From a1de921567c0e45efa9cf1a8c9a947582a667796 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 22 Aug 2021 13:17:08 +0300
Subject: [PATCH] Use a persistent OVERLAPPED structure in EventReader

---
 source/io/windows/eventreader.cpp | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/source/io/windows/eventreader.cpp b/source/io/windows/eventreader.cpp
index 62c9763..8a4c862 100644
--- a/source/io/windows/eventreader.cpp
+++ b/source/io/windows/eventreader.cpp
@@ -11,12 +11,13 @@ namespace IO {
 
 struct EventReader::Private
 {
-	OVERLAPPED *overlapped;
+	OVERLAPPED overlapped;
 	Handle event;
 	unsigned buf_size;
 	char *buffer;
 	unsigned buf_avail;
 	char *buf_next;
+	bool pending;
 };
 
 
@@ -24,18 +25,19 @@ EventReader::EventReader(Handle &h, unsigned size):
 	handle(h),
 	priv(new Private)
 {
-	priv->overlapped = 0;
+	memset(&priv->overlapped, 0, sizeof(OVERLAPPED));
 	*priv->event = CreateEvent(0, true, false, 0);
+	priv->overlapped.hEvent = *priv->event;
 	priv->buf_size = size;
 	priv->buffer = new char[priv->buf_size];
 	priv->buf_avail = 0;
 	priv->buf_next = priv->buffer;
+	priv->pending = false;
 }
 
 EventReader::~EventReader()
 {
 	CloseHandle(*priv->event);
-	delete priv->overlapped;
 	delete[] priv->buffer;
 	delete priv;
 }
@@ -48,43 +50,38 @@ const Handle &EventReader::get_event()
 
 void EventReader::start()
 {
-	if(priv->buf_avail || priv->overlapped)
+	if(priv->buf_avail || priv->pending)
 		return;
 
-	priv->overlapped = new OVERLAPPED;
-	memset(priv->overlapped, 0, sizeof(OVERLAPPED));
-	priv->overlapped->hEvent = *priv->event;
-
 	DWORD ret;
 	priv->buf_next = priv->buffer;
-	if(!ReadFile(*handle, priv->buffer, priv->buf_size, &ret, priv->overlapped))
+	if(!ReadFile(*handle, priv->buffer, priv->buf_size, &ret, &priv->overlapped))
 	{
 		unsigned err = GetLastError();
-		if(err!=ERROR_IO_PENDING)
+		if(err==ERROR_IO_PENDING)
+			priv->pending = true;
+		else
 			throw system_error("ReadFile");
 	}
 	else
 	{
 		priv->buf_avail = ret;
-		delete priv->overlapped;
-		priv->overlapped = 0;
 		SetEvent(*priv->event);
 	}
 }
 
 void EventReader::wait()
 {
-	if(!priv->overlapped)
+	if(!priv->pending)
 		return;
 
 	DWORD ret;
-	if(!GetOverlappedResult(*handle, priv->overlapped, &ret, true))
+	if(!GetOverlappedResult(*handle, &priv->overlapped, &ret, true))
 		throw system_error("GetOverlappedResult");
 	else
 	{
 		priv->buf_avail = ret;
-		delete priv->overlapped;
-		priv->overlapped = 0;
+		priv->pending = false;
 	}
 }
 
-- 
2.43.0