Working With Variable-Length Pointers in UPS Patches

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Working With Variable-Length Pointers in UPS Patches

Postby Simion32 » February 26th, 2013, 3:53 pm

You aren't expected to know how to use this. It's for curious programmers that happen to notice this topic and want to know how to decode one of these pesky UPS pointers.

I had a very difficult time figuring this thing out, due to the documentation on the UPS format being overly general.

So, here's the code, in all its glory (use as you wish, no credit required):

#include <cstddef>
#include <vector>
#define vector std::vector

typedef unsigned long long Hex64;
typedef unsigned char Hex08;

Hex64 decodeUPS(vector<Hex08>& data, size_t& current_address)
{
Hex64 ups = 0x0000000000000000LL;
Hex64 shift = 1;
while(true)
{
Hex08 x = (data[current_address++] & 0xFF);
ups += ((x & 0x7F) * shift);
if(x & 0x80) break;
shift <<= 7;
ups += shift;
}
return ups;
}

void encodeUPS(vector<Hex08>& data, Hex64 ups)
{
while(true)
{
Hex64 x = (ups & 0x000000000000007FLL);
ups >>= 7;
if(ups == 0)
{
data.push_back( (0x80 | x) & 0xFF );
break;
}
data.push_back( x & 0xFF );
ups--;
}
}

If you have any questions about the code, feel free to ask.
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