kvisc/dos/str/strrev.k

; 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)
;
strrev:
    test b[ax1], b[ax1]
    cmovz b[ax0], 0
    cretz

    ; save str's location
    mov rdx, ax1

    ; go to str's end, just before
    ; the null terminator
.1:
    test b[ax1+1], b[ax1+1]
    cincnz ax1
    cjmpnz .1

.2:
    ; copy, going backward though str
    ; and forward through buf
    mov b[ax0], b[ax1]

    cmp ax1, rdx
    cmovz b[ax0+1], 0
    cretz

    inc ax0
    dec ax1
    jmp .2