home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Tech Arsenal 1
/
Tech Arsenal (Arsenal Computer).ISO
/
tek-01
/
strlibs.zip
/
MEMREV.ASM
< prev
next >
Wrap
Assembly Source File
|
1993-01-04
|
2KB
|
97 lines
; Static Name Aliases
;
TITLE memrev
; NAME memrev.C
; memrev(dst, src, len)
; moves len bytes from src to dst, in REVERSE order. NUL characters
; receive no special treatment, they are moved like the rest. It is
; to strrev as memcpy is to strcpy.
;
; Note: this function is perfectly happy to reverse a block into the
; same place, memrev(x, x, L) will work.
;
; It will not work for partially overlapping source and destination.
;
; Returns a pointer to the beginning of the dst.
.287
_TEXT SEGMENT BYTE PUBLIC 'CODE'
_TEXT ENDS
_DATA SEGMENT WORD PUBLIC 'DATA'
_DATA ENDS
CONST SEGMENT WORD PUBLIC 'CONST'
CONST ENDS
_BSS SEGMENT WORD PUBLIC 'BSS'
_BSS ENDS
DGROUP GROUP CONST, _BSS, _DATA
ASSUME CS: _TEXT, DS: DGROUP, SS: DGROUP, ES: DGROUP
EXTRN __chkstk:NEAR
_TEXT SEGMENT
PUBLIC _memrev
_memrev PROC NEAR
push bp
mov bp,sp
mov ax,8
call __chkstk
push di
push si
; dsta = 4
; register si = dsta
; srca = 6
; register di = srca
; len = 8
; dstz = -4
; srcz = -6
; result = -2
mov si,[bp+4] ;dsta
mov di,[bp+6] ;srca
mov [bp-2],si ;result
cmp WORD PTR [bp+8],0 ;len
jle $I16
mov ax,[bp+8] ;len
add ax,di
mov [bp-6],ax ;srcz
mov ax,[bp+8] ;len
add ax,si
mov [bp-4],ax ;dstz
jmp SHORT $L20001
$WC17:
dec WORD PTR [bp-6] ;srcz
mov bx,[bp-6] ;srcz
mov cl,[bx]
dec WORD PTR [bp-4] ;dstz
mov bx,[bp-4] ;dstz
mov al,[di]
inc di
mov [bx],al
mov [si],cl
inc si
$L20001:
cmp [bp-6],di ;srcz
ja $WC17
$I16:
mov ax,[bp-2] ;result
pop si
pop di
mov sp,bp
pop bp
ret
_memrev ENDP
_TEXT ENDS
END