software: add prng

code is from http://vserver.13thfloor.at/Stuff/prng.c

software/prng/prng.c

@@ -0,0 +1,67 @@
+/**********************************************************************
+**  prng.c
+**      Pseudo Random Number Generator
+**      Version 1.2
+**
+**  Copyright (C) 2014-2020 H.Poetzl
+**
+**      This program is free software: you can redistribute it and/or
+**      modify it under the terms of the GNU General Public License
+**      as published by the Free Software Foundation, either version
+**      2 of the License, or (at your option) any later version.
+**
+**********************************************************************/
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+
+#define BUF_SIZE 4096
+
+static uint64_t buf[BUF_SIZE];
+
+static inline uint64_t
+xoroshiro128plus(uint64_t s[2])
+{
+    uint64_t s0 = s[0];
+    uint64_t s1 = s[1];
+    uint64_t result = s0 + s1;
+    s1 ^= s0;
+    s[0] = ((s0 << 55) | (s0 >> 9)) ^ s1 ^ (s1 << 14);
+    s[1] = (s1 << 36) | (s1 >> 28);
+    return result;
+}
+
+int main(int argc, char *argv[])
+{
+    uint64_t s[2];
+
+    int fd = open(argv[1], O_RDONLY);
+    if (fd < 0) {
+	perror("open seed");
+	exit(1);
+    }
+
+    ssize_t len = read(fd, s, sizeof(s));
+    if (len != sizeof(s)) {
+	perror("read seed");
+	exit(2);
+    }
+    close(fd);
+
+    do {
+	for (int i=0; i<BUF_SIZE; i++)	
+	    buf[i] = xoroshiro128plus(s);
+
+	len = write(1, buf, sizeof(buf));
+    } while (len == sizeof(buf));
+
+    exit(0);
+}
+