Revert "cronet wrapper code"

3 files changed, 0 insertions, 794 deletions

diff --git a/src/core/ext/transport/cronet/client/secure/cronet_channel_create.c b/src/core/ext/transport/cronet/client/secure/cronet_channel_create.c
deleted file mode 100644
index df1acddcc0..0000000000
--- a/src/core/ext/transport/cronet/client/secure/cronet_channel_create.c
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- *
- * Copyright 2016, 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 <grpc/impl/codegen/port_platform.h>
-
-#include <stdio.h>
-#include <string.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-
-#include "src/core/lib/surface/channel.h"
-#include "src/core/lib/transport/transport_impl.h"
-
-// Cronet transport object
-typedef struct cronet_transport {
-  grpc_transport base;  // must be first element in this structure
-  void *engine;
-  char *host;
-} cronet_transport;
-
-extern grpc_transport_vtable grpc_cronet_vtable;
-
-GRPCAPI grpc_channel *grpc_cronet_secure_channel_create(
-    void *engine, const char *target, const grpc_channel_args *args,
-    void *reserved) {
-  cronet_transport *ct = gpr_malloc(sizeof(cronet_transport));
-  ct->base.vtable = &grpc_cronet_vtable;
-  ct->engine = engine;
-  ct->host = gpr_malloc(strlen(target) + 1);
-  strcpy(ct->host, target);
-  gpr_log(GPR_DEBUG,
-          "grpc_create_cronet_transport: cronet_engine = %p, target=%s", engine,
-          ct->host);
-
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  return grpc_channel_create(&exec_ctx, target, args,
-                             GRPC_CLIENT_DIRECT_CHANNEL, (grpc_transport *)ct);
-}
diff --git a/src/core/ext/transport/cronet/transport/cronet_api_dummy.c b/src/core/ext/transport/cronet/transport/cronet_api_dummy.c
deleted file mode 100644
index 687026c9fd..0000000000
--- a/src/core/ext/transport/cronet/transport/cronet_api_dummy.c
+++ /dev/null
@@ -1,85 +0,0 @@
-/*
- *
- * Copyright 2016, 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.
- *
- */
-
-/* This file has empty implementation of all the functions exposed by the cronet
-library, so we can build it in all environments */
-
-#include <stdbool.h>
-
-#include <grpc/support/log.h>
-
-#include "third_party/objective_c/Cronet/cronet_c_for_grpc.h"
-
-#ifdef GRPC_COMPILE_WITH_CRONET
-/* link with the real CRONET library in the build system */
-#else
-/* Dummy implementation of cronet API just to test for build-ability */
-cronet_bidirectional_stream* cronet_bidirectional_stream_create(
-    cronet_engine* engine, void* annotation,
-    cronet_bidirectional_stream_callback* callback) {
-  GPR_ASSERT(0);
-  return NULL;
-}
-
-int cronet_bidirectional_stream_destroy(cronet_bidirectional_stream* stream) {
-  GPR_ASSERT(0);
-  return 0;
-}
-
-int cronet_bidirectional_stream_start(
-    cronet_bidirectional_stream* stream, const char* url, int priority,
-    const char* method, const cronet_bidirectional_stream_header_array* headers,
-    bool end_of_stream) {
-  GPR_ASSERT(0);
-  return 0;
-}
-
-int cronet_bidirectional_stream_read(cronet_bidirectional_stream* stream,
-                                     char* buffer, int capacity) {
-  GPR_ASSERT(0);
-  return 0;
-}
-
-int cronet_bidirectional_stream_write(cronet_bidirectional_stream* stream,
-                                      const char* buffer, int count,
-                                      bool end_of_stream) {
-  GPR_ASSERT(0);
-  return 0;
-}
-
-int cronet_bidirectional_stream_cancel(cronet_bidirectional_stream* stream) {
-  GPR_ASSERT(0);
-  return 0;
-}
-
-#endif /* GRPC_COMPILE_WITH_CRONET */
diff --git a/src/core/ext/transport/cronet/transport/cronet_transport.c b/src/core/ext/transport/cronet/transport/cronet_transport.c
deleted file mode 100644
index 5bb085195c..0000000000
--- a/src/core/ext/transport/cronet/transport/cronet_transport.c
+++ /dev/null
@@ -1,640 +0,0 @@
-/*
- *
- * Copyright 2016, 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 <string.h>
-
-#include <grpc/impl/codegen/port_platform.h>
-#include <grpc/support/alloc.h>
-#include <grpc/support/host_port.h>
-#include <grpc/support/log.h>
-#include <grpc/support/slice_buffer.h>
-#include <grpc/support/string_util.h>
-#include <grpc/support/useful.h>
-
-#include "src/core/ext/transport/chttp2/transport/incoming_metadata.h"
-#include "src/core/lib/iomgr/exec_ctx.h"
-#include "src/core/lib/support/string.h"
-#include "src/core/lib/surface/channel.h"
-#include "src/core/lib/transport/metadata_batch.h"
-#include "src/core/lib/transport/transport_impl.h"
-#include "third_party/objective_c/Cronet/cronet_c_for_grpc.h"
-
-#define GRPC_HEADER_SIZE_IN_BYTES 5
-
-// Global flag that gets set with GRPC_TRACE env variable
-int grpc_cronet_trace = 1;
-
-// Cronet transport object
-struct grpc_cronet_transport {
-  grpc_transport base; /* must be first element in this structure */
-  cronet_engine *engine;
-  char *host;
-};
-
-typedef struct grpc_cronet_transport grpc_cronet_transport;
-
-enum send_state {
-  CRONET_SEND_IDLE = 0,
-  CRONET_REQ_STARTED,
-  CRONET_SEND_HEADER,
-  CRONET_WRITE,
-  CRONET_WRITE_COMPLETED,
-};
-
-enum recv_state {
-  CRONET_RECV_IDLE = 0,
-  CRONET_RECV_READ_LENGTH,
-  CRONET_RECV_READ_DATA,
-  CRONET_RECV_CLOSED,
-};
-
-static const char *recv_state_name[] = {
-    "CRONET_RECV_IDLE", "CRONET_RECV_READ_LENGTH", "CRONET_RECV_READ_DATA,",
-    "CRONET_RECV_CLOSED"};
-
-// Enum that identifies calling function.
-enum e_caller {
-  PERFORM_STREAM_OP,
-  ON_READ_COMPLETE,
-  ON_RESPONSE_HEADERS_RECEIVED,
-  ON_RESPONSE_TRAILERS_RECEIVED
-};
-
-enum callback_id {
-  CB_SEND_INITIAL_METADATA = 0,
-  CB_SEND_MESSAGE,
-  CB_SEND_TRAILING_METADATA,
-  CB_RECV_MESSAGE,
-  CB_RECV_INITIAL_METADATA,
-  CB_RECV_TRAILING_METADATA,
-  CB_NUM_CALLBACKS
-};
-
-struct stream_obj {
-  // we store received bytes here as they trickle in.
-  gpr_slice_buffer write_slice_buffer;
-  cronet_bidirectional_stream *cbs;
-  gpr_slice slice;
-  gpr_slice_buffer read_slice_buffer;
-  struct grpc_slice_buffer_stream sbs;
-  char *read_buffer;
-  int remaining_read_bytes;
-  int total_read_bytes;
-
-  char *write_buffer;
-  size_t write_buffer_size;
-
-  // Hold the URL
-  char *url;
-
-  bool response_headers_received;
-  bool read_requested;
-  bool response_trailers_received;
-  bool read_closed;
-
-  // Recv message stuff
-  grpc_byte_buffer **recv_message;
-  // Initial metadata stuff
-  grpc_metadata_batch *recv_initial_metadata;
-  // Trailing metadata stuff
-  grpc_metadata_batch *recv_trailing_metadata;
-  grpc_chttp2_incoming_metadata_buffer imb;
-
-  // This mutex protects receive state machine execution
-  gpr_mu recv_mu;
-  // we can queue up up to 2 callbacks for each OP
-  grpc_closure *callback_list[CB_NUM_CALLBACKS][2];
-
-  // storage for header
-  cronet_bidirectional_stream_header *headers;
-  uint32_t num_headers;
-  cronet_bidirectional_stream_header_array header_array;
-  // state tracking
-  enum recv_state cronet_recv_state;
-  enum send_state cronet_send_state;
-};
-
-typedef struct stream_obj stream_obj;
-
-static void next_send_step(stream_obj *s);
-static void next_recv_step(stream_obj *s, enum e_caller caller);
-
-static void set_pollset_do_nothing(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
-                                   grpc_stream *gs, grpc_pollset *pollset) {}
-
-static void enqueue_callbacks(grpc_closure *callback_list[]) {
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  if (callback_list[0]) {
-    grpc_exec_ctx_enqueue(&exec_ctx, callback_list[0], true, NULL);
-    callback_list[0] = NULL;
-  }
-  if (callback_list[1]) {
-    grpc_exec_ctx_enqueue(&exec_ctx, callback_list[1], true, NULL);
-    callback_list[1] = NULL;
-  }
-  grpc_exec_ctx_finish(&exec_ctx);
-}
-
-static void on_canceled(cronet_bidirectional_stream *stream) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "on_canceled %p", stream);
-  }
-}
-
-static void on_failed(cronet_bidirectional_stream *stream, int net_error) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "on_failed %p, error = %d", stream, net_error);
-  }
-}
-
-static void on_succeeded(cronet_bidirectional_stream *stream) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "on_succeeded %p", stream);
-  }
-}
-
-static void on_response_trailers_received(
-    cronet_bidirectional_stream *stream,
-    const cronet_bidirectional_stream_header_array *trailers) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "R: on_response_trailers_received");
-  }
-  stream_obj *s = (stream_obj *)stream->annotation;
-
-  memset(&s->imb, 0, sizeof(s->imb));
-  grpc_chttp2_incoming_metadata_buffer_init(&s->imb);
-  unsigned int i = 0;
-  for (i = 0; i < trailers->count; i++) {
-    grpc_chttp2_incoming_metadata_buffer_add(
-        &s->imb, grpc_mdelem_from_metadata_strings(
-                     grpc_mdstr_from_string(trailers->headers[i].key),
-                     grpc_mdstr_from_string(trailers->headers[i].value)));
-  }
-  s->response_trailers_received = true;
-  next_recv_step(s, ON_RESPONSE_TRAILERS_RECEIVED);
-}
-
-static void on_write_completed(cronet_bidirectional_stream *stream,
-                               const char *data) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "W: on_write_completed");
-  }
-  stream_obj *s = (stream_obj *)stream->annotation;
-  enqueue_callbacks(s->callback_list[CB_SEND_MESSAGE]);
-  s->cronet_send_state = CRONET_WRITE_COMPLETED;
-  next_send_step(s);
-}
-
-static void process_recv_message(stream_obj *s, const uint8_t *recv_data) {
-  gpr_slice read_data_slice = gpr_slice_malloc((uint32_t)s->total_read_bytes);
-  uint8_t *dst_p = GPR_SLICE_START_PTR(read_data_slice);
-  memcpy(dst_p, recv_data, (size_t)s->total_read_bytes);
-  gpr_slice_buffer_add(&s->read_slice_buffer, read_data_slice);
-  grpc_slice_buffer_stream_init(&s->sbs, &s->read_slice_buffer, 0);
-  *s->recv_message = (grpc_byte_buffer *)&s->sbs;
-}
-
-static int parse_grpc_header(const uint8_t *data) {
-  const uint8_t *p = data + 1;
-  int length = 0;
-  length |= ((uint8_t)*p++) << 24;
-  length |= ((uint8_t)*p++) << 16;
-  length |= ((uint8_t)*p++) << 8;
-  length |= ((uint8_t)*p++);
-  return length;
-}
-
-static void on_read_completed(cronet_bidirectional_stream *stream, char *data,
-                              int count) {
-  stream_obj *s = (stream_obj *)stream->annotation;
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "R: on_read_completed count=%d, total=%d, remaining=%d",
-            count, s->total_read_bytes, s->remaining_read_bytes);
-  }
-  if (count > 0) {
-    GPR_ASSERT(s->recv_message);
-    s->remaining_read_bytes -= count;
-    next_recv_step(s, ON_READ_COMPLETE);
-  } else {
-    s->read_closed = true;
-    next_recv_step(s, ON_READ_COMPLETE);
-  }
-}
-
-static void on_response_headers_received(
-    cronet_bidirectional_stream *stream,
-    const cronet_bidirectional_stream_header_array *headers,
-    const char *negotiated_protocol) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "R: on_response_headers_received");
-  }
-  stream_obj *s = (stream_obj *)stream->annotation;
-  enqueue_callbacks(s->callback_list[CB_RECV_INITIAL_METADATA]);
-  s->response_headers_received = true;
-  next_recv_step(s, ON_RESPONSE_HEADERS_RECEIVED);
-}
-
-static void on_request_headers_sent(cronet_bidirectional_stream *stream) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "W: on_request_headers_sent");
-  }
-  stream_obj *s = (stream_obj *)stream->annotation;
-  enqueue_callbacks(s->callback_list[CB_SEND_INITIAL_METADATA]);
-  s->cronet_send_state = CRONET_SEND_HEADER;
-  next_send_step(s);
-}
-
-// Callback function pointers (invoked by cronet in response to events)
-static cronet_bidirectional_stream_callback callbacks = {
-    on_request_headers_sent,
-    on_response_headers_received,
-    on_read_completed,
-    on_write_completed,
-    on_response_trailers_received,
-    on_succeeded,
-    on_failed,
-    on_canceled};
-
-static void invoke_closing_callback(stream_obj *s) {
-  grpc_chttp2_incoming_metadata_buffer_publish(&s->imb,
-                                               s->recv_trailing_metadata);
-  if (s->callback_list[CB_RECV_TRAILING_METADATA]) {
-    enqueue_callbacks(s->callback_list[CB_RECV_TRAILING_METADATA]);
-  }
-}
-
-static void set_recv_state(stream_obj *s, enum recv_state state) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "next_state = %s", recv_state_name[state]);
-  }
-  s->cronet_recv_state = state;
-}
-
-// This is invoked from perform_stream_op, and all on_xxxx callbacks.
-static void next_recv_step(stream_obj *s, enum e_caller caller) {
-  gpr_mu_lock(&s->recv_mu);
-  switch (s->cronet_recv_state) {
-    case CRONET_RECV_IDLE:
-      if (grpc_cronet_trace) {
-        gpr_log(GPR_DEBUG, "cronet_recv_state = CRONET_RECV_IDLE");
-      }
-      if (caller == PERFORM_STREAM_OP ||
-          caller == ON_RESPONSE_HEADERS_RECEIVED) {
-        if (s->read_closed && s->response_trailers_received) {
-          invoke_closing_callback(s);
-          set_recv_state(s, CRONET_RECV_CLOSED);
-        } else if (s->response_headers_received == true &&
-                   s->read_requested == true) {
-          set_recv_state(s, CRONET_RECV_READ_LENGTH);
-          s->total_read_bytes = s->remaining_read_bytes =
-              GRPC_HEADER_SIZE_IN_BYTES;
-          GPR_ASSERT(s->read_buffer);
-          if (grpc_cronet_trace) {
-            gpr_log(GPR_DEBUG, "R: cronet_bidirectional_stream_read()");
-          }
-          cronet_bidirectional_stream_read(s->cbs, s->read_buffer,
-                                           s->remaining_read_bytes);
-        }
-      }
-      break;
-    case CRONET_RECV_READ_LENGTH:
-      if (grpc_cronet_trace) {
-        gpr_log(GPR_DEBUG, "cronet_recv_state = CRONET_RECV_READ_LENGTH");
-      }
-      if (caller == ON_READ_COMPLETE) {
-        if (s->read_closed) {
-          invoke_closing_callback(s);
-          enqueue_callbacks(s->callback_list[CB_RECV_MESSAGE]);
-          set_recv_state(s, CRONET_RECV_CLOSED);
-        } else {
-          GPR_ASSERT(s->remaining_read_bytes == 0);
-          set_recv_state(s, CRONET_RECV_READ_DATA);
-          s->total_read_bytes = s->remaining_read_bytes =
-              parse_grpc_header((const uint8_t *)s->read_buffer);
-          s->read_buffer =
-              gpr_realloc(s->read_buffer, (uint32_t)s->remaining_read_bytes);
-          GPR_ASSERT(s->read_buffer);
-          if (grpc_cronet_trace) {
-            gpr_log(GPR_DEBUG, "R: cronet_bidirectional_stream_read()");
-          }
-          cronet_bidirectional_stream_read(s->cbs, (char *)s->read_buffer,
-                                           s->remaining_read_bytes);
-        }
-      }
-      break;
-    case CRONET_RECV_READ_DATA:
-      if (grpc_cronet_trace) {
-        gpr_log(GPR_DEBUG, "cronet_recv_state = CRONET_RECV_READ_DATA");
-      }
-      if (caller == ON_READ_COMPLETE) {
-        if (s->remaining_read_bytes > 0) {
-          int offset = s->total_read_bytes - s->remaining_read_bytes;
-          GPR_ASSERT(s->read_buffer);
-          if (grpc_cronet_trace) {
-            gpr_log(GPR_DEBUG, "R: cronet_bidirectional_stream_read()");
-          }
-          cronet_bidirectional_stream_read(
-              s->cbs, (char *)s->read_buffer + offset, s->remaining_read_bytes);
-        } else {
-          gpr_slice_buffer_init(&s->read_slice_buffer);
-          uint8_t *p = (uint8_t *)s->read_buffer;
-          process_recv_message(s, p);
-          set_recv_state(s, CRONET_RECV_IDLE);
-          enqueue_callbacks(s->callback_list[CB_RECV_MESSAGE]);
-        }
-      }
-      break;
-    case CRONET_RECV_CLOSED:
-      break;
-    default:
-      GPR_ASSERT(0);  // Should not reach here
-      break;
-  }
-  gpr_mu_unlock(&s->recv_mu);
-}
-
-// This function takes the data from s->write_slice_buffer and assembles into
-// a contiguous byte stream with 5 byte gRPC header prepended.
-static void create_grpc_frame(stream_obj *s) {
-  gpr_slice slice = gpr_slice_buffer_take_first(&s->write_slice_buffer);
-  uint8_t *raw_data = GPR_SLICE_START_PTR(slice);
-  size_t length = GPR_SLICE_LENGTH(slice);
-  s->write_buffer_size = length + GRPC_HEADER_SIZE_IN_BYTES;
-  s->write_buffer = gpr_realloc(s->write_buffer, s->write_buffer_size);
-  uint8_t *p = (uint8_t *)s->write_buffer;
-  // Append 5 byte header
-  *p++ = 0;
-  *p++ = (uint8_t)(length >> 24);
-  *p++ = (uint8_t)(length >> 16);
-  *p++ = (uint8_t)(length >> 8);
-  *p++ = (uint8_t)(length);
-  // append actual data
-  memcpy(p, raw_data, length);
-}
-
-static void do_write(stream_obj *s) {
-  gpr_slice_buffer *sb = &s->write_slice_buffer;
-  GPR_ASSERT(sb->count <= 1);
-  if (sb->count > 0) {
-    create_grpc_frame(s);
-    if (grpc_cronet_trace) {
-      gpr_log(GPR_DEBUG, "W: cronet_bidirectional_stream_write");
-    }
-    cronet_bidirectional_stream_write(s->cbs, s->write_buffer,
-                                      (int)s->write_buffer_size, false);
-  }
-}
-
-//
-static void next_send_step(stream_obj *s) {
-  switch (s->cronet_send_state) {
-    case CRONET_SEND_IDLE:
-      GPR_ASSERT(
-          s->cbs);  // cronet_bidirectional_stream is not initialized yet.
-      s->cronet_send_state = CRONET_REQ_STARTED;
-      if (grpc_cronet_trace) {
-        gpr_log(GPR_DEBUG, "cronet_bidirectional_stream_start to %s", s->url);
-      }
-      cronet_bidirectional_stream_start(s->cbs, s->url, 0, "POST",
-                                        &s->header_array, false);
-      // we no longer need the memory that was allocated earlier.
-      gpr_free(s->header_array.headers);
-      break;
-    case CRONET_SEND_HEADER:
-      do_write(s);
-      s->cronet_send_state = CRONET_WRITE;
-      break;
-    case CRONET_WRITE_COMPLETED:
-      do_write(s);
-      break;
-    default:
-      GPR_ASSERT(0);
-      break;
-  }
-}
-
-static void convert_metadata_to_cronet_headers(grpc_linked_mdelem *head,
-                                               const char *host,
-                                               stream_obj *s) {
-  grpc_linked_mdelem *curr = head;
-  // Walk the linked list and get number of header fields
-  uint32_t num_headers_available = 0;
-  while (curr != NULL) {
-    curr = curr->next;
-    num_headers_available++;
-  }
-  // Allocate enough memory
-  s->headers = (cronet_bidirectional_stream_header *)gpr_malloc(
-      sizeof(cronet_bidirectional_stream_header) * num_headers_available);
-
-  // Walk the linked list again, this time copying the header fields.
-  // s->num_headers
-  // can be less than num_headers_available, as some headers are not used for
-  // cronet
-  curr = head;
-  s->num_headers = 0;
-  while (s->num_headers < num_headers_available) {
-    grpc_mdelem *mdelem = curr->md;
-    curr = curr->next;
-    const char *key = grpc_mdstr_as_c_string(mdelem->key);
-    const char *value = grpc_mdstr_as_c_string(mdelem->value);
-    if (strcmp(key, ":scheme") == 0 || strcmp(key, ":method") == 0 ||
-        strcmp(key, ":authority") == 0) {
-      // Cronet populates these fields on its own.
-      continue;
-    }
-    if (strcmp(key, ":path") == 0) {
-      // Create URL by appending :path value to the hostname
-      gpr_asprintf(&s->url, "https://%s%s", host, value);
-      if (grpc_cronet_trace) {
-        gpr_log(GPR_DEBUG, "extracted URL = %s", s->url);
-      }
-      continue;
-    }
-    s->headers[s->num_headers].key = key;
-    s->headers[s->num_headers].value = value;
-    s->num_headers++;
-    if (curr == NULL) {
-      break;
-    }
-  }
-}
-
-static void perform_stream_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
-                              grpc_stream *gs, grpc_transport_stream_op *op) {
-  grpc_cronet_transport *ct = (grpc_cronet_transport *)gt;
-  GPR_ASSERT(ct->engine);
-  stream_obj *s = (stream_obj *)gs;
-  if (op->recv_trailing_metadata) {
-    if (grpc_cronet_trace) {
-      gpr_log(GPR_DEBUG,
-              "perform_stream_op - recv_trailing_metadata: on_complete=%p",
-              op->on_complete);
-    }
-    s->recv_trailing_metadata = op->recv_trailing_metadata;
-    GPR_ASSERT(!s->callback_list[CB_RECV_TRAILING_METADATA][0]);
-    s->callback_list[CB_RECV_TRAILING_METADATA][0] = op->on_complete;
-  }
-  if (op->recv_message) {
-    if (grpc_cronet_trace) {
-      gpr_log(GPR_DEBUG, "perform_stream_op - recv_message: on_complete=%p",
-              op->on_complete);
-    }
-    s->recv_message = (grpc_byte_buffer **)op->recv_message;
-    GPR_ASSERT(!s->callback_list[CB_RECV_MESSAGE][0]);
-    GPR_ASSERT(!s->callback_list[CB_RECV_MESSAGE][1]);
-    s->callback_list[CB_RECV_MESSAGE][0] = op->recv_message_ready;
-    s->callback_list[CB_RECV_MESSAGE][1] = op->on_complete;
-    s->read_requested = true;
-    next_recv_step(s, PERFORM_STREAM_OP);
-  }
-  if (op->recv_initial_metadata) {
-    if (grpc_cronet_trace) {
-      gpr_log(GPR_DEBUG, "perform_stream_op - recv_initial_metadata:=%p",
-              op->on_complete);
-    }
-    s->recv_initial_metadata = op->recv_initial_metadata;
-    GPR_ASSERT(!s->callback_list[CB_RECV_INITIAL_METADATA][0]);
-    GPR_ASSERT(!s->callback_list[CB_RECV_INITIAL_METADATA][1]);
-    s->callback_list[CB_RECV_INITIAL_METADATA][0] =
-        op->recv_initial_metadata_ready;
-    s->callback_list[CB_RECV_INITIAL_METADATA][1] = op->on_complete;
-  }
-  if (op->send_initial_metadata) {
-    if (grpc_cronet_trace) {
-      gpr_log(GPR_DEBUG,
-              "perform_stream_op - send_initial_metadata: on_complete=%p",
-              op->on_complete);
-    }
-    s->num_headers = 0;
-    convert_metadata_to_cronet_headers(op->send_initial_metadata->list.head,
-                                       ct->host, s);
-    s->header_array.count = s->num_headers;
-    s->header_array.capacity = s->num_headers;
-    s->header_array.headers = s->headers;
-    GPR_ASSERT(!s->callback_list[CB_SEND_INITIAL_METADATA][0]);
-    s->callback_list[CB_SEND_INITIAL_METADATA][0] = op->on_complete;
-  }
-  if (op->send_message) {
-    if (grpc_cronet_trace) {
-      gpr_log(GPR_DEBUG, "perform_stream_op - send_message: on_complete=%p",
-              op->on_complete);
-    }
-    grpc_byte_stream_next(exec_ctx, op->send_message, &s->slice,
-                          op->send_message->length, NULL);
-    // Check that compression flag is not ON. We don't support compression yet.
-    // TODO (makdharma): add compression support
-    GPR_ASSERT(op->send_message->flags == 0);
-    gpr_slice_buffer_add(&s->write_slice_buffer, s->slice);
-    if (s->cbs == NULL) {
-      if (grpc_cronet_trace) {
-        gpr_log(GPR_DEBUG, "cronet_bidirectional_stream_create");
-      }
-      s->cbs = cronet_bidirectional_stream_create(ct->engine, s, &callbacks);
-      GPR_ASSERT(s->cbs);
-      s->read_closed = false;
-      s->response_trailers_received = false;
-      s->response_headers_received = false;
-      s->cronet_send_state = CRONET_SEND_IDLE;
-      s->cronet_recv_state = CRONET_RECV_IDLE;
-    }
-    GPR_ASSERT(!s->callback_list[CB_SEND_MESSAGE][0]);
-    s->callback_list[CB_SEND_MESSAGE][0] = op->on_complete;
-    next_send_step(s);
-  }
-  if (op->send_trailing_metadata) {
-    if (grpc_cronet_trace) {
-      gpr_log(GPR_DEBUG,
-              "perform_stream_op - send_trailing_metadata: on_complete=%p",
-              op->on_complete);
-    }
-    GPR_ASSERT(!s->callback_list[CB_SEND_TRAILING_METADATA][0]);
-    s->callback_list[CB_SEND_TRAILING_METADATA][0] = op->on_complete;
-    if (s->cbs) {
-      // Send an "empty" write to the far end to signal that we're done.
-      // This will induce the server to send down trailers.
-      if (grpc_cronet_trace) {
-        gpr_log(GPR_DEBUG, "W: cronet_bidirectional_stream_write");
-      }
-      cronet_bidirectional_stream_write(s->cbs, "abc", 0, true);
-    } else {
-      // We never created a stream. This was probably an empty request.
-      invoke_closing_callback(s);
-    }
-  }
-}
-
-static int init_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
-                       grpc_stream *gs, grpc_stream_refcount *refcount,
-                       const void *server_data) {
-  stream_obj *s = (stream_obj *)gs;
-  memset(s->callback_list, 0, sizeof(s->callback_list));
-  s->cbs = NULL;
-  gpr_mu_init(&s->recv_mu);
-  s->read_buffer = gpr_malloc(GRPC_HEADER_SIZE_IN_BYTES);
-  s->write_buffer = gpr_malloc(GRPC_HEADER_SIZE_IN_BYTES);
-  gpr_slice_buffer_init(&s->write_slice_buffer);
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "cronet_transport - init_stream");
-  }
-  return 0;
-}
-
-static void destroy_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
-                           grpc_stream *gs, void *and_free_memory) {
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "Destroy stream");
-  }
-  stream_obj *s = (stream_obj *)gs;
-  s->cbs = NULL;
-  gpr_free(s->read_buffer);
-  gpr_free(s->write_buffer);
-  gpr_free(s->url);
-  gpr_mu_destroy(&s->recv_mu);
-  if (and_free_memory) {
-    gpr_free(and_free_memory);
-  }
-}
-
-static void destroy_transport(grpc_exec_ctx *exec_ctx, grpc_transport *gt) {
-  grpc_cronet_transport *ct = (grpc_cronet_transport *)gt;
-  gpr_free(ct->host);
-  if (grpc_cronet_trace) {
-    gpr_log(GPR_DEBUG, "Destroy transport");
-  }
-}
-
-const grpc_transport_vtable grpc_cronet_vtable = {
-    sizeof(stream_obj),     "cronet_http",     init_stream,
-    set_pollset_do_nothing, perform_stream_op, NULL,
-    destroy_stream,         destroy_transport, NULL};