73 lines
1.0 KiB
Plaintext
73 lines
1.0 KiB
Plaintext
; The OS/K Team licenses this file to you under the MIT license.
|
|
; See the LICENSE file in the project root for more information.
|
|
|
|
;
|
|
; void strrev(char *buf, const char *str)
|
|
;
|
|
; buf and src must NOT overlap
|
|
;
|
|
strrev:
|
|
bzr b[ax1], .z
|
|
|
|
; save str's location
|
|
mov rsi, ax1
|
|
|
|
; go to str's end, just before
|
|
; the null terminator
|
|
mov rcx, STRLEN_MAX
|
|
scasb.rep.nz ax1, zero
|
|
dec ax1, 1
|
|
|
|
.l:
|
|
; copy, going backward though str
|
|
; and forward through buf
|
|
mov b[ax0], b[ax1]
|
|
|
|
beq ax1, rsi, .r
|
|
|
|
inc ax0, 1
|
|
dec ax1, 1
|
|
jmp .l
|
|
|
|
.r:
|
|
mov b[ax0+1], zero
|
|
ret
|
|
|
|
.z:
|
|
mov b[ax0], zero
|
|
ret
|
|
|
|
;
|
|
; void strrev2(char *str)
|
|
;
|
|
; Inverses str
|
|
;
|
|
strrev2:
|
|
bzr b[ax0], .r
|
|
|
|
mov ax1, ax0
|
|
|
|
; go to str's end, just before
|
|
; the null terminator
|
|
mov rcx, STRLEN_MAX
|
|
scasb.rep.nz ax1, zero
|
|
dec ax1, 1
|
|
|
|
; increase ax0 while decreasing ax1, performing exchanges
|
|
.l:
|
|
blteu ax1, ax0, .r
|
|
|
|
xchg b[ax0], b[ax1]
|
|
|
|
inc ax0, 1
|
|
dec ax1, 1
|
|
jmp .l
|
|
|
|
.r:
|
|
ret
|
|
|
|
|
|
|
|
|
|
|