1 files changed, 547 insertions, 0 deletions
diff --git a/src/core/ext/filters/http/message_compress/message_compress_filter.cc b/src/core/ext/filters/http/message_compress/message_compress_filter.cc
new file mode 100644
index 0000000000..f785e1355d
--- /dev/null
+++ b/src/core/ext/filters/http/message_compress/message_compress_filter.cc
@@ -0,0 +1,547 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <assert.h>
+#include <string.h>
+
+#include <grpc/compression.h>
+#include <grpc/slice_buffer.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/ext/filters/http/message_compress/message_compress_filter.h"
+#include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/compression/algorithm_metadata.h"
+#include "src/core/lib/compression/message_compress.h"
+#include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/slice/slice_internal.h"
+#include "src/core/lib/slice/slice_string_helpers.h"
+#include "src/core/lib/support/string.h"
+#include "src/core/lib/surface/call.h"
+#include "src/core/lib/transport/static_metadata.h"
+
+typedef enum {
+  // Initial metadata not yet seen.
+  INITIAL_METADATA_UNSEEN = 0,
+  // Initial metadata seen; compression algorithm set.
+  HAS_COMPRESSION_ALGORITHM,
+  // Initial metadata seen; no compression algorithm set.
+  NO_COMPRESSION_ALGORITHM,
+} initial_metadata_state;
+
+typedef struct call_data {
+  grpc_call_combiner *call_combiner;
+  grpc_linked_mdelem compression_algorithm_storage;
+  grpc_linked_mdelem stream_compression_algorithm_storage;
+  grpc_linked_mdelem accept_encoding_storage;
+  grpc_linked_mdelem accept_stream_encoding_storage;
+  /** Compression algorithm we'll try to use. It may be given by incoming
+   * metadata, or by the channel's default compression settings. */
+  grpc_compression_algorithm compression_algorithm;
+  initial_metadata_state send_initial_metadata_state;
+  grpc_error *cancel_error;
+  grpc_closure start_send_message_batch_in_call_combiner;
+  grpc_transport_stream_op_batch *send_message_batch;
+  grpc_slice_buffer slices; /**< Buffers up input slices to be compressed */
+  grpc_slice_buffer_stream replacement_stream;
+  grpc_closure *original_send_message_on_complete;
+  grpc_closure send_message_on_complete;
+  grpc_closure on_send_message_next_done;
+} call_data;
+
+typedef struct channel_data {
+  /** The default, channel-level, compression algorithm */
+  grpc_compression_algorithm default_compression_algorithm;
+  /** Bitset of enabled algorithms */
+  uint32_t enabled_algorithms_bitset;
+  /** Supported compression algorithms */
+  uint32_t supported_compression_algorithms;
+
+  /** The default, channel-level, stream compression algorithm */
+  grpc_stream_compression_algorithm default_stream_compression_algorithm;
+  /** Bitset of enabled stream compression algorithms */
+  uint32_t enabled_stream_compression_algorithms_bitset;
+  /** Supported stream compression algorithms */
+  uint32_t supported_stream_compression_algorithms;
+} channel_data;
+
+static bool skip_compression(grpc_call_element *elem, uint32_t flags,
+                             bool has_compression_algorithm) {
+  call_data *calld = (call_data *)elem->call_data;
+  channel_data *channeld = (channel_data *)elem->channel_data;
+
+  if (flags & (GRPC_WRITE_NO_COMPRESS | GRPC_WRITE_INTERNAL_COMPRESS)) {
+    return true;
+  }
+  if (has_compression_algorithm) {
+    if (calld->compression_algorithm == GRPC_COMPRESS_NONE) {
+      return true;
+    }
+    return false; /* we have an actual call-specific algorithm */
+  }
+  /* no per-call compression override */
+  return channeld->default_compression_algorithm == GRPC_COMPRESS_NONE;
+}
+
+/** Filter initial metadata */
+static grpc_error *process_send_initial_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+    grpc_metadata_batch *initial_metadata,
+    bool *has_compression_algorithm) GRPC_MUST_USE_RESULT;
+static grpc_error *process_send_initial_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+    grpc_metadata_batch *initial_metadata, bool *has_compression_algorithm) {
+  call_data *calld = (call_data *)elem->call_data;
+  channel_data *channeld = (channel_data *)elem->channel_data;
+  *has_compression_algorithm = false;
+  grpc_stream_compression_algorithm stream_compression_algorithm =
+      GRPC_STREAM_COMPRESS_NONE;
+  if (initial_metadata->idx.named.grpc_internal_stream_encoding_request !=
+      NULL) {
+    grpc_mdelem md =
+        initial_metadata->idx.named.grpc_internal_stream_encoding_request->md;
+    if (!grpc_stream_compression_algorithm_parse(
+            GRPC_MDVALUE(md), &stream_compression_algorithm)) {
+      char *val = grpc_slice_to_c_string(GRPC_MDVALUE(md));
+      gpr_log(GPR_ERROR,
+              "Invalid stream compression algorithm: '%s' (unknown). Ignoring.",
+              val);
+      gpr_free(val);
+      stream_compression_algorithm = GRPC_STREAM_COMPRESS_NONE;
+    }
+    if (!GPR_BITGET(channeld->enabled_stream_compression_algorithms_bitset,
+                    stream_compression_algorithm)) {
+      char *val = grpc_slice_to_c_string(GRPC_MDVALUE(md));
+      gpr_log(
+          GPR_ERROR,
+          "Invalid stream compression algorithm: '%s' (previously disabled). "
+          "Ignoring.",
+          val);
+      gpr_free(val);
+      stream_compression_algorithm = GRPC_STREAM_COMPRESS_NONE;
+    }
+    *has_compression_algorithm = true;
+    grpc_metadata_batch_remove(
+        exec_ctx, initial_metadata,
+        initial_metadata->idx.named.grpc_internal_stream_encoding_request);
+    /* Disable message-wise compression */
+    calld->compression_algorithm = GRPC_COMPRESS_NONE;
+    if (initial_metadata->idx.named.grpc_internal_encoding_request != NULL) {
+      grpc_metadata_batch_remove(
+          exec_ctx, initial_metadata,
+          initial_metadata->idx.named.grpc_internal_encoding_request);
+    }
+  } else if (initial_metadata->idx.named.grpc_internal_encoding_request !=
+             NULL) {
+    grpc_mdelem md =
+        initial_metadata->idx.named.grpc_internal_encoding_request->md;
+    if (!grpc_compression_algorithm_parse(GRPC_MDVALUE(md),
+                                          &calld->compression_algorithm)) {
+      char *val = grpc_slice_to_c_string(GRPC_MDVALUE(md));
+      gpr_log(GPR_ERROR,
+              "Invalid compression algorithm: '%s' (unknown). Ignoring.", val);
+      gpr_free(val);
+      calld->compression_algorithm = GRPC_COMPRESS_NONE;
+    }
+    *has_compression_algorithm = true;
+    grpc_metadata_batch_remove(
+        exec_ctx, initial_metadata,
+        initial_metadata->idx.named.grpc_internal_encoding_request);
+  } else {
+    /* If no algorithm was found in the metadata and we aren't
+     * exceptionally skipping compression, fall back to the channel
+     * default */
+    if (channeld->default_stream_compression_algorithm !=
+        GRPC_STREAM_COMPRESS_NONE) {
+      stream_compression_algorithm =
+          channeld->default_stream_compression_algorithm;
+      calld->compression_algorithm = GRPC_COMPRESS_NONE;
+    } else {
+      calld->compression_algorithm = channeld->default_compression_algorithm;
+    }
+    *has_compression_algorithm = true;
+  }
+
+  grpc_error *error = GRPC_ERROR_NONE;
+  /* hint compression algorithm */
+  if (stream_compression_algorithm != GRPC_STREAM_COMPRESS_NONE) {
+    error = grpc_metadata_batch_add_tail(
+        exec_ctx, initial_metadata,
+        &calld->stream_compression_algorithm_storage,
+        grpc_stream_compression_encoding_mdelem(stream_compression_algorithm));
+  } else if (calld->compression_algorithm != GRPC_COMPRESS_NONE) {
+    error = grpc_metadata_batch_add_tail(
+        exec_ctx, initial_metadata, &calld->compression_algorithm_storage,
+        grpc_compression_encoding_mdelem(calld->compression_algorithm));
+  }
+
+  if (error != GRPC_ERROR_NONE) return error;
+
+  /* convey supported compression algorithms */
+  error = grpc_metadata_batch_add_tail(
+      exec_ctx, initial_metadata, &calld->accept_encoding_storage,
+      GRPC_MDELEM_ACCEPT_ENCODING_FOR_ALGORITHMS(
+          channeld->supported_compression_algorithms));
+
+  if (error != GRPC_ERROR_NONE) return error;
+
+  /* Do not overwrite accept-encoding header if it already presents. */
+  if (!initial_metadata->idx.named.accept_encoding) {
+    error = grpc_metadata_batch_add_tail(
+        exec_ctx, initial_metadata, &calld->accept_stream_encoding_storage,
+        GRPC_MDELEM_ACCEPT_STREAM_ENCODING_FOR_ALGORITHMS(
+            channeld->supported_stream_compression_algorithms));
+  }
+
+  return error;
+}
+
+static void send_message_on_complete(grpc_exec_ctx *exec_ctx, void *arg,
+                                     grpc_error *error) {
+  grpc_call_element *elem = (grpc_call_element *)arg;
+  call_data *calld = (call_data *)elem->call_data;
+  grpc_slice_buffer_reset_and_unref_internal(exec_ctx, &calld->slices);
+  GRPC_CLOSURE_RUN(exec_ctx, calld->original_send_message_on_complete,
+                   GRPC_ERROR_REF(error));
+}
+
+static void send_message_batch_continue(grpc_exec_ctx *exec_ctx,
+                                        grpc_call_element *elem) {
+  call_data *calld = (call_data *)elem->call_data;
+  // Note: The call to grpc_call_next_op() results in yielding the
+  // call combiner, so we need to clear calld->send_message_batch
+  // before we do that.
+  grpc_transport_stream_op_batch *send_message_batch =
+      calld->send_message_batch;
+  calld->send_message_batch = NULL;
+  grpc_call_next_op(exec_ctx, elem, send_message_batch);
+}
+
+static void finish_send_message(grpc_exec_ctx *exec_ctx,
+                                grpc_call_element *elem) {
+  call_data *calld = (call_data *)elem->call_data;
+  // Compress the data if appropriate.
+  grpc_slice_buffer tmp;
+  grpc_slice_buffer_init(&tmp);
+  uint32_t send_flags =
+      calld->send_message_batch->payload->send_message.send_message->flags;
+  bool did_compress = grpc_msg_compress(exec_ctx, calld->compression_algorithm,
+                                        &calld->slices, &tmp);
+  if (did_compress) {
+    if (GRPC_TRACER_ON(grpc_compression_trace)) {
+      const char *algo_name;
+      const size_t before_size = calld->slices.length;
+      const size_t after_size = tmp.length;
+      const float savings_ratio = 1.0f - (float)after_size / (float)before_size;
+      GPR_ASSERT(grpc_compression_algorithm_name(calld->compression_algorithm,
+                                                 &algo_name));
+      gpr_log(GPR_DEBUG, "Compressed[%s] %" PRIuPTR " bytes vs. %" PRIuPTR
+                         " bytes (%.2f%% savings)",
+              algo_name, before_size, after_size, 100 * savings_ratio);
+    }
+    grpc_slice_buffer_swap(&calld->slices, &tmp);
+    send_flags |= GRPC_WRITE_INTERNAL_COMPRESS;
+  } else {
+    if (GRPC_TRACER_ON(grpc_compression_trace)) {
+      const char *algo_name;
+      GPR_ASSERT(grpc_compression_algorithm_name(calld->compression_algorithm,
+                                                 &algo_name));
+      gpr_log(GPR_DEBUG,
+              "Algorithm '%s' enabled but decided not to compress. Input size: "
+              "%" PRIuPTR,
+              algo_name, calld->slices.length);
+    }
+  }
+  grpc_slice_buffer_destroy_internal(exec_ctx, &tmp);
+  // Swap out the original byte stream with our new one and send the
+  // batch down.
+  grpc_byte_stream_destroy(
+      exec_ctx, calld->send_message_batch->payload->send_message.send_message);
+  grpc_slice_buffer_stream_init(&calld->replacement_stream, &calld->slices,
+                                send_flags);
+  calld->send_message_batch->payload->send_message.send_message =
+      &calld->replacement_stream.base;
+  calld->original_send_message_on_complete =
+      calld->send_message_batch->on_complete;
+  calld->send_message_batch->on_complete = &calld->send_message_on_complete;
+  send_message_batch_continue(exec_ctx, elem);
+}
+
+static void fail_send_message_batch_in_call_combiner(grpc_exec_ctx *exec_ctx,
+                                                     void *arg,
+                                                     grpc_error *error) {
+  call_data *calld = (call_data *)arg;
+  if (calld->send_message_batch != NULL) {
+    grpc_transport_stream_op_batch_finish_with_failure(
+        exec_ctx, calld->send_message_batch, GRPC_ERROR_REF(error),
+        calld->call_combiner);
+    calld->send_message_batch = NULL;
+  }
+}
+
+// Pulls a slice from the send_message byte stream and adds it to calld->slices.
+static grpc_error *pull_slice_from_send_message(grpc_exec_ctx *exec_ctx,
+                                                call_data *calld) {
+  grpc_slice incoming_slice;
+  grpc_error *error = grpc_byte_stream_pull(
+      exec_ctx, calld->send_message_batch->payload->send_message.send_message,
+      &incoming_slice);
+  if (error == GRPC_ERROR_NONE) {
+    grpc_slice_buffer_add(&calld->slices, incoming_slice);
+  }
+  return error;
+}
+
+// Reads as many slices as possible from the send_message byte stream.
+// If all data has been read, invokes finish_send_message().  Otherwise,
+// an async call to grpc_byte_stream_next() has been started, which will
+// eventually result in calling on_send_message_next_done().
+static void continue_reading_send_message(grpc_exec_ctx *exec_ctx,
+                                          grpc_call_element *elem) {
+  call_data *calld = (call_data *)elem->call_data;
+  while (grpc_byte_stream_next(
+      exec_ctx, calld->send_message_batch->payload->send_message.send_message,
+      ~(size_t)0, &calld->on_send_message_next_done)) {
+    grpc_error *error = pull_slice_from_send_message(exec_ctx, calld);
+    if (error != GRPC_ERROR_NONE) {
+      // Closure callback; does not take ownership of error.
+      fail_send_message_batch_in_call_combiner(exec_ctx, calld, error);
+      GRPC_ERROR_UNREF(error);
+      return;
+    }
+    if (calld->slices.length ==
+        calld->send_message_batch->payload->send_message.send_message->length) {
+      finish_send_message(exec_ctx, elem);
+      break;
+    }
+  }
+}
+
+// Async callback for grpc_byte_stream_next().
+static void on_send_message_next_done(grpc_exec_ctx *exec_ctx, void *arg,
+                                      grpc_error *error) {
+  grpc_call_element *elem = (grpc_call_element *)arg;
+  call_data *calld = (call_data *)elem->call_data;
+  if (error != GRPC_ERROR_NONE) {
+    // Closure callback; does not take ownership of error.
+    fail_send_message_batch_in_call_combiner(exec_ctx, calld, error);
+    return;
+  }
+  error = pull_slice_from_send_message(exec_ctx, calld);
+  if (error != GRPC_ERROR_NONE) {
+    // Closure callback; does not take ownership of error.
+    fail_send_message_batch_in_call_combiner(exec_ctx, calld, error);
+    GRPC_ERROR_UNREF(error);
+    return;
+  }
+  if (calld->slices.length ==
+      calld->send_message_batch->payload->send_message.send_message->length) {
+    finish_send_message(exec_ctx, elem);
+  } else {
+    continue_reading_send_message(exec_ctx, elem);
+  }
+}
+
+static void start_send_message_batch(grpc_exec_ctx *exec_ctx, void *arg,
+                                     grpc_error *unused) {
+  grpc_call_element *elem = (grpc_call_element *)arg;
+  call_data *calld = (call_data *)elem->call_data;
+  if (skip_compression(
+          elem,
+          calld->send_message_batch->payload->send_message.send_message->flags,
+          calld->send_initial_metadata_state == HAS_COMPRESSION_ALGORITHM)) {
+    send_message_batch_continue(exec_ctx, elem);
+  } else {
+    continue_reading_send_message(exec_ctx, elem);
+  }
+}
+
+static void compress_start_transport_stream_op_batch(
+    grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+    grpc_transport_stream_op_batch *batch) {
+  call_data *calld = (call_data *)elem->call_data;
+  GPR_TIMER_BEGIN("compress_start_transport_stream_op_batch", 0);
+  // Handle cancel_stream.
+  if (batch->cancel_stream) {
+    GRPC_ERROR_UNREF(calld->cancel_error);
+    calld->cancel_error =
+        GRPC_ERROR_REF(batch->payload->cancel_stream.cancel_error);
+    if (calld->send_message_batch != NULL) {
+      if (calld->send_initial_metadata_state == INITIAL_METADATA_UNSEEN) {
+        GRPC_CALL_COMBINER_START(
+            exec_ctx, calld->call_combiner,
+            GRPC_CLOSURE_CREATE(fail_send_message_batch_in_call_combiner, calld,
+                                grpc_schedule_on_exec_ctx),
+            GRPC_ERROR_REF(calld->cancel_error), "failing send_message op");
+      } else {
+        grpc_byte_stream_shutdown(
+            exec_ctx,
+            calld->send_message_batch->payload->send_message.send_message,
+            GRPC_ERROR_REF(calld->cancel_error));
+      }
+    }
+  } else if (calld->cancel_error != GRPC_ERROR_NONE) {
+    grpc_transport_stream_op_batch_finish_with_failure(
+        exec_ctx, batch, GRPC_ERROR_REF(calld->cancel_error),
+        calld->call_combiner);
+    goto done;
+  }
+  // Handle send_initial_metadata.
+  if (batch->send_initial_metadata) {
+    GPR_ASSERT(calld->send_initial_metadata_state == INITIAL_METADATA_UNSEEN);
+    bool has_compression_algorithm;
+    grpc_error *error = process_send_initial_metadata(
+        exec_ctx, elem,
+        batch->payload->send_initial_metadata.send_initial_metadata,
+        &has_compression_algorithm);
+    if (error != GRPC_ERROR_NONE) {
+      grpc_transport_stream_op_batch_finish_with_failure(exec_ctx, batch, error,
+                                                         calld->call_combiner);
+      goto done;
+    }
+    calld->send_initial_metadata_state = has_compression_algorithm
+                                             ? HAS_COMPRESSION_ALGORITHM
+                                             : NO_COMPRESSION_ALGORITHM;
+    // If we had previously received a batch containing a send_message op,
+    // handle it now.  Note that we need to re-enter the call combiner
+    // for this, since we can't send two batches down while holding the
+    // call combiner, since the connected_channel filter (at the bottom of
+    // the call stack) will release the call combiner for each batch it sees.
+    if (calld->send_message_batch != NULL) {
+      GRPC_CALL_COMBINER_START(
+          exec_ctx, calld->call_combiner,
+          &calld->start_send_message_batch_in_call_combiner, GRPC_ERROR_NONE,
+          "starting send_message after send_initial_metadata");
+    }
+  }
+  // Handle send_message.
+  if (batch->send_message) {
+    GPR_ASSERT(calld->send_message_batch == NULL);
+    calld->send_message_batch = batch;
+    // If we have not yet seen send_initial_metadata, then we have to
+    // wait.  We save the batch in calld and then drop the call
+    // combiner, which we'll have to pick up again later when we get
+    // send_initial_metadata.
+    if (calld->send_initial_metadata_state == INITIAL_METADATA_UNSEEN) {
+      GRPC_CALL_COMBINER_STOP(
+          exec_ctx, calld->call_combiner,
+          "send_message batch pending send_initial_metadata");
+      goto done;
+    }
+    start_send_message_batch(exec_ctx, elem, GRPC_ERROR_NONE);
+  } else {
+    // Pass control down the stack.
+    grpc_call_next_op(exec_ctx, elem, batch);
+  }
+done:
+  GPR_TIMER_END("compress_start_transport_stream_op_batch", 0);
+}
+
+/* Constructor for call_data */
+static grpc_error *init_call_elem(grpc_exec_ctx *exec_ctx,
+                                  grpc_call_element *elem,
+                                  const grpc_call_element_args *args) {
+  call_data *calld = (call_data *)elem->call_data;
+  calld->call_combiner = args->call_combiner;
+  calld->cancel_error = GRPC_ERROR_NONE;
+  grpc_slice_buffer_init(&calld->slices);
+  GRPC_CLOSURE_INIT(&calld->start_send_message_batch_in_call_combiner,
+                    start_send_message_batch, elem, grpc_schedule_on_exec_ctx);
+  GRPC_CLOSURE_INIT(&calld->on_send_message_next_done,
+                    on_send_message_next_done, elem, grpc_schedule_on_exec_ctx);
+  GRPC_CLOSURE_INIT(&calld->send_message_on_complete, send_message_on_complete,
+                    elem, grpc_schedule_on_exec_ctx);
+  return GRPC_ERROR_NONE;
+}
+
+/* Destructor for call_data */
+static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+                              const grpc_call_final_info *final_info,
+                              grpc_closure *ignored) {
+  call_data *calld = (call_data *)elem->call_data;
+  grpc_slice_buffer_destroy_internal(exec_ctx, &calld->slices);
+  GRPC_ERROR_UNREF(calld->cancel_error);
+}
+
+/* Constructor for channel_data */
+static grpc_error *init_channel_elem(grpc_exec_ctx *exec_ctx,
+                                     grpc_channel_element *elem,
+                                     grpc_channel_element_args *args) {
+  channel_data *channeld = (channel_data *)elem->channel_data;
+
+  /* Configuration for message compression */
+  channeld->enabled_algorithms_bitset =
+      grpc_channel_args_compression_algorithm_get_states(args->channel_args);
+
+  channeld->default_compression_algorithm =
+      grpc_channel_args_get_compression_algorithm(args->channel_args);
+  /* Make sure the default isn't disabled. */
+  if (!GPR_BITGET(channeld->enabled_algorithms_bitset,
+                  channeld->default_compression_algorithm)) {
+    gpr_log(GPR_DEBUG,
+            "compression algorithm %d not enabled: switching to none",
+            channeld->default_compression_algorithm);
+    channeld->default_compression_algorithm = GRPC_COMPRESS_NONE;
+  }
+
+  channeld->supported_compression_algorithms =
+      (((1u << GRPC_COMPRESS_ALGORITHMS_COUNT) - 1) &
+       channeld->enabled_algorithms_bitset) |
+      1u;
+
+  /* Configuration for stream compression */
+  channeld->enabled_stream_compression_algorithms_bitset =
+      grpc_channel_args_stream_compression_algorithm_get_states(
+          args->channel_args);
+
+  channeld->default_stream_compression_algorithm =
+      grpc_channel_args_get_stream_compression_algorithm(args->channel_args);
+
+  if (!GPR_BITGET(channeld->enabled_stream_compression_algorithms_bitset,
+                  channeld->default_stream_compression_algorithm)) {
+    gpr_log(GPR_DEBUG,
+            "stream compression algorithm %d not enabled: switching to none",
+            channeld->default_stream_compression_algorithm);
+    channeld->default_stream_compression_algorithm = GRPC_STREAM_COMPRESS_NONE;
+  }
+
+  channeld->supported_stream_compression_algorithms =
+      (((1u << GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT) - 1) &
+       channeld->enabled_stream_compression_algorithms_bitset) |
+      1u;
+
+  GPR_ASSERT(!args->is_last);
+  return GRPC_ERROR_NONE;
+}
+
+/* Destructor for channel data */
+static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
+                                 grpc_channel_element *elem) {}
+
+const grpc_channel_filter grpc_message_compress_filter = {
+    compress_start_transport_stream_op_batch,
+    grpc_channel_next_op,
+    sizeof(call_data),
+    init_call_elem,
+    grpc_call_stack_ignore_set_pollset_or_pollset_set,
+    destroy_call_elem,
+    sizeof(channel_data),
+    init_channel_elem,
+    destroy_channel_elem,
+    grpc_channel_next_get_info,
+    "message_compress"};