ccutil/hashfn.h File Reference

#include "host.h"

Go to the source code of this file.

Functions

• INT32 hash (INT32 bits, void *key, INT32 keysize)

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Function Documentation

INT32 hash	(	INT32	bits,
		void *	key,
		INT32	keysize
	)

Simple hash function working on power of 2 table sizes.

Uses xor function. Needs linear rehash.

See http://en.wikipedia.org/wiki/Hash_table

Definition at line 30 of file hashfn.cpp.

Referenced by MALLOC_CALL::count_freeer(), and MEM_ALLOCATOR::hash_caller().

            {
  INT32 bitindex;                //current bit count
  UINT32 keybits;                //bit buffer
  UINT32 hcode;                  //current hash code
  UINT32 mask;                   //bit mask

  mask = (1 << bits) - 1;
  keysize *= 8;                  //in bits
  bitindex = 0;
  keybits = 0;
  hcode = 0;
  do {
    while (keysize > 0 && bitindex <= 24) {
      keybits |= *((UINT8 *) key) << bitindex;
      key = (UINT8 *) key + 1;
      bitindex += 8;
      keysize -= 8;
    }
    hcode ^= keybits & mask;     //key new key
    keybits >>= bits;
  }
  while (keysize > 0);
  return hcode;                  //initial hash
}

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