----------
From: Bryon Daly <[EMAIL PROTECTED]>
On 2/9/06, The Fool <[EMAIL PROTECTED]> wrote:
>
> So I needed to create C++ class that would be used to create a static
> copy of some data the program already Uses (but sometimes changes),
for
> which it would need to revert to its original state (it also non
> contiguous). It also needs to be able to 'fiddle' with the data at
the
> byte/bit level.
>
> So I create part of the class, but when I tested it I got these weird
> results. It seemed to be putting say integer (32bit) data bytes
> backwards..
Sounds like an endian issue to me. Are you on a PC? Pentiums are
little
endian, so the LSByte is written first (ie: to the lowest address).
Let's
say you want to write the 32-bit hex integer value 0x76543210 to
address
0.
Most Significant Byte: 0x76
Least Significant Byte: 0x10
Address Byte
-----------------------
000000 0x10
000001 0x32
000002 0x54
000003 0x76
When the CPU reads an integer (or other 4-byte value), it
automatically arranges the bytes around so they are MSB..LSB in the
processor and the endian-ness is transparent to the user. But if you
manipulate the individual bytes of a multi-byte value, you need to be
aware
of the endianness of the machine and deal with it accordingly.
Now imagine the headaches when you have little endian hardware sharing
raw
data buffers with big endian hardware and welcome to my world. :-)
I tried to be concise here - let me know if you want further
elaboration.
------
Ok so this is what I've been doing:
int IMem::PutInt(const long PutAt, const int PutMe)
{
if ((PutAt * __Int_Size__) <= CurrentSize)
{
try //
{
*((int *) &Mem[PutAt * __Int_Size__]) = PutMe;
}
catch (...)
{
Enterprise();
MessageBox(hiwind,"IMem PutInt Threw an Exception","REALLY
bad",MB_OK);
// Call Panic Save HERE
Excelsior();
return No;
}
return Yes;
}
else //
{
return No;
}
}
But you are telling me I need to create a union / structure fill it
with the value, manually flip the bytes around and then store it?
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