From 1604784669fb88255f80d981d61fbe132cd1446e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robert=20M=C3=BCller?= <robytemueller@gmail.com>
Date: Tue, 5 Sep 2023 13:50:03 +0200
Subject: [PATCH] Improve Windows pipe (FIFO) support

Use `WaitForPipeDrain` to deterministically wait for the pipe to drain instead of using `Start-Sleep`.

Use `Dispose` instead of `Close` to properly flush and close the pipe stream.

Add error handling for connection timeout and I/O errors.

Handle `ERROR_BROKEN_PIPE` separately when peeking at pipe, as this happens when the pipe is disconnected immediately after connecting it or after reading the previous message.

Don't ignore `ERROR_BAD_PIPE` anymore, as the pipe should never be in a disconnected (i.e. bad) state at this point of the function.
---
 scripts/send_named_pipe.ps1 | 34 +++++++++++++++++++++-------------
 src/engine/shared/fifo.cpp  |  8 +++++++-
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/scripts/send_named_pipe.ps1 b/scripts/send_named_pipe.ps1
index fa659deb3..f3dcfe86c 100644
--- a/scripts/send_named_pipe.ps1
+++ b/scripts/send_named_pipe.ps1
@@ -4,7 +4,7 @@
 # The second argument is the message to send.
 if ($args.length -lt 2) {
 	Write-Output "Usage: ./send_named_pipe.ps1 <pipename> <message> [message] ... [message]"
-	return
+	exit -1
 }
 
 $Wrapper = [pscustomobject]@{
@@ -18,16 +18,24 @@ $Wrapper = [pscustomobject]@{
 	Reader = $null
 	Writer = $null
 }
-$Wrapper.Pipe.Connect(5000)
-if (!$?) {
-	return
+try {
+	$Wrapper.Pipe.Connect(5000)
+	$Wrapper.Reader = New-Object System.IO.StreamReader($Wrapper.Pipe)
+	$Wrapper.Writer = New-Object System.IO.StreamWriter($Wrapper.Pipe)
+	$Wrapper.Writer.AutoFlush = $true
+	for ($i = 1; $i -lt $args.length; $i++) {
+		$Wrapper.Writer.WriteLine($args[$i])
+	}
+	# Wait for pipe contents to be read.
+	$Wrapper.Pipe.WaitForPipeDrain()
+	# Dispose the pipe, which also calls Flush and Close.
+	$Wrapper.Pipe.Dispose()
+	# Explicity set error level 0 for success, as otherwise the current error level is kept.
+	exit 0
+} catch [TimeoutException] {
+	Write-Output "Timeout connecting to pipe"
+	exit 1
+} catch [System.IO.IOException] {
+	Write-Output "Broken pipe"
+	exit 2
 }
-$Wrapper.Reader = New-Object System.IO.StreamReader($Wrapper.Pipe)
-$Wrapper.Writer = New-Object System.IO.StreamWriter($Wrapper.Pipe)
-$Wrapper.Writer.AutoFlush = $true
-for ($i = 1; $i -lt $args.length; $i++) {
-	$Wrapper.Writer.WriteLine($args[$i])
-}
-# We need to wait because the lines will not be written if we close the pipe immediately
-Start-Sleep -Seconds 1.5
-$Wrapper.Pipe.Close()
diff --git a/src/engine/shared/fifo.cpp b/src/engine/shared/fifo.cpp
index 7ed0b296b..af2b49f09 100644
--- a/src/engine/shared/fifo.cpp
+++ b/src/engine/shared/fifo.cpp
@@ -154,7 +154,13 @@ void CFifo::Update()
 		if(!PeekNamedPipe(m_pPipe, NULL, 0, NULL, &BytesAvailable, NULL))
 		{
 			const DWORD LastError = GetLastError();
-			if(LastError != ERROR_BAD_PIPE) // pipe not connected, not an error
+			if(LastError == ERROR_BROKEN_PIPE)
+			{
+				// Pipe was disconnected from the other side, either immediately
+				// after connecting or after reading the previous message.
+				DisconnectNamedPipe(m_pPipe);
+			}
+			else
 			{
 				const std::string ErrorMsg = windows_format_system_message(LastError);
 				dbg_msg("fifo", "failed to peek at pipe '%s' (%ld %s)", m_aFilename, LastError, ErrorMsg.c_str());