n-api: add API for asynchronous functions

Bundle a `uv_async_t`, a `uv_idle_t`, a `uv_mutex_t`, a `uv_cond_t`,
and a `v8::Persistent<v8::Function>` to make it possible to call into JS
from another thread. The API accepts a void data pointer and a callback
which will be invoked on the loop thread and which will receive the
`napi_value` representing the JavaScript function to call so as to
perform the call into JS. The callback is run inside a
`node::CallbackScope`.

A `std::queue<void*>` is used to store calls from the secondary
threads, and an idle loop is started by the `uv_async_t` callback on the
loop thread to drain the queue, calling into JS with each item.

Items can be added to the queue blockingly or non-blockingly.

The thread-safe function can be referenced or unreferenced, with the
same semantics as libuv handles.

Re: https://github.com/nodejs/help/issues/1035
Re: https://github.com/nodejs/node/issues/20964
Fixes: https://github.com/nodejs/node/issues/13512
PR-URL: https://github.com/nodejs/node/pull/17887
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

1 files changed, 27 insertions, 1 deletions

diff --git a/src/node_api_types.h b/src/node_api_types.h
index f7f3ee6275..af7d7c7f95 100644
--- a/src/node_api_types.h
+++ b/src/node_api_types.h
@@ -20,6 +20,9 @@ typedef struct napi_callback_info__* napi_callback_info;
 typedef struct napi_async_context__* napi_async_context;
 typedef struct napi_async_work__* napi_async_work;
 typedef struct napi_deferred__* napi_deferred;
+#ifdef NAPI_EXPERIMENTAL
+typedef struct napi_threadsafe_function__* napi_threadsafe_function;
+#endif  // NAPI_EXPERIMENTAL
 
 typedef enum {
   napi_default = 0,
@@ -72,9 +75,25 @@ typedef enum {
   napi_cancelled,
   napi_escape_called_twice,
   napi_handle_scope_mismatch,
-  napi_callback_scope_mismatch
+  napi_callback_scope_mismatch,
+#ifdef NAPI_EXPERIMENTAL
+  napi_queue_full,
+  napi_closing,
+#endif  // NAPI_EXPERIMENTAL
 } napi_status;
 
+#ifdef NAPI_EXPERIMENTAL
+typedef enum {
+  napi_tsfn_release,
+  napi_tsfn_abort
+} napi_threadsafe_function_release_mode;
+
+typedef enum {
+  napi_tsfn_nonblocking,
+  napi_tsfn_blocking
+} napi_threadsafe_function_call_mode;
+#endif  // NAPI_EXPERIMENTAL
+
 typedef napi_value (*napi_callback)(napi_env env,
                                     napi_callback_info info);
 typedef void (*napi_finalize)(napi_env env,
@@ -86,6 +105,13 @@ typedef void (*napi_async_complete_callback)(napi_env env,
                                              napi_status status,
                                              void* data);
 
+#ifdef NAPI_EXPERIMENTAL
+typedef void (*napi_threadsafe_function_call_js)(napi_env env,
+                                                 napi_value js_callback,
+                                                 void* context,
+                                                 void* data);
+#endif  // NAPI_EXPERIMENTAL
+
 typedef struct {
   // One of utf8name or name should be NULL.
   const char* utf8name;