grpc_compression_algorithm)i, &name));
    GPR_ASSERT(grpc_compression_algorithm_parse(
        grpc_slice_from_static_string(name), &parsed));
    GPR_ASSERT((int)parsed == i);
    mdstr = grpc_slice_from_copied_string(name);
    GPR_ASSERT(grpc_slice_eq(mdstr, grpc_compression_algorithm_slice(parsed)));
    GPR_ASSERT(parsed == grpc_compression_algorithm_from_slice(mdstr));
    mdelem = grpc_compression_encoding_mdelem(parsed);
    GPR_ASSERT(grpc_slice_eq(GRPC_MDVALUE(mdelem), mdstr));
    GPR_ASSERT(grpc_slice_eq(GRPC_MDKEY(mdelem), GRPC_MDSTR_GRPC_ENCODING));
    grpc_slice_unref_internal(&exec_ctx, mdstr);
    GRPC_MDELEM_UNREF(&exec_ctx, mdelem);
    grpc_exec_ctx_finish(&exec_ctx);
  }

  /* test failure */
  GPR_ASSERT(GRPC_MDISNULL(
      grpc_compression_encoding_mdelem(GRPC_COMPRESS_ALGORITHMS_COUNT)));
}

static grpc_chttp2_hptbl_find_result find_simple(grpc_chttp2_hptbl *tbl,
                                                 const char *key,
                                                 const char *value) {
  grpc_mdelem *md = grpc_mdelem_from_strings(key, value);
  grpc_chttp2_hptbl_find_result r = grpc_chttp2_hptbl_find(tbl, md);
  GRPC_MDELEM_UNREF(md);
  return r;
}

void grpc_chttp2_hpack_compressor_destroy(grpc_chttp2_hpack_compressor *c) {
  int i;
  for (i = 0; i < GRPC_CHTTP2_HPACKC_NUM_VALUES; i++) {
    if (c->entries_keys[i]) GRPC_MDSTR_UNREF(c->entries_keys[i]);
    if (c->entries_elems[i]) GRPC_MDELEM_UNREF(c->entries_elems[i]);
  }
  gpr_free(c->table_elem_size);
}

static void destroy_channel(grpc_exec_ctx *exec_ctx, grpc_channel *channel) {
  grpc_channel_stack_destroy(exec_ctx, CHANNEL_STACK_FROM_CHANNEL(channel));
  while (channel->registered_calls) {
    registered_call *rc = channel->registered_calls;
    channel->registered_calls = rc->next;
    GRPC_MDELEM_UNREF(rc->path);
    if (rc->authority) {
      GRPC_MDELEM_UNREF(rc->authority);
    }
    gpr_free(rc);
  }
  if (channel->default_authority != NULL) {
    GRPC_MDELEM_UNREF(channel->default_authority);
  }
  gpr_mu_destroy(&channel->registered_call_mu);
  gpr_free(channel->target);
  gpr_free(channel);
}

void grpc_chttp2_incoming_metadata_buffer_destroy(
    grpc_chttp2_incoming_metadata_buffer *buffer) {
  size_t i;
  if (!buffer->published) {
    for (i = 0; i < buffer->count; i++) {
      GRPC_MDELEM_UNREF(buffer->elems[i].md);
    }
  }
  gpr_free(buffer->elems);
}

/* Evict one element from the table */
static void evict1(grpc_chttp2_hptbl *tbl) {
  grpc_mdelem *first_ent = tbl->ents[tbl->first_ent];
  size_t elem_bytes = GPR_SLICE_LENGTH(first_ent->key->slice) +
                      GPR_SLICE_LENGTH(first_ent->value->slice) +
                      GRPC_CHTTP2_HPACK_ENTRY_OVERHEAD;
  GPR_ASSERT(elem_bytes <= tbl->mem_used);
  tbl->mem_used -= (uint32_t)elem_bytes;
  tbl->first_ent = ((tbl->first_ent + 1) % tbl->cap_entries);
  tbl->num_ents--;
  GRPC_MDELEM_UNREF(first_ent);
}

void grpc_chttp2_hpack_compressor_destroy(grpc_exec_ctx *exec_ctx,
                                          grpc_chttp2_hpack_compressor *c) {
  int i;
  for (i = 0; i < GRPC_CHTTP2_HPACKC_NUM_VALUES; i++) {
    if (c->entries_keys[i].refcount != &terminal_slice_refcount) {
      grpc_slice_unref_internal(exec_ctx, c->entries_keys[i]);
    }
    GRPC_MDELEM_UNREF(exec_ctx, c->entries_elems[i]);
  }
  gpr_free(c->table_elem_size);
}

static void onhdr(grpc_exec_ctx *exec_ctx, void *ud, grpc_mdelem md) {
  const char *ekey, *evalue;
  test_checker *chk = ud;
  ekey = va_arg(chk->args, char *);
  GPR_ASSERT(ekey);
  evalue = va_arg(chk->args, char *);
  GPR_ASSERT(evalue);
  GPR_ASSERT(grpc_slice_str_cmp(GRPC_MDKEY(md), ekey) == 0);
  GPR_ASSERT(grpc_slice_str_cmp(GRPC_MDVALUE(md), evalue) == 0);
  GRPC_MDELEM_UNREF(exec_ctx, md);
}

static void onhdr(void *ud, grpc_mdelem *md) {
  const char *ekey, *evalue;
  test_checker *chk = ud;
  ekey = va_arg(chk->args, char *);
  GPR_ASSERT(ekey);
  evalue = va_arg(chk->args, char *);
  GPR_ASSERT(evalue);
  GPR_ASSERT(gpr_slice_str_cmp(md->key->slice, ekey) == 0);
  GPR_ASSERT(gpr_slice_str_cmp(md->value->slice, evalue) == 0);
  GRPC_MDELEM_UNREF(md);
}