asio/http optimizations (#449)

This change primarily introduces improved logic for dealing with sending data from file references. 

This is intended to reduce the amount of memory-mapping we end up doing when sending data from files. Windows now uses `TransmitFile` to send file data more efficiently using kernel-side I/O, but Linux/Mac basically behaves as before since they don't offer any true async file I/O support via asio. This should be implemented separately using a background I/O thread pool.

This PR also includes improved memory management for http/asio with reduced allocation counts, and a fix for a potential use-after-free in very high load scenarios.

1 files changed, 2 insertions, 27 deletions

diff --git a/src/zenserver/diag/diagsvcs.cpp b/src/zenserver/diag/diagsvcs.cpp
index 8abf6e8a3..d8d53b0e3 100644
--- a/src/zenserver/diag/diagsvcs.cpp
+++ b/src/zenserver/diag/diagsvcs.cpp
@@ -28,30 +28,6 @@ GetHealthTag()
 
 using namespace std::literals;
 
-static bool
-ReadLogFile(const std::string& Path, StringBuilderBase& Out)
-{
-	try
-	{
-		constexpr auto ReadSize	  = std::size_t{4096};
-		auto		   FileStream = std::ifstream{Path};
-
-		std::string Buf(ReadSize, '\0');
-		while (FileStream.read(&Buf[0], ReadSize))
-		{
-			Out.Append(std::string_view(&Buf[0], FileStream.gcount()));
-		}
-		Out.Append(std::string_view(&Buf[0], FileStream.gcount()));
-
-		return true;
-	}
-	catch (const std::exception&)
-	{
-		Out.Reset();
-		return false;
-	}
-}
-
 HttpHealthService::HttpHealthService()
 {
 	ZEN_MEMSCOPE(GetHealthTag());
@@ -95,10 +71,9 @@ HttpHealthService::HttpHealthService()
 				return m_HealthInfo.AbsLogPath.empty() ? m_HealthInfo.DataRoot / "logs/zenserver.log" : m_HealthInfo.AbsLogPath;
 			}();
 
-			ExtendableStringBuilder<4096> Sb;
-			if (ReadLogFile(Path.string(), Sb) && Sb.Size() > 0)
+			if (IoBuffer LogBuffer = IoBufferBuilder::MakeFromFile(Path))
 			{
-				HttpReq.WriteResponse(HttpResponseCode::OK, HttpContentType::kText, Sb.ToView());
+				HttpReq.WriteResponse(HttpResponseCode::OK, HttpContentType::kText, LogBuffer);
 			}
 			else
 			{