should be it

external/duckdb/extension/tpch/dbgen/rng64.cpp

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+/*
+ * Copyright owned by the Transaction Processing Performance Council.
+ *
+ * A copy of the license is included under extension/tpch/dbgen/LICENSE
+ * in this repository.
+ *
+ * You may not use this file except in compliance with the License.
+ *
+ * THE TPC SOFTWARE IS AVAILABLE WITHOUT CHARGE FROM TPC.
+ */
+/*
+ * $Id: rng64.c,v 1.7 2008/03/21 17:38:39 jms Exp $
+ *
+ * This software contains proprietary and confidential information of Gradient
+ * Systems Inc.  By accepting transfer of this copy, Recipient agrees
+ * to retain this software in confidence, to prevent disclosure to others, and
+ * to make no use of this software other than that for which it was delivered.
+ * This is an unpublished copyright work Gradient Systems, Inc.  Execpt as
+ * permitted by federal law, 17 USC 117, copying is strictly prohibited.
+ *
+ * Gradient Systems Inc. CONFIDENTIAL - (Gradient Systems Inc. Confidential
+ * when combined with the aggregated modules for this product)
+ * OBJECT CODE ONLY SOURCE MATERIALS
+ * (C) COPYRIGHT Gradient Systems Inc. 2003
+ *
+ * All Rights Reserved
+ * THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF GRADIENT SYSTEMS, INC.
+ * The copyright notice above does not evidence any
+ * actual or intended publication of such source code.
+ *
+ * Revision History
+ * ===================
+ * $Log: rng64.c,v $
+ * Revision 1.7  2008/03/21 17:38:39  jms
+ * changes for 2.6.3
+ *
+ * Revision 1.6  2006/04/26 23:20:05  jms
+ * Data type clenaup for qgen
+ *
+ * Revision 1.5  2006/03/08 21:25:27  jms
+ * change to RNG64 to address overflow/underflow issues
+ *
+ * Revision 1.4  2005/10/25 17:26:38  jms
+ * check in integration between microsoft changes and baseline code
+ *
+ * Revision 1.3  2005/03/04 19:48:39  jms
+ * Changes from Doug Johnson to address very large scale factors
+ *
+ * Revision 1.2  2005/01/03 20:08:59  jms
+ * change line terminations
+ *
+ * Revision 1.1.1.1  2004/11/24 23:31:47  jms
+ * re-establish external server
+ *
+ * Revision 1.2  2004/02/18 16:45:30  jms
+ * remove C++ style comments for AIX compiler
+ *
+ * Revision 1.1.1.1  2003/08/08 21:57:34  jms
+ * recreation after CVS crash
+ *
+ * Revision 1.1  2003/08/08 21:57:34  jms
+ * first integration of rng64 for o_custkey and l_partkey
+ *
+ */
+#include "dbgen/rng64.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+void dss_random64(DSS_HUGE *tgt, DSS_HUGE nLow, DSS_HUGE nHigh, seed_t *seed) {
+	DSS_HUGE nTemp;
+
+	if (nLow > nHigh) {
+		nTemp = nLow;
+		nLow = nHigh;
+		nHigh = nTemp;
+	}
+
+	seed->value = NextRand64(seed->value);
+	nTemp = seed->value;
+	if (nTemp < 0)
+		nTemp = -nTemp;
+	nTemp %= (nHigh - nLow + 1);
+	*tgt = nLow + nTemp;
+	seed->usage += 1;
+#ifdef RNG_TEST
+	seed->nCalls += 1;
+#endif
+
+	return;
+}
+
+DSS_HUGE
+NextRand64(DSS_HUGE nSeed) {
+
+	DSS_HUGE a = (unsigned DSS_HUGE)RNG_A;
+	DSS_HUGE c = (unsigned DSS_HUGE)RNG_C;
+	nSeed = (nSeed * a + c); /* implicitely truncated to 64bits */
+
+	return (nSeed);
+}
+
+DSS_HUGE AdvanceRand64(DSS_HUGE nSeed, DSS_HUGE nCount) {
+	unsigned DSS_HUGE a = RNG_A;
+	unsigned DSS_HUGE c = RNG_C;
+	int nBit;
+	unsigned DSS_HUGE Apow = a, Dsum = c;
+
+	/* if nothing to do, do nothing ! */
+	if (nCount == 0)
+		return nSeed;
+
+	/* Recursively compute X(n) = A * X(n-1) + C */
+	/* */
+	/* explicitely: */
+	/* X(n) = A^n * X(0) + { A^(n-1) + A^(n-2) + ... A + 1 } * C */
+	/* */
+	/* we write this as: */
+	/* X(n) = Apow(n) * X(0) + Dsum(n) * C */
+	/* */
+	/* we use the following relations: */
+	/* Apow(n) = A^(n%2)*Apow(n/2)*Apow(n/2) */
+	/* Dsum(n) =   (n%2)*Apow(n/2)*Apow(n/2) + (Apow(n/2) + 1) * Dsum(n/2) */
+	/* */
+
+	/* first get the highest non-zero bit */
+	for (nBit = 0; (nCount >> nBit) != RNG_C; nBit++) {
+	}
+
+	/* go 1 bit at the time */
+	while (--nBit >= 0) {
+		Dsum *= (Apow + 1);
+		Apow = Apow * Apow;
+		if (((nCount >> nBit) % 2) == 1) { /* odd value */
+			Dsum += Apow;
+			Apow *= a;
+		}
+	}
+	nSeed = nSeed * Apow + Dsum * c;
+	return nSeed;
+}