C code if (get_le_long(buf + 96) & 0x0008) ???

Bluesuperman · 12-11-2005, 10:36 PM

Hello,

I do not understand the following piece of code:

if (get_le_long(buf + 96) & 0x0008)

What does the "&" do ? I believe get_le_long retrieves 96 bytes from buf ? But is the "&" active like a place holder ?

Thanks

Michael

paulsm4 · 12-11-2005, 11:36 PM

"get_le_long()" returns the little-endian 32-bit integer long that it finds at network buffer position "buf+96".

The "&" is the C bitwise "and" operator.

Let's say the value at buf+96 is "6". The value will be:

0x0000 0006
& 0x0000 0008
-----------
0000 0000

Why?
decimal(6) = binary(0110)
decimal(8) = binary(1000)

Left-to-right:
0 AND 1 = 0
1 AND 0 = 0
1 AND 0 = 0
0 AND 0 = 0