pg_bitstring_helpers/bitstring_helpers.c at master · tomhebbron/pg_bitstring_helpers · GitHub

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#include "postgres.h"
#include "catalog/pg_type.h"
#include "fmgr.h"
#include "funcapi.h"
#include "utils/varbit.h"
#include "utils/array.h"

#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif

Datum popcount(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(popcount);

Datum popcount(PG_FUNCTION_ARGS)
{
	VarBit *arg1 = PG_GETARG_VARBIT_P(0);
	int32 result;
	int len, i;
	bits8 *b;
	bits8 mask;
	len = VARBITLEN(arg1);
	b = VARBITS(arg1);
	result = 0;

	for (i=0; i< VARBITBYTES(arg1); i++)
	{
		mask = *b++;
		while (mask)
		{
			if (mask & 1) result++;
			mask >>= 1;
		}
	}
	PG_RETURN_INT32(result);
}


Datum shuffled_ints(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(shuffled_ints);

Datum shuffled_ints(PG_FUNCTION_ARGS)
{
	ArrayType *result;
	Datum *nums;
	long i, swap, limit;
	int64 tmp;
	limit = (long) PG_GETARG_INT64(0);
	nums = (Datum *)palloc(limit * sizeof(Datum));

	if (limit > 0)
	{
		for (i=0; i < limit; i++)
		{
			//elog( NOTICE, "%i", i );
			nums[i] = Int64GetDatum(i);
		}

		//elog(NOTICE,"finished building the array");
		//now shuffle
		for (i=limit-1; i >=0; i--)
		{
			swap = random()%(long)limit;
			//elog(NOTICE, "%i %i",i,swap);
			tmp = DatumGetInt64(nums[swap]);
			nums[swap] = nums[i];
			nums[i] = Int64GetDatum(tmp);
		}
	}

	result = construct_array(nums, limit, INT8OID, sizeof(int64), false,'d');

	pfree(nums);
	PG_RETURN_ARRAYTYPE_P(result);
}