From 00f78dd646cbdd382c69c8a6b8953652a1cafd4b Mon Sep 17 00:00:00 2001
From: Bill Somerville <g4wjs@classdesign.com>
Date: Mon, 14 Dec 2015 22:37:56 +0000
Subject: [PATCH] Add missing files from last commit

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6273 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
---
 lib/init_random_seed.c   | 76 ++++++++++++++++++++++++++++++++++++++++
 lib/init_random_seed.f90 | 55 +++++++++++++++++++++++++++++
 lib/init_random_seed.h   | 20 +++++++++++
 3 files changed, 151 insertions(+)
 create mode 100644 lib/init_random_seed.c
 create mode 100644 lib/init_random_seed.f90
 create mode 100644 lib/init_random_seed.h

diff --git a/lib/init_random_seed.c b/lib/init_random_seed.c
new file mode 100644
index 000000000..75ee932b6
--- /dev/null
+++ b/lib/init_random_seed.c
@@ -0,0 +1,76 @@
+#include "init_random_seed.h"
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <time.h>
+#include <unistd.h>
+
+/* basic PRNG to use for improving the basic seed selection */
+static unsigned lcg (uint64_t seed)
+{
+  if (0 ==seed)
+    {
+      seed = UINT64_C(104729);
+    }
+  else
+    {
+      seed %= UINT64_C(4294967296);
+    }
+  seed = (seed * UINT64_C(279470273)) % UINT64_C(4294967291);
+  return seed % UINT64_MAX;
+}
+
+/* Generate a good PRNG seed value */
+void init_random_seed(void)
+{
+  unsigned seed = 0u;
+  int have_seed = 0;
+
+  // try /dev/urandom for an initial seed
+  int random_source;
+  if (0  == (random_source = open ("/dev/urandom", O_RDONLY)))
+    {
+      size_t random_data_length = 0;
+      have_seed = -1;
+      while (random_data_length < sizeof seed)
+        {
+          ssize_t result = read (random_source, &seed + random_data_length, (sizeof seed) - random_data_length);
+          if (result < 0)
+            {
+              // error, unable to read /dev/random
+              have_seed = 0;
+            }
+          random_data_length += result;
+        }
+      close (random_source);
+    }
+  if (!have_seed)
+    {
+      // fallback to XOR:ing the time and pid
+      seed = time (NULL) ^ getpid ();
+      seed = lcg (seed);
+    }
+  srand (seed);
+}
+
+#ifdef TEST
+#include <stdio.h>
+
+int main (int argc, char * argv[])
+{
+  init_random_seed ();
+  int i, j;
+  int r[10][4];
+  for (i = 0; i < 10; ++i)
+    {
+      for (j = 0; j < 4; ++j)
+        {
+          printf ("%10d ", rand ());
+        }
+      printf ("\n");
+    }
+  return 0;
+}
+#endif
diff --git a/lib/init_random_seed.f90 b/lib/init_random_seed.f90
new file mode 100644
index 000000000..7d85f9ddb
--- /dev/null
+++ b/lib/init_random_seed.f90
@@ -0,0 +1,55 @@
+!
+! Generate a seed for the RANDOM_NUMBER PRNG that is guaranteed to be
+! unique even if many processes are started simultaneously
+!
+subroutine init_random_seed()
+  use iso_fortran_env, only: int64
+  implicit none
+  integer, allocatable :: seed(:)
+  integer :: i, n, un, istat, dt(8), pid
+  integer(int64) :: t
+
+  call random_seed(size = n)
+  allocate(seed(n))
+  ! First try if the OS provides a random number generator
+  open(newunit=un, file="/dev/urandom", access="stream", &
+       form="unformatted", action="read", status="old", iostat=istat)
+  if (istat == 0) then
+     read(un) seed
+     close(un)
+  else
+     ! Fallback to XOR:ing the current time and pid. The PID is
+     ! useful in case one launches multiple instances of the same
+     ! program in parallel.
+     call system_clock(t)
+     if (t == 0) then
+        call date_and_time(values=dt)
+        t = (dt(1) - 1970) * 365_int64 * 24 * 60 * 60 * 1000 &
+             + dt(2) * 31_int64 * 24 * 60 * 60 * 1000 &
+             + dt(3) * 24_int64 * 60 * 60 * 1000 &
+             + dt(5) * 60 * 60 * 1000 &
+             + dt(6) * 60 * 1000 + dt(7) * 1000 &
+             + dt(8)
+     end if
+     pid = getpid()
+     t = ieor(t, int(pid, kind(t)))
+     do i = 1, n
+        seed(i) = lcg(t)
+     end do
+  end if
+  call random_seed(put=seed)
+contains
+  ! This simple PRNG might not be good enough for real work, but is
+  ! sufficient for seeding a better PRNG.
+  function lcg(s)
+    integer :: lcg
+    integer(int64) :: s
+    if (s == 0) then
+       s = 104729
+    else
+       s = mod(s, 4294967296_int64)
+    end if
+    s = mod(s * 279470273_int64, 4294967291_int64)
+    lcg = int(mod(s, int(huge(0), int64)), kind(0))
+  end function lcg
+end subroutine init_random_seed
diff --git a/lib/init_random_seed.h b/lib/init_random_seed.h
new file mode 100644
index 000000000..aa9500514
--- /dev/null
+++ b/lib/init_random_seed.h
@@ -0,0 +1,20 @@
+#ifndef INIT_RANDOM_SEED_H__
+#define INIT_RANDOM_SEED_H__
+
+#ifdef __cplusplus
+exten "C" {
+#endif
+
+  /*
+   * Generate a seed for the RANDOM_NUMBER PRNG that is guaranteed to
+   * be unique even if many processes are started simultaneously
+   *
+   * Not suitable for multi-threaded requirements
+   */
+  void init_random_seed (void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif