Move libdrm/ up one level

1 files changed, 208 insertions, 0 deletions

diff --git a/xf86drmRandom.c b/xf86drmRandom.c
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+/* xf86drmRandom.c -- "Minimal Standard" PRNG Implementation
+ * Created: Mon Apr 19 08:28:13 1999 by faith@precisioninsight.com
+ *
+ * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ * 
+ * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
+ *
+ * DESCRIPTION
+ *
+ * This file contains a simple, straightforward implementation of the Park
+ * & Miller "Minimal Standard" PRNG [PM88, PMS93], which is a Lehmer
+ * multiplicative linear congruential generator (MLCG) with a period of
+ * 2^31-1.
+ *
+ * This implementation is intended to provide a reliable, portable PRNG
+ * that is suitable for testing a hash table implementation and for
+ * implementing skip lists.
+ *
+ * FUTURE ENHANCEMENTS
+ *
+ * If initial seeds are not selected randomly, two instances of the PRNG
+ * can be correlated.  [Knuth81, pp. 32-33] describes a shuffling technique
+ * that can eliminate this problem.
+ *
+ * If PRNGs are used for simulation, the period of the current
+ * implementation may be too short.  [LE88] discusses methods of combining
+ * MLCGs to produce much longer periods, and suggests some alternative
+ * values for A and M.  [LE90 and Sch92] also provide information on
+ * long-period PRNGs.
+ *
+ * REFERENCES
+ *
+ * [Knuth81] Donald E. Knuth. The Art of Computer Programming.  Volume 2:
+ * Seminumerical Algorithms.  Reading, Massachusetts: Addison-Wesley, 1981.
+ *
+ * [LE88] Pierre L'Ecuyer. "Efficient and Portable Combined Random Number
+ * Generators".  CACM 31(6), June 1988, pp. 742-774.
+ *
+ * [LE90] Pierre L'Ecuyer. "Random Numbers for Simulation". CACM 33(10,
+ * October 1990, pp. 85-97.
+ *
+ * [PM88] Stephen K. Park and Keith W. Miller. "Random Number Generators:
+ * Good Ones are Hard to Find". CACM 31(10), October 1988, pp. 1192-1201.
+ *
+ * [Sch92] Bruce Schneier. "Pseudo-Ransom Sequence Generator for 32-Bit
+ * CPUs".  Dr. Dobb's Journal 17(2), February 1992, pp. 34, 37-38, 40.
+ *
+ * [PMS93] Stephen K. Park, Keith W. Miller, and Paul K. Stockmeyer.  In
+ * "Technical Correspondence: Remarks on Choosing and Implementing Random
+ * Number Generators". CACM 36(7), July 1993, pp. 105-110.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define RANDOM_MAIN 0
+
+#if !RANDOM_MAIN
+# include "xf86drm.h"
+#endif
+
+#define RANDOM_MAGIC 0xfeedbeef
+#define RANDOM_DEBUG 0
+
+#if RANDOM_MAIN
+#define RANDOM_ALLOC malloc
+#define RANDOM_FREE  free
+#else
+#define RANDOM_ALLOC drmMalloc
+#define RANDOM_FREE  drmFree
+#endif
+
+typedef struct RandomState {
+    unsigned long magic;
+    unsigned long a;
+    unsigned long m;
+    unsigned long q;		/* m div a */
+    unsigned long r;		/* m mod a */
+    unsigned long check;
+    long          seed;
+} RandomState;
+
+#if RANDOM_MAIN
+extern void          *drmRandomCreate(unsigned long seed);
+extern int           drmRandomDestroy(void *state);
+extern unsigned long drmRandom(void *state);
+extern double        drmRandomDouble(void *state);
+#endif
+
+void *drmRandomCreate(unsigned long seed)
+{
+    RandomState  *state;
+
+    state           = RANDOM_ALLOC(sizeof(*state));
+    if (!state) return NULL;
+    state->magic    = RANDOM_MAGIC;
+#if 0
+				/* Park & Miller, October 1988 */
+    state->a        = 16807;
+    state->m        = 2147483647;
+    state->check    = 1043618065; /* After 10000 iterations */
+#else
+				/* Park, Miller, and Stockmeyer, July 1993 */
+    state->a        = 48271;
+    state->m        = 2147483647;
+    state->check    = 399268537; /* After 10000 iterations */
+#endif
+    state->q        = state->m / state->a;
+    state->r        = state->m % state->a;
+
+    state->seed     = seed;
+				/* Check for illegal boundary conditions,
+                                   and choose closest legal value. */
+    if (state->seed <= 0)        state->seed = 1;
+    if (state->seed >= state->m) state->seed = state->m - 1;
+
+    return state;
+}
+
+int drmRandomDestroy(void *state)
+{
+    RANDOM_FREE(state);
+    return 0;
+}
+
+unsigned long drmRandom(void *state)
+{
+    RandomState   *s = (RandomState *)state;
+    long          hi;
+    long          lo;
+
+    hi      = s->seed / s->q;
+    lo      = s->seed % s->q;
+    s->seed = s->a * lo - s->r * hi;
+    if (s->seed <= 0) s->seed += s->m;
+
+    return s->seed;
+}
+
+double drmRandomDouble(void *state)
+{
+    RandomState *s = (RandomState *)state;
+    
+    return (double)drmRandom(state)/(double)s->m;
+}
+
+#if RANDOM_MAIN
+static void check_period(long seed)
+{
+    unsigned long count = 0;
+    unsigned long initial;
+    void          *state;
+    
+    state = drmRandomCreate(seed);
+    initial = drmRandom(state);
+    ++count;
+    while (initial != drmRandom(state)) {
+	if (!++count) break;
+    }
+    printf("With seed of %10ld, period = %10lu (0x%08lx)\n",
+	   seed, count, count);
+    drmRandomDestroy(state);
+}
+
+int main(void)
+{
+    RandomState   *state;
+    int           i;
+    unsigned long rand;
+
+    state = drmRandomCreate(1);
+    for (i = 0; i < 10000; i++) {
+	rand = drmRandom(state);
+    }
+    printf("After 10000 iterations: %lu (%lu expected): %s\n",
+	   rand, state->check,
+	   rand - state->check ? "*INCORRECT*" : "CORRECT");
+    drmRandomDestroy(state);
+
+    printf("Checking periods...\n");
+    check_period(1);
+    check_period(2);
+    check_period(31415926);
+    
+    return 0;
+}
+#endif