Remove some unnecessary string copy related to substr.

Patch By: phosit
Differential Revision: https://code.wildfiregames.com/D4772
This was SVN commit r27271.

source/gui/ObjectBases/IGUIObject.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -33,6 +33,7 @@
 #include "soundmanager/ISoundManager.h"
 
 #include <algorithm>
+#include <string_view>
 #include <unordered_map>
 
 const CStr IGUIObject::EventNameMouseEnter = "MouseEnter";
@@ -461,7 +462,7 @@ CStr IGUIObject::GetPresentableName() const
 	if (m_Name.length() <= 12)
 		return m_Name;
 
-	if (m_Name.substr(0, 10) == "__internal")
+	if (std::string_view{m_Name}.substr(0, 10) == "__internal")
 		return CStr("[unnamed object]");
 	else
 		return m_Name;

source/gui/ObjectTypes/CInput.cpp

@@ -635,7 +635,7 @@ InReaction CInput::ManuallyHandleHotkeyEvent(const SDL_Event_* ev)
 
 		// Check max length
 		if (m_MaxLength != 0 && caption.length() + text.length() > static_cast<size_t>(m_MaxLength))
-			text = text.substr(0, static_cast<size_t>(m_MaxLength) - caption.length());
+			text.erase(static_cast<size_t>(m_MaxLength) - caption.length());
 
 		if (SelectingText())
 			DeleteCurSelection();
@@ -1552,7 +1552,7 @@ void CInput::UpdateText(int from, int to_before, int to_after)
 	CStrW& caption = m_Caption.GetMutable();
 
 	if (m_MaxLength != 0 && caption.length() > static_cast<size_t>(m_MaxLength))
-		caption = caption.substr(0, m_MaxLength);
+		caption.erase(m_MaxLength);
 
 	CStrIntern font_name(m_Font->ToUTF8());
 

source/gui/Scripting/JSInterface_GUIProxy_impl.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -28,6 +28,7 @@
 #include "scriptinterface/ScriptRequest.h"
 
 #include <string>
+#include <string_view>
 
 template <typename T>
 JSI_GUIProxy<T>& JSI_GUIProxy<T>::Singleton()
@@ -307,7 +308,7 @@ bool JSI_GUIProxy<T>::delete_(JSContext* cx, JS::HandleObject proxy, JS::HandleI
 		return result.fail(JSMSG_BAD_PROP_ID);
 
 	// event handlers
-	if (propName.substr(0, 2) == "on")
+	if (std::string_view{propName}.substr(0, 2) == "on")
 	{
 		CStr eventName(propName.substr(2));
 		e->UnsetScriptHandler(eventName);

source/gui/SettingTypes/MouseEventMask.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -29,6 +29,8 @@
 #include "ps/CStr.h"
 #include "scriptinterface/ScriptConversions.h"
 
+#include <string_view>
+
 class IGUIObject;
 class IGUISetting;
 
@@ -83,11 +85,12 @@ public:
 	static constexpr std::string_view identifier = "texture:";
 	static constexpr size_t specOffset = identifier.size();
 
-	static std::unique_ptr<CGUIMouseEventMaskTexture> Create(const std::string& spec)
+	static std::unique_ptr<CGUIMouseEventMaskTexture> Create(const std::string_view spec)
 	{
 		std::shared_ptr<u8> shapeFile;
 		CCacheLoader loader(g_VFS, L".dds");
-		VfsPath sourcePath = VfsPath("art") / L"textures" / L"ui" / spec.substr(specOffset);
+		VfsPath sourcePath = VfsPath("art") / L"textures" / L"ui" /
+			std::string{spec.substr(specOffset)};
 		VfsPath archivePath = loader.ArchiveCachePath(sourcePath);
 		Status status;
 		size_t size;

source/lib/sysdep/os/win/wsysdep.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -43,6 +43,8 @@
 # include <boost/algorithm/string.hpp>
 #endif
 
+#include <string_view>
+
 
 #if MSC_VERSION
 #pragma comment(lib, "shell32.lib")	// for sys_pick_directory SH* calls
@@ -538,9 +540,10 @@ static std::wstring parse_proxy(const std::wstring& input)
 	std::vector<std::wstring> parts;
 	split(parts, input, boost::algorithm::is_any_of("; \t\r\n"), boost::algorithm::token_compress_on);
 
-	for(size_t i = 0; i < parts.size(); ++i)
-		if(boost::algorithm::starts_with(parts[i], "http="))
-			return parts[i].substr(5);
+	constexpr std::wstring_view http{L"http="};
+	for(const std::wstring& part : parts)
+		if(std::wstring_view{part}.substr(0, http.size()) == http)
+			return part.substr(http.size());
 
 	// If we got this far, proxies were only set for non-HTTP protocols
 	return L"";

source/ps/CConsole.cpp

@@ -41,6 +41,7 @@
 #include "scriptinterface/ScriptInterface.h"
 #include "scriptinterface/JSON.h"
 
+#include <string_view>
 #include <vector>
 #include <wctype.h>
 
@@ -548,7 +549,8 @@ void CConsole::InsertMessage(const std::string& message)
 			m_MsgHistory.push_front(wrapAround.substr(oldNewline, distance));
 			oldNewline += distance+1;
 		}
-		m_MsgHistory.push_front(wrapAround.substr(oldNewline));
+		wrapAround.erase(0, oldNewline);
+		m_MsgHistory.push_front(std::move(wrapAround));
 	}
 }
 
@@ -615,7 +617,7 @@ void CConsole::LoadHistory()
 		{
 			if (pos > 0)
 				m_BufHistory.push_front(str.Left(str[pos-1] == '\r' ? pos - 1 : pos));
-			str = str.substr(pos + 1);
+			str.erase(0, pos + 1);
 		}
 		else if (str.length() > 0)
 			m_BufHistory.push_front(str);

source/ps/TemplateLoader.cpp

@@ -40,7 +40,7 @@ bool CTemplateLoader::LoadTemplateFile(CParamNode& node, std::string_view templa
 	// Handle infinite loops more gracefully than running out of stack space and crashing
 	if (depth > 100)
 	{
-		LOGERROR("Probable infinite inheritance loop in entity template '%s'", std::string(templateName));
+		LOGERROR("Probable infinite inheritance loop in entity template '%s'", templateName);
 		return false;
 	}
 

source/ps/XMB/XMBStorage.cpp

@@ -28,6 +28,7 @@
 #include "scriptinterface/ScriptInterface.h"
 
 #include <libxml/parser.h>
+#include <string_view>
 #include <unordered_map>
 
 const char* XMBStorage::HeaderMagicStr = "XMB0";
@@ -235,7 +236,8 @@ bool JSNodeData::Setup(XMBStorageWriter& xmb, JS::HandleValue value)
 		std::string_view name = prop;
 		if (!attrib && !prop.empty() && prop.back() == '@')
 		{
-			size_t idx = prop.substr(0, prop.size()-1).find_last_of('@');
+			const size_t idx = std::string_view{prop}.substr(0, prop.size() - 1)
+				.find_last_of('@');
 			if (idx == std::string::npos)
 			{
 				LOGERROR("Object key name cannot end with an '@' unless it is an index specifier.");

source/ps/tests/test_CLogger.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2009 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -85,7 +85,7 @@ public:
 		std::string s = mainlog->str();
 		size_t start = s.find(header_end);
 		TS_ASSERT_DIFFERS(start, s.npos);
-		s = s.substr(start + header_end.length());
+		s.erase(0, start + header_end.length());
 
 		size_t n = 0, m;
 		while (s.npos != (m = s.find('\n', n)))

source/renderer/PostprocManager.cpp

@@ -36,6 +36,8 @@
 #include "renderer/RenderingOptions.h"
 #include "tools/atlas/GameInterface/GameLoop.h"
 
+#include <string_view>
+
 CPostprocManager::CPostprocManager()
 	: m_IsInitialized(false), m_PostProcEffect(L"default"), m_WhichBuffer(true),
 	m_Sharpness(0.3f), m_UsingMultisampleBuffer(false), m_MultisampleCount(0)
@@ -617,12 +619,13 @@ void CPostprocManager::UpdateAntiAliasingTechnique()
 	// We have to hardcode names in the engine, because anti-aliasing
 	// techinques strongly depend on the graphics pipeline.
 	// We might use enums in future though.
-	const CStr msaaPrefix = "msaa";
+	constexpr std::string_view msaaPrefix{"msaa"};
 	if (m_AAName == "fxaa")
 	{
 		m_AATech = g_Renderer.GetShaderManager().LoadEffect(CStrIntern("fxaa"));
 	}
-	else if (m_AAName.size() > msaaPrefix.size() && m_AAName.substr(0, msaaPrefix.size()) == msaaPrefix)
+	else if (m_AAName.size() > msaaPrefix.size() &&
+		std::string_view{m_AAName}.substr(0, msaaPrefix.size()) == msaaPrefix)
 	{
 		// We don't want to enable MSAA in Atlas, because it uses wxWidgets and its canvas.
 		if (g_AtlasGameLoop && g_AtlasGameLoop->running)

source/simulation2/helpers/Selection.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -31,6 +31,8 @@
 #include "simulation2/components/ICmpUnitRenderer.h"
 #include "simulation2/system/ComponentManager.h"
 
+#include <string_view>
+
 entity_id_t EntitySelection::PickEntityAtPoint(CSimulation2& simulation, const CCamera& camera, int screenX, int screenY, player_id_t player, bool allowEditorSelectables)
 {
 	PROFILE2("PickEntityAtPoint");
@@ -215,9 +217,11 @@ std::vector<entity_id_t> EntitySelection::PickSimilarEntities(CSimulation2& simu
 		if (matchRank)
 		{
 			// Exact template name matching, optionally also allowing foundations
-			std::string curTemplateName = cmpTemplateManager->GetCurrentTemplateName(ent);
+			const std::string curTemplateName = cmpTemplateManager->GetCurrentTemplateName(ent);
 			bool matches = (curTemplateName == templateName ||
-			                (allowFoundations && curTemplateName.substr(0, 11) == "foundation|" && curTemplateName.substr(11) == templateName));
+				(allowFoundations &&
+				std::string_view{curTemplateName}.substr(0, 11) == "foundation|" &&
+				std::string_view{curTemplateName}.substr(11) == templateName));
 			if (!matches)
 				continue;
 		}

source/simulation2/system/ComponentManager.cpp

@@ -32,6 +32,8 @@
 #include "simulation2/system/ParamNode.h"
 #include "simulation2/system/SimContext.h"
 
+#include <string_view>
+
 /**
  * Used for script-only message types.
  */
@@ -273,26 +275,27 @@ void CComponentManager::Script_RegisterComponentType_Common(int iid, const std::
 		return;
 	}
 
-	for (std::vector<std::string>::const_iterator it = methods.begin(); it != methods.end(); ++it)
+	for (const std::string& method : methods)
 	{
-		// TODO C++17: string_view
-		if (strncmp((it->c_str()), "On", 2) != 0)
+		if (std::string_view{method}.substr(0, 2) != "On")
 			continue;
 
-		std::string name = (*it).substr(2); // strip the "On" prefix
+		std::string_view name{std::string_view{method}.substr(2)}; // strip the "On" prefix
 
 		// Handle "OnGlobalFoo" functions specially
 		bool isGlobal = false;
-		if (strncmp(name.c_str(), "Global", 6) == 0)
+		if (std::string_view{name}.substr(0, 6) == "Global")
 		{
 			isGlobal = true;
-			name = name.substr(6);
+			name.remove_prefix(6);
 		}
 
-		std::map<std::string, MessageTypeId>::const_iterator mit = m_MessageTypeIdsByName.find(name);
+		auto mit = m_MessageTypeIdsByName.find(std::string{name});
 		if (mit == m_MessageTypeIdsByName.end())
 		{
-			ScriptException::Raise(rq, "Registered component has unrecognized '%s' message handler method", it->c_str());
+			ScriptException::Raise(rq,
+				"Registered component has unrecognized '%s' message handler method",
+				method.c_str());
 			return;
 		}
 

source/simulation2/system/ParamNode.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -28,6 +28,7 @@
 #include "scriptinterface/ScriptRequest.h"
 
 #include <sstream>
+#include <string_view>
 
 #include <boost/algorithm/string.hpp>
 
@@ -143,21 +144,31 @@ void CParamNode::ApplyLayer(const XMBData& xmb, const XMBElement& element, const
 
 				// Merge the two lists
 				std::vector<std::string> tokens = oldTokens;
-				for (size_t i = 0; i < newTokens.size(); ++i)
+				for (const std::string& newToken : newTokens)
 				{
-					if (newTokens[i][0] == '-')
+					if (newToken[0] == '-')
 					{
-						std::vector<std::string>::iterator tokenIt = std::find(tokens.begin(), tokens.end(), newTokens[i].substr(1));
+						std::vector<std::string>::iterator tokenIt =
+							std::find(tokens.begin(), tokens.end(),
+								std::string_view{newToken}.substr(1));
 						if (tokenIt != tokens.end())
 							tokens.erase(tokenIt);
 						else
-							LOGWARNING("[ParamNode] Could not remove token '%s' from node '%s'%s; not present in list nor inherited (possible typo?)",
-								newTokens[i].substr(1), name, sourceIdentifier ? (" in '" + utf8_from_wstring(sourceIdentifier) + "'").c_str() : "");
+						{
+							const std::string identifier{
+								sourceIdentifier ? (" in '" +
+									utf8_from_wstring(sourceIdentifier) + "'") : ""};
+							LOGWARNING("[ParamNode] Could not remove token "
+								"'%s' from node '%s'%s; not present in "
+								"list nor inherited (possible typo?)",
+								std::string_view{newToken}.substr(1), name,
+								identifier);
+						}
 					}
 					else
 					{
-						if (std::find(oldTokens.begin(), oldTokens.end(), newTokens[i]) == oldTokens.end())
-							tokens.push_back(newTokens[i]);
+						if (std::find(oldTokens.begin(), oldTokens.end(), newToken) == oldTokens.end())
+							tokens.push_back(newToken);
 					}
 				}