Question

Something::methodname()
{  
    (unsigned char*) ptr = (unsigned char*) m_pptr;

    while ((*ptr || *(ptr+1)) && (((unsigned char*)m_pptr+BUFSIZE)<ptr))
        ptr++;

    if(ptr == m_pptr)
        return ptr; 

    return ptr + 1;
}

m_pptr is a protected member of a class. ptr is local to this function

Could someone help me with the logic of this code? I know it compiles but the answers I’m getting out are not the ones I’m expecting. I am memset-ing a buffer full of A5’s and the while loop fails somehow. It skips right past it. Any help would be great.

This will go through a buffer and if the value of the pointer or the value of (ptr+1) is true it will increment the pointer AND the ptr can’t exceed the size of the buffer(which is found by m_pptr “pointer to the beginning of the buffer” + buffer size) has to be true also. The if statement says if m_pptr(pointer to beginning of the buffer is the same as ptr then return just the pointer.

this function returns a void* and is passed nothing

Answer 1

 (((unsigned char*)m_pptr+BUFSIZE)<ptr))

looks backward:

 (((unsigned char*)m_pptr+BUFSIZE)>ptr))

would be more likely; Even more sane:

while (ptr < ((unsigned char*) m_pptr + BUFSIZE)) // until end of buffer
{
    if (!*ptr)      // null char reached
        break;
    if (!*(ptr+1))  // null char almost reached
        break;

    // do stuff

    ptr++;
}