[jcifs] SmbComWriteAndX writes corrupt offset to wire

[Richard Heap]

yes, certain...
in the writexxx routines the (byte) down-casting will mask correctly
demotion casting is generally ok - it's promotion casting where you have 
to be careful
like in readInt2
    static int readInt2( byte[] src, int srcIndex ) {
        return ( src[srcIndex] & 0xFF ) +
                (( src[srcIndex + 1] & 0xFF ) << 8 );
    }

this *does* need the masks as this boils down to...
int a = [sign extend] src[srcIndex];
int b = [sign extend] src[srcIndex + 1];
a &= 0xff; // trims any sign extension back off to get back to 8 
significant bits in an int
b &= 0xff; // ditto
return (b << 8) + a; // done as integer maths

Michael B Allen wrote:

>eglass1 at comcast.net said:
>  
>
>>>   static void writeInt4( long val, byte[] dst, int dstIndex ) {
>>>       dst[dstIndex++] = (byte)(val);
>>>       dst[dstIndex++] = (byte)(val >> 8);
>>>       dst[dstIndex++] = (byte)(val >> 16);
>>>       dst[dstIndex++] = (byte)(val >> 32);
>>>   }
>>>      
>>>
>>The last shift in writeInt4 should be 24, not 32.  It's also faster
>>(although
>>probably negligibly for our purposes) to do:
>>
>>    static void writeInt4( long val, byte[] dst, int dstIndex ) {
>>        dst[dstIndex] = (byte)(val);
>>        dst[++dstIndex] = (byte)(val >>= 8);
>>        dst[++dstIndex] = (byte)(val >>= 8);
>>        dst[++dstIndex] = (byte)(val >> 8);
>>    }
>>    
>>
>
>Are we certain that the masks are unnecessary? I suppose I was thinking of
>C when I wrote these routines where the highbit is used to indicate the
>sign. For example, if an int or short with the highbit is passed to this
>and the type is promoted to long will the bit pattern still be what we
>expect?
>
>Mike
>
>  
>
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