1 files changed, 119 insertions, 0 deletions

diff --git a/firmware/libc/random.c b/firmware/libc/random.c
new file mode 100644
index 0000000000..f3efe89351
--- /dev/null
+++ b/firmware/libc/random.c
@@ -0,0 +1,119 @@
+/*
+   A C-program for MT19937, with initialization improved 2002/2/10.
+   Coded by Takuji Nishimura and Makoto Matsumoto.
+   This is a faster version by taking Shawn Cokus's optimization,
+   Matthe Bellew's simplification.
+
+   Before using, initialize the state by using srand(seed).
+
+   Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
+   All rights reserved.
+
+   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. The names of its contributors may not 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.
+
+   Any feedback is very welcome.
+   http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
+   email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
+*/
+
+/*
+   Adapted to Rockbox by Jens Arnold
+*/
+ 
+#include <stdlib.h>
+
+/* Period parameters */
+#define N            624
+#define M            397
+#define MATRIX_A     0x9908b0dfUL /* constant vector a */
+#define UMASK        0x80000000UL /* most significant w-r bits */
+#define LMASK        0x7fffffffUL /* least significant r bits */
+#define MIXBITS(u,v) ( ((u) & UMASK) | ((v) & LMASK) )
+#define TWIST(u,v)   ((MIXBITS(u,v) >> 1) ^ ((v)&1UL ? MATRIX_A : 0UL))
+
+static unsigned long state[N]; /* the array for the state vector  */
+static int left = 0;
+static unsigned long *next;
+
+/* initializes state[N] with a seed */
+void srand(unsigned int seed)
+{
+    unsigned long x = seed  & 0xffffffffUL;
+    unsigned long *s = state;
+    int j;
+
+    for (*s++ = x, j = 1; j < N; j++) {
+        x = (1812433253UL * (x ^ (x >> 30)) + j) & 0xffffffffUL;
+        *s++ = x;
+        /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
+        /* In the previous versions, MSBs of the seed affect   */
+        /* only MSBs of the array state[].                     */
+        /* 2002/01/09 modified by Makoto Matsumoto             */
+    }
+    left = 1;
+}
+
+static void next_state(void)
+{
+    unsigned long *p = state;
+    int j;
+
+    /* if srand() has not been called, */
+    /* a default initial seed is used  */
+    if (left < 0)
+        srand(5489UL);
+
+    left = N;
+    next = state;
+    
+    for (j = N - M + 1; --j; p++)
+        *p = p[M] ^ TWIST(p[0], p[1]);
+
+    for (j = M; --j; p++)
+        *p = p[M-N] ^ TWIST(p[0], p[1]);
+
+    *p = p[M-N] ^ TWIST(p[0], state[0]);
+}
+
+/* generates a random number on [0,RAND_MAX]-interval */
+int rand(void)
+{
+    unsigned long y;
+
+    if (--left <= 0)
+        next_state();
+    y = *next++;
+
+    /* Tempering */
+    y ^= (y >> 11);
+    y ^= (y << 7) & 0x9d2c5680UL;
+    y ^= (y << 15) & 0xefc60000UL;
+    y ^= (y >> 18);
+
+    return ((unsigned int)y) >> 1;
+}