asOBJ_REF and asOBJ_VALUE at the same time

A type cannot be both value type and reference type at the same time. However, you don't need that to register the removeSections function, instead register the output parameter as 'string &out'.

r = engine->RegisterGlobalFunction("void removeSections(string &out, const string ∈, const string ∈, const string ∈, bool)", asFUNCTION(StringUtils::removeSections), asCALL_CDECL); assert( r >= 0 );

Thanks for answer. Its working, but I prefer '@' befour result param, to show, that this param to show that this param will be changed(programing style only). I understand, that I cant use only @ in ref type objects?

removeSections(@strToRet, str, "<--", "-->", true);

Correct. @ can only be used for reference types. It is used to show that you want to do something with the handle of the object rather than the object itself.

Thanks for reply. Im new in angelscript but I like it. I write a ref string class and it works for my test scripts. Coudl you take a look if all is correct?

#pragma once
#include <string>

class asIScriptEngine;

class RefString
{
	friend RefString& operator+(const RefString& str1, const RefString& str2);
	friend bool operator==(const RefString& lhs, const RefString& rhs);
	friend RefString* StringFactory(RefString& refString);
	friend void RegisterRefString(asIScriptEngine *engine);

	mutable int* refCount;
	std::string* pString;
	static asIScriptEngine* mEngine;
public:
	RefString();
	RefString(unsigned int byteLength, const char *s);
	RefString(const std::string& str);
	~RefString();

	void setString(const std::string& str) { if(pString) *pString = str; else pString = new std::string(str); }
	std::string* getString() { return pString; }
	
	RefString& operator=(const RefString& str);

	void addRef() const;
	void release() const;

	static void RegisterRefString(asIScriptEngine *engine);
	static void RegisterStdStringUtils(asIScriptEngine *engine);
};

RefString& operator+(const RefString& str1, const RefString& str2);
bool operator==(const RefString& str1, const RefString& str2);

#include "RefString.h"
#include <assert.h>
#include <angelscript.h>
#include "..\StringUtils.h"

using namespace std;

asIScriptEngine* RefString::mEngine = NULL;

RefString::RefString()
{
	// Let the constructor initialize the reference counter to 1
	refCount = new int(1);
	pString = new std::string;
}

RefString::RefString(unsigned int byteLength, const char *s)
{
	// Let the constructor initialize the reference counter to 1
	refCount = new int(1);
	pString = new std::string(s, byteLength);
}

RefString::RefString(const std::string& str)
{
	refCount = new int(1);
	pString = new std::string(str);
}

RefString::~RefString()
{
	delete refCount;
	delete pString;
}

RefString* StringFactory()
{
	// The class constructor is initializing the reference counter to 1
	RefString* stringRefCounter = new RefString(); 
	return stringRefCounter;//->getString();
}

RefString* StringFactory(RefString& refString)
{
	(*refString.refCount)++;
	return &refString
}

// Our string factory implementation
RefString* StringFactory(unsigned int byteLength, const char *s)
{
	RefString* stringRefCounter = new RefString(byteLength, s); 
	return stringRefCounter;//->getString();
}

void RefString::addRef() const
{
	// Increase the reference counter
	(*refCount)++;
}
void RefString::release() const 
{
	// Decrease ref count and delete if it reaches 0
		if( --(*refCount) == 0 )
		delete this;
}

bool operator==(const RefString& str1, const RefString& str2)
{
	return *(str1.pString) == *(str2.pString);
}

RefString& RefString::operator=(const RefString& str)
{
	if(*this == str) return *this;

	if(this->pString) delete this->pString;

	str.addRef();
	this->pString = str.pString;
	this->refCount = str.refCount;
	return *this;
}

RefString& operator+(const RefString& str1, const RefString& str2)
{
	return *(new RefString(*(str1.pString) + *(str2.pString))); 
}

void RefString::RegisterRefString(asIScriptEngine *engine)
{
	RefString::mEngine = engine;

	int r;
	// Register the string type
	r = engine->RegisterObjectType("string", sizeof(RefString), asOBJ_REF); assert( r >= 0 );
	// Registering the factory behaviour
	r = engine->RegisterObjectBehaviour("string", asBEHAVE_FACTORY, "string@ f()", asFUNCTIONPR(StringFactory, (), RefString*), asCALL_CDECL); assert( r >= 0 );
	r = engine->RegisterObjectBehaviour("string", asBEHAVE_FACTORY, "string@ f(string@)", asFUNCTIONPR(StringFactory, (RefString&), RefString*), asCALL_CDECL); assert( r >= 0 );
	// Registering the addref/release behaviours
	r = engine->RegisterObjectBehaviour("string", asBEHAVE_ADDREF,  "void f()", asMETHOD(RefString,addRef), asCALL_THISCALL); assert( r >= 0 );
	r = engine->RegisterObjectBehaviour("string", asBEHAVE_RELEASE, "void f()", asMETHOD(RefString,release), asCALL_THISCALL); assert( r >= 0 );

	// Registering the string factory
	r = engine->RegisterStringFactory("string@", asFUNCTIONPR(StringFactory, (unsigned int, const char*), RefString*), asCALL_CDECL); assert( r >= 0 );

	r = engine->RegisterObjectMethod("string", "string &opAssign(const string ∈)", asMETHODPR(RefString, operator =, (const RefString&), RefString&), asCALL_THISCALL); assert( r >= 0 );
	r = engine->RegisterObjectMethod("string", "string@ opAdd(const string ∈) const", asFUNCTIONPR(operator+, (const RefString&, const RefString&), RefString&), asCALL_CDECL_OBJFIRST); assert( r >= 0 );
	r = engine->RegisterObjectMethod("string", "bool opEquals(const string ∈) const", asFUNCTIONPR(operator==, (const RefString &, const RefString &), bool), asCALL_CDECL_OBJFIRST); assert( r >= 0 );
}

void RefString::RegisterStdStringUtils(asIScriptEngine * engine)
{
	int r;
	r = engine->RegisterGlobalFunction("void removeHtmlTags(string@, const string& in)", asFUNCTION(StringUtils::removeHtmlTags), asCALL_CDECL); assert( r >= 0 );
	r = engine->RegisterGlobalFunction("void removeSections(string @, const string& in, const string& in, const string& in, bool)", asFUNCTION(StringUtils::removeSections), asCALL_CDECL); assert( r >= 0 );	
	r = engine->RegisterGlobalFunction("void removeWhiteCharsAtBeging(string@, const string& in)", asFUNCTION(StringUtils::removeWhiteCharsAtBeging), asCALL_CDECL); assert( r >= 0 );
	r = engine->RegisterGlobalFunction("void removeWhiteCharsAtEnding(string@, const string& in)", asFUNCTION(StringUtils::removeWhiteCharsAtEnding), asCALL_CDECL); assert( r >= 0 );
	r = engine->RegisterGlobalFunction("void removeMultipleEnters(string@, const string& in)", asFUNCTION(StringUtils::removeMultipleEnters), asCALL_CDECL); assert( r >= 0 );
}

void main()
{
	print("Hello world\n");
	print("AB" + "CD" + "\n");

	string sr1 = "raz";
	string sr2 = "dwa";
	string str3("dupa\n");
	print(sr1);
	print(sr2);
	print(str3);
	if(sr1 == sr2) print("rowne");
	else print("rozne");
}

It appears to be correct.

It interesting to see that you went with a shared internal buffer and reference counter. I have long had in mind to attempt to do a performance comparison with a design like this compared to the ordinary std::string. Perhaps you have some numbers to show?

Remember to make the reference counter threadsafe if you plan to use multithreading.

Hi, thanks for help :)

I don't make any comparison, becouse this is my only implementation. I am beginner with angelscript, so I dont do a rocket science :) I used shared refPointer becouse i dont want to copy string when I use operator=. Honestly I am afraid, that my implementation will be slower than ordinary std::string.

void RefString::release() const 
{
	// Decrease ref count and delete if it reaches 0
	if( --(*refCount) == 0 )
	{
		for(size_t i=0; i<clones->size(); i++)
		{
			if((*clones)[i] == this) continue;
			delete (*clones)[i];
		}

		delete this->refCount;
		delete this->pString;
		delete this->clones;

		delete this;
	}
}


RefString& RefString::operator=(const RefString& str)
{
	if(this->pString == str.pString) return *this;

	std::vector<RefString*> thisClonesCopy = *(this->clones);
	std::vector<RefString*> strClonesCopy = *(str.clones);

	sort(strClonesCopy.begin(), strClonesCopy.end());
	sort(thisClonesCopy.begin(), thisClonesCopy.end());
	this->clones->resize(strClonesCopy.size() + thisClonesCopy.size());

	std::vector<RefString*>::iterator it = set_union(strClonesCopy.begin(), strClonesCopy.end(), thisClonesCopy.begin(), thisClonesCopy.end(), this->clones->begin());
	this->clones->resize(it - this->clones->begin());

	*(str.refCount) += *(this->refCount);

	if(this->pString) delete this->pString;
	if(this->refCount) delete this->refCount;
	if(str.clones) delete str.clones;

	for(size_t i=0; i<clones->size(); i++)
	{
		(*clones)[i]->pString = str.pString;
		(*clones)[i]->clones = this->clones;
		(*clones)[i]->refCount = str.refCount;
	}

	return *this;
}

Best regards

It is unnecessary to hold RefString's clones in each RefString instance. Simply replace pString with a smart pointer to a reference-counted version of std::string. This way there are two reference counting mechanisms involved:

1. Each reference-counted std::string holds the number of RefString's that refer to it.

2. RefString's own reference count holds the number of AngelScript (or C++, if necessary) objects that refer to it, such as string handles.

So RefString's assignment can simply acquire the source RefString's smart pointer to the reference-counted std::string. By doing so it will release the reference-counted std::string it held previously (if any), decreasing its reference counter, which will result in its deletion if and only if no other RefString holds a reference to it.

That aside, unless you are handling reference of your string object inside ScriptUtils object, you may want to register your functions with signatures like

"void removeHtmlTags(string@+, const string& in)"

+ indicating an autohandle.

About COW strings in general, they often prove to be more trouble than they are worth. If lots of raw assignments are expected, they might be a good thing. See http://stackoverflow.com/questions/707014/why-vc-strings-are-not-reference-counted for some reasons why many stl implementations just skip it (at least vc++ and stlport do; gcc libs apparently do not).