[ros-dev] [ros-diffs] [greatlrd] 23826: Wrote RtlUshotByteSwap RtlUlongByteSwap and RtlUlonglongByteSwap to asm code. but we need a C api for header to linking it right. Put the asm version to i386

[Reuel ben Yisrael]

greatlrd at svn.reactos.org wrote:

>Author: greatlrd
>Date: Thu Aug 31 01:17:53 2006
>New Revision: 23826
>
>URL: http://svn.reactos.org/svn/reactos?rev=23826&view=rev
>Log:
>Wrote  RtlUshotByteSwap RtlUlongByteSwap and  RtlUlonglongByteSwap to asm code. 
>   but we need a C api for header to linking it right. Put the asm version to i386 
>  
>
sure there must be away to avoid this double-function-call overhead?

>+.globl _UlongByteSwap
>+ 
>+.intel_syntax noprefix
>+
>+/* FUNCTIONS ***************************************************************/
>+
>+_UlongByteSwap:
>+                       push  ebp          // save base 
>+                       mov   ebp,esp      // move stack to base
>+                       mov   eax,[ebp+8]  // load the ULONG                       
>+                       bswap eax          // swap the ULONG
>+                       pop   ebp          // restore the base   
>+                       ret
>  
>
this should work:

_UlongByteSwap:
                       mov   eax,[esp+8]  // load the ULONG                       
                       bswap eax          // swap the ULONG
                       ret


>+.globl _UlonglongByteSwap
>+ 
>+.intel_syntax noprefix
>+
>+/* FUNCTIONS ***************************************************************/
>+
>+_UlonglongByteSwap:
>+                       push  ebp          // save base 
>+                       mov   ebp,esp      // move stack to base
>+                       mov   edx,[ebp+8]  // load the higher part of ULONGLONG
>+                       mov   eax,[ebp+12] // load the lower part of ULONGLONG    
>+                       bswap edx          // swap the higher part
>+                       bswap eax          // swap the lower part 
>+                       pop   ebp          // restore the base   
>+                       ret
>  
>
_UlonglongByteSwap:
                       mov   edx,[esp+8]  // load the higher part of ULONGLONG
                       mov   eax,[esp+12] // load the lower part of ULONGLONG    
                       bswap edx          // swap the higher part
                       bswap eax          // swap the lower part 
                       ret

>+_UshortByteSwap:
>+                       push  ebp          // save base 
>+                       mov   ebp,esp      // move stack to base
>+                       mov   eax,[ebp+8]  // load the USHORT                       
>+                       bswap eax          // swap the USHORT, xchg is slow so we use bswap with rol 
>+                       rol   eax,16       // make it USHORT
>+                       pop   ebp          // restore the base   
>+                       ret
>  
>

_UshortByteSwap:
                       mov   eax,[esp+8]  // load the USHORT                       
                       bswap eax          // swap the USHORT, xchg is slow so we use bswap with rol 
                       rol   eax,16       // make it USHORT
                       ret


or to save a byte...

_UshortByteSwap:
                       mov   ebx,[esp+8]  // load the USHORT                       
                       mov   al, bh
                       mov   ah, bl
                       ret