Question

void PrintMACaddress(unsigned char MACData[]){
    php_sprintf("MAC Address: %02X-%02X-%02X-%02X-%02X-%02X\n", 
        MACData[0], MACData[1], MACData[2], MACData[3], MACData[4], MACData[5]);
}

Output code is:

return PrintMACaddress(MACData);

When i click ‘build’, it show this error:

error C2664: ‘php_sprintf’ : cannot convert parameter 2 from ‘unsigned char’ to ‘const char *‘

Please help, I’m newbie in c++ and I already search around many days for this error.

Answer 1

I assume that php_sprintf refers to the internal PHP function used when you write extensions for PHP. Then it has the same parameters as the C function sprintf.

Are you trying to print the MAC address to the standard output or to a string?

If you want to print to the standard output (and subsequently to a console), then use php_printf.
So you code can look like:

void PrintMACaddress(unsigned char MACData[]){
    php_printf("MAC Address: %02X-%02X-%02X-%02X-%02X-%02X\n", 
        MACData[0], MACData[1], MACData[2], MACData[3], MACData[4], MACData[5]);
}

If you want to return the value instead of printing it to the output, the there are few points to note:

• When you work with strings in C++, you can represent it as either char * or std::string
• Using std::string is the C++ way to go.
• Using char * is more C-ish style. You have to manage the memory array by yourself (allocate on the stack or by using new [] and delete [])

If I rewrite the method using std::string:

std::string PrintMACaddress(unsigned char MACData[]){
    char tmp_[32]; // The output string should be always 32 bytes long
    php_sprintf(tmp_,"MAC Address: %02X-%02X-%02X-%02X-%02X-%02X\n", 
        MACData[0], MACData[1], MACData[2], MACData[3], MACData[4], MACData[5]);
    return std::string(tmp_);
}

If you want to (or have to) use char *:

char *PrintMACaddress(char *MACString, unsigned char MACData[]){
    php_sprintf(MACString,"MAC Address: %02X-%02X-%02X-%02X-%02X-%02X\n", 
        MACData[0], MACData[1], MACData[2], MACData[3], MACData[4], MACData[5]);
    return MACString;
}

Here, the method gets one new parameter – pointer to allocated array of at least 32 bytes. It then returns the pointer to this array. You would use it like:

char macString[44];
PrintMACaddress(macString, MACData);
/* Use the string stored in macString */   

or

char* macString = new char[44];
PrintMACaddress(macString, MACData);
/* Use the string stored in macString */   
delete [] macString;

EDIT: Updated second part of the answer with php_sprintf