feat(pty): add multithread support

Adds the option `use_threads` to PTY (enabled by default) which improves
performance when enabled. For example, running `time cat file.txt` where
file is ~4.5MB will take ~0.250s with threads enabled, versus >20s when
disabled.

addons/godot_xterm/native/src/pty.cpp

@@ -1,6 +1,12 @@
 #include "pty.h"
 
+#include <godot_cpp/classes/mutex.hpp>
+#include <godot_cpp/classes/node.hpp>
+#include <godot_cpp/classes/os.hpp>
 #include <godot_cpp/classes/project_settings.hpp>
+#include <godot_cpp/classes/semaphore.hpp>
+#include <godot_cpp/classes/thread.hpp>
+#include <godot_cpp/core/mutex_lock.hpp>
 #include <uv.h>
 
 #if (defined(__linux__) || defined(__APPLE__)) && !defined(_PTY_DISABLED)
@@ -8,6 +14,9 @@
 #include <unistd.h>
 #endif
 
+// Require buffer to be flushed after reaching this size.
+#define BUFFER_LIMIT 1048576 // 1MB
+
 #define UV_ERR_MSG(uv_err)                                                     \
     String(uv_err_name(uv_err)) + String(": ") + String(uv_strerror(uv_err))
 
@@ -18,9 +27,8 @@
 using namespace godot;
 
 void _alloc_buffer(uv_handle_t *handle, size_t suggested_size, uv_buf_t *buf);
-void _read_cb(uv_stream_t *pipe, ssize_t nread, const uv_buf_t *buf);
 void _write_cb(uv_write_t *req, int status) { std::free(req); }
-void _close_cb(uv_handle_t *handle);
+void _close_cb(uv_handle_t *handle) { /* no-op */ };
 
 void PTY::_bind_methods() {
     BIND_ENUM_CONSTANT(SIGNAL_SIGHUP);
@@ -50,6 +58,10 @@ void PTY::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_use_os_env", "use_os_env"), &PTY::set_use_os_env);
 	ClassDB::add_property("PTY", PropertyInfo(Variant::BOOL, "use_os_env"), "set_use_os_env", "get_use_os_env");
 
+	ClassDB::bind_method(D_METHOD("set_use_threads", "enabled"), &PTY::set_use_threads);
+	ClassDB::bind_method(D_METHOD("is_using_threads"), &PTY::is_using_threads);
+	ClassDB::add_property("PTY", PropertyInfo(Variant::BOOL, "use_threads"), "set_use_threads", "is_using_threads");
+
 	ClassDB::bind_method(D_METHOD("get_pts"), &PTY::get_pts);
 
 	ClassDB::bind_method(D_METHOD("fork", "file", "args", "cwd", "cols", "rows"), &PTY::fork, DEFVAL(""), DEFVAL(PackedStringArray()), DEFVAL("."), DEFVAL(80), DEFVAL(24));
@@ -63,10 +75,18 @@ void PTY::_bind_methods() {
 }
 
 PTY::PTY() {
+    use_threads = true;
+
+    set_process_internal(false);
+    thread.instantiate();
+    buffer_write_mutex.instantiate();
+    buffer_cleared.instantiate();
+
     env["TERM"] = "xterm-256color";
     env["COLORTERM"] = "truecolor";
 
     #if defined(__linux__) || defined(__APPLE__)
+    uv_async_init(uv_default_loop(), &async_handle, [](uv_async_t *handle) {});
     uv_pipe_init(uv_default_loop(), &pipe, false);
     pipe.data = this;
     #endif
@@ -96,6 +116,15 @@ void PTY::set_use_os_env(const bool value) {
    use_os_env = value;
 }
 
+void PTY::set_use_threads(bool p_use) {
+    ERR_FAIL_COND(status != STATUS_CLOSED);
+    use_threads = p_use;
+}
+
+bool PTY::is_using_threads() const {
+    return use_threads;
+}
+
 String PTY::get_pts() const {
     return pts;
 }
@@ -117,17 +146,19 @@ Error PTY::fork(const String &file, const PackedStringArray &args, const String
     pid = result["pid"];
     pts = result["pty"];
 
+    status = STATUS_OPEN;
+
     #if defined(__linux__) || defined(__APPLE__)
-    err = _pipe_open(fd);
+    _pipe_open(fd);
-    if (err != OK) {
+    uv_read_start((uv_stream_t *)&pipe, _alloc_buffer, _read_cb);
-        status = STATUS_ERROR;
-        ERR_FAIL_V_MSG(err, "Failed to open pipe.");
-    }
     #endif
 
-    status = STATUS_OPEN;
+    if (use_threads) {
-    set_process_internal(true);
+        stop_thread.clear();
+        thread->start(callable_mp(this, &PTY::_thread_func));
+    }
 
+    set_process_internal(true);
     return OK;
 }
 
@@ -192,35 +223,61 @@ void PTY::_notification(int p_what) {
     switch (p_what)
     {
     case  NOTIFICATION_INTERNAL_PROCESS:
-        switch (status)
     {
-        case STATUS_OPEN:
+        #if defined(__linux__) || defined(__APPLE__)
-            _run(UV_RUN_NOWAIT);
+        if (!use_threads) uv_run(uv_default_loop(), UV_RUN_NOWAIT);
+        #endif
+
+        buffer_write_mutex->lock();
+        if (buffer.size() > 0) {
+            emit_signal("data_received", buffer);
+            buffer.clear();
+            buffer_cleared->post();
         }
+        buffer_write_mutex->unlock();
+
         break;
+    }
     case NOTIFICATION_EXIT_TREE:
         _close();
         break;
     }
 }
 
-void PTY::_run(uv_run_mode mode) {
+void PTY::_thread_func() {
+    while (!stop_thread.is_set()) {
+        if (buffer.size() < BUFFER_LIMIT) {
             #if defined(__linux__) || defined(__APPLE__)
-    if (!uv_is_active((uv_handle_t *)&pipe)) {
+            uv_run(uv_default_loop(), UV_RUN_ONCE);
-        uv_read_start((uv_stream_t *)&pipe, _alloc_buffer, _read_cb);
-    }
-
-    uv_run(uv_default_loop(), mode);
             #endif
+        } else {
+            buffer_cleared->wait();
+        }
+    }
 }
 
 void PTY::_close() {
+    if (use_threads) {
+        if (thread->is_started()) {
+            stop_thread.set();
+            #if defined(__linux__) || defined(__APPLE__)
+            uv_async_send(&async_handle);
+            #endif
+            thread->wait_to_finish();
+        }
+    }
+
     #if defined(__linux__) || defined(__APPLE__)
     if (!uv_is_closing((uv_handle_t *)&pipe)) {
         uv_close((uv_handle_t *)&pipe, _close_cb);
-        uv_run(uv_default_loop(), UV_RUN_ONCE);
     }
 
+    if (!uv_is_closing((uv_handle_t *)&async_handle)) {
+        uv_close((uv_handle_t *)&async_handle, _close_cb);
+    }
+
+    uv_run(uv_default_loop(), UV_RUN_NOWAIT);
+
     if (fd > 0) close(fd);
     if (pid > 0) kill(SIGNAL_SIGHUP);
     #endif
@@ -306,7 +363,7 @@ PackedStringArray PTY::_parse_env(const Dictionary &env) const {
 }
 
 void PTY::_on_exit(int exit_code, int exit_signal) {
-    emit_signal(StringName("exited"), exit_code, exit_signal);
+    call_deferred("emit_signal", "exited", exit_code, exit_signal);
 }
 
 #if defined(__linux__) || defined(__APPLE__)
@@ -316,7 +373,7 @@ void _alloc_buffer(uv_handle_t *handle, size_t suggested_size, uv_buf_t *buf) {
   buf->len = suggested_size;
 }
 
-void _read_cb(uv_stream_t *pipe, ssize_t nread, const uv_buf_t *buf) {
+void PTY::_read_cb(uv_stream_t *pipe, ssize_t nread, const uv_buf_t *buf) {
     PTY *pty = static_cast<PTY *>(pipe->data);
 
     if (nread < 0) {
@@ -335,22 +392,17 @@ void _read_cb(uv_stream_t *pipe, ssize_t nread, const uv_buf_t *buf) {
       return;
     }
 
-    PackedByteArray data;
+    if (nread > 0) {
-    data.resize(nread);
+        MutexLock lock(*pty->buffer_write_mutex.ptr());
-    memcpy(data.ptrw(), buf->base, nread);
+
+        int old_size = pty->buffer.size();
+        int new_size = old_size + nread;
+
+        pty->buffer.resize(new_size);
+        memcpy(pty->buffer.ptrw() + old_size, buf->base, nread);
+
         std::free((char *)buf->base);
-    pty->call_deferred("emit_signal", "data_received", data);
-
-    // Stop reading until the next poll, otherwise _read_cb could be called
-    // repeatedly, blocking Godot, and eventually resulting in a memory pool
-    // allocation error. This can be triggered with the command `cat /dev/urandom`
-    // if reading is not stopped.
-    uv_read_stop(pipe);
     }
-
-void _close_cb(uv_handle_t *pipe) {
-    PTY *pty = static_cast<PTY *>(pipe->data);
-    pty->status = PTY::Status::STATUS_CLOSED;
 }
 
 Error PTY::_pipe_open(const int fd) {

addons/godot_xterm/native/src/pty.h

@@ -3,8 +3,11 @@
 
 #pragma once
 
+#include <godot_cpp/classes/mutex.hpp>
 #include <godot_cpp/classes/node.hpp>
 #include <godot_cpp/classes/os.hpp>
+#include <godot_cpp/classes/semaphore.hpp>
+#include <godot_cpp/classes/thread.hpp>
 #include <uv.h>
 
 namespace godot
@@ -52,6 +55,9 @@ namespace godot
     bool get_use_os_env() const;
     void set_use_os_env(const bool value);
 
+    void set_use_threads(bool p_use);
+    bool is_using_threads() const;
+
     String get_pts() const;
 
     Error fork(const String &file = "", const PackedStringArray &args = PackedStringArray(), const String &cwd = ".", const int cols = 80, const int rows = 24);
@@ -62,7 +68,6 @@ namespace godot
     void write(const Variant &data) const;
 
     void _notification(int p_what);
-    void _run(uv_run_mode mode);
 
   protected:
     static void _bind_methods();
@@ -85,11 +90,21 @@ namespace godot
     void _on_exit(int exit_code, int exit_signal);
     void _close();
 
+    Ref<Thread> thread;
+    Ref<Mutex> buffer_write_mutex;
+    Ref<Semaphore> buffer_cleared;
+    PackedByteArray buffer;
+    SafeFlag stop_thread;
+    uv_async_t async_handle;
+    bool use_threads;
+    void _thread_func();
+
     #if defined(__linux__) || defined(__APPLE__)
     uv_pipe_t pipe;
     Error _pipe_open(const int fd);
     #endif
 
+    static void _read_cb(uv_stream_t *pipe, ssize_t nread, const uv_buf_t *buf);
     static Error uv_err_to_godot_err(const int uv_err);
   };
 } // namespace godot

test/test_nix.gd

@@ -1,4 +1,4 @@
-class_name UnixTest extends GutTest
+class_name NixTest extends GutTest
 
 var pty: PTY
 var helper: Helper
@@ -112,6 +112,15 @@ func test_emits_exited_with_signal():
 	assert_signal_emitted_with_parameters(pty, "exited", [0, PTY.SIGNAL_SIGSEGV])
 
 
+# Run the same tests, but with use_threads = false.
+class TestNoThreads:
+	extends NixTest
+
+	func before_each():
+		super.before_each()
+		pty.use_threads = false
+
+
 class Helper:
 	static func get_pts() -> Array:
 		assert(false)  #,"Abstract method")