Re: [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]

[e-mail] 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