kvisc/ka/crt/str/strcmp.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.

;
; int strcmp(const char *str1, const char *str2)
;
; Returns:
;    0 if the contents of both strings are equal
;   >0 if the first character that does not match has a greater value in str1 than in str2
;   <0 if the first character that does not match has a lower value in str1 than in str2
;
strcmp:
    mov rcx, zero
.l:
    movzx rax, b[ax0+rcx]
    movzx rdx, b[ax1+rcx]

    cmp rax, rdx
    jmp.nz .r

    ; both zero?
    add rbx, rax, rdx
    jmp.bxz .r

    add rcx, rcx, 1
    jmp .l

.r:
    sub rax, rax, rdx
    ret

;
; int strncmp(const char *str1, const char *str2, int maxn)
;
strncmp:
    mov rcx, ax2
    jmp.cxz .r

.l:
    movzx rax, b[ax0]
    movzx rdx, b[ax1]

    cmp rax, rdx
    jmp.nz .r

    add ax0, ax0, 1
    add ax1, ax1, 1
    loop .l

.r:
    sub rax, rax, rdx
    ret