[v2,2/7] support: Add pseudo-random number generator interface

diff --git a/support/Makefile b/support/Makefile
index 9063046c23..db46be606e 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -56,6 +56,7 @@  libsupport-routines = \
   support_openpty \
   support_quote_blob \
   support_record_failure \
+  support_random \
   support_run_diff \
   support_shared_allocate \
   support_test_compare_blob \
@@ -161,7 +162,7 @@  tests = \
   tst-support_record_failure \
   tst-test_compare \
   tst-test_compare_blob \
-  tst-xreadlink \
+  tst-xreadlink
 
 ifeq ($(run-built-tests),yes)
 tests-special = \
diff --git a/support/support_random.c b/support/support_random.c
new file mode 100644
index 0000000000..5feee1a213
--- /dev/null
+++ b/support/support_random.c
@@ -0,0 +1,90 @@ 
+/* Function for pseudo-random number generation.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <assert.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/random.h>
+
+#include <support/support_random.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+
+void
+support_random_seed (support_random_state *state, uint32_t seed)
+{
+  unsigned short int seed16v[3] = { 0 };
+  memcpy (seed16v, &seed, sizeof (seed));
+  seed48_r (seed16v, state);
+}
+
+void
+support_random_rseed (support_random_state *state)
+{
+  unsigned short int buf[3];
+  size_t len = sizeof buf;
+
+  ssize_t ret = getrandom (buf, len, 0);
+  if (ret != len)
+    {
+      int fd = xopen ("/dev/urandom", O_RDONLY, 0);
+      uintptr_t pbuf = (uintptr_t) buf;
+      uintptr_t pend = pbuf + len;
+      while (pbuf < pend)
+	{
+	  ret = read (fd, buf, pend - pbuf);
+	  if (ret <= 0)
+	    FAIL_EXIT1 ("read %zu bytes from /dev/urandom failed: %m",
+			pend - pbuf);
+          pbuf += ret;
+	}
+      close (fd);
+    }
+
+  seed48_r (buf, state);
+}
+
+uint32_t
+support_random_u32 (support_random_state *state)
+{
+  long int rl;
+  mrand48_r (state, &rl);
+  return rl;
+}
+
+void
+support_random_buf (support_random_state *state, void *buf, size_t nbytes)
+{
+  size_t nw = nbytes / sizeof (uint32_t);
+  for (size_t i = 0; i < nw; i++)
+    {
+      uint32_t r = support_random_u32 (state);
+      memcpy (buf, &r, sizeof (uint32_t));
+      buf = (void*)((uintptr_t)buf + sizeof (uint32_t));
+    }
+
+  size_t nb = nbytes % sizeof (uint32_t);
+  if (nb != 0)
+    {
+      uint32_t r = support_random_u32 (state);
+      memcpy (buf, &r, nb);
+    }
+}
diff --git a/support/support_random.h b/support/support_random.h
new file mode 100644
index 0000000000..8224c2b774
--- /dev/null
+++ b/support/support_random.h
@@ -0,0 +1,59 @@ 
+/* Function for pseudo-random number generation.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_MT_RAND_H
+#define SUPPORT_MT_RAND_H
+
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct drand48_data support_random_state;
+
+void support_random_seed (support_random_state *state, uint32_t seed);
+void support_random_rseed (support_random_state *state);
+
+uint32_t support_random_u32 (support_random_state *state);
+void support_random_buf (support_random_state *state, void *buf,
+			 size_t nbytes);
+
+/* Scales the number NUMBER to the uniformly distributed closed internal
+   [min, max].  */
+static inline uint32_t
+support_random_uniform_distribution (support_random_state *state,
+				     uint32_t min, uint32_t max)
+{
+  uint32_t ret;
+  uint32_t range = max - min;
+  /* It assumes the input random number RANDOM range is as larger or equal
+     than the RANGE, so the result will either returned or downscaled.  */
+  if (range != UINT32_MAX)
+    {
+      uint32_t urange = range + 1;  /* range can be 0.  */
+      uint32_t scaling = UINT32_MAX / urange;
+      uint32_t past = urange * scaling;
+      do
+        ret = support_random_u32 (state);
+      while (ret >= past);
+      ret /= scaling;
+    }
+  else
+    ret = support_random_u32 (state);
+  return ret + min;
+}
+
+#endif