汇编-memcpy的实现

memcpystack proc dest,src,cnt
    
    ;cnt is a count of dwords
    ;this function has a granularity of dwords
    mov edx,src
    mov eax,dest
    sub eax,edx
    sub eax,4
    mov ecx,cnt
    xchg esp,edx
    .repeat
        pop dword ptr[esp+eax]
        dec ecx
    .until zero?
    xchg esp,edx
    ret

memcpystack endp

memcpy1 proc dest,src,cnt
    
    mov edx,src
    mov ebx,dest
    mov ecx,cnt
    .repeat
        mov eax,dword ptr[edx]
        mov dword ptr[ebx],eax
        add edx,4
        add eax,4
        dec ecx
    .until zero?
    ret

memcpy1 endp

memcpy2 proc dest,src,cnt
    
    mov edx,src
    mov ebx,dest
    mov ecx,cnt
    .repeat
        push dword ptr[edx]
        pop dword ptr[ebx]
        add edx,4
        add ebx,4
        dec ecx
    .until zero?
    ret

memcpy2 endp

memcpy3 proc dest,src,cnt
    
    mov esi,src
    mov edi,dest
    mov ecx,cnt
    rep movsd
    ret

memcpy3 endp