Most efficient replacement for IsBadReadPtr?

Question

I have some Visual C++ code that receives a pointer to a buffer with data that needs to be processed by my code and the length of that buffer. Due to a bug outside my contro

Answer 1

The fastest solution I can think of is to consult the virtual memory manager using VirtualQuery to see if there is a readable page at the given address, and cache the results (however any caching will reduce the accuracy of the check).

Example (without caching):

BOOL CanRead(LPVOID p)
{
  MEMORY_BASIC_INFORMATION mbi;
  mbi.Protect = 0;
  ::VirtualQuery(((LPCSTR)p) + len - 1, &mbi, sizeof(mbi));
  return ((mbi.Protect & 0xE6) != 0 && (mbi.Protect & PAGE_GUARD) == 0);
}