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)

4 files changed, 38 insertions, 18 deletions

diff --git a/src/zenhttp/httpserver.cpp b/src/zenhttp/httpserver.cpp
index 1fbe22628..27a09f339 100644
--- a/src/zenhttp/httpserver.cpp
+++ b/src/zenhttp/httpserver.cpp
@@ -31,6 +31,8 @@
 #include <span>
 #include <string_view>
 
+#include <EASTL/fixed_vector.h>
+
 namespace zen {
 
 using namespace std::literals;
@@ -529,7 +531,7 @@ HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, HttpContentType
 {
 	std::span<const SharedBuffer> Segments = Payload.GetSegments();
 
-	std::vector<IoBuffer> Buffers;
+	eastl::fixed_vector<IoBuffer, 64> Buffers;
 	Buffers.reserve(Segments.size());
 
 	for (auto& Segment : Segments)
@@ -537,7 +539,7 @@ HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, HttpContentType
 		Buffers.push_back(Segment.AsIoBuffer());
 	}
 
-	WriteResponse(ResponseCode, ContentType, Buffers);
+	WriteResponse(ResponseCode, ContentType, std::span<IoBuffer>(begin(Buffers), end(Buffers)));
 }
 
 std::string
diff --git a/src/zenhttp/include/zenhttp/httpserver.h b/src/zenhttp/include/zenhttp/httpserver.h
index 7b87cb84b..217455dba 100644
--- a/src/zenhttp/include/zenhttp/httpserver.h
+++ b/src/zenhttp/include/zenhttp/httpserver.h
@@ -208,7 +208,7 @@ class HttpRouterRequest
 public:
 	HttpRouterRequest(HttpServerRequest& Request) : m_HttpRequest(Request) {}
 
-	ZENCORE_API std::string	  GetCapture(uint32_t Index) const;
+	std::string_view		  GetCapture(uint32_t Index) const;
 	inline HttpServerRequest& ServerRequest() { return m_HttpRequest; }
 
 private:
@@ -220,12 +220,14 @@ private:
 	friend class HttpRequestRouter;
 };
 
-inline std::string
+inline std::string_view
 HttpRouterRequest::GetCapture(uint32_t Index) const
 {
 	ZEN_ASSERT(Index < m_Match.size());
 
-	return m_Match[Index];
+	const auto& Match = m_Match[Index];
+
+	return std::string_view(&*Match.first, Match.second - Match.first);
 }
 
 /** HTTP request router helper
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
diff --git a/src/zenhttp/servers/httpsys.cpp b/src/zenhttp/servers/httpsys.cpp
index 87128c0c9..3bdcdf098 100644
--- a/src/zenhttp/servers/httpsys.cpp
+++ b/src/zenhttp/servers/httpsys.cpp
@@ -16,6 +16,8 @@
 #include <zencore/trace.h>
 #include <zenhttp/packageformat.h>
 
+#include <EASTL/fixed_vector.h>
+
 #if ZEN_WITH_HTTPSYS
 #	define _WINSOCKAPI_
 #	include <zencore/windows.h>
@@ -381,14 +383,14 @@ public:
 	void						   SuppressResponseBody();	// typically used for HEAD requests
 
 private:
-	std::vector<HTTP_DATA_CHUNK> m_HttpDataChunks;
-	uint64_t					 m_TotalDataSize	   = 0;	 // Sum of all chunk sizes
-	uint16_t					 m_ResponseCode		   = 0;
-	uint32_t					 m_NextDataChunkOffset = 0;	 // Cursor used for very large chunk lists
-	uint32_t					 m_RemainingChunkCount = 0;	 // Backlog for multi-call sends
-	bool						 m_IsInitialResponse   = true;
-	HttpContentType				 m_ContentType		   = HttpContentType::kBinary;
-	std::vector<IoBuffer>		 m_DataBuffers;
+	eastl::fixed_vector<HTTP_DATA_CHUNK, 16> m_HttpDataChunks;
+	uint64_t								 m_TotalDataSize	   = 0;	 // Sum of all chunk sizes
+	uint16_t								 m_ResponseCode		   = 0;
+	uint32_t								 m_NextDataChunkOffset = 0;	 // Cursor used for very large chunk lists
+	uint32_t								 m_RemainingChunkCount = 0;	 // Backlog for multi-call sends
+	bool									 m_IsInitialResponse   = true;
+	HttpContentType							 m_ContentType		   = HttpContentType::kBinary;
+	eastl::fixed_vector<IoBuffer, 16>		 m_DataBuffers;
 
 	void InitializeForPayload(uint16_t ResponseCode, std::span<IoBuffer> Blobs);
 };