Buffer

[pskyboy]

Hey Guys

Does anyone know how to copy a DWORD into a BYTE Array i guess you would have to split the DWORD into each byte then write them into the BYTE array one at a time but i dont know how to do this any help would be great.


Cheers
Peter Liddle

[Zaei]

DWORD dwrd = 0x11223344;
BYTE* buff;
buff = new BYTE[4];
memcpy(buff, &dwrd, 4);

[/code]

You will be able to get each byte from buff (ie, buff[0] == 0x44). Beware, the bytes are backwards from the way you assigned them. Intel Architecture at work.

Z.

[jim mcnamara]

Zaei's code is straightforward, but it'd be simpler if you created a union. This is why they were invented.

union MyType        // Declare a union that can hold the following:
{
    
    DWORD        lValue;  // long value
    BYTE       cValue[4];  // char array
}; 

[Zaei]

That was actually my first thought, but i've never actually used a union, so i decided to go with what I know =).

Z.

[pskyboy]

cheers guys

is there anyway of doing it without using existing functions ie. not using mscpy() i mean how would it actually work copying the DWORD to a buffer. The problem is the mscpy command doesn't work properly for what i need because as soon as i add characters to the buffer it over writes the data from the dwords.

cheers

[Zaei]

b[0] = HIBYTE(HIWORD(dwrd));
b[1] = LOBYTE(HIWORD(dwrd));
b[2] = HIBYTE(LOWORD(dwrd));
b[3] = LOBYTE(LOWORD(dwrd));

Z.

[pskyboy]

Cheers Z

Thats what i needed to know and amazingly the basic c is what i prefer programming with rather then all these pre written functions. I guess i liked to know whats going on.


Pete

[kedaman]

say you want to have a int 12345678 into a[5] in a char[20]
just cast the address to *int

char a[20];
*(int*)(a+5)=12345678; 

this will ofcourse fit into a single mov instruction as it is assignment of a constant