Re: Good hash for pointers

On 24/05/2024 19:28, Bonita Montero wrote:

Am 23.05.2024 um 13:11 schrieb Malcolm McLean:

>
What is a good hash function for pointers to use in portable ANSI C?
>
The pointers are nodes of a tree, which are read only, and I want to associate read/write data with them. So potentially a lage number of pointers,and they might be consecutively ordered if they are taken from an array, or they might be returned from repeared calls to malloc() with small allocations. Obviously I have no control over pointer size or internal representation.
>

 Use FNV.
>

Here's an attempt.
/* FNV hash of a pointer */
static unsigned int hash(void *address)
{
     int i;
     unsigned long answer = 2166136261;
     unsigned char *byte = (unsigned char *) &address;
     for (i = 0; i < sizeof(void *); i++)
     {
         answer *= 16777619;
         answer ^= byte[i];
     }
     return (unsigned int) (answer & 0xFFFFFFFF);
}
Now what will compilers make of that?
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