Separate XorShift128 PRNG from /dev/urandom and make it generally available.

2026-06-06 16:50:55 +08:00 · 2016-08-20 11:36:02 -06:00
parent a5440fff64
commit 6f833be9d5
5 changed files with 254 additions and 62 deletions
@@ -36,7 +36,7 @@
 # Add the internal C files to the build

 CSRCS += lib_stream.c lib_filesem.c lib_utsname.c
-CSRCS += lib_tea_encrypt.c lib_tea_decrypt.c
+CSRCS += lib_xorshift128.c lib_tea_encrypt.c lib_tea_decrypt.c

 # Support for platforms that do not have long long types

@@ -0,0 +1,123 @@
+/****************************************************************************
+ * libc/misc/lib_xorshift.c
+ *
+ *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+ *   Author: David S. Alessio
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/* This random number generator is simple, fast and portable.
+ *      Ref:  https://en.wikipedia.org/wiki/Xorshift
+ */
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <stdint.h>
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct xorshift128_state_s
+{
+  uint32_t x;
+  uint32_t y;
+  uint32_t z;
+  uint32_t w;
+};
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static struct xorshift128_state_s g_prng;
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: xorshift128_seed
+ *
+ * Description:
+ *   Seed the XorShift128 PRNG
+ *
+ * Input Parameters:
+ *   w, x, y, z:  Values for XorShift128 generation state.
+ *
+ * Returned Value:
+ *   No
+ *
+ ****************************************************************************/
+
+void xorshift128_seed(uint32_t w, uint32_t x, uint32_t y, uint32_t z)
+{
+  /* Seed the PRNG */
+
+  g_prng.w = w;
+  g_prng.x = x;
+  g_prng.y = y;
+  g_prng.z = z;
+}
+
+/****************************************************************************
+ * Name: xorshift128
+ *
+ * Description:
+ *   Generate one 32-bit pseudo-random number
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   The generated pseudo-random number
+ *
+ ****************************************************************************/
+
+uint32_t xorshift128(void)
+{
+  uint32_t t;
+
+  t        = g_prng.x;
+  t       ^= t << 11;
+  t       ^= t >> 8;
+
+  g_prng.x = g_prng.y;
+  g_prng.y = g_prng.z;
+  g_prng.z = g_prng.w;
+
+  g_prng.w ^= g_prng.w >> 19;
+  g_prng.w ^= t;
+
+  return g_prng.w;
+}