Create your own MetaTrader extension (dll) - page 14
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Hi Mladen!
When I try to get the value of the buffer[0] the value is something like Buffer: 2147483647
So I think this is not right... There should be a value something like: 1,23584
as I made a test and set: buffer = Rates[10].close;
Any ideas?
Thanks a lot and bye, ATThat values is what is known as EMPTY_VALUE
From mql side check if all is OK with your buffer declaration and values assignment. Also check how are you handling buffer (array) elements from a C++ side
Hi Mladen!
I tried something in calling the DLL and also with buffers, BUT without any positiv results...
I tried to set the buffer value in the C++ code to 1, buffer[]=1; No change...
I attched the DLL (please just rename it from .zip do .dll), which I call with the following MQL4 code
Thanks for any inputs/hints...
Bye, AT
sma_rec.dll.zip
#property indicator_buffers 1 // one indicator line to be plotted
#property indicator_color1 Red // plot colour is red - change via GUI
#import "sma_rec.dll"
void updateBuffer(MqlRates &rates[], double& buffer[], int bars, int indicator_counted, int period, double& internal_calcs[2] );
#import
extern int ma_period = 10; // default period is 10 - change via GUI
extern int ma_shift = 0; // default is no shift - change via GUI
double buffer[]; // the indicator buffer - the DLL will // write to this and it will be plotted
MqlRates Rates[];
double internal_calcs[2];
int init(){
// set up the indicator buffer
IndicatorBuffers(2);
SetIndexStyle(0, DRAW_LINE);
SetIndexShift(0, ma_shift);
SetIndexBuffer(0, buffer);
SetIndexLabel(0, "Recursive SMA");
IndicatorDigits(Digits);
return(0);
}
int start(){
ArrayCopyRates(Rates);
updateBuffer( Rates, buffer, Bars, IndicatorCounted(), ma_period, internal_calcs );
// Print("4 - close: ",Rates[0].close,"\n");
//Print("Buffer: ",buffer[0],"\n");
return(0);
}Hi Mladen!
I tried something in calling the DLL and also with buffers, BUT without any positiv results...
I tried to set the buffer value in the C++ code to 1, buffer[]=1; No change...
I attched the DLL (please just rename it from .zip do .dll), which I call with the following MQL4 code
Thanks for any inputs/hints...
Bye, AT
sma_rec.dll.zip
#property indicator_buffers 1 // one indicator line to be plotted
#property indicator_color1 Red // plot colour is red - change via GUI
#import "sma_rec.dll"
void updateBuffer(MqlRates &rates[], double& buffer[], int bars, int indicator_counted, int period, double& internal_calcs[2] );
#import
extern int ma_period = 10; // default period is 10 - change via GUI
extern int ma_shift = 0; // default is no shift - change via GUI
double buffer[]; // the indicator buffer - the DLL will // write to this and it will be plotted
MqlRates Rates[];
double internal_calcs[2];
int init(){
// set up the indicator buffer
IndicatorBuffers(2);
SetIndexStyle(0, DRAW_LINE);
SetIndexShift(0, ma_shift);
SetIndexBuffer(0, buffer);
SetIndexLabel(0, "Recursive SMA");
IndicatorDigits(Digits);
return(0);
}
int start(){
ArrayCopyRates(Rates);
updateBuffer( Rates, buffer, Bars, IndicatorCounted(), ma_period, internal_calcs );
// Print("4 - close: ",Rates[0].close,"\n");
//Print("Buffer: ",buffer[0],"\n");
return(0);
}You can not use buffer[]=1; - it means nothing in mql. You have to use some index in the buffer[] part (like buffer[0]=1; )
Hi Mladen!
I used the following for it in C++
buffer = 1;
So this should normaly work...
The C++ code looks like below.
Thanks for help!!
Bye, AT
#include
#include "stdafx.h"
#include
#define WIN32_LEAN_AND_MEAN
#define MT4_EXPFUNC __declspec(dllexport)
//+------------------------------------------------------------------+
//| MT4 HISTORY DATA STRUCT |
//+------------------------------------------------------------------+
#pragma pack(push,1)
struct RateInfo
{
__int64 ctm;
double open;
double low;
double high;
double close;
unsigned __int64 vol_tick;
int spread;
unsigned __int64 vol_real;
};
#pragma pack(pop)
struct MqlStr
{
int len;
char *string;
};
MT4_EXPFUNC void __stdcall updateBuffer(const RateInfo* Rates, double buffer[],int Bars, int IndicatorCounted, int ma_period, double internal_calcs[2] )
{
//---
if(Rates==NULL)
{
printf("updateBuffer: NULL array\n");
}
//---
if(Rates != NULL)
{
printf("updateBuffer: something is in array\n");
}
//---
if(buffer==NULL)
{
printf("updateBuffer: NULL array\n");
}
//---
if(Bars<0)
{
printf("updateBuffer: wrong Bars number (%d)\n", Bars);
}
//---
if(ma_period<0)
{
printf("updateBuffer: wrong MA Period (%d)\n", ma_period);
}
//---
if(ma_period==10)
{
printf("updateBuffer: 10 MA Period (%d)\n", ma_period);
}
// buffer = 1;
//buffer = ( buffer - internal_calcs[0] ) + ( Rates.close/ma_period ); // calculate new SMA value//
// check if the DLL is being called for the very first time
if ( IndicatorCounted == 0 )
{
buffer[0] = Rates[0].close;
buffer[1] = ( Rates[0].close + Rates[1].close ) / 2.0;
for( int ii = 2 ; ii < ma_period ; ii++ )
{
buffer = ( ( buffer * ii ) / (ii+1) ) + ( Rates.close/(ii+1) );
}
for( int ii = ma_period ; ii < Bars - 1 ; ii++ )
{
buffer = ( buffer - (Rates.close/ma_period) ) + ( Rates.close/ma_period );
}
internal_calcs[0] = (Rates.close/ma_period);
internal_calcs[1] = Bars - 1; // how many indicator values calculated so far
}
if ( IndicatorCounted > 0 && (Bars - 1) > internal_calcs[1] ) // evaluates to TRUE if there is a new bar
{
buffer = ( buffer - internal_calcs[0] ) + ( Rates.close/ma_period ); // calculate new SMA value
internal_calcs[0] = (Rates.close/ma_period); // update // internal_calcs with new value for next SMA calc.
internal_calcs[1] = Bars - 1; // update how many indicator values calculated so far
} // end of ( IndicatorCounted > 0 && (Bars - 1) > internal_calcs[1]) if // statement
} // end of main function call
I'm having an issue with a c++ dll that I created to connect to a server, send commands and close. I am using the boost asio C++ libraries and took an example from their website. I tested the code as a stand alone executable in the console and it works swimmingly, but when I converted it to a dll, that's where I am seeing a weird string truncation issue.
Only the first character in the string seems to get passed to the server. Currently I am sending a test string "get time\n" but only "g" is seen when the message is received.
The API looks like this (the full function is below):
MT4_EXPFUNC int __stdcall messageOrder(char* message, int length)
I've read that the string in MQL is actually a structure and I've tried the MqlStr structure that was suggested,.......
struct MqlStr
{
int len;
char *string;
};
...... but that doesn't seem to work, either. It hangs the server with an invalid string.
What has worked the "best" so far is what I have listed below.
Below is my test ea that does nothing but send the same string to the server every tick.
---------------
#property version "1.00"
#property strict
#import "Boost.dll";
int messageOrder(string message, int length);
#import
//+------------------------------------------------------------------+
//| Expert initialization function |
//+------------------------------------------------------------------+
int OnInit()
{
//---
//---
return(INIT_SUCCEEDED);
}
//+------------------------------------------------------------------+
//| Expert deinitialization function |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
{
//---
}
//+------------------------------------------------------------------+
//| Expert tick function |
//+------------------------------------------------------------------+
void OnTick()
{
//---
string message = "get time\n";
//Print("message: ", message, " length = ", StringLen(message));
messageOrder(message, StringLen(message));
}
//+------------------------------------------------------------------+
The dll export is below. I am creating a std::string after the message is received and then sending that string to the server. The issue at hand is the MQL string to C++ char * conversion.
I'm obviously doing something wrong. Can anyone help with this?
extern "C"
{
#define MT4_EXPFUNC __declspec(dllexport)
MT4_EXPFUNC int __stdcall messageOrder(char* message, int length)
{
try
{
boost::asio::io_service io_service;
tcp::resolver r(io_service);
client c(io_service);
//char * p;
//char msg[1024];
//int i;
//for(i = 0, p= message; i < length; i++, p++)
//{
// msg = *p;
//}
//std::string line = std::string(msg);
std::string line = message;
c.assignMessage(line);
c.start(r.resolve(tcp::resolver::query("127.0.0.1", "100")));
io_service.run();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}
}
I'm having an issue with a c++ dll that I created to connect to a server, send commands and close. I am using the boost asio C++ libraries and took an example from their website. I tested the code as a stand alone executable in the console and it works swimmingly, but when I converted it to a dll, that's where I am seeing a weird string truncation issue.
Only the first character in the string seems to get passed to the server. Currently I am sending a test string "get time\n" but only "g" is seen when the message is received.
The API looks like this (the full function is below):
MT4_EXPFUNC int __stdcall messageOrder(char* message, int length)
I've read that the string in MQL is actually a structure and I've tried the MqlStr structure that was suggested,.......
struct MqlStr
{
int len;
char *string;
};
...... but that doesn't seem to work, either. It hangs the server with an invalid string.
What has worked the "best" so far is what I have listed below.
Below is my test ea that does nothing but send the same string to the server every tick.
---------------
#property version "1.00"
#property strict
#import "Boost.dll";
int messageOrder(string message, int length);
#import
//+------------------------------------------------------------------+
//| Expert initialization function |
//+------------------------------------------------------------------+
int OnInit()
{
//---
//---
return(INIT_SUCCEEDED);
}
//+------------------------------------------------------------------+
//| Expert deinitialization function |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
{
//---
}
//+------------------------------------------------------------------+
//| Expert tick function |
//+------------------------------------------------------------------+
void OnTick()
{
//---
string message = "get time\n";
//Print("message: ", message, " length = ", StringLen(message));
messageOrder(message, StringLen(message));
}
//+------------------------------------------------------------------+
The dll export is below. I am creating a std::string after the message is received and then sending that string to the server. The issue at hand is the MQL string to C++ char * conversion.
I'm obviously doing something wrong. Can anyone help with this?
extern "C"
{
#define MT4_EXPFUNC __declspec(dllexport)
MT4_EXPFUNC int __stdcall messageOrder(char* message, int length)
{
try
{
boost::asio::io_service io_service;
tcp::resolver r(io_service);
client c(io_service);
//char * p;
//char msg[1024];
//int i;
//for(i = 0, p= message; i < length; i++, p++)
//{
// msg = *p;
//}
//std::string line = std::string(msg);
std::string line = message;
c.assignMessage(line);
c.start(r.resolve(tcp::resolver::query("127.0.0.1", "100")));
io_service.run();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}
}As it turns out when I was using the MqlStr struct I was unpacking it improperly.
Now I am doing:
struct MqlStr
{
int len;
char *string;
};
extern "C"
{
#define MT4_EXPFUNC __declspec(dllexport)
MT4_EXPFUNC int __stdcall messageOrder(MqlStr * message, int length)
/// MT4_EXPFUNC int __stdcall messageOrder(char* message, int length)
{
std::string line;
try
{
boost::asio::io_service io_service;
tcp::resolver r(io_service);
client c(io_service);
//char * p;
//char msg[1024];
//int i;
//for(i = 0, p= message; i < length; i++, p++)
//{
// msg = *p;
//}
//std::string line = std::string(msg);
line = message[0].string;
c.assignMessage(line);
c.start(r.resolve(tcp::resolver::query("127.0.0.1", "100")));
io_service.run();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
//return line.length();
return strlen(message[0].string);
//return message[0].len;
}
}
[/CODE]
I return the length of the MqlStr string and it is always 1. So it is doing exactly the same as the implementation above.
Here's the MQL code.
[CODE]
#property version "1.00"
#property strict
#import "Boost.dll";
int messageOrder(string message, int length);
#import
//+------------------------------------------------------------------+
//| Expert initialization function |
//+------------------------------------------------------------------+
int OnInit()
{
//---
//---
return(INIT_SUCCEEDED);
}
//+------------------------------------------------------------------+
//| Expert deinitialization function |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
{
//---
}
//+------------------------------------------------------------------+
//| Expert tick function |
//+------------------------------------------------------------------+
void OnTick()
{
//--- int len = 0;
string message = "get time\n";
//Print("message: ", message, " length = ", StringLen(message));
len = messageOrder(message, StringLen(message)); Print("len ", len);
}
//+------------------------------------------------------------------+
I am now exploring a C# DLL instead based on a link in an earlier post.
derp! I guess I coulda looked at the example under scripts. disregard. Thanks...... Ah! Unicode.
derp! I guess I coulda looked at the example under scripts. disregard. Thanks...... Ah! Unicode.
Wasn't that a length of a message?
Hi revalfx,
You want to use wchar_t instad of char! I had the same problem! ;-)
Bye, AT
Compiling DLLSample.cpp generates 27 unresolved external symbols.
Why?
How to fix this?
Where should DLL files be placed for mq4 to find them?