crc32 with RtlComputeCrc32 (ntdll.dll)

bingo · Post by **bingo** » Thu Mar 15, 2007 10:59 am

Import "ntdll.lib"
RtlComputeCrc32(dwInitial.l,pData.l,iLen.l)
EndImport

buffer.s = "1234567" + Space(512) + "1234567"
lenbuffer.l = Len(buffer)

counter.l = 999999

For s=1 To 3

timer = GetTickCount_()
For i=1 To counter
CRC32Fingerprint(@buffer,lenbuffer) 
Next
Debug "pb... " + Str(GetTickCount_() - timer)
Debug Hex(CRC32Fingerprint(@buffer,lenbuffer))

timer = GetTickCount_()
For i=1 To counter
RtlComputeCrc32(0,@buffer,lenbuffer)
Next
Debug "api..." + Str(GetTickCount_() - timer)
Debug Hex(RtlComputeCrc32(0,@buffer,lenbuffer))

Next

my xp pc:

pb... 1860
D359D67E
api...1484
D359D67E
pb... 1844
D359D67E
api...1484
D359D67E
pb... 1828
D359D67E
api...1485
D359D67E

my vista pc:

pb... 2247
D359D67E
api...1903
D359D67E
pb... 2199
D359D67E
api...1857
D359D67E
pb... 2215
D359D67E
api...1872
D359D67E

RtlComputeCrc32 15-20% faster as CRC32Fingerprint ?

SFSxOI · Post by **SFSxOI** » Thu Mar 15, 2007 1:20 pm

hmmm...nice idea but doesn't work here on my Vista Pc. Unresolved External Symbol - RtlComputeCrc32.

Rescator · Post by **Rescator** » Thu Mar 15, 2007 1:43 pm

That function is not in the PSDK, also ntdll is not documented "officially".
I would not rely on anything in it as it could change from Windows release/build to the next.

PS! The reason it is faster is that it most likely use file memory mapping,
not to mention being on a kernel level I think?

bingo · Post by **bingo** » Thu Mar 15, 2007 1:47 pm

RtlComputeCrc32 is not in pb-standard ntdll.lib ! create a new or use http://kyf.net/tmp/ntdll.zip and it works ...

okasvi · Post by **okasvi** » Mon Mar 19, 2007 1:56 pm

bingo wrote:RtlComputeCrc32 is not in pb-standard ntdll.lib ! create a new or use http://kyf.net/tmp/ntdll.zip and it works ...

or just use LoadLibrary/GetProcAddress...

Post by **Rings** » Mon Mar 19, 2007 2:33 pm

Did not work with w2k, works with win-xp
here is a more friendly version:

Code: Select all

LibName.s="ntdll.dll"
FuncName.s="RtlComputeCrc32"

Prototype PrototypeRtlComputeCrc32(dwInitial.l,pData.l,iLen.l)

LibNR=LoadLibrary_(Libname)
If LibNR
 FuncPointer=GetProcAddress_(LibNR,FuncName)
 If FuncPointer
  RtlComputeCrc32.PrototypeRtlComputeCrc32=FuncPointer 
  buffer.s = "1234567" + Space(512) + "1234567"
  lenbuffer.l = Len(buffer)
  counter.l = 999999
  For s=1 To 3
   timer = GetTickCount_()
   For i=1 To counter
    CRC32Fingerprint(@buffer,lenbuffer)
   Next
   Debug "pb... " + Str(GetTickCount_() - timer)
   Debug Hex(CRC32Fingerprint(@buffer,lenbuffer))
   timer = GetTickCount_()
   For i=1 To counter
    RtlComputeCrc32(0,@buffer,lenbuffer)
   Next
   Debug "api..." + Str(GetTickCount_() - timer)
   Debug Hex(RtlComputeCrc32(0,@buffer,lenbuffer))
  Next
 Else
  Debug "Cannot find entrypoint for " + Funcname
 EndIf
 FreeLibrary_(LibNR)
Else
  Debug "Cannot open library " + Libname
EndIf

blueznl · Post by **blueznl** » Mon Mar 19, 2007 3:02 pm

Highly distracting signature, Rings...

Seldon · Post by **Seldon** » Fri Mar 23, 2007 9:44 am

Hi ! What are the specs for the Vista PC ? I hope it is slower than the one with XP because of a slower CPU and not for the OS.