examples: get C++ hello_world module working

Changes required by commit 68fbbe3 ("Use Rust Loader for running
examples (#993)"):
 - Add and use a config that doesn't include a translator node.
 - Add C++ code that is equivalent to oak::grpc::server::init().

Change required by commit 64d3f90 ("Use bytes to represent gRPC
message body (#833)"):
 - Re-work hand-coded response message for current GrpcResponse proto
   message definition.

For #1009

examples/hello_world/config/BUILD

@@ -37,5 +37,5 @@ serialized_config(
     modules = {
         "app": "//examples/hello_world/module/cpp:hello_world.wasm",
     },
-    textproto = ":config.textproto",
+    textproto = ":config_no_translator.textproto",
 )

examples/hello_world/config/config_no_translator.textproto

@@ -0,0 +1,18 @@
+node_configs {
+  name: "app"
+  wasm_config {
+    module_bytes: "<bytes>"
+  }
+}
+node_configs {
+  name: "grpc-server"
+  grpc_server_config {
+    address: "[::]:8080"
+  }
+}
+node_configs {
+  name: "log"
+  log_config {}
+}
+initial_node_config_name: "app"
+initial_entrypoint_name: "grpc_oak_main"

examples/hello_world/module/cpp/hello_world.cc

@@ -46,8 +46,46 @@ WASM_IMPORT("oak")
 uint32_t channel_write(uint64_t handle, uint8_t* buff, size_t usize, uint8_t* handle_buff,
                        size_t handle_count);
 WASM_IMPORT("oak") uint32_t channel_close(uint64_t handle);
+WASM_IMPORT("oak")
+uint32_t channel_create(uint64_t* write_handle, uint64_t* read_handle, uint8_t* label_buf,
+                        size_t label_size);
+WASM_IMPORT("oak")
+uint32_t node_create(uint8_t* config_buf, size_t config_size, uint8_t* entrypoint_buf,
+                     size_t entrypoint_size, uint8_t* label_buf, size_t label_size,
+                     uint64_t handle);
+
+WASM_EXPORT void grpc_oak_main(uint64_t _handle) {
+  // Create a channel to the gRPC server pseudo-Node.
+  uint64_t write_handle;
+  uint64_t read_handle;
+  uint32_t result = channel_create(&write_handle, &read_handle, nullptr, 0);
+  if (result != oak::OakStatus::OK) {
+    return;
+  }
+
+  // Create a gRPC server pseudo-Node
+  char config_name[] = "grpc-server";
+  result = node_create((uint8_t*)config_name, sizeof(config_name) - 1, nullptr, 0, nullptr, 0,
+                       read_handle);
+  if (result != oak::OakStatus::OK) {
+    return;
+  }
+  channel_close(read_handle);
+
+  // Create a separate channel for receiving invocations and pass it to the gRPC pseudo-Node.
+  uint64_t grpc_out_handle;
+  uint64_t grpc_in_handle;
+  result = channel_create(&grpc_out_handle, &grpc_in_handle, nullptr, 0);
+  if (result != oak::OakStatus::OK) {
+    return;
+  }
+  result = channel_write(write_handle, nullptr, 0, (uint8_t*)&grpc_out_handle, 1);
+  if (result != oak::OakStatus::OK) {
+    return;
+  }
+  channel_close(grpc_out_handle);
+  channel_close(write_handle);
 
-WASM_EXPORT void oak_main(uint64_t grpc_in_handle) {
   // TODO(#744): Add C++ helpers for dealing with handle notification space.
   uint8_t handle_space[9] = {
       static_cast<uint8_t>(grpc_in_handle & 0xff),
@@ -62,7 +100,7 @@ WASM_EXPORT void oak_main(uint64_t grpc_in_handle) {
   };
 
   while (true) {
-    int32_t result = wait_on_channels(handle_space, 1);
+    uint32_t result = wait_on_channels(handle_space, 1);
     if (result != oak::OakStatus::OK) {
       return;
     }
@@ -87,14 +125,12 @@ WASM_EXPORT void oak_main(uint64_t grpc_in_handle) {
     // Manually create an encapsulated GrpcResponse protobuf and send it back.
     //    0a                 b00001.010 = tag 1 (GrpcResponse.rsp_msg), length-delimited field
     //    0b                 length=11
-    //      12                 b00010.010 = tag 2 (Any.value), length-delimited field
-    //      09                 length=9
-    //        0A                 b00001.010 = tag 1 (HelloResponse.reply), length-delimited field
-    //        07                 length=7
-    //          74657374696e67   "testing"
+    //      0A                 b00001.010 = tag 1 (HelloResponse.reply), length-delimited field
+    //      07                 length=7
+    //        74657374696e67   "testing"
     //    18                 b00011.000 = tag 3 (GrpcResponse.last), varint
     //    01                 true
-    uint8_t rsp_buf[] = "\x0a\x0b\x12\x09\x0A\x07\x74\x65\x73\x74\x69\x6e\x67\x18\x01";
+    uint8_t rsp_buf[] = "\x0a\x0b\x0A\x07\x74\x65\x73\x74\x69\x6e\x67\x18\x01";
     // TODO(#422): replace with use of message type and serialization.
     channel_write(rsp_handle, rsp_buf, sizeof(rsp_buf) - 1, nullptr, 0);
     channel_close(rsp_handle);

scripts/run_examples

@@ -34,16 +34,11 @@ while getopts "s:l:h" opt; do
   esac
 done
 
-# TODO(#1009): Re-enable C++ examples after supporting them with Rust Oak Loader.
-if [[ "${languages}" == "cpp" ]]; then
-  echo "C++ examples are currently not supported"
-  exit 1
-fi
-
 # Run all examples.
 for language in ${languages}; do
   # TODO(#594): Re-enable rustfmt when upstream rustc internal error is fixed.
-  examples="$(find examples -mindepth 2 -maxdepth 4 -type d -regex '.*/module.*/'"${language}"'$' | cut -d'/' -f2 | uniq | grep -v rustfmt)"
+  # TODO(#1009): Re-enable C++ tensorflow example after supporting them with Rust Oak Loader.
+  examples="$(find examples -mindepth 2 -maxdepth 4 -type d -regex '.*/module.*/'"${language}"'$' | cut -d'/' -f2 | uniq | grep -v rustfmt | grep -v tensorflow)"
   for example in ${examples}; do
     if [[ "${example}" == "chat" ]]; then
         "${SCRIPTS_DIR}/run_example" -s "${server}" -l "${language}" -e chat -- --test