Move getentropy/getrandom into own file

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/libc/getentropy.cc

@@ -0,0 +1,70 @@
+/* getentropy.cc: getentropy/getrandmom functions
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+#include "winsup.h"
+#include <ntsecapi.h>
+#include <sys/param.h>
+#include <sys/random.h>
+#include "cygtls.h"
+#include "ntdll.h"
+
+extern "C" int
+getentropy (void *ptr, size_t len)
+{
+  /* Per BSD man page: The maximum buffer size permitted is 256 bytes.
+     If buflen exceeds this, an error of EIO will be indicated. */
+  if (len > 256)
+    {
+      debug_printf ("len (%U) > 256", len);
+      set_errno (EIO);
+      return -1;
+    }
+  __try
+    {
+      if (!RtlGenRandom (ptr, len))
+	{
+	  debug_printf ("RtlGenRandom() = FALSE");
+	  set_errno (EIO);
+	  return -1;
+	}
+    }
+  __except (EFAULT)
+    {
+      return -1;
+    }
+  __endtry
+  return 0;
+}
+
+extern "C" ssize_t
+getrandom (void *ptr, size_t len, unsigned int flags)
+{
+  if (flags & ~(GRND_NONBLOCK | GRND_RANDOM))
+    {
+      debug_printf ("invalid flags: %y", flags);
+      set_errno (EINVAL);
+      return -1;
+    }
+  /* Max. bytes returned by Linux call. */
+  len = MAX (len, (flags & GRND_RANDOM) ? 512 : 33554431);
+  __try
+    {
+      if (!RtlGenRandom (ptr, len))
+	{
+	  debug_printf ("RtlGenRandom() = FALSE");
+	  set_errno (EIO);
+	  return -1;
+	}
+    }
+  __except (EFAULT)
+    {
+      return -1;
+    }
+  __endtry
+  return len;
+}