how to deal with extern cpp's string

[abakoboParticipant]

I have an extern method i’d like to import/wrap to mx2 but it has a cpp string& as argument. I’ve already successful played with extern cher* using Cstring but can’t figure out how to play with thesestd cpp strings.
Is there something out of the box provided in mx2 (like Cstring/String.FromCstring) or do i have to convert it by myself cpp side?

the method (the std::string& errorMsg is my trouble):

Monkey

readFromFile(const char* filename, std::string& errorMsg, b2World* existingWorld = NULL);

1	readFromFile(const char* filename, std::string& errorMsg, b2World* existingWorld = NULL);

[abakoboParticipant]

there’s the std::string.c_str() method that returns a char array, i’ll go with thar cpp side..

[nerobotParticipant]

Also there is a method std::string::data() but:

There are no guarantees that a null character terminates the character sequence pointed by the value returned by this function.

AFAIK monkey’s CString is null-terminated, therefore  c_str() is a right choice.

[abakoboParticipant]

I finaly decided to go with std::copy so I keep the memory allocated by mx2 and don’t have to worry about GC/memory stuffs.
It’s passing a fixed size char_t array and then transforms it to string when back to mx2. It the way I felt the safest (with my knowledge;)

the aim was to deal with the error message..

cpp side

Monkey

b2World* b2dJsonReadFromFile_ext (const char* filename, char* charErrMsg, int charsize, b2World* existingWorld) { std::string errMsg; b2dJson json; b2World* returnWorld = json.readFromFile(filename, errMsg, existingWorld ); if (charsize>8) { // the char array must have a certain size.. if (errMsg.size()<charsize-2){ std::copy(errMsg.begin(), errMsg.end(), charErrMsg); } else { std::string errMsgBis; errMsgBis = errMsg.substr (0,charsize-3); std::copy(errMsgBis.begin(), errMsgBis.end(), charErrMsg); charErrMsg[errMsgBis.size()] = '\0'; // terminating the cstring } } return returnWorld; }

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b2World* b2dJsonReadFromFile_ext (const char* filename, char* charErrMsg, int charsize, b2World* existingWorld) {   std::string errMsg; b2dJson json; b2World* returnWorld = json.readFromFile(filename, errMsg, existingWorld );   if (charsize>8) { // the char array must have a certain size.. if (errMsg.size()<charsize-2){ std::copy(errMsg.begin(), errMsg.end(), charErrMsg); } else { std::string errMsgBis; errMsgBis = errMsg.substr (0,charsize-3); std::copy(errMsgBis.begin(), errMsgBis.end(), charErrMsg); charErrMsg[errMsgBis.size()] = '\0'; // terminating the cstring } }     return returnWorld;   }

mx2 side

Monkey

Extern Function b2dJsonReadFromFile_ext:b2World(filename:CString , errorMsg:char_t Ptr , charsize:Int , existingWorld:b2World = Null) Public Function b2dJsonReadFromFile:b2World(filename:String , existingWorld:b2World = Null) Local maxChrSize:Int=321 Local buf:=New char_t[maxChrSize] Local retWorld:=b2dJsonReadFromFile_ext(filename , buf.Data , maxChrSize , existingWorld ) #If __DEBUG__ 'print the error message if in debug mode Print String.FromCString( buf.Data ) #Endif Return retWorld End

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Extern   Function b2dJsonReadFromFile_ext:b2World(filename:CString , errorMsg:char_t Ptr , charsize:Int , existingWorld:b2World = Null)   Public   Function b2dJsonReadFromFile:b2World(filename:String , existingWorld:b2World = Null) Local maxChrSize:Int=321 Local buf:=New char_t[maxChrSize] Local retWorld:=b2dJsonReadFromFile_ext(filename , buf.Data , maxChrSize , existingWorld ) #If __DEBUG__ 'print the error message if in debug mode Print String.FromCString( buf.Data ) #Endif Return retWorld End

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