casting &Byte[] to long value

  • Thread starter Thread starter Guest
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G

Guest

Hi,

I have an array of bytes like

Byte m_Data[] = new Byte[2000] ;

Byte sequences starting at a random index (4 byte aligned) should be
interpreted as unsigned long values and compared with each other.


My first try was

if ( reinterpret_cast<UInt32*>(&m_Data[20]) ==
reinterpret_cast<UInt32*>(&m_Data[104]) )
{ ... }

but the results were not always as expected (guess due to the == operator
handling the pointers).


The second try was

__value UInt32* a = reinterpret_cast<__value UInt32*>(&m_Data[20] ) ;
__value UInt32* b = reinterpret_cast<__value UInt32*>(&m_Data[104]) ;

if ( *a == *b )
{ ... }

That seems to work, but I dislike the need of extra variables (due to
performance reasons).


Has someone a really good idea about that?


Thanks

Carl
 
In your first example, you are comparing two UInt32* pointers which should
never be equal. In the second example, you are getting the pointers and
then comparing what they point at, which seems more useful.
 
__value UInt32* a = reinterpret_cast<__value UInt32*>(&m_Data[20] ) ;
__value UInt32* b = reinterpret_cast<__value UInt32*>(&m_Data[104]) ;
if ( *a == *b )
{ ... }

That seems to work, but I dislike the need of extra variables (due to
performance reasons).
Click to expand...

if (*reinterpret_cast<__value UInt32*>(&m_Data[20]) ==
*reinterpret_cast<__value UInt32*>(&m_Data[104]))
{ ... }
 
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