ubytes to ulong problem

[Charles Hixson]

I was planning to ask if there were a better way to do this, but instead 
I need to ask what's my mistake?
For some reason, if called with an uninitialized ubyte array, and an 
index of 0, it returns a value of 8, even though all the values in the 
array are 0.
The error has to be somewhere in the "ret = " statement, but I sure 
don't see it.

/**    Convert 8 consecutive bytes sliced from a ubyte[] into a ulong
  * @param    block    The array from which to slice.
  * @param    n    The starting index within the block    */
ulong    ubytesToUlong(ubyte[] block, int n)
{    ulong    ret;
     assert (n >= 0);
     assert (n + 8 <= block.length);
     writefln ("n = %s", n);
     writefln ("block[0] = %s", cast(ulong)block[0]);
     writefln ("block[1] = %s", cast(ulong)block[1]);
     writefln ("block[2] = %s", cast(ulong)block[2]);
     writefln ("block[3] = %s", cast(ulong)block[3]);
     writefln ("block[4] = %s", cast(ulong)block[4]);
     writefln ("block[5] = %s", cast(ulong)block[5]);
     writefln ("block[6] = %s", cast(ulong)block[6]);
     writefln ("block[7] = %s", cast(ulong)block[7]);
     ret    =    cast(ulong)block[n] * 2^21
             +    cast(ulong)block[n+1] * 2^18
             +    cast(ulong)block[n+2] * 2^15
             +    cast(ulong)block[n+3] * 2^12
             +    cast(ulong)block[n+4] * 2^9
             +    cast(ulong)block[n+5] * 2^6
             +    cast(ulong)block[n+6] * 2^3
             +    cast(ulong)block[n+7] * 2^0;
     writefln ("ret = %s", ret);
     return    ret;
}

-- 
Charles Hixson