problem while using ReadFile WinAPI function...

[cyberglassed]

Hello folks, I have spent all the afternoon trying to get the following code works.

After tried it with no success, I built a completely different code with Windows APIs to use the correct names from Kernel32 library but also didn't work.

https://msdn.microsoft.com/en-us/library/windows/desktop/aa365467%28v=vs.85%29.aspx

Then, I write this post with the initial code I got from:

https://www.mql5.com/en/articles/1540

I need this custom function to read the entire content of a TXT file on whatever location on the file system.

With the following erroneous script I get:

content: []
Error opening file D:\file.txt

when I should get:

content: [Hello world!]

The script code is ready to copy/paste/run:

#define OF_READ               0
#define OF_WRITE              1
#define OF_READWRITE          2
#define OF_SHARE_COMPAT       3
#define OF_SHARE_DENY_NONE    4
#define OF_SHARE_DENY_READ    5
#define OF_SHARE_DENY_WRITE   6
#define OF_SHARE_EXCLUSIVE    7

#import "kernel32.dll"
        int _lopen(string path, int of);
        int _lcreat(string path, int attrib);
        int _llseek(int handle, int offset, int origin);
        int _lread(int handle, string buffer, int bytes);
        int _lwrite(int handle, string buffer, int bytes);
        int _lclose(int handle);
#import

string ReadFile(string path) {

        int handle = _lopen(path, OF_READ);
        int read_size = 50;
        string char50 = "x                                                 ";

        if (handle < 0) {
                Print("Error opening file ", path);
                return ("");
        }
        int result = _llseek(handle, 0, 0);
        if (result < 0) {
                Print("Error placing the pointer");
                return ("");
        }

        string buffer = "";
        int count = 0;
        int last = 0;

        result = _lread(handle, char50, read_size);
        while (result > 0 && result == read_size) {
                buffer = buffer + char50;
                count++;
                result = _lread(handle, char50, read_size);
                last = result;
        }
        printf("The last read block has the size of %d bytes:", last);
        char50 = StringSubstr(char50, 0, last);
        buffer = buffer + char50;
        result = _lclose(handle);
        if (result < 0)
                Print("Error closing file ", path);
        return (buffer);
}

void OnStart() {
        // the following is a TXT file with the content: "Hello world!"
        string content = ReadFile("D:\\file.txt");
        printf("content: [%s]", content);
}

Thank you!

[Marco vd Heijden]

i can only think of two things

one is that import dll is disabled and 2 the file path is incorrect/does not exist at the specified location.

i would first try to reach a file in the local directory then crawl my way out to where i need to be sometimes specifying the correct paths can be advantageous.

[cyberglassed]

Marco vd Heijden:

i can only think of two things

one is that import dll is disabled and 2 the file path is incorrect/does not exist at the specified location.

i would first try to reach a file in the local directory then crawl my way out to where i need to be sometimes specifying the correct paths can be advantageous.

- the option: "Options / Expert Advisors / Allow DLL imports" is checked

- the path is correct

¿could you check by your self that script with DLL allowed and a valid TXT file with content: "Hello world!"?

Thank you Marco!

[Marco vd Heijden]

so i get the same outcome but i did notice there were issues with access rights to the file so make sure u run as administrator.

[cyberglassed]

Marco vd Heijden:
so i get the same outcome but i did notice there were issues with access rights to the file so make sure u run as administrator.

I accessed as administrator (runned MT5 as admin) :(

but if you get the same output as administrator then that's not te problem.

The "_lopen" function works correctly because I get a handle. Also "_llseek" rise no error,

but the problem is the function: "_lread".

[Marco vd Heijden]

http://winapi.freetechsecrets.com/win32/WIN32lread.htm

The _lread function reads data from the specified file. This function is provided for compatibility with 16-bit versions of Windows.

Win32-based applications should use the ReadFile function.

http://winapi.freetechsecrets.com/win32/WIN32ReadFile.htm

BOOL ReadFile( HANDLE hFile, // handle of file to read LPVOID lpBuffer, // address of buffer that receives data DWORD nNumberOfBytesToRead, // number of bytes to read LPDWORD lpNumberOfBytesRead, // address of number of bytes read LPOVERLAPPED lpOverlapped // address of structure for data );

[cyberglassed]

Marco vd Heijden:

http://winapi.freetechsecrets.com/win32/WIN32lread.htm

The _lread function reads data from the specified file. This function is provided for compatibility with 16-bit versions of Windows.

Win32-based applications should use the ReadFile function.

http://winapi.freetechsecrets.com/win32/WIN32ReadFile.htm

BOOL ReadFile( HANDLE hFile, // handle of file to read LPVOID lpBuffer, // address of buffer that receives data DWORD nNumberOfBytesToRead, // number of bytes to read LPDWORD lpNumberOfBytesRead, // address of number of bytes read LPOVERLAPPED lpOverlapped // address of structure for data );

Thank you Marco!