.text
        .global mystrspn
mystrspn:
        push    %ebp
        mov     %esp, %ebp
        push    %esi
        push    %edx
        push    %edi
        mov     8(%ebp), %eax
        mov     12(%ebp), %esi
        movl    $0, %ebx
        movl    $0, %edi
        movzb   (%esi), %edx
        movzb   (%eax), %ecx
continue:
        sub     %edx, %ecx
        jz      equal
        jmp     not_equal
equal:
        incl    %edi
        inc     %esi
        movzb   (%esi), %edx
        test    %edx, %edx
        jz      max_before_end
        inc     %eax
        movzb   (%eax), %ecx
        test    %ecx, %ecx
        jnz     continue
        jmp     max_before_end
not_equal:
        cmp     $0, %edi
        jae     max
not_equal_later:
        inc     %esi
        movzb   (%esi), %edx
        mov     8(%ebp), %eax
        movzb   (%eax), %ecx
        test    %edx, %edx
        jnz     continue
        jmp     end
max:
        cmp     %ebx, %edi
        ja      need_change
        mov     $0, %edi
        jmp     not_equal_later
need_change:
        mov     %edi, %ebx
        mov     $0, %edi
        jmp     not_equal_later
max_before_end:
        cmp     %ebx, %edi
        ja      need_change_before_end
        jmp     end
need_change_before_end:
        mov     %edi, %ebx
        jmp     end
end:
        mov     %ebx, %eax
        pop     %edi
        pop     %edx
        pop     %esi
        movl    %ebp, %esp
        popl    %ebp
        ret