text: /*
   * contrib/btree_gist/btree_uuid.c
   */
  #include "postgres.h"
  
  #include "btree_gist.h"
  #include "btree_utils_num.h"
  #include "port/pg_bswap.h"
  #include "utils/uuid.h"
  
  typedef struct
  {
  	pg_uuid_t	lower,
  				upper;
  } uuidKEY;
  
  
  /*
   * UUID ops
   */
  PG_FUNCTION_INFO_V1(gbt_uuid_compress);
  PG_FUNCTION_INFO_V1(gbt_uuid_fetch);
  PG_FUNCTION_INFO_V1(gbt_uuid_union);
  PG_FUNCTION_INFO_V1(gbt_uuid_picksplit);
  PG_FUNCTION_INFO_V1(gbt_uuid_consistent);
  PG_FUNCTION_INFO_V1(gbt_uuid_penalty);
  PG_FUNCTION_INFO_V1(gbt_uuid_same);
  
  
  static int
  uuid_internal_cmp(const pg_uuid_t *arg1, const pg_uuid_t *arg2)
  {
  	return memcmp(arg1->data, arg2->data, UUID_LEN);
  }
  
  static bool
  gbt_uuidgt(const void *a, const void *b)
  {
  	return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) > 0;
  }
  
  static bool
  gbt_uuidge(const void *a, const void *b)
  {
  	return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) >= 0;
  }
  
  static bool
  gbt_uuideq(const void *a, const void *b)
  {
  	return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) == 0;
  }
  
  static bool
  gbt_uuidle(const void *a, const void *b)
  {
  	return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) <= 0;
  }
  
  static bool
  gbt_uuidlt(const void *a, const void *b)
  {
  	return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) < 0;
  }
  
  static int
  gbt_uuidkey_cmp(const void *a, const void *b)
  {
  	uuidKEY    *ia = (uuidKEY *) (((const Nsrt *) a)->t);
  	uuidKEY    *ib = (uuidKEY *) (((const Nsrt *) b)->t);
  	int			res;
  
  	res = uuid_internal_cmp(&ia->lower, &ib->lower);
  	if (res == 0)
  		res = uuid_internal_cmp(&ia->upper, &ib->upper);
  	return res;
  }
  
  
  static const gbtree_ninfo tinfo =
  {
  	gbt_t_uuid,
  	UUID_LEN,
  	32,							/* sizeof(gbtreekey32) */
  	gbt_uuidgt,
  	gbt_uuidge,
  	gbt_uuideq,
  	gbt_uuidle,
  	gbt_uuidlt,
  	gbt_uuidkey_cmp,
  	NULL
  };
  
  
  /**************************************************
   * uuid ops
   **************************************************/
  
  
  Datum
  gbt_uuid_compress(PG_FUNCTION_ARGS)
  {
  	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
  	GISTENTRY  *retval;
  
  	if (entry->leafkey)
  	{
  		char	   *r = (char *) palloc(2 * UUID_LEN);
  		pg_uuid_t  *key = DatumGetUUIDP(entry->key);
  
  		retval = palloc(sizeof(GISTENTRY));
  
  		memcpy((void *) r, (void *) key, UUID_LEN);
  		memcpy((void *) (r + UUID_LEN), (void *) key, UUID_LEN);
  		gistentryinit(*retval, PointerGetDatum(r),
  					  entry->rel, entry->page,
  					  entry->offset, FALSE);
  	}
  	else
  		retval = entry;
  
  	PG_RETURN_POINTER(retval);
  }
  
  Datum
  gbt_uuid_fetch(PG_FUNCTION_ARGS)
  {
  	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
  
  	PG_RETURN_POINTER(gbt_num_fetch(entry, &tinfo));
  }
  
  Datum
  gbt_uuid_consistent(PG_FUNCTION_ARGS)
  {
  	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
  	pg_uuid_t  *query = PG_GETARG_UUID_P(1);
  	StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);
  
  	/* Oid		subtype = PG_GETARG_OID(3); */
  	bool	   *recheck = (bool *) PG_GETARG_POINTER(4);
  	uuidKEY    *kkk = (uuidKEY *) DatumGetPointer(entry->key);
  	GBT_NUMKEY_R key;
  
  	/* All cases served by this function are exact */
  	*recheck = false;
  
  	key.lower = (GBT_NUMKEY *) &kkk->lower;
  	key.upper = (GBT_NUMKEY *) &kkk->upper;
  
  	PG_RETURN_BOOL(
  				   gbt_num_consistent(&key, (void *) query, &strategy,
  									  GIST_LEAF(entry), &tinfo)
  		);
  }
  
  Datum
  gbt_uuid_union(PG_FUNCTION_ARGS)
  {
  	GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
  	void	   *out = palloc(sizeof(uuidKEY));
  
  	*(int *) PG_GETARG_POINTER(1) = sizeof(uuidKEY);
  	PG_RETURN_POINTER(gbt_num_union((void *) out, entryvec, &tinfo));
  }
  
  /*
   * Convert a uuid to a "double" value for estimating sizes of ranges.
   */
  static double
  uuid_2_double(const pg_uuid_t *u)
  {
  	uint64		uu[2];
  	const double two64 = 18446744073709551616.0;		/* 2^64 */
  
  	/* Source data may not be suitably aligned, so copy */
  	memcpy(uu, u->data, UUID_LEN);
  
  	/*
  	 * uuid values should be considered as big-endian numbers, since that
  	 * corresponds to how memcmp will compare them.  On a little-endian
  	 * machine, byte-swap each half so we can use native uint64 arithmetic.
  	 */
  #ifndef WORDS_BIGENDIAN
  	uu[0] = BSWAP64(uu[0]);
  	uu[1] = BSWAP64(uu[1]);
  #endif
  
  	/*
  	 * 2^128 is about 3.4e38, which in theory could exceed the range of
  	 * "double" (POSIX only requires 1e37).  To avoid any risk of overflow,
  	 * put the decimal point between the two halves rather than treating the
  	 * uuid value as a 128-bit integer.
  	 */
  	return (double) uu[0] + (double) uu[1] / two64;
  }
  
  Datum
  gbt_uuid_penalty(PG_FUNCTION_ARGS)
  {
  	uuidKEY    *origentry = (uuidKEY *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(0))->key);
  	uuidKEY    *newentry = (uuidKEY *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(1))->key);
  	float	   *result = (float *) PG_GETARG_POINTER(2);
  	double		olower,
  				oupper,
  				nlower,
  				nupper;
  
  	olower = uuid_2_double(&origentry->lower);
  	oupper = uuid_2_double(&origentry->upper);
  	nlower = uuid_2_double(&newentry->lower);
  	nupper = uuid_2_double(&newentry->upper);
  
  	penalty_num(result, olower, oupper, nlower, nupper);
  
  	PG_RETURN_POINTER(result);
  }
  
  Datum
  gbt_uuid_picksplit(PG_FUNCTION_ARGS)
  {
  	PG_RETURN_POINTER(gbt_num_picksplit(
  									(GistEntryVector *) PG_GETARG_POINTER(0),
  									  (GIST_SPLITVEC *) PG_GETARG_POINTER(1),
  										&tinfo
  										));
  }
  
  Datum
  gbt_uuid_same(PG_FUNCTION_ARGS)
  {
  	uuidKEY    *b1 = (uuidKEY *) PG_GETARG_POINTER(0);
  	uuidKEY    *b2 = (uuidKEY *) PG_GETARG_POINTER(1);
  	bool	   *result = (bool *) PG_GETARG_POINTER(2);
  
  	*result = gbt_num_same((void *) b1, (void *) b2, &tinfo);
  	PG_RETURN_POINTER(result);
  }
  