Skip to content
Snippets Groups Projects
Select Git revision
  • 3af0908140fb23d2fd7369989e5fd701896c2220
  • master default protected
  • arm-aarch-platform
  • arm-platform
  • vjpai-patch-3
  • vjpai-patch-1
  • v1.27.x
  • jtattermusch-patch-2
  • jtattermusch-patch-1
  • update-java-worker-example-in-performance-docs
  • revert-21805-revert-21797-reintroduce_21527
  • revert-21804-tls-credentials-1
  • zhen_cleanup_namecheck
  • revert-21806-revert-21767-revert-21725-revert-21680-cq_ordering
  • vjpai-patch-2
  • revert-21766-tls-credentials-1
  • revert-21640-change_local_tcp_security_level
  • revert-21680-cq_ordering
  • revert-21527-unify_boringssl_deps2
  • revert-20803-grpclb_stabilization
  • fix-kokoro-rvm-key
  • v1.27.0
  • v1.27.0-pre2
  • v1.27.0-pre1
  • v1.26.0
  • v1.26.0-pre1
  • v1.25.0
  • v1.25.0-pre1
  • v1.24.3
  • v1.24.2
  • v1.24.1
  • v1.23.1
  • v1.24.0
  • v1.24.0-pre2
  • v1.24.0-pre1
  • v1.22.1
  • v1.23.0
  • v1.23.0-pre1
  • v1.22.0
  • v1.22.0-pre1
  • v1.21.4
41 results

byte_buffer_proto_helper.cc

Blame
  • call.c 63.06 KiB
    /*
     *
     * Copyright 2015, Google Inc.
     * All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions are
     * met:
     *
     *     * Redistributions of source code must retain the above copyright
     * notice, this list of conditions and the following disclaimer.
     *     * Redistributions in binary form must reproduce the above
     * copyright notice, this list of conditions and the following disclaimer
     * in the documentation and/or other materials provided with the
     * distribution.
     *     * Neither the name of Google Inc. nor the names of its
     * contributors may be used to endorse or promote products derived from
     * this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     *
     */
    #include <assert.h>
    #include <limits.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    #include <grpc/compression.h>
    #include <grpc/grpc.h>
    #include <grpc/support/alloc.h>
    #include <grpc/support/log.h>
    #include <grpc/support/slice.h>
    #include <grpc/support/string_util.h>
    #include <grpc/support/useful.h>
    
    #include "src/core/lib/channel/channel_stack.h"
    #include "src/core/lib/compression/algorithm_metadata.h"
    #include "src/core/lib/iomgr/timer.h"
    #include "src/core/lib/profiling/timers.h"
    #include "src/core/lib/support/string.h"
    #include "src/core/lib/surface/api_trace.h"
    #include "src/core/lib/surface/call.h"
    #include "src/core/lib/surface/channel.h"
    #include "src/core/lib/surface/completion_queue.h"
    #include "src/core/lib/transport/metadata.h"
    #include "src/core/lib/transport/static_metadata.h"
    #include "src/core/lib/transport/transport.h"
    
    /** The maximum number of concurrent batches possible.
        Based upon the maximum number of individually queueable ops in the batch
       api:
          - initial metadata send
          - message send
          - status/close send (depending on client/server)
          - initial metadata recv
          - message recv
          - status/close recv (depending on client/server) */
    #define MAX_CONCURRENT_BATCHES 6
    
    #define MAX_SEND_EXTRA_METADATA_COUNT 3
    
    /* Status data for a request can come from several sources; this
       enumerates them all, and acts as a priority sorting for which
       status to return to the application - earlier entries override
       later ones */
    typedef enum {
      /* Status came from the application layer overriding whatever
         the wire says */
      STATUS_FROM_API_OVERRIDE = 0,
      /* Status came from 'the wire' - or somewhere below the surface
         layer */
      STATUS_FROM_WIRE,
      /* Status was created by some internal channel stack operation */
      STATUS_FROM_CORE,
      /* Status came from the server sending status */
      STATUS_FROM_SERVER_STATUS,
      STATUS_SOURCE_COUNT
    } status_source;
    
    typedef struct {
      uint8_t is_set;
      grpc_status_code code;
      grpc_mdstr *details;
    } received_status;
    
    typedef struct batch_control {
      grpc_call *call;
      grpc_cq_completion cq_completion;
      grpc_closure finish_batch;
      void *notify_tag;
      gpr_refcount steps_to_complete;
      grpc_error *error;
    
      uint8_t send_initial_metadata;
      uint8_t send_message;
      uint8_t send_final_op;
      uint8_t recv_initial_metadata;
      uint8_t recv_message;
      uint8_t recv_final_op;
      uint8_t is_notify_tag_closure;
    } batch_control;
    
    struct grpc_call {
      grpc_completion_queue *cq;
      grpc_polling_entity pollent;
      grpc_channel *channel;
      grpc_call *parent;
      grpc_call *first_child;
      /* TODO(ctiller): share with cq if possible? */
      gpr_mu mu;
    
      /* client or server call */
      bool is_client;
      /* is the alarm set */
      bool have_alarm;
      /** has grpc_call_destroy been called */
      bool destroy_called;
      /** flag indicating that cancellation is inherited */
      bool cancellation_is_inherited;
      /** bitmask of live batches */
      uint8_t used_batches;
      /** which ops are in-flight */
      bool sent_initial_metadata;
      bool sending_message;
      bool sent_final_op;
      bool received_initial_metadata;
      bool receiving_message;
      bool requested_final_op;
      bool received_final_op;
    
      /* have we received initial metadata */
      bool has_initial_md_been_received;
    
      batch_control active_batches[MAX_CONCURRENT_BATCHES];
    
      /* first idx: is_receiving, second idx: is_trailing */
      grpc_metadata_batch metadata_batch[2][2];
    
      /* Buffered read metadata waiting to be returned to the application.
         Element 0 is initial metadata, element 1 is trailing metadata. */
      grpc_metadata_array *buffered_metadata[2];
    
      /* Received call statuses from various sources */
      received_status status[STATUS_SOURCE_COUNT];
    
      /* Call stats: only valid after trailing metadata received */
      grpc_call_stats stats;
    
      /* Compression algorithm for *incoming* data */
      grpc_compression_algorithm incoming_compression_algorithm;
      /* Supported encodings (compression algorithms), a bitset */
      uint32_t encodings_accepted_by_peer;
    
      /* Contexts for various subsystems (security, tracing, ...). */
      grpc_call_context_element context[GRPC_CONTEXT_COUNT];
    
      /* Deadline alarm - if have_alarm is non-zero */
      grpc_timer alarm;
    
      /* for the client, extra metadata is initial metadata; for the
         server, it's trailing metadata */
      grpc_linked_mdelem send_extra_metadata[MAX_SEND_EXTRA_METADATA_COUNT];
      int send_extra_metadata_count;
      gpr_timespec send_deadline;
    
      /** siblings: children of the same parent form a list, and this list is
         protected under
          parent->mu */
      grpc_call *sibling_next;
      grpc_call *sibling_prev;
    
      grpc_slice_buffer_stream sending_stream;
      grpc_byte_stream *receiving_stream;
      grpc_byte_buffer **receiving_buffer;
      gpr_slice receiving_slice;
      grpc_closure receiving_slice_ready;
      grpc_closure receiving_stream_ready;
      grpc_closure receiving_initial_metadata_ready;
      uint32_t test_only_last_message_flags;
    
      union {
        struct {
          grpc_status_code *status;
          char **status_details;
          size_t *status_details_capacity;
        } client;
        struct {
          int *cancelled;
        } server;
      } final_op;
    
      void *saved_receiving_stream_ready_bctlp;
    };
    
    #define CALL_STACK_FROM_CALL(call) ((grpc_call_stack *)((call) + 1))
    #define CALL_FROM_CALL_STACK(call_stack) (((grpc_call *)(call_stack)) - 1)
    #define CALL_ELEM_FROM_CALL(call, idx) \
      grpc_call_stack_element(CALL_STACK_FROM_CALL(call), idx)
    #define CALL_FROM_TOP_ELEM(top_elem) \
      CALL_FROM_CALL_STACK(grpc_call_stack_from_top_element(top_elem))
    
    static void set_deadline_alarm(grpc_exec_ctx *exec_ctx, grpc_call *call,
                                   gpr_timespec deadline);
    static void execute_op(grpc_exec_ctx *exec_ctx, grpc_call *call,
                           grpc_transport_stream_op *op);
    static grpc_call_error cancel_with_status(grpc_exec_ctx *exec_ctx, grpc_call *c,
                                              grpc_status_code status,
                                              const char *description);
    static grpc_call_error close_with_status(grpc_exec_ctx *exec_ctx, grpc_call *c,
                                             grpc_status_code status,
                                             const char *description);
    static void destroy_call(grpc_exec_ctx *exec_ctx, void *call_stack,
                             grpc_error *error);
    static void receiving_slice_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
                                      grpc_error *error);
    
    grpc_call *grpc_call_create(
        grpc_channel *channel, grpc_call *parent_call, uint32_t propagation_mask,
        grpc_completion_queue *cq, grpc_pollset_set *pollset_set_alternative,
        const void *server_transport_data, grpc_mdelem **add_initial_metadata,
        size_t add_initial_metadata_count, gpr_timespec send_deadline) {
      size_t i, j;
      grpc_channel_stack *channel_stack = grpc_channel_get_channel_stack(channel);
      grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
      grpc_call *call;
      GPR_TIMER_BEGIN("grpc_call_create", 0);
      call = gpr_malloc(sizeof(grpc_call) + channel_stack->call_stack_size);
      memset(call, 0, sizeof(grpc_call));
      gpr_mu_init(&call->mu);
      call->channel = channel;
      call->cq = cq;
      call->parent = parent_call;
      /* Always support no compression */
      GPR_BITSET(&call->encodings_accepted_by_peer, GRPC_COMPRESS_NONE);
      call->is_client = server_transport_data == NULL;
      if (call->is_client) {
        GPR_ASSERT(add_initial_metadata_count < MAX_SEND_EXTRA_METADATA_COUNT);
        for (i = 0; i < add_initial_metadata_count; i++) {
          call->send_extra_metadata[i].md = add_initial_metadata[i];
        }
        call->send_extra_metadata_count = (int)add_initial_metadata_count;
      } else {
        GPR_ASSERT(add_initial_metadata_count == 0);
        call->send_extra_metadata_count = 0;
      }
      for (i = 0; i < 2; i++) {
        for (j = 0; j < 2; j++) {
          call->metadata_batch[i][j].deadline = gpr_inf_future(GPR_CLOCK_MONOTONIC);
        }
      }
      call->send_deadline = send_deadline;
      GRPC_CHANNEL_INTERNAL_REF(channel, "call");
      /* initial refcount dropped by grpc_call_destroy */
      grpc_error* error = grpc_call_stack_init(&exec_ctx, channel_stack, 1,
                                               destroy_call, call, call->context,
                                               server_transport_data,
                                               CALL_STACK_FROM_CALL(call));
      if (error != GRPC_ERROR_NONE) {
        intptr_t status;
        if (!grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, &status))
          status = GRPC_STATUS_UNKNOWN;
        const char* error_string = grpc_error_string(error);
        received_status* status_struct = &call->status[STATUS_FROM_CORE];
        status_struct->is_set = true;
        status_struct->code = status;
        status_struct->details = grpc_mdstr_from_string(error_string);
        grpc_error_free_string(error_string);
        grpc_error_unref(error);
      }
      if (cq != NULL) {
        GPR_ASSERT(
            pollset_set_alternative == NULL &&
            "Only one of 'cq' and 'pollset_set_alternative' should be non-NULL.");
        GRPC_CQ_INTERNAL_REF(cq, "bind");
        call->pollent =
            grpc_polling_entity_create_from_pollset(grpc_cq_pollset(cq));
      }
      if (pollset_set_alternative != NULL) {
        call->pollent =
            grpc_polling_entity_create_from_pollset_set(pollset_set_alternative);
      }
      if (!grpc_polling_entity_is_empty(&call->pollent)) {
        grpc_call_stack_set_pollset_or_pollset_set(
            &exec_ctx, CALL_STACK_FROM_CALL(call), &call->pollent);
      }
      if (parent_call != NULL) {
        GRPC_CALL_INTERNAL_REF(parent_call, "child");
        GPR_ASSERT(call->is_client);
        GPR_ASSERT(!parent_call->is_client);
    
        gpr_mu_lock(&parent_call->mu);
    
        if (propagation_mask & GRPC_PROPAGATE_DEADLINE) {
          send_deadline = gpr_time_min(
              gpr_convert_clock_type(send_deadline,
                                     parent_call->send_deadline.clock_type),
              parent_call->send_deadline);
        }
        /* for now GRPC_PROPAGATE_TRACING_CONTEXT *MUST* be passed with
         * GRPC_PROPAGATE_STATS_CONTEXT */
        /* TODO(ctiller): This should change to use the appropriate census start_op
         * call. */
        if (propagation_mask & GRPC_PROPAGATE_CENSUS_TRACING_CONTEXT) {
          GPR_ASSERT(propagation_mask & GRPC_PROPAGATE_CENSUS_STATS_CONTEXT);
          grpc_call_context_set(call, GRPC_CONTEXT_TRACING,
                                parent_call->context[GRPC_CONTEXT_TRACING].value,
                                NULL);
        } else {
          GPR_ASSERT(propagation_mask & GRPC_PROPAGATE_CENSUS_STATS_CONTEXT);
        }
        if (propagation_mask & GRPC_PROPAGATE_CANCELLATION) {
          call->cancellation_is_inherited = 1;
        }
    
        if (parent_call->first_child == NULL) {
          parent_call->first_child = call;
          call->sibling_next = call->sibling_prev = call;
        } else {
          call->sibling_next = parent_call->first_child;
          call->sibling_prev = parent_call->first_child->sibling_prev;
          call->sibling_next->sibling_prev = call->sibling_prev->sibling_next =
              call;
        }
    
        gpr_mu_unlock(&parent_call->mu);
      }
      if (gpr_time_cmp(send_deadline, gpr_inf_future(send_deadline.clock_type)) !=
          0) {
        set_deadline_alarm(&exec_ctx, call, send_deadline);
      }
      grpc_exec_ctx_finish(&exec_ctx);
      GPR_TIMER_END("grpc_call_create", 0);
      return call;
    }
    
    void grpc_call_set_completion_queue(grpc_exec_ctx *exec_ctx, grpc_call *call,
                                        grpc_completion_queue *cq) {
      GPR_ASSERT(cq);
    
      if (grpc_polling_entity_pollset_set(&call->pollent) != NULL) {
        gpr_log(GPR_ERROR, "A pollset_set is already registered for this call.");
        abort();
      }
      call->cq = cq;
      GRPC_CQ_INTERNAL_REF(cq, "bind");
      call->pollent = grpc_polling_entity_create_from_pollset(grpc_cq_pollset(cq));
      grpc_call_stack_set_pollset_or_pollset_set(
          exec_ctx, CALL_STACK_FROM_CALL(call), &call->pollent);
    }
    
    #ifdef GRPC_STREAM_REFCOUNT_DEBUG
    #define REF_REASON reason
    #define REF_ARG , const char *reason
    #else
    #define REF_REASON ""
    #define REF_ARG
    #endif
    void grpc_call_internal_ref(grpc_call *c REF_ARG) {
      GRPC_CALL_STACK_REF(CALL_STACK_FROM_CALL(c), REF_REASON);
    }
    void grpc_call_internal_unref(grpc_exec_ctx *exec_ctx, grpc_call *c REF_ARG) {
      GRPC_CALL_STACK_UNREF(exec_ctx, CALL_STACK_FROM_CALL(c), REF_REASON);
    }
    
    static void destroy_call(grpc_exec_ctx *exec_ctx, void *call,
                             grpc_error *error) {
      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(exec_ctx, c->receiving_stream);
      }
      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");
      }
      grpc_channel *channel = c->channel;
      grpc_call_stack_destroy(exec_ctx, CALL_STACK_FROM_CALL(c), &c->stats, c);
      GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel, "call");
      GPR_TIMER_END("destroy_call", 0);
    }
    
    static void set_status_code(grpc_call *call, status_source source,
                                uint32_t status) {
      if (call->status[source].is_set) return;
    
      call->status[source].is_set = 1;
      call->status[source].code = (grpc_status_code)status;
    
      /* TODO(ctiller): what to do about the flush that was previously here */
    }
    
    static void set_incoming_compression_algorithm(
        grpc_call *call, grpc_compression_algorithm algo) {
      GPR_ASSERT(algo < GRPC_COMPRESS_ALGORITHMS_COUNT);
      call->incoming_compression_algorithm = algo;
    }
    
    grpc_compression_algorithm grpc_call_test_only_get_compression_algorithm(
        grpc_call *call) {
      grpc_compression_algorithm algorithm;
      gpr_mu_lock(&call->mu);
      algorithm = call->incoming_compression_algorithm;
      gpr_mu_unlock(&call->mu);
      return algorithm;
    }
    
    static grpc_compression_algorithm compression_algorithm_for_level_locked(
        grpc_call *call, grpc_compression_level level) {
      return grpc_compression_algorithm_for_level(level,
                                                  call->encodings_accepted_by_peer);
    }
    
    uint32_t grpc_call_test_only_get_message_flags(grpc_call *call) {
      uint32_t flags;
      gpr_mu_lock(&call->mu);
      flags = call->test_only_last_message_flags;
      gpr_mu_unlock(&call->mu);
      return flags;
    }
    
    static void destroy_encodings_accepted_by_peer(void *p) { return; }
    
    static void set_encodings_accepted_by_peer(grpc_call *call, grpc_mdelem *mdel) {
      size_t i;
      grpc_compression_algorithm algorithm;
      gpr_slice_buffer accept_encoding_parts;
      gpr_slice accept_encoding_slice;
      void *accepted_user_data;
    
      accepted_user_data =
          grpc_mdelem_get_user_data(mdel, destroy_encodings_accepted_by_peer);
      if (accepted_user_data != NULL) {
        call->encodings_accepted_by_peer =
            (uint32_t)(((uintptr_t)accepted_user_data) - 1);
        return;
      }
    
      accept_encoding_slice = mdel->value->slice;
      gpr_slice_buffer_init(&accept_encoding_parts);
      gpr_slice_split(accept_encoding_slice, ",", &accept_encoding_parts);
    
      /* No need to zero call->encodings_accepted_by_peer: grpc_call_create already
       * zeroes the whole grpc_call */
      /* Always support no compression */
      GPR_BITSET(&call->encodings_accepted_by_peer, GRPC_COMPRESS_NONE);
      for (i = 0; i < accept_encoding_parts.count; i++) {
        const gpr_slice *accept_encoding_entry_slice =
            &accept_encoding_parts.slices[i];
        if (grpc_compression_algorithm_parse(
                (const char *)GPR_SLICE_START_PTR(*accept_encoding_entry_slice),
                GPR_SLICE_LENGTH(*accept_encoding_entry_slice), &algorithm)) {
          GPR_BITSET(&call->encodings_accepted_by_peer, algorithm);
        } else {
          char *accept_encoding_entry_str =
              gpr_dump_slice(*accept_encoding_entry_slice, GPR_DUMP_ASCII);
          gpr_log(GPR_ERROR,
                  "Invalid entry in accept encoding metadata: '%s'. Ignoring.",
                  accept_encoding_entry_str);
          gpr_free(accept_encoding_entry_str);
        }
      }
    
      gpr_slice_buffer_destroy(&accept_encoding_parts);
    
      grpc_mdelem_set_user_data(
          mdel, destroy_encodings_accepted_by_peer,
          (void *)(((uintptr_t)call->encodings_accepted_by_peer) + 1));
    }
    
    uint32_t grpc_call_test_only_get_encodings_accepted_by_peer(grpc_call *call) {
      uint32_t encodings_accepted_by_peer;
      gpr_mu_lock(&call->mu);
      encodings_accepted_by_peer = call->encodings_accepted_by_peer;
      gpr_mu_unlock(&call->mu);
      return encodings_accepted_by_peer;
    }
    
    static void set_status_details(grpc_call *call, status_source source,
                                   grpc_mdstr *status) {
      if (call->status[source].details != NULL) {
        GRPC_MDSTR_UNREF(call->status[source].details);
      }
      call->status[source].details = status;
    }
    
    static void get_final_status(grpc_call *call,
                                 void (*set_value)(grpc_status_code code,
                                                   void *user_data),
                                 void *set_value_user_data) {
      int i;
      for (i = 0; i < STATUS_SOURCE_COUNT; i++) {
        if (call->status[i].is_set) {
          set_value(call->status[i].code, set_value_user_data);
          return;
        }
      }
      if (call->is_client) {
        set_value(GRPC_STATUS_UNKNOWN, set_value_user_data);
      } else {
        set_value(GRPC_STATUS_OK, set_value_user_data);
      }
    }
    
    static void get_final_details(grpc_call *call, char **out_details,
                                  size_t *out_details_capacity) {
      int i;
      for (i = 0; i < STATUS_SOURCE_COUNT; i++) {
        if (call->status[i].is_set) {
          if (call->status[i].details) {
            gpr_slice details = call->status[i].details->slice;
            size_t len = GPR_SLICE_LENGTH(details);
            if (len + 1 > *out_details_capacity) {
              *out_details_capacity =
                  GPR_MAX(len + 1, *out_details_capacity * 3 / 2);
              *out_details = gpr_realloc(*out_details, *out_details_capacity);
            }
            memcpy(*out_details, GPR_SLICE_START_PTR(details), len);
            (*out_details)[len] = 0;
          } else {
            goto no_details;
          }
          return;
        }
      }
    
    no_details:
      if (0 == *out_details_capacity) {
        *out_details_capacity = 8;
        *out_details = gpr_malloc(*out_details_capacity);
      }
      **out_details = 0;
    }
    
    static grpc_linked_mdelem *linked_from_md(grpc_metadata *md) {
      return (grpc_linked_mdelem *)&md->internal_data;
    }
    
    static grpc_metadata *get_md_elem(grpc_metadata *metadata,
                                      grpc_metadata *additional_metadata, int i,
                                      int count) {
      grpc_metadata *res =
          i < count ? &metadata[i] : &additional_metadata[i - count];
      GPR_ASSERT(res);
      return res;
    }
    
    static int prepare_application_metadata(grpc_call *call, int count,
                                            grpc_metadata *metadata,
                                            int is_trailing,
                                            int prepend_extra_metadata,
                                            grpc_metadata *additional_metadata,
                                            int additional_metadata_count) {
      int total_count = count + additional_metadata_count;
      int i;
      grpc_metadata_batch *batch =
          &call->metadata_batch[0 /* is_receiving */][is_trailing];
      for (i = 0; i < total_count; i++) {
        const grpc_metadata *md =
            get_md_elem(metadata, additional_metadata, i, count);
        grpc_linked_mdelem *l = (grpc_linked_mdelem *)&md->internal_data;
        GPR_ASSERT(sizeof(grpc_linked_mdelem) == sizeof(md->internal_data));
        l->md = grpc_mdelem_from_string_and_buffer(
            md->key, (const uint8_t *)md->value, md->value_length);
        if (!grpc_header_key_is_legal(grpc_mdstr_as_c_string(l->md->key),
                                      GRPC_MDSTR_LENGTH(l->md->key))) {
          gpr_log(GPR_ERROR, "attempt to send invalid metadata key: %s",
                  grpc_mdstr_as_c_string(l->md->key));
          break;
        } else if (!grpc_is_binary_header(grpc_mdstr_as_c_string(l->md->key),
                                          GRPC_MDSTR_LENGTH(l->md->key)) &&
                   !grpc_header_nonbin_value_is_legal(
                       grpc_mdstr_as_c_string(l->md->value),
                       GRPC_MDSTR_LENGTH(l->md->value))) {
          gpr_log(GPR_ERROR, "attempt to send invalid metadata value");
          break;
        }
      }
      if (i != total_count) {
        for (int j = 0; j <= i; j++) {
          const grpc_metadata *md =
              get_md_elem(metadata, additional_metadata, j, count);
          grpc_linked_mdelem *l = (grpc_linked_mdelem *)&md->internal_data;
          GRPC_MDELEM_UNREF(l->md);
        }
        return 0;
      }
      if (prepend_extra_metadata) {
        if (call->send_extra_metadata_count == 0) {
          prepend_extra_metadata = 0;
        } else {
          for (i = 0; i < call->send_extra_metadata_count; i++) {
            GRPC_MDELEM_REF(call->send_extra_metadata[i].md);
          }
          for (i = 1; i < call->send_extra_metadata_count; i++) {
            call->send_extra_metadata[i].prev = &call->send_extra_metadata[i - 1];
          }
          for (i = 0; i < call->send_extra_metadata_count - 1; i++) {
            call->send_extra_metadata[i].next = &call->send_extra_metadata[i + 1];
          }
        }
      }
      for (i = 1; i < total_count; i++) {
        grpc_metadata *md = get_md_elem(metadata, additional_metadata, i, count);
        grpc_metadata *prev_md =
            get_md_elem(metadata, additional_metadata, i - 1, count);
        linked_from_md(md)->prev = linked_from_md(prev_md);
      }
      for (i = 0; i < total_count - 1; i++) {
        grpc_metadata *md = get_md_elem(metadata, additional_metadata, i, count);
        grpc_metadata *next_md =
            get_md_elem(metadata, additional_metadata, i + 1, count);
        linked_from_md(md)->next = linked_from_md(next_md);
      }
    
      switch (prepend_extra_metadata * 2 + (total_count != 0)) {
        case 0:
          /* no prepend, no metadata => nothing to do */
          batch->list.head = batch->list.tail = NULL;
          break;
        case 1: {
          /* metadata, but no prepend */
          grpc_metadata *first_md =
              get_md_elem(metadata, additional_metadata, 0, count);
          grpc_metadata *last_md =
              get_md_elem(metadata, additional_metadata, total_count - 1, count);
          batch->list.head = linked_from_md(first_md);
          batch->list.tail = linked_from_md(last_md);
          batch->list.head->prev = NULL;
          batch->list.tail->next = NULL;
          break;
        }
        case 2:
          /* prepend, but no md */
          batch->list.head = &call->send_extra_metadata[0];
          batch->list.tail =
              &call->send_extra_metadata[call->send_extra_metadata_count - 1];
          batch->list.head->prev = NULL;
          batch->list.tail->next = NULL;
          break;
        case 3: {
          /* prepend AND md */
          grpc_metadata *first_md =
              get_md_elem(metadata, additional_metadata, 0, count);
          grpc_metadata *last_md =
              get_md_elem(metadata, additional_metadata, total_count - 1, count);
          batch->list.head = &call->send_extra_metadata[0];
          call->send_extra_metadata[call->send_extra_metadata_count - 1].next =
              linked_from_md(first_md);
          linked_from_md(first_md)->prev =
              &call->send_extra_metadata[call->send_extra_metadata_count - 1];
          batch->list.tail = linked_from_md(last_md);
          batch->list.head->prev = NULL;
          batch->list.tail->next = NULL;
          break;
        }
        default:
          GPR_UNREACHABLE_CODE(return 0);
      }
    
      return 1;
    }
    
    void grpc_call_destroy(grpc_call *c) {
      int cancel;
      grpc_call *parent = c->parent;
      grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
    
      GPR_TIMER_BEGIN("grpc_call_destroy", 0);
      GRPC_API_TRACE("grpc_call_destroy(c=%p)", 1, (c));
    
      if (parent) {
        gpr_mu_lock(&parent->mu);
        if (c == parent->first_child) {
          parent->first_child = c->sibling_next;
          if (c == parent->first_child) {
            parent->first_child = NULL;
          }
          c->sibling_prev->sibling_next = c->sibling_next;
          c->sibling_next->sibling_prev = c->sibling_prev;
        }
        gpr_mu_unlock(&parent->mu);
        GRPC_CALL_INTERNAL_UNREF(&exec_ctx, parent, "child");
      }
    
      gpr_mu_lock(&c->mu);
      GPR_ASSERT(!c->destroy_called);
      c->destroy_called = 1;
      if (c->have_alarm) {
        grpc_timer_cancel(&exec_ctx, &c->alarm);
      }
      cancel = !c->received_final_op;
      gpr_mu_unlock(&c->mu);
      if (cancel) grpc_call_cancel(c, NULL);
      GRPC_CALL_INTERNAL_UNREF(&exec_ctx, c, "destroy");
      grpc_exec_ctx_finish(&exec_ctx);
      GPR_TIMER_END("grpc_call_destroy", 0);
    }
    
    grpc_call_error grpc_call_cancel(grpc_call *call, void *reserved) {
      GRPC_API_TRACE("grpc_call_cancel(call=%p, reserved=%p)", 2, (call, reserved));
      GPR_ASSERT(!reserved);
      return grpc_call_cancel_with_status(call, GRPC_STATUS_CANCELLED, "Cancelled",
                                          NULL);
    }
    
    grpc_call_error grpc_call_cancel_with_status(grpc_call *c,
                                                 grpc_status_code status,
                                                 const char *description,
                                                 void *reserved) {
      grpc_call_error r;
      grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
      GRPC_API_TRACE(
          "grpc_call_cancel_with_status("
          "c=%p, status=%d, description=%s, reserved=%p)",
          4, (c, (int)status, description, reserved));
      GPR_ASSERT(reserved == NULL);
      gpr_mu_lock(&c->mu);
      r = cancel_with_status(&exec_ctx, c, status, description);
      gpr_mu_unlock(&c->mu);
      grpc_exec_ctx_finish(&exec_ctx);
      return r;
    }
    
    typedef struct termination_closure {
      grpc_closure closure;
      grpc_call *call;
      grpc_status_code status;
      gpr_slice optional_message;
      grpc_closure *op_closure;
      enum { TC_CANCEL, TC_CLOSE } type;
    } termination_closure;
    
    static void done_termination(grpc_exec_ctx *exec_ctx, void *tcp,
                                 grpc_error *error) {
      termination_closure *tc = tcp;
      switch (tc->type) {
        case TC_CANCEL:
          GRPC_CALL_INTERNAL_UNREF(exec_ctx, tc->call, "cancel");
          break;
        case TC_CLOSE:
          GRPC_CALL_INTERNAL_UNREF(exec_ctx, tc->call, "close");
          break;
      }
      gpr_slice_unref(tc->optional_message);
      grpc_exec_ctx_sched(exec_ctx, tc->op_closure, GRPC_ERROR_NONE, NULL);
      gpr_free(tc);
    }
    
    static void send_cancel(grpc_exec_ctx *exec_ctx, void *tcp, grpc_error *error) {
      grpc_transport_stream_op op;
      termination_closure *tc = tcp;
      memset(&op, 0, sizeof(op));
      op.cancel_with_status = tc->status;
      /* reuse closure to catch completion */
      grpc_closure_init(&tc->closure, done_termination, tc);
      op.on_complete = &tc->closure;
      execute_op(exec_ctx, tc->call, &op);
    }
    
    static void send_close(grpc_exec_ctx *exec_ctx, void *tcp, grpc_error *error) {
      grpc_transport_stream_op op;
      termination_closure *tc = tcp;
      memset(&op, 0, sizeof(op));
      tc->optional_message = gpr_slice_ref(tc->optional_message);
      grpc_transport_stream_op_add_close(&op, tc->status, &tc->optional_message);
      /* reuse closure to catch completion */
      grpc_closure_init(&tc->closure, done_termination, tc);
      tc->op_closure = op.on_complete;
      op.on_complete = &tc->closure;
      execute_op(exec_ctx, tc->call, &op);
    }
    
    static grpc_call_error terminate_with_status(grpc_exec_ctx *exec_ctx,
                                                 termination_closure *tc) {
      grpc_mdstr *details = NULL;
      if (GPR_SLICE_LENGTH(tc->optional_message) > 0) {
        tc->optional_message = gpr_slice_ref(tc->optional_message);
        details = grpc_mdstr_from_slice(tc->optional_message);
      }
    
      set_status_code(tc->call, STATUS_FROM_API_OVERRIDE, (uint32_t)tc->status);
      set_status_details(tc->call, STATUS_FROM_API_OVERRIDE, details);
    
      if (tc->type == TC_CANCEL) {
        grpc_closure_init(&tc->closure, send_cancel, tc);
        GRPC_CALL_INTERNAL_REF(tc->call, "cancel");
      } else if (tc->type == TC_CLOSE) {
        grpc_closure_init(&tc->closure, send_close, tc);
        GRPC_CALL_INTERNAL_REF(tc->call, "close");
      }
      grpc_exec_ctx_sched(exec_ctx, &tc->closure, GRPC_ERROR_NONE, NULL);
      return GRPC_CALL_OK;
    }
    
    static grpc_call_error cancel_with_status(grpc_exec_ctx *exec_ctx, grpc_call *c,
                                              grpc_status_code status,
                                              const char *description) {
      termination_closure *tc = gpr_malloc(sizeof(*tc));
      memset(tc, 0, sizeof(termination_closure));
      tc->type = TC_CANCEL;
      tc->call = c;
      tc->optional_message = gpr_slice_from_copied_string(description);
      GPR_ASSERT(status != GRPC_STATUS_OK);
      tc->status = status;
    
      return terminate_with_status(exec_ctx, tc);
    }
    
    static grpc_call_error close_with_status(grpc_exec_ctx *exec_ctx, grpc_call *c,
                                             grpc_status_code status,
                                             const char *description) {
      termination_closure *tc = gpr_malloc(sizeof(*tc));
      memset(tc, 0, sizeof(termination_closure));
      tc->type = TC_CLOSE;
      tc->call = c;
      tc->optional_message = gpr_slice_from_copied_string(description);
      GPR_ASSERT(status != GRPC_STATUS_OK);
      tc->status = status;
    
      return terminate_with_status(exec_ctx, tc);
    }
    
    static void execute_op(grpc_exec_ctx *exec_ctx, grpc_call *call,
                           grpc_transport_stream_op *op) {
      grpc_call_element *elem;
    
      GPR_TIMER_BEGIN("execute_op", 0);
      elem = CALL_ELEM_FROM_CALL(call, 0);
      op->context = call->context;
      elem->filter->start_transport_stream_op(exec_ctx, elem, op);
      GPR_TIMER_END("execute_op", 0);
    }
    
    char *grpc_call_get_peer(grpc_call *call) {
      grpc_call_element *elem = CALL_ELEM_FROM_CALL(call, 0);
      grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
      char *result;
      GRPC_API_TRACE("grpc_call_get_peer(%p)", 1, (call));
      result = elem->filter->get_peer(&exec_ctx, elem);
      if (result == NULL) {
        result = grpc_channel_get_target(call->channel);
      }
      if (result == NULL) {
        result = gpr_strdup("unknown");
      }
      grpc_exec_ctx_finish(&exec_ctx);
      return result;
    }
    
    grpc_call *grpc_call_from_top_element(grpc_call_element *elem) {
      return CALL_FROM_TOP_ELEM(elem);
    }
    
    static void call_alarm(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
      grpc_call *call = arg;
      gpr_mu_lock(&call->mu);
      call->have_alarm = 0;
      if (error != GRPC_ERROR_CANCELLED) {
        cancel_with_status(exec_ctx, call, GRPC_STATUS_DEADLINE_EXCEEDED,
                           "Deadline Exceeded");
      }
      gpr_mu_unlock(&call->mu);
      GRPC_CALL_INTERNAL_UNREF(exec_ctx, call, "alarm");
    }
    
    static void set_deadline_alarm(grpc_exec_ctx *exec_ctx, grpc_call *call,
                                   gpr_timespec deadline) {
      if (call->have_alarm) {
        gpr_log(GPR_ERROR, "Attempt to set deadline alarm twice");
        assert(0);
        return;
      }
      GRPC_CALL_INTERNAL_REF(call, "alarm");
      call->have_alarm = 1;
      call->send_deadline = gpr_convert_clock_type(deadline, GPR_CLOCK_MONOTONIC);
      grpc_timer_init(exec_ctx, &call->alarm, call->send_deadline, call_alarm, call,
                      gpr_now(GPR_CLOCK_MONOTONIC));
    }
    
    /* we offset status by a small amount when storing it into transport metadata
       as metadata cannot store a 0 value (which is used as OK for grpc_status_codes
       */
    #define STATUS_OFFSET 1
    static void destroy_status(void *ignored) {}
    
    static uint32_t decode_status(grpc_mdelem *md) {
      uint32_t status;
      void *user_data;
      if (md == GRPC_MDELEM_GRPC_STATUS_0) return 0;
      if (md == GRPC_MDELEM_GRPC_STATUS_1) return 1;
      if (md == GRPC_MDELEM_GRPC_STATUS_2) return 2;
      user_data = grpc_mdelem_get_user_data(md, destroy_status);
      if (user_data != NULL) {
        status = ((uint32_t)(intptr_t)user_data) - STATUS_OFFSET;
      } else {
        if (!gpr_parse_bytes_to_uint32(grpc_mdstr_as_c_string(md->value),
                                       GPR_SLICE_LENGTH(md->value->slice),
                                       &status)) {
          status = GRPC_STATUS_UNKNOWN; /* could not parse status code */
        }
        grpc_mdelem_set_user_data(md, destroy_status,
                                  (void *)(intptr_t)(status + STATUS_OFFSET));
      }
      return status;
    }
    
    static grpc_compression_algorithm decode_compression(grpc_mdelem *md) {
      grpc_compression_algorithm algorithm =
          grpc_compression_algorithm_from_mdstr(md->value);
      if (algorithm == GRPC_COMPRESS_ALGORITHMS_COUNT) {
        const char *md_c_str = grpc_mdstr_as_c_string(md->value);
        gpr_log(GPR_ERROR,
                "Invalid incoming compression algorithm: '%s'. Interpreting "
                "incoming data as uncompressed.",
                md_c_str);
        return GRPC_COMPRESS_NONE;
      }
      return algorithm;
    }
    
    static grpc_mdelem *recv_common_filter(grpc_call *call, grpc_mdelem *elem) {
      if (elem->key == GRPC_MDSTR_GRPC_STATUS) {
        GPR_TIMER_BEGIN("status", 0);
        set_status_code(call, STATUS_FROM_WIRE, decode_status(elem));
        GPR_TIMER_END("status", 0);
        return NULL;
      } else if (elem->key == GRPC_MDSTR_GRPC_MESSAGE) {
        GPR_TIMER_BEGIN("status-details", 0);
        set_status_details(call, STATUS_FROM_WIRE, GRPC_MDSTR_REF(elem->value));
        GPR_TIMER_END("status-details", 0);
        return NULL;
      }
      return elem;
    }
    
    static grpc_mdelem *publish_app_metadata(grpc_call *call, grpc_mdelem *elem,
                                             int is_trailing) {
      grpc_metadata_array *dest;
      grpc_metadata *mdusr;
      GPR_TIMER_BEGIN("publish_app_metadata", 0);
      dest = call->buffered_metadata[is_trailing];
      if (dest->count == dest->capacity) {
        dest->capacity = GPR_MAX(dest->capacity + 8, dest->capacity * 2);
        dest->metadata =
            gpr_realloc(dest->metadata, sizeof(grpc_metadata) * dest->capacity);
      }
      mdusr = &dest->metadata[dest->count++];
      mdusr->key = grpc_mdstr_as_c_string(elem->key);
      mdusr->value = grpc_mdstr_as_c_string(elem->value);
      mdusr->value_length = GPR_SLICE_LENGTH(elem->value->slice);
      GPR_TIMER_END("publish_app_metadata", 0);
      return elem;
    }
    
    static grpc_mdelem *recv_initial_filter(void *callp, grpc_mdelem *elem) {
      grpc_call *call = callp;
      elem = recv_common_filter(call, elem);
      if (elem == NULL) {
        return NULL;
      } else if (elem->key == GRPC_MDSTR_GRPC_ENCODING) {
        GPR_TIMER_BEGIN("incoming_compression_algorithm", 0);
        set_incoming_compression_algorithm(call, decode_compression(elem));
        GPR_TIMER_END("incoming_compression_algorithm", 0);
        return NULL;
      } else if (elem->key == GRPC_MDSTR_GRPC_ACCEPT_ENCODING) {
        GPR_TIMER_BEGIN("encodings_accepted_by_peer", 0);
        set_encodings_accepted_by_peer(call, elem);
        GPR_TIMER_END("encodings_accepted_by_peer", 0);
        return NULL;
      } else {
        return publish_app_metadata(call, elem, 0);
      }
    }
    
    static grpc_mdelem *recv_trailing_filter(void *callp, grpc_mdelem *elem) {
      grpc_call *call = callp;
      elem = recv_common_filter(call, elem);
      if (elem == NULL) {
        return NULL;
      } else {
        return publish_app_metadata(call, elem, 1);
      }
    }
    
    grpc_call_stack *grpc_call_get_call_stack(grpc_call *call) {
      return CALL_STACK_FROM_CALL(call);
    }
    
    /*
     * BATCH API IMPLEMENTATION
     */
    
    static void set_status_value_directly(grpc_status_code status, void *dest) {
      *(grpc_status_code *)dest = status;
    }
    
    static void set_cancelled_value(grpc_status_code status, void *dest) {
      *(int *)dest = (status != GRPC_STATUS_OK);
    }
    
    static bool are_write_flags_valid(uint32_t flags) {
      /* check that only bits in GRPC_WRITE_(INTERNAL?)_USED_MASK are set */
      const uint32_t allowed_write_positions =
          (GRPC_WRITE_USED_MASK | GRPC_WRITE_INTERNAL_USED_MASK);
      const uint32_t invalid_positions = ~allowed_write_positions;
      return !(flags & invalid_positions);
    }
    
    static bool are_initial_metadata_flags_valid(uint32_t flags, bool is_client) {
      /* check that only bits in GRPC_WRITE_(INTERNAL?)_USED_MASK are set */
      uint32_t invalid_positions = ~GRPC_INITIAL_METADATA_USED_MASK;
      if (!is_client) {
        invalid_positions |= GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST;
      }
      return !(flags & invalid_positions);
    }
    
    static batch_control *allocate_batch_control(grpc_call *call) {
      size_t i;
      for (i = 0; i < MAX_CONCURRENT_BATCHES; i++) {
        if ((call->used_batches & (1 << i)) == 0) {
          call->used_batches = (uint8_t)(call->used_batches | (uint8_t)(1 << i));
          return &call->active_batches[i];
        }
      }
      return NULL;
    }
    
    static void finish_batch_completion(grpc_exec_ctx *exec_ctx, void *user_data,
                                        grpc_cq_completion *storage) {
      batch_control *bctl = user_data;
      grpc_call *call = bctl->call;
      gpr_mu_lock(&call->mu);
      call->used_batches = (uint8_t)(
          call->used_batches & ~(uint8_t)(1 << (bctl - call->active_batches)));
      gpr_mu_unlock(&call->mu);
      GRPC_CALL_INTERNAL_UNREF(exec_ctx, call, "completion");
    }
    
    static void post_batch_completion(grpc_exec_ctx *exec_ctx,
                                      batch_control *bctl) {
      grpc_call *call = bctl->call;
      if (bctl->is_notify_tag_closure) {
        /* unrefs bctl->error */
        grpc_exec_ctx_sched(exec_ctx, bctl->notify_tag, bctl->error, NULL);
        gpr_mu_lock(&call->mu);
        bctl->call->used_batches =
            (uint8_t)(bctl->call->used_batches &
                      ~(uint8_t)(1 << (bctl - bctl->call->active_batches)));
        gpr_mu_unlock(&call->mu);
        GRPC_CALL_INTERNAL_UNREF(exec_ctx, call, "completion");
      } else {
        /* unrefs bctl->error */
        grpc_cq_end_op(exec_ctx, bctl->call->cq, bctl->notify_tag, bctl->error,
                       finish_batch_completion, bctl, &bctl->cq_completion);
      }
    }
    
    static void continue_receiving_slices(grpc_exec_ctx *exec_ctx,
                                          batch_control *bctl) {
      grpc_call *call = bctl->call;
      for (;;) {
        size_t remaining = call->receiving_stream->length -
                           (*call->receiving_buffer)->data.raw.slice_buffer.length;
        if (remaining == 0) {
          call->receiving_message = 0;
          grpc_byte_stream_destroy(exec_ctx, call->receiving_stream);
          call->receiving_stream = NULL;
          if (gpr_unref(&bctl->steps_to_complete)) {
            post_batch_completion(exec_ctx, bctl);
          }
          return;
        }
        if (grpc_byte_stream_next(exec_ctx, call->receiving_stream,
                                  &call->receiving_slice, remaining,
                                  &call->receiving_slice_ready)) {
          gpr_slice_buffer_add(&(*call->receiving_buffer)->data.raw.slice_buffer,
                               call->receiving_slice);
        } else {
          return;
        }
      }
    }
    
    static void receiving_slice_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
                                      grpc_error *error) {
      batch_control *bctl = bctlp;
      grpc_call *call = bctl->call;
    
      if (error == GRPC_ERROR_NONE) {
        gpr_slice_buffer_add(&(*call->receiving_buffer)->data.raw.slice_buffer,
                             call->receiving_slice);
        continue_receiving_slices(exec_ctx, bctl);
      } else {
        if (grpc_trace_operation_failures) {
          GRPC_LOG_IF_ERROR("receiving_slice_ready", GRPC_ERROR_REF(error));
        }
        grpc_byte_stream_destroy(exec_ctx, call->receiving_stream);
        call->receiving_stream = NULL;
        grpc_byte_buffer_destroy(*call->receiving_buffer);
        *call->receiving_buffer = NULL;
        if (gpr_unref(&bctl->steps_to_complete)) {
          post_batch_completion(exec_ctx, bctl);
        }
      }
    }
    
    static void process_data_after_md(grpc_exec_ctx *exec_ctx, batch_control *bctl,
                                      bool success) {
      grpc_call *call = bctl->call;
      if (call->receiving_stream == NULL) {
        *call->receiving_buffer = NULL;
        call->receiving_message = 0;
        if (gpr_unref(&bctl->steps_to_complete)) {
          post_batch_completion(exec_ctx, bctl);
        }
      } else if (call->receiving_stream->length >
                 grpc_channel_get_max_message_length(call->channel)) {
        cancel_with_status(exec_ctx, call, GRPC_STATUS_INTERNAL,
                           "Max message size exceeded");
        grpc_byte_stream_destroy(exec_ctx, call->receiving_stream);
        call->receiving_stream = NULL;
        *call->receiving_buffer = NULL;
        call->receiving_message = 0;
        if (gpr_unref(&bctl->steps_to_complete)) {
          post_batch_completion(exec_ctx, bctl);
        }
      } else {
        call->test_only_last_message_flags = call->receiving_stream->flags;
        if ((call->receiving_stream->flags & GRPC_WRITE_INTERNAL_COMPRESS) &&
            (call->incoming_compression_algorithm > GRPC_COMPRESS_NONE)) {
          *call->receiving_buffer = grpc_raw_compressed_byte_buffer_create(
              NULL, 0, call->incoming_compression_algorithm);
        } else {
          *call->receiving_buffer = grpc_raw_byte_buffer_create(NULL, 0);
        }
        grpc_closure_init(&call->receiving_slice_ready, receiving_slice_ready,
                          bctl);
        continue_receiving_slices(exec_ctx, bctl);
        /* early out */
        return;
      }
    }
    
    static void receiving_stream_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
                                       grpc_error *error) {
      batch_control *bctl = bctlp;
      grpc_call *call = bctl->call;
    
      gpr_mu_lock(&bctl->call->mu);
      if (bctl->call->has_initial_md_been_received || error != GRPC_ERROR_NONE ||
          call->receiving_stream == NULL) {
        gpr_mu_unlock(&bctl->call->mu);
        process_data_after_md(exec_ctx, bctlp, error);
      } else {
        call->saved_receiving_stream_ready_bctlp = bctlp;
        gpr_mu_unlock(&bctl->call->mu);
      }
    }
    
    static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
                                           batch_control *bctl) {
      grpc_call *call = bctl->call;
      /* validate call->incoming_compression_algorithm */
      if (call->incoming_compression_algorithm != GRPC_COMPRESS_NONE) {
        const grpc_compression_algorithm algo =
            call->incoming_compression_algorithm;
        char *error_msg = NULL;
        const grpc_compression_options compression_options =
            grpc_channel_compression_options(call->channel);
        /* check if algorithm is known */
        if (algo >= GRPC_COMPRESS_ALGORITHMS_COUNT) {
          gpr_asprintf(&error_msg, "Invalid compression algorithm value '%d'.",
                       algo);
          gpr_log(GPR_ERROR, "%s", error_msg);
          close_with_status(exec_ctx, call, GRPC_STATUS_UNIMPLEMENTED, error_msg);
        } else if (grpc_compression_options_is_algorithm_enabled(
                       &compression_options, algo) == 0) {
          /* check if algorithm is supported by current channel config */
          char *algo_name;
          grpc_compression_algorithm_name(algo, &algo_name);
          gpr_asprintf(&error_msg, "Compression algorithm '%s' is disabled.",
                       algo_name);
          gpr_log(GPR_ERROR, "%s", error_msg);
          close_with_status(exec_ctx, call, GRPC_STATUS_UNIMPLEMENTED, error_msg);
        } else {
          call->incoming_compression_algorithm = algo;
        }
        gpr_free(error_msg);
      }
    
      /* make sure the received grpc-encoding is amongst the ones listed in
       * grpc-accept-encoding */
      GPR_ASSERT(call->encodings_accepted_by_peer != 0);
      if (!GPR_BITGET(call->encodings_accepted_by_peer,
                      call->incoming_compression_algorithm)) {
        extern int grpc_compression_trace;
        if (grpc_compression_trace) {
          char *algo_name;
          grpc_compression_algorithm_name(call->incoming_compression_algorithm,
                                          &algo_name);
          gpr_log(GPR_ERROR,
                  "Compression algorithm (grpc-encoding = '%s') not present in "
                  "the bitset of accepted encodings (grpc-accept-encodings: "
                  "'0x%x')",
                  algo_name, call->encodings_accepted_by_peer);
        }
      }
    }
    
    static void receiving_initial_metadata_ready(grpc_exec_ctx *exec_ctx,
                                                 void *bctlp, grpc_error *error) {
      batch_control *bctl = bctlp;
      grpc_call *call = bctl->call;
    
      gpr_mu_lock(&call->mu);
    
      if (error != GRPC_ERROR_NONE) {
        bctl->error = GRPC_ERROR_REF(error);
      } else {
        grpc_metadata_batch *md =
            &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
        grpc_metadata_batch_filter(md, recv_initial_filter, call);
    
        GPR_TIMER_BEGIN("validate_filtered_metadata", 0);
        validate_filtered_metadata(exec_ctx, bctl);
        GPR_TIMER_END("validate_filtered_metadata", 0);
    
        if (gpr_time_cmp(md->deadline, gpr_inf_future(md->deadline.clock_type)) !=
                0 &&
            !call->is_client) {
          GPR_TIMER_BEGIN("set_deadline_alarm", 0);
          set_deadline_alarm(exec_ctx, call, md->deadline);
          GPR_TIMER_END("set_deadline_alarm", 0);
        }
      }
    
      call->has_initial_md_been_received = true;
      if (call->saved_receiving_stream_ready_bctlp != NULL) {
        grpc_closure *saved_rsr_closure = grpc_closure_create(
            receiving_stream_ready, call->saved_receiving_stream_ready_bctlp);
        call->saved_receiving_stream_ready_bctlp = NULL;
        grpc_exec_ctx_sched(exec_ctx, saved_rsr_closure, error, NULL);
      }
    
      gpr_mu_unlock(&call->mu);
    
      if (gpr_unref(&bctl->steps_to_complete)) {
        post_batch_completion(exec_ctx, bctl);
      }
    }
    
    static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp,
                             grpc_error *error) {
      batch_control *bctl = bctlp;
      grpc_call *call = bctl->call;
      grpc_call *child_call;
      grpc_call *next_child_call;
    
      GRPC_ERROR_REF(error);
    
      gpr_mu_lock(&call->mu);
      if (bctl->send_initial_metadata) {
        if (error != GRPC_ERROR_NONE) {
          set_status_code(call, STATUS_FROM_CORE, GRPC_STATUS_UNAVAILABLE);
        }
        grpc_metadata_batch_destroy(
            &call->metadata_batch[0 /* is_receiving */][0 /* is_trailing */]);
      }
      if (bctl->send_message) {
        call->sending_message = 0;
      }
      if (bctl->send_final_op) {
        grpc_metadata_batch_destroy(
            &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */]);
      }
      if (bctl->recv_final_op) {
        grpc_metadata_batch *md =
            &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
        grpc_metadata_batch_filter(md, recv_trailing_filter, call);
    
        call->received_final_op = true;
        if (call->have_alarm) {
          grpc_timer_cancel(exec_ctx, &call->alarm);
        }
        /* propagate cancellation to any interested children */
        child_call = call->first_child;
        if (child_call != NULL) {
          do {
            next_child_call = child_call->sibling_next;
            if (child_call->cancellation_is_inherited) {
              GRPC_CALL_INTERNAL_REF(child_call, "propagate_cancel");
              grpc_call_cancel(child_call, NULL);
              GRPC_CALL_INTERNAL_UNREF(exec_ctx, child_call, "propagate_cancel");
            }
            child_call = next_child_call;
          } while (child_call != call->first_child);
        }
    
        if (call->is_client) {
          get_final_status(call, set_status_value_directly,
                           call->final_op.client.status);
          get_final_details(call, call->final_op.client.status_details,
                            call->final_op.client.status_details_capacity);
        } else {
          get_final_status(call, set_cancelled_value,
                           call->final_op.server.cancelled);
        }
    
        GRPC_ERROR_UNREF(error);
        error = GRPC_ERROR_NONE;
      }
      GRPC_ERROR_UNREF(bctl->error);
      bctl->error = GRPC_ERROR_REF(error);
      gpr_mu_unlock(&call->mu);
      if (gpr_unref(&bctl->steps_to_complete)) {
        post_batch_completion(exec_ctx, bctl);
      }
    
      GRPC_ERROR_UNREF(error);
    }
    
    static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
                                            grpc_call *call, const grpc_op *ops,
                                            size_t nops, void *notify_tag,
                                            int is_notify_tag_closure) {
      grpc_transport_stream_op stream_op;
      size_t i;
      const grpc_op *op;
      batch_control *bctl;
      int num_completion_callbacks_needed = 1;
      grpc_call_error error = GRPC_CALL_OK;
    
      GPR_TIMER_BEGIN("grpc_call_start_batch", 0);
    
      GRPC_CALL_LOG_BATCH(GPR_INFO, call, ops, nops, notify_tag);
    
      memset(&stream_op, 0, sizeof(stream_op));
    
      /* TODO(ctiller): this feels like it could be made lock-free */
      gpr_mu_lock(&call->mu);
      bctl = allocate_batch_control(call);
      memset(bctl, 0, sizeof(*bctl));
      bctl->call = call;
      bctl->notify_tag = notify_tag;
      bctl->is_notify_tag_closure = (uint8_t)(is_notify_tag_closure != 0);
    
      if (nops == 0) {
        GRPC_CALL_INTERNAL_REF(call, "completion");
        bctl->error = GRPC_ERROR_NONE;
        if (!is_notify_tag_closure) {
          grpc_cq_begin_op(call->cq, notify_tag);
        }
        gpr_mu_unlock(&call->mu);
        post_batch_completion(exec_ctx, bctl);
        error = GRPC_CALL_OK;
        goto done;
      }
    
      /* rewrite batch ops into a transport op */
      for (i = 0; i < nops; i++) {
        op = &ops[i];
        if (op->reserved != NULL) {
          error = GRPC_CALL_ERROR;
          goto done_with_error;
        }
        switch (op->op) {
          case GRPC_OP_SEND_INITIAL_METADATA:
            /* Flag validation: currently allow no flags */
            if (!are_initial_metadata_flags_valid(op->flags, call->is_client)) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (call->sent_initial_metadata) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            /* process compression level */
            grpc_metadata compression_md;
            memset(&compression_md, 0, sizeof(grpc_metadata));
            size_t additional_metadata_count = 0;
            grpc_compression_level effective_compression_level;
            bool level_set = false;
            if (op->data.send_initial_metadata.maybe_compression_level.is_set) {
              effective_compression_level =
                  op->data.send_initial_metadata.maybe_compression_level.level;
              level_set = true;
            } else {
              const grpc_compression_options copts =
                  grpc_channel_compression_options(call->channel);
              level_set = copts.default_level.is_set;
              if (level_set) {
                effective_compression_level = copts.default_level.level;
              }
            }
            if (level_set && !call->is_client) {
              const grpc_compression_algorithm calgo =
                  compression_algorithm_for_level_locked(
                      call, effective_compression_level);
              char *calgo_name;
              grpc_compression_algorithm_name(calgo, &calgo_name);
              // the following will be picked up by the compress filter and used as
              // the call's compression algorithm.
              compression_md.key = GRPC_COMPRESSION_REQUEST_ALGORITHM_MD_KEY;
              compression_md.value = calgo_name;
              compression_md.value_length = strlen(calgo_name);
              additional_metadata_count++;
            }
    
            if (op->data.send_initial_metadata.count + additional_metadata_count >
                INT_MAX) {
              error = GRPC_CALL_ERROR_INVALID_METADATA;
              goto done_with_error;
            }
            bctl->send_initial_metadata = 1;
            call->sent_initial_metadata = 1;
            if (!prepare_application_metadata(
                    call, (int)op->data.send_initial_metadata.count,
                    op->data.send_initial_metadata.metadata, 0, call->is_client,
                    &compression_md, (int)additional_metadata_count)) {
              error = GRPC_CALL_ERROR_INVALID_METADATA;
              goto done_with_error;
            }
            /* TODO(ctiller): just make these the same variable? */
            call->metadata_batch[0][0].deadline = call->send_deadline;
            stream_op.send_initial_metadata =
                &call->metadata_batch[0 /* is_receiving */][0 /* is_trailing */];
            stream_op.send_initial_metadata_flags = op->flags;
            break;
          case GRPC_OP_SEND_MESSAGE:
            if (!are_write_flags_valid(op->flags)) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (op->data.send_message == NULL) {
              error = GRPC_CALL_ERROR_INVALID_MESSAGE;
              goto done_with_error;
            }
            if (call->sending_message) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            bctl->send_message = 1;
            call->sending_message = 1;
            grpc_slice_buffer_stream_init(
                &call->sending_stream,
                &op->data.send_message->data.raw.slice_buffer, op->flags);
            stream_op.send_message = &call->sending_stream.base;
            break;
          case GRPC_OP_SEND_CLOSE_FROM_CLIENT:
            /* Flag validation: currently allow no flags */
            if (op->flags != 0) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (!call->is_client) {
              error = GRPC_CALL_ERROR_NOT_ON_SERVER;
              goto done_with_error;
            }
            if (call->sent_final_op) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            bctl->send_final_op = 1;
            call->sent_final_op = 1;
            stream_op.send_trailing_metadata =
                &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */];
            break;
          case GRPC_OP_SEND_STATUS_FROM_SERVER:
            /* Flag validation: currently allow no flags */
            if (op->flags != 0) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (call->is_client) {
              error = GRPC_CALL_ERROR_NOT_ON_CLIENT;
              goto done_with_error;
            }
            if (call->sent_final_op) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            if (op->data.send_status_from_server.trailing_metadata_count >
                INT_MAX) {
              error = GRPC_CALL_ERROR_INVALID_METADATA;
              goto done_with_error;
            }
            bctl->send_final_op = 1;
            call->sent_final_op = 1;
            call->send_extra_metadata_count = 1;
            call->send_extra_metadata[0].md = grpc_channel_get_reffed_status_elem(
                call->channel, op->data.send_status_from_server.status);
            if (op->data.send_status_from_server.status_details != NULL) {
              call->send_extra_metadata[1].md = grpc_mdelem_from_metadata_strings(
                  GRPC_MDSTR_GRPC_MESSAGE,
                  grpc_mdstr_from_string(
                      op->data.send_status_from_server.status_details));
              call->send_extra_metadata_count++;
              set_status_details(
                  call, STATUS_FROM_API_OVERRIDE,
                  GRPC_MDSTR_REF(call->send_extra_metadata[1].md->value));
            }
            set_status_code(call, STATUS_FROM_API_OVERRIDE,
                            (uint32_t)op->data.send_status_from_server.status);
            if (!prepare_application_metadata(
                    call,
                    (int)op->data.send_status_from_server.trailing_metadata_count,
                    op->data.send_status_from_server.trailing_metadata, 1, 1, NULL,
                    0)) {
              error = GRPC_CALL_ERROR_INVALID_METADATA;
              goto done_with_error;
            }
            stream_op.send_trailing_metadata =
                &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */];
            break;
          case GRPC_OP_RECV_INITIAL_METADATA:
            /* Flag validation: currently allow no flags */
            if (op->flags != 0) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (call->received_initial_metadata) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            call->received_initial_metadata = 1;
            call->buffered_metadata[0] = op->data.recv_initial_metadata;
            grpc_closure_init(&call->receiving_initial_metadata_ready,
                              receiving_initial_metadata_ready, bctl);
            bctl->recv_initial_metadata = 1;
            stream_op.recv_initial_metadata =
                &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
            stream_op.recv_initial_metadata_ready =
                &call->receiving_initial_metadata_ready;
            num_completion_callbacks_needed++;
            break;
          case GRPC_OP_RECV_MESSAGE:
            /* Flag validation: currently allow no flags */
            if (op->flags != 0) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (call->receiving_message) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            call->receiving_message = 1;
            bctl->recv_message = 1;
            call->receiving_buffer = op->data.recv_message;
            stream_op.recv_message = &call->receiving_stream;
            grpc_closure_init(&call->receiving_stream_ready, receiving_stream_ready,
                              bctl);
            stream_op.recv_message_ready = &call->receiving_stream_ready;
            num_completion_callbacks_needed++;
            break;
          case GRPC_OP_RECV_STATUS_ON_CLIENT:
            /* Flag validation: currently allow no flags */
            if (op->flags != 0) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (!call->is_client) {
              error = GRPC_CALL_ERROR_NOT_ON_SERVER;
              goto done_with_error;
            }
            if (call->requested_final_op) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            call->requested_final_op = 1;
            call->buffered_metadata[1] =
                op->data.recv_status_on_client.trailing_metadata;
            call->final_op.client.status = op->data.recv_status_on_client.status;
            call->final_op.client.status_details =
                op->data.recv_status_on_client.status_details;
            call->final_op.client.status_details_capacity =
                op->data.recv_status_on_client.status_details_capacity;
            bctl->recv_final_op = 1;
            stream_op.recv_trailing_metadata =
                &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
            stream_op.collect_stats = &call->stats.transport_stream_stats;
            break;
          case GRPC_OP_RECV_CLOSE_ON_SERVER:
            /* Flag validation: currently allow no flags */
            if (op->flags != 0) {
              error = GRPC_CALL_ERROR_INVALID_FLAGS;
              goto done_with_error;
            }
            if (call->is_client) {
              error = GRPC_CALL_ERROR_NOT_ON_CLIENT;
              goto done_with_error;
            }
            if (call->requested_final_op) {
              error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
              goto done_with_error;
            }
            call->requested_final_op = 1;
            call->final_op.server.cancelled =
                op->data.recv_close_on_server.cancelled;
            bctl->recv_final_op = 1;
            stream_op.recv_trailing_metadata =
                &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
            stream_op.collect_stats = &call->stats.transport_stream_stats;
            break;
        }
      }
    
      GRPC_CALL_INTERNAL_REF(call, "completion");
      if (!is_notify_tag_closure) {
        grpc_cq_begin_op(call->cq, notify_tag);
      }
      gpr_ref_init(&bctl->steps_to_complete, num_completion_callbacks_needed);
    
      stream_op.context = call->context;
      grpc_closure_init(&bctl->finish_batch, finish_batch, bctl);
      stream_op.on_complete = &bctl->finish_batch;
      gpr_mu_unlock(&call->mu);
    
      execute_op(exec_ctx, call, &stream_op);
    
    done:
      GPR_TIMER_END("grpc_call_start_batch", 0);
      return error;
    
    done_with_error:
      /* reverse any mutations that occured */
      if (bctl->send_initial_metadata) {
        call->sent_initial_metadata = 0;
        grpc_metadata_batch_clear(&call->metadata_batch[0][0]);
      }
      if (bctl->send_message) {
        call->sending_message = 0;
        grpc_byte_stream_destroy(exec_ctx, &call->sending_stream.base);
      }
      if (bctl->send_final_op) {
        call->sent_final_op = 0;
        grpc_metadata_batch_clear(&call->metadata_batch[0][1]);
      }
      if (bctl->recv_initial_metadata) {
        call->received_initial_metadata = 0;
      }
      if (bctl->recv_message) {
        call->receiving_message = 0;
      }
      if (bctl->recv_final_op) {
        call->requested_final_op = 0;
      }
      gpr_mu_unlock(&call->mu);
      goto done;
    }
    
    grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
                                          size_t nops, void *tag, void *reserved) {
      grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
      grpc_call_error err;
    
      GRPC_API_TRACE(
          "grpc_call_start_batch(call=%p, ops=%p, nops=%lu, tag=%p, "
          "reserved=%p)",
          5, (call, ops, (unsigned long)nops, tag, reserved));
    
      if (reserved != NULL) {
        err = GRPC_CALL_ERROR;
      } else {
        err = call_start_batch(&exec_ctx, call, ops, nops, tag, 0);
      }
    
      grpc_exec_ctx_finish(&exec_ctx);
      return err;
    }
    
    grpc_call_error grpc_call_start_batch_and_execute(grpc_exec_ctx *exec_ctx,
                                                      grpc_call *call,
                                                      const grpc_op *ops,
                                                      size_t nops,
                                                      grpc_closure *closure) {
      return call_start_batch(exec_ctx, call, ops, nops, closure, 1);
    }
    
    void grpc_call_context_set(grpc_call *call, grpc_context_index elem,
                               void *value, void (*destroy)(void *value)) {
      if (call->context[elem].destroy) {
        call->context[elem].destroy(call->context[elem].value);
      }
      call->context[elem].value = value;
      call->context[elem].destroy = destroy;
    }
    
    void *grpc_call_context_get(grpc_call *call, grpc_context_index elem) {
      return call->context[elem].value;
    }
    
    uint8_t grpc_call_is_client(grpc_call *call) { return call->is_client; }
    
    grpc_compression_algorithm grpc_call_compression_for_level(
        grpc_call *call, grpc_compression_level level) {
      gpr_mu_lock(&call->mu);
      grpc_compression_algorithm algo =
          compression_algorithm_for_level_locked(call, level);
      gpr_mu_unlock(&call->mu);
      return algo;
    }
    
    const char *grpc_call_error_to_string(grpc_call_error error) {
      switch (error) {
        case GRPC_CALL_ERROR:
          return "GRPC_CALL_ERROR";
        case GRPC_CALL_ERROR_ALREADY_ACCEPTED:
          return "GRPC_CALL_ERROR_ALREADY_ACCEPTED";
        case GRPC_CALL_ERROR_ALREADY_FINISHED:
          return "GRPC_CALL_ERROR_ALREADY_FINISHED";
        case GRPC_CALL_ERROR_ALREADY_INVOKED:
          return "GRPC_CALL_ERROR_ALREADY_INVOKED";
        case GRPC_CALL_ERROR_BATCH_TOO_BIG:
          return "GRPC_CALL_ERROR_BATCH_TOO_BIG";
        case GRPC_CALL_ERROR_INVALID_FLAGS:
          return "GRPC_CALL_ERROR_INVALID_FLAGS";
        case GRPC_CALL_ERROR_INVALID_MESSAGE:
          return "GRPC_CALL_ERROR_INVALID_MESSAGE";
        case GRPC_CALL_ERROR_INVALID_METADATA:
          return "GRPC_CALL_ERROR_INVALID_METADATA";
        case GRPC_CALL_ERROR_NOT_INVOKED:
          return "GRPC_CALL_ERROR_NOT_INVOKED";
        case GRPC_CALL_ERROR_NOT_ON_CLIENT:
          return "GRPC_CALL_ERROR_NOT_ON_CLIENT";
        case GRPC_CALL_ERROR_NOT_ON_SERVER:
          return "GRPC_CALL_ERROR_NOT_ON_SERVER";
        case GRPC_CALL_ERROR_NOT_SERVER_COMPLETION_QUEUE:
          return "GRPC_CALL_ERROR_NOT_SERVER_COMPLETION_QUEUE";
        case GRPC_CALL_ERROR_PAYLOAD_TYPE_MISMATCH:
          return "GRPC_CALL_ERROR_PAYLOAD_TYPE_MISMATCH";
        case GRPC_CALL_ERROR_TOO_MANY_OPERATIONS:
          return "GRPC_CALL_ERROR_TOO_MANY_OPERATIONS";
        case GRPC_CALL_OK:
          return "GRPC_CALL_OK";
      }
      GPR_UNREACHABLE_CODE(return "GRPC_CALL_ERROR_UNKNOW");
    }