投稿者: Yamanouchi Katsura

I’ll show you here a useful ‘dll’ for MQL4 of MetaTrader4 for Windows.
You may need ‘VisualStudio2013 & C++’. Of course, also MT4.
At first, I introduce you to some helpful web sites below; Many thanks to these genius authors!!.

Basic References
https://msdn.microsoft.com/ja-jp/library/60k1461a.aspx MSDN References for VisualC++
http://www7b.biglobe.ne.jp/~robe/cpphtml/index.html Mr. roberr
http://www.asahi-net.or.jp/~yf8k-kbys/newcpp5.html C++ entrance

Modern Coding C++
https://cybozu.atlassian.net/wiki/pages/viewpage.action?pageId=8159240 Modern C++ Mr.Yamamoto(Cyboze co Ltd)
https://isocpp.org/get-started ModernC++11,14
http://www.geocities.co.jp/bleis_tift/cpp/badstd.html std namespace? what is that

Stream
http://99blues.dyndns.org/blog/2010/02/std_stringstream/ Stream general help
http://homepage2.nifty.com/well/Stream.html Stream basic
http://ppp-lab.sakura.ne.jp/ProgrammingPlacePlus/cpp/language/006.html filestream basic
http://mementoo.info/archives/611 file coding

Unicode specific
http://vllv.us/Junk/_T/ Code general
http://loops.at.webry.info/201011/article_3.html Unicode problem
http://www.02.246.ne.jp/~torutk/cxx/vc/misc_tchar.html TCHAR coding
https://social.msdn.microsoft.com/Forums/vstudio/ja-JP/a0bcb7d6-525b-4da8-8ea9-c02dd82e8cd4/basicifstream TCHAR Coding for filehandle
http://www-06.ibm.com/jp/linux/tech/doc/007aca9b.html character code of filename references on windows file system version(Unicode,sjis Japanese)

MT4
http://www.green.dti.ne.jp/sdimension/mql/mql_2011_03.pdf#search=’mql+dll’ Mr.amenbo Helpful document with 4step development method
https://www.tradersquare.jp/community/topic/47-mt4-%E5%90%91%E3%81%91-dll-%E3%81%AE%E9%96%A2%E6%95%B0%E3%82%A8%E3%82%AF%E3%82%B9%E3%83%9D%E3%83%BC%E3%83%88/ Document about MQL4 and DLL export table

Test fo file handling and string transition

I chose the 4 step method suggested by Mr.amenbo(see link), and add a bit shortcut.
Step 1 is the same as the original idea, so let’s begin.
I wrote ‘test.cpp’ as my solution name, but you can change as you like, within coding regulations.
‘%…%’ means replace proper string.
Many impressive sites exist, but difficult for beginners. My comments in the .cpp code below might be helpful for your .dll coding for MQL4. Because I spend considerable hours to understand how to call dll from MQL4, if you like this message, please give me your expected expenses.
You may try this code at a debug mode. Push ‘local debugger,’ and you can see a console window and prompt on the window.
Here, step 1 must be complete, easy? Or difficult?
If you have a question, please comment on this message. I don’t receive any e-mail from an unknown person.
Finally some important notices, I cannot speak English, as you know?… and I’m a native Japanese living in Japan.

Step 1-1 Create full code on C++

[cpp]
// test.cpp : Test for Console application for MT4
#include "stdafx.h"	// you must add these header below in this headerfile
// #include "targetver.h"
// #include <tchar.h>
// #include <locale>
// #include <string>
// #include <fstream>
// #include <iostream>
// #include <stdexcept>
// #include <limits>
#if defined(_UNICODE) || defined(UNICODE)
#  define tcout std::wcout
#  define tcin std::wcin
#else
#  define tcout std::cout
#  define tcin std::cin
#endif
typedef std::basic_string<_TCHAR> tstring;
typedef std::basic_ifstream<_TCHAR> tifstream; // file in stream
typedef std::basic_stringstream<_TCHAR> tstringstream; // string in stream
_TINT no;	//Just for debugging
_TCHAR* hello(_TCHAR *file_name);	//prototype statement
_TINT _tmain(_TINT argc, _TCHAR* argv[]){
    _tsetlocale(LC_ALL, _T("ja-JP"));	//locale is important, don't forget
    _TCHAR file_name[] = _T("% fullpath and filename here %");
    tcout << hello(file_name);
    tcin >> no;	// test use only, just for prevent close console window
    return 0;
}
//+---------- function-------------------------------------------+
_TCHAR* hello(_TCHAR *file_name){
    // return and pass is both 'char pointer', it's important
    tstring s;	// string
    tstring ss;	// if you need formatted string, you can use 'tstringstream'
    FILE *fs;
    errno_t err;
    err= _tfopen_s(&fs, file_name, _T("rt, ccs=UNICODE"));
        // open err
        if (err != 0){
	    return _T("fail not open that file");	//takecare, file exist?
	}
	else{
	    // success open file
	    tifstream ifs(fs);	// make a filestream
	    while (ifs >> s){	// you don't need use 'getline' method
	 	ss += s;	// just for string case. if you want to use stream...
 		// ss << s;	// like this.
  	    }
	    tcout << ss;	//just for this test, strip this line when you copy code.
	_TCHAR out[1000]; //no intention this number, not too short and not too much
		err = _tcscpy_s(out, 1000, ss.c_str());		//also above
		if (err == 0){
			static _TCHAR *outp = out;	//keep address for MQL4
			return outp;
		}
		else return _T("copy fail");
	}
}
[/cpp]

Step1-2 Create MQL side code

This method is an alternate method for Mr.amenbo’s.
The interface of mql and dll is quite easy. If you put ‘string’ to dll, the mql send that as a pointer to that string to dll. Dll receives as it and then return pointer, and the mql takes that as a string with an arrow. So you don’t need to create a ‘call program’ as step3 in Mr.amenbo’s method.
And there is one tip, ‘Alert’ method in mql does not work well, that title is ok, but contents may fail to draw the proper character.
If you can correct that problem, please tell me how to do that.
Partially, I choose the ‘MessageBoxW’ with windows API, imported by WinUser32.mqh.

[cpp]
//+------------------------------------------------------------------+
//|                                                         test.mq4 |
//|                               Copyright 2015, UHL Software Corp. |
//|                            https://www.yamanouchi-katsura.jp/fx/ |
//+------------------------------------------------------------------+
#property copyright "Copyright 2015, UHL Software Corp."
#property link      "https://www.yamanouchi-katsura.jp/fx/"
#property version   "1.00"
#property strict
#include <stdlib.mqh>
#include <WinUser32.mqh>
#import "test.dll"
	string hello(string);	//put filename type 'string' and get data as 'string' in facto pointer
#import
#property script_show_inputs
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
input string InpFilter="*";
void OnStart(){
    string file_name;	//NTFS=unicode、FAT=sjis
    int    i=1;
    long search_handle=FileFindFirst(InpFilter,file_name);
    if(search_handle!=INVALID_HANDLE){
 	do{
		ResetLastError();
		FileIsExist(file_name);
		//PrintFormat("%d : %s name = %s",i,GetLastError()==5018 ? "Directory" : "File",file_name);	//just for debug
		i++;
	}while(FileFindNext(search_handle,file_name));
	//--- executional code ---
	string terminal_data_path=TerminalInfoString(TERMINAL_DATA_PATH);	//search install path
	file_name=terminal_data_path+"\\MQL4\\Files\\"+file_name;	//test pattern
	//--- close search handle
	//PrintFormat("fullpath in MQL4: %s",file_name);	//just for debug
	string ret=hello2(file_name);
	int flg=MB_ICONINFORMATION+MB_TOPMOST;
	MessageBoxW(0,ret,ret,flg);		//I cannot get over the 'alert' problem, so I use a windowsAPI on user32.dll, see header file
	//Alert(ret);		//You may see a error with charcter code probrem
	FileFindClose(search_handle);
    }
    else Print("Files not found");
}
[/cpp]

Step2 Create dll code

Important note is just below;
1) #define MT4_EXPFUNC __declspec(dllexport)
2) __stdcall
That is it.

1) Copy the header and target function code from the full system create above.
//+———- function——————————————-+
_TCHAR* hello(_TCHAR *file_name){……

2) Change that title of the target function below.
MT4_EXPFUNC _TCHAR* __stdcall hello(_TCHAR *file_name){……

3 Set build mode to ‘Release’, and select menu project>property>, and set ‘Structure Property>c++>code create-runtime library’ to ‘multiple sleds(/MT)’.

4 Build it.

You don’t need to create a module definition (.def) file. (at least on VC++2013? I’m not sure in facto… Please tell me, genius wizard)

Step3 Test!!

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