text: /*
   *
   * 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 "src/core/channel/channel_stack.h"
  #include <grpc/support/log.h>
  
  #include <stdlib.h>
  #include <string.h>
  
  int grpc_trace_channel = 0;
  
  /* Memory layouts.
  
     Channel stack is laid out as: {
       grpc_channel_stack stk;
       padding to GPR_MAX_ALIGNMENT
       grpc_channel_element[stk.count];
       per-filter memory, aligned to GPR_MAX_ALIGNMENT
     }
  
     Call stack is laid out as: {
       grpc_call_stack stk;
       padding to GPR_MAX_ALIGNMENT
       grpc_call_element[stk.count];
       per-filter memory, aligned to GPR_MAX_ALIGNMENT
     } */
  
  /* Given a size, round up to the next multiple of sizeof(void*) */
  #define ROUND_UP_TO_ALIGNMENT_SIZE(x) \
    (((x) + GPR_MAX_ALIGNMENT - 1) & ~(GPR_MAX_ALIGNMENT - 1))
  
  size_t grpc_channel_stack_size(const grpc_channel_filter **filters,
                                 size_t filter_count) {
    /* always need the header, and size for the channel elements */
    size_t size =
        ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(grpc_channel_stack)) +
        ROUND_UP_TO_ALIGNMENT_SIZE(filter_count * sizeof(grpc_channel_element));
    size_t i;
  
    GPR_ASSERT((GPR_MAX_ALIGNMENT & (GPR_MAX_ALIGNMENT - 1)) == 0 &&
               "GPR_MAX_ALIGNMENT must be a power of two");
  
    /* add the size for each filter */
    for (i = 0; i < filter_count; i++) {
      size += ROUND_UP_TO_ALIGNMENT_SIZE(filters[i]->sizeof_channel_data);
    }
  
    return size;
  }
  
  #define CHANNEL_ELEMS_FROM_STACK(stk)                                   \
    ((grpc_channel_element *)((char *)(stk) + ROUND_UP_TO_ALIGNMENT_SIZE( \
                                                  sizeof(grpc_channel_stack))))
  
  #define CALL_ELEMS_FROM_STACK(stk)       \
    ((grpc_call_element *)((char *)(stk) + \
                           ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(grpc_call_stack))))
  
  grpc_channel_element *grpc_channel_stack_element(
      grpc_channel_stack *channel_stack, size_t index) {
    return CHANNEL_ELEMS_FROM_STACK(channel_stack) + index;
  }
  
  grpc_channel_element *grpc_channel_stack_last_element(
      grpc_channel_stack *channel_stack) {
    return grpc_channel_stack_element(channel_stack, channel_stack->count - 1);
  }
  
  grpc_call_element *grpc_call_stack_element(grpc_call_stack *call_stack,
                                             size_t index) {
    return CALL_ELEMS_FROM_STACK(call_stack) + index;
  }
  
  void grpc_channel_stack_init(const grpc_channel_filter **filters,
                               size_t filter_count, grpc_channel *master,
                               const grpc_channel_args *args,
                               grpc_mdctx *metadata_context,
                               grpc_channel_stack *stack) {
    size_t call_size =
        ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(grpc_call_stack)) +
        ROUND_UP_TO_ALIGNMENT_SIZE(filter_count * sizeof(grpc_call_element));
    grpc_channel_element *elems;
    char *user_data;
    size_t i;
  
    stack->count = filter_count;
    elems = CHANNEL_ELEMS_FROM_STACK(stack);
    user_data =
        ((char *)elems) +
        ROUND_UP_TO_ALIGNMENT_SIZE(filter_count * sizeof(grpc_channel_element));
  
    /* init per-filter data */
    for (i = 0; i < filter_count; i++) {
      elems[i].filter = filters[i];
      elems[i].channel_data = user_data;
      elems[i].filter->init_channel_elem(&elems[i], master, args,
                                         metadata_context, i == 0,
                                         i == (filter_count - 1));
      user_data += ROUND_UP_TO_ALIGNMENT_SIZE(filters[i]->sizeof_channel_data);
      call_size += ROUND_UP_TO_ALIGNMENT_SIZE(filters[i]->sizeof_call_data);
    }
  
    GPR_ASSERT(user_data > (char *)stack);
    GPR_ASSERT((gpr_uintptr)(user_data - (char *)stack) ==
               grpc_channel_stack_size(filters, filter_count));
  
    stack->call_stack_size = call_size;
  }
  
  void grpc_channel_stack_destroy(grpc_channel_stack *stack) {
    grpc_channel_element *channel_elems = CHANNEL_ELEMS_FROM_STACK(stack);
    size_t count = stack->count;
    size_t i;
  
    /* destroy per-filter data */
    for (i = 0; i < count; i++) {
      channel_elems[i].filter->destroy_channel_elem(&channel_elems[i]);
    }
  }
  
  void grpc_call_stack_init(grpc_channel_stack *channel_stack,
                            const void *transport_server_data,
                            grpc_transport_stream_op *initial_op,
                            grpc_call_stack *call_stack) {
    grpc_channel_element *channel_elems = CHANNEL_ELEMS_FROM_STACK(channel_stack);
    size_t count = channel_stack->count;
    grpc_call_element *call_elems;
    char *user_data;
    size_t i;
  
    call_stack->count = count;
    call_elems = CALL_ELEMS_FROM_STACK(call_stack);
    user_data = ((char *)call_elems) +
                ROUND_UP_TO_ALIGNMENT_SIZE(count * sizeof(grpc_call_element));
  
    /* init per-filter data */
    for (i = 0; i < count; i++) {
      call_elems[i].filter = channel_elems[i].filter;
      call_elems[i].channel_data = channel_elems[i].channel_data;
      call_elems[i].call_data = user_data;
      call_elems[i].filter->init_call_elem(&call_elems[i], transport_server_data,
                                           initial_op);
      user_data +=
          ROUND_UP_TO_ALIGNMENT_SIZE(call_elems[i].filter->sizeof_call_data);
    }
  }
  
  void grpc_call_stack_destroy(grpc_call_stack *stack) {
    grpc_call_element *elems = CALL_ELEMS_FROM_STACK(stack);
    size_t count = stack->count;
    size_t i;
  
    /* destroy per-filter data */
    for (i = 0; i < count; i++) {
      elems[i].filter->destroy_call_elem(&elems[i]);
    }
  }
  
  void grpc_call_next_op(grpc_call_element *elem, grpc_transport_stream_op *op) {
    grpc_call_element *next_elem = elem + 1;
    next_elem->filter->start_transport_stream_op(next_elem, op);
  }
  
  char *grpc_call_next_get_peer(grpc_call_element *elem) {
    grpc_call_element *next_elem = elem + 1;
    return next_elem->filter->get_peer(next_elem);
  }
  
  void grpc_channel_next_op(grpc_channel_element *elem, grpc_transport_op *op) {
    grpc_channel_element *next_elem = elem + 1;
    next_elem->filter->start_transport_op(next_elem, op);
  }
  
  grpc_channel_stack *grpc_channel_stack_from_top_element(
      grpc_channel_element *elem) {
    return (grpc_channel_stack *)((char *)(elem)-ROUND_UP_TO_ALIGNMENT_SIZE(
        sizeof(grpc_channel_stack)));
  }
  
  grpc_call_stack *grpc_call_stack_from_top_element(grpc_call_element *elem) {
    return (grpc_call_stack *)((char *)(elem)-ROUND_UP_TO_ALIGNMENT_SIZE(
        sizeof(grpc_call_stack)));
  }
  
  void grpc_call_element_send_cancel(grpc_call_element *cur_elem) {
    grpc_transport_stream_op op;
    memset(&op, 0, sizeof(op));
    op.cancel_with_status = GRPC_STATUS_CANCELLED;
    grpc_call_next_op(cur_elem, &op);
  }
  