add ff_random_get_seed to be used in conjunction with random functions

Originally committed as revision 17868 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/Makefile

@@ -36,6 +36,7 @@ OBJS = adler32.o                                                        \
        md5.o                                                            \
        mem.o                                                            \
        random.o                                                         \
+       random_seed.o                                                    \
        rational.o                                                       \
        rc4.o                                                            \
        sha1.o                                                           \

libavutil/random_seed.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <unistd.h>
+#include <fcntl.h>
+#include "timer.h"
+#include "random_seed.h"
+
+uint32_t ff_random_get_seed(void)
+{
+    uint32_t seed;
+    int fd;
+
+    if ((fd = open("/dev/random", O_RDONLY)) == -1)
+        fd = open("/dev/urandom", O_RDONLY);
+    if (fd != -1){
+        read(fd, &seed, 4);
+        close(fd);
+        return seed;
+    }
+#ifdef AV_READ_TIME
+    seed = AV_READ_TIME();
+#endif
+    // XXX what to do ?
+    return seed;
+}

libavutil/random_seed.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_RANDOM_SEED_H
+#define AVUTIL_RANDOM_SEED_H
+
+#include <stdint.h>
+
+/**
+ * Get a seed to use in conjuction with random functions
+ */
+uint32_t ff_random_get_seed();
+
+#endif /* AVUTIL_RANDOM_SEED_H */