I had been just assigning consecutive integer values to each unique ID.
This worked fine but I ran into some situations (installing/uninstalling
options) where the integer ID changed for a specific unique ID string. This
meant that any integer ID that I had saved in the driver was no longer valid.
I was looking for an algorithm to convert the unique ID strings into unique
ID integers. I don't really need all ID integers to be unique, just all
those in the same list (MediaSizeList, MediaTypeList, etc) need to be
unique. I also need them to be consistent even if new ID's are added or
Norbert suggested the algorithm used to generate the LPTENUM checksum. I
hunted down the algorithm and found that it generates unique ID integers
for all the ID strings in the sample implementation. I would be a little
happier if it generated 32-bit ID integers, but so far it works fine.
Here's the code:
0000000, 0140301, 0140601, 0000500,
0141401, 0001700, 0001200, 0141101,
0143001, 0003300, 0003600, 0143501,
0002400, 0142701, 0142201, 0002100,
0000000, 0146001, 0154001, 0012000,
0170001, 0036000, 0024000, 0162001,
0120001, 0066000, 0074000, 0132001,
0050000, 0116001, 0104001, 0043000,
short Get_CRC_CheckSum(void *pBuffer, ULONG ulSize)
for (pb=(BYTE *)pBuffer; ulSize; ulSize--, pb++)
bTmp=(BYTE)(((WORD)*pb)^((WORD)ulSeed)); // Xor CRC with new char
ulSeed=((ulSeed)>>8) ^ wCRC16a[bTmp&0x0F] ^ wCRC16b[bTmp>>4];
The seed is set to 0 each time so that the ID will always be the same for a
If anyone has any comments or suggestions for a 32-bit CRC, I'd be happy hear.
This archive was generated by hypermail 2b29 : Thu Oct 04 2001 - 11:54:06 EDT