;*****************************************************************************
;*
;* Open Watcom Project
;*
;* Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
;*
;* ========================================================================
;*
;* This file contains Original Code and/or Modifications of Original
;* Code as defined in and that are subject to the Sybase Open Watcom
;* Public License version 1.0 (the 'License'). You may not use this file
;* except in compliance with the License. BY USING THIS FILE YOU AGREE TO
;* ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
;* provided with the Original Code and Modifications, and is also
;* available at www.sybase.com/developer/opensource.
;*
;* The Original Code and all software distributed under the License are
;* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
;* EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
;* ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
;* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
;* NON-INFRINGEMENT. Please see the License for the specific language
;* governing rights and limitations under the License.
;*
;* ========================================================================
;*
;* Description: Intel 386 implementation strcmp().
;*
;*****************************************************************************
include mdef.inc
include struct.inc
ifdef _PROFILE
include p5prof.inc
endif
modstart _strcmp,para
cmp4 macro off
mov ebx,off[eax] ; get dword from op1
mov ecx,off[edx] ; get dword from op2
cmp ecx,ebx ; compare them
jne unequal ; quit if not equal
ife off-12
add eax,off+4 ; point to next group of dwords
add edx,off+4 ; ...
endif
not ecx ; ...
add ebx,0FEFEFEFFh ; determine if '\0' is one of bytes
and ebx,ecx ; ...
and ebx,80808080h ; ebx will be non-zero if '\0' found
endm
defpe strcmp
xdefp "C",strcmp
ifdef _PROFILE
P5Prolog
endif
ifdef __STACK__
mov eax,4[esp] ; get p1
mov edx,8[esp] ; get p2
endif
cmp eax,edx ; pointers equal ?
je equalnorst ; yes, return 0
ifndef __STACK__
push ecx ; save register
endif
test al,3 ; p1 aligned ?
jne realign ; no, go and realign
test dl,3 ; p2 aligned ?
jne slowcpy ; no, do the slow copy (impossible to align both)
fastcpy:
push ebx ; save register
align 4
_loop ; - loop
cmp4 0 ; - - compare first dword
_quif ne ; - - quit if end of string
cmp4 4 ; - - compare second dword
_quif ne ; - - quit if end of string
cmp4 8 ; - - compare third dword
_quif ne ; - - quit if end of string
cmp4 12 ; - - compare fourth dword
_until ne ; - until end of string
equalrst: ; strings equal, restore registers
pop ebx ; restore register
ifndef __STACK__
pop ecx ; ...
endif
equalnorst: ; strings equal, skip register restore
sub eax,eax ; indicate strings equal
ifdef _PROFILE
P5Epilog
endif
ret ; return
unequal: ; dword was not equal
_guess ; guess strings are equal
cmp bl,cl ; - check low bytes
_quif ne ; - quit if not equal
cmp bl,0 ; - stop if end of string
je equalrst ; - ...
cmp bh,ch ; - check next bytes
_quif ne ; - quit if not equal
cmp bh,0 ; - stop if end of string
je equalrst ; - ...
shr ebx,16 ; - shift top 2 bytes to bottom
shr ecx,16 ; - ...
cmp bl,cl ; - check third byte
_quif ne ; - quit if not equal
cmp bl,0 ; - stop if end of string
je equalrst ; - ...
cmp bh,ch ; - check high order byte
;; we know at this point that bh != ch, just have to do the compare
;; _quif ne ; - quit if not equal
;; cmp bh,0 ; - stop if end of string
;; je equalrst ; - ...
_endguess ; endguess
sbb eax,eax ; eax = 0 if op1>op2, -1 if op1<op2
or al,1 ; eax = 1 if op1>op2, -1 if op1<op2
pop ebx ; restore registers
ifndef __STACK__
pop ecx ; ...
endif
ifdef _PROFILE
P5Epilog
endif
ret ; return
align 4
realign:
_loop ; - loop
mov cl,[eax] ; get byte from p1
inc eax ; point to next byte
mov ch,[edx] ; get byte from p2
inc edx ; point to next byte
cmp cl,ch ; bytes equal?
jne unequal2 ; unequal, quit
or cl,cl ; end of string ?
je equal2 ; yes, quit
test al,3 ; check alignment
_until e ; until aligned
test dl,3 ; p2 aligned ?
je fastcpy ; yes
align 4
slowcpy:
_loop
mov ecx,[eax] ; get aligned 4 bytes
cmp cl,[edx] ; check 1st byte
jne unequal2 ; bytes not equal
or cl,cl ; end of string?
je equal2 ; yes, quit
cmp ch,[edx+1] ; check 2nd byte
jne unequal2 ; bytes not equal
or ch,ch ; end of string?
je equal2 ; yes, quit
shr ecx,16 ; move next pair of bytes to be tested
cmp cl,[edx+2] ; check 3rd byte
jne unequal2 ; bytes not equal
or cl,cl ; end of string?
je equal2 ; yes, quit
cmp ch,[edx+3] ; check 4th byte
jne unequal2 ; bytes not equal
or ch,ch ; end of string?
je equal2 ; yes, quit
mov ecx,[eax+4] ; get next aligned 4 bytes
cmp cl,[edx+4] ; check 5th byte
jne unequal2 ; bytes not equal
or cl,cl ; end of string?
je equal2 ; yes, quit
cmp ch,[edx+5] ; check 6th byte
jne unequal2 ; bytes not equal
or ch,ch ; end of string?
je equal2 ; yes, quit
shr ecx,16 ; move next pair of bytes to be tested
cmp cl,[edx+6] ; check 7th byte
jne unequal2 ; bytes not equal
or cl,cl ; end of string?
je equal2 ; yes, quit
cmp ch,[edx+7] ; check 8th byte
jne unequal2 ; bytes not equal
add eax,8 ; next 8 bytes
add edx,8 ; next 8 bytes
or ch,ch ; end of string?
_until e ; until equal
equal2:
xor eax,eax ; return 0
ifndef __STACK__
pop ecx ; restore registers
endif
ifdef _PROFILE
P5Epilog
endif
ret ; return
unequal2:
sbb eax,eax ; eax = 0 if op1>op2, -1 if op1<op2
or al,1 ; eax = 1 if op1>op2, -1 if op1<op2
ifndef __STACK__
pop ecx ; restore registers
endif
ifdef _PROFILE
P5Epilog
endif
ret ; return
endproc strcmp
endmod
end