Re: Good hash for pointers

On 5/24/2024 10:49 AM, Chris M. Thomasson wrote:

On 5/24/2024 4:05 AM, Malcolm McLean wrote:
[...]

Then I can't be the first person to want to use a pointer as a key for hash table.
>
And I don't want things to break if pointer representation changes.

 Check this out, it relies on hashing pointers, the multex... ;^)
 https://groups.google.com/g/comp.lang.c++/c/sV4WC_cBb9Q/m/SkSqpSxGCAAJ
 It can be used for many different things...
 

The naive hash is:
______________________
// A table of locks
struct mutex_table
{
   std::vector<std::mutex> m_locks;
   mutex_table(std::size_t size) : m_locks(size) { assert(size > 0); }
   // totally contrived simple hash...
   std::size_t hash(void const* ptr)
   {
     std::uintptr_t ptr_uint = (std::uintptr_t)ptr;
     return (std::size_t)(((ptr_uint << 9) * 103) % m_locks.size());
   }
};
______________________
;^)