ntdll!strlen

7c902645 8b4c2404        mov     ecx,dword ptr [esp+4]
7c902649 f7c103000000    test    ecx,3 ;check if the address is 4 bytes aligned
7c90264f 7412            je      ntdll!strlen+0x20 (7c902663)
7c902651 8a01            mov     al,byte ptr [ecx] ; calculate length byte by byte
7c902653 41              inc     ecx
7c902654 84c0            test    al,al
7c902656 7440            je      ntdll!strlen+0x53 (7c902698)
7c902658 f7c103000000    test    ecx,3
7c90265e 75f1            jne     ntdll!strlen+0xc (7c902651)
7c902660 83c000          add     eax,0
7c902663 8b01            mov     eax,dword ptr [ecx]
7c902665 bafffefe7e      mov     edx,7EFEFEFFh   ; the algorithm is little bit confusing..
7c90266a 03d0            add     edx,eax
7c90266c 83f0ff          xor     eax,0FFFFFFFFh
7c90266f 33c2            xor     eax,edx
7c902671 83c104          add     ecx,4
7c902674 a900010181      test    eax,81010100h   ; If the content of [ecx] is 0 the next jump is not taken.
7c902679 74e8            je      ntdll!strlen+0x20 (7c902663) ; calculate length by dword.
7c90267b 8b41fc          mov     eax,dword ptr [ecx-4]
7c90267e 84c0            test    al,al    ; add the lowest byte
7c902680 7434            je      ntdll!strlen+0x71 (7c9026b6)
7c902682 84e4            test    ah,ah    ; add the second lowest byte
7c902684 7426            je      ntdll!strlen+0x67 (7c9026ac)
7c902686 a90000ff00      test    eax,0FF0000h   ; add the third one
7c90268b 7415            je      ntdll!strlen+0x5d (7c9026a2)
7c90268d a9000000ff      test    eax,0FF000000h   ; add the last one
7c902692 75cf            jne     ntdll!strlen+0x20 (7c902663)
7c902694 eb02            jmp     ntdll!strlen+0x53 (7c902698)
7c902696 ebcb            jmp     ntdll!strlen+0x20 (7c902663)
7c902698 8d41ff          lea     eax,[ecx-1]
7c90269b 8b4c2404        mov     ecx,dword ptr [esp+4]
7c90269f 2bc1            sub     eax,ecx
7c9026a1 c3              ret
7c9026a2 8d41fe          lea     eax,[ecx-2]
7c9026a5 8b4c2404        mov     ecx,dword ptr [esp+4]
7c9026a9 2bc1            sub     eax,ecx
7c9026ab c3              ret
7c9026ac 8d41fd          lea     eax,[ecx-3]
7c9026af 8b4c2404        mov     ecx,dword ptr [esp+4]
7c9026b3 2bc1            sub     eax,ecx
7c9026b5 c3              ret
7c9026b6 8d41fc          lea     eax,[ecx-4]
7c9026b9 8b4c2404        mov     ecx,dword ptr [esp+4]
7c9026bd 2bc1            sub     eax,ecx
7c9026bf c3              ret