From 920120bbcec9f91df3336f62970b3e010a4fa6c2 Mon Sep 17 00:00:00 2001
From: Stefan Boberg <stefan.boberg@epicgames.com>
Date: Thu, 6 Mar 2025 16:18:32 +0100
Subject: reduced memory churn using fixed_xxx containers (#236)

* Added EASTL to help with eliminating memory allocations
* Applied EASTL to eliminate memory allocations, primarily by using `fixed_vector` et al to use stack allocations / inline struct allocations

Reduces memory events in traces by close to a factor of 10 in test scenario (starting editor for project F)
---
 src/zenhttp/packageformat.cpp | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

(limited to 'src/zenhttp/packageformat.cpp')

diff --git a/src/zenhttp/packageformat.cpp b/src/zenhttp/packageformat.cpp
index 676fc73fd..ae80851e4 100644
--- a/src/zenhttp/packageformat.cpp
+++ b/src/zenhttp/packageformat.cpp
@@ -19,6 +19,8 @@
 #include <span>
 #include <vector>
 
+#include <EASTL/fixed_vector.h>
+
 #if ZEN_PLATFORM_WINDOWS
 #	include <zencore/windows.h>
 #endif
@@ -31,6 +33,10 @@ namespace zen {
 
 const std::string_view HandlePrefix(":?#:");
 
+typedef eastl::fixed_vector<IoBuffer, 16> IoBufferVec_t;
+
+IoBufferVec_t FormatPackageMessageInternal(const CbPackage& Data, FormatFlags Flags, void* TargetProcessHandle);
+
 std::vector<IoBuffer>
 FormatPackageMessage(const CbPackage& Data, void* TargetProcessHandle)
 {
@@ -42,10 +48,18 @@ FormatPackageMessageBuffer(const CbPackage& Data, void* TargetProcessHandle)
 	return FormatPackageMessageBuffer(Data, FormatFlags::kDefault, TargetProcessHandle);
 }
 
+std::vector<IoBuffer>
+FormatPackageMessage(const CbPackage& Data, FormatFlags Flags, void* TargetProcessHandle)
+{
+	auto Vec = FormatPackageMessageInternal(Data, Flags, TargetProcessHandle);
+	return std::vector<IoBuffer>(begin(Vec), end(Vec));
+}
+
 CompositeBuffer
 FormatPackageMessageBuffer(const CbPackage& Data, FormatFlags Flags, void* TargetProcessHandle)
 {
-	return CompositeBuffer(FormatPackageMessage(Data, Flags, TargetProcessHandle));
+	auto Vec = FormatPackageMessageInternal(Data, Flags, TargetProcessHandle);
+	return CompositeBuffer(std::span{begin(Vec), end(Vec)});
 }
 
 static void
@@ -54,7 +68,7 @@ MarshalLocal(CbAttachmentEntry*&		  AttachmentInfo,
 			 CbAttachmentReferenceHeader& LocalRef,
 			 const IoHash&				  AttachmentHash,
 			 bool						  IsCompressed,
-			 std::vector<IoBuffer>&		  ResponseBuffers)
+			 IoBufferVec_t&				  ResponseBuffers)
 {
 	IoBuffer RefBuffer(sizeof(CbAttachmentReferenceHeader) + Path8.size());
 
@@ -146,8 +160,8 @@ IsLocalRef(tsl::robin_map<void*, std::string>& FileNameMap,
 	return true;
 };
 
-std::vector<IoBuffer>
-FormatPackageMessage(const CbPackage& Data, FormatFlags Flags, void* TargetProcessHandle)
+IoBufferVec_t
+FormatPackageMessageInternal(const CbPackage& Data, FormatFlags Flags, void* TargetProcessHandle)
 {
 	ZEN_TRACE_CPU("FormatPackageMessage");
 
@@ -177,7 +191,7 @@ FormatPackageMessage(const CbPackage& Data, FormatFlags Flags, void* TargetProce
 #endif	// ZEN_PLATFORM_WINDOWS
 
 	const std::span<const CbAttachment>& Attachments = Data.GetAttachments();
-	std::vector<IoBuffer>				 ResponseBuffers;
+	IoBufferVec_t						 ResponseBuffers;
 
 	ResponseBuffers.reserve(2 + Attachments.size());  // TODO: may want to use an additional fudge factor here to avoid growing since each
 													  // attachment is likely to consist of several buffers
-- 
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