1 files changed, 115 insertions, 0 deletions
diff --git a/media/libav/libavutil/random_seed.c b/media/libav/libavutil/random_seed.c
new file mode 100644
index 000000000..26884cbcd
--- /dev/null
+++ b/media/libav/libavutil/random_seed.c
@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#if HAVE_CRYPTGENRANDOM
+#include <windows.h>
+#include <wincrypt.h>
+#endif
+#include <fcntl.h>
+#include <math.h>
+#include <time.h>
+#include "internal.h"
+#include "intreadwrite.h"
+#include "mem.h"
+#include "timer.h"
+#include "random_seed.h"
+#include "sha.h"
+
+static int read_random(uint32_t *dst, const char *file)
+{
+#if HAVE_UNISTD_H
+    int fd = avpriv_open(file, O_RDONLY);
+    int err = -1;
+
+    if (fd == -1)
+        return -1;
+    err = read(fd, dst, sizeof(*dst));
+    close(fd);
+
+    return err;
+#else
+    return -1;
+#endif
+}
+
+static uint32_t get_generic_seed(void)
+{
+    struct AVSHA *sha = av_sha_alloc();
+    clock_t last_t  = 0;
+    static uint64_t i = 0;
+    static uint32_t buffer[512] = { 0 };
+    unsigned char digest[20];
+    uint64_t last_i = i;
+
+    for (;;) {
+        clock_t t = clock();
+
+        if (last_t == t) {
+            buffer[i & 511]++;
+        } else {
+            buffer[++i & 511] += (t - last_t) % 3294638521U;
+            if (last_i && i - last_i > 4 || i - last_i > 64)
+                break;
+        }
+        last_t = t;
+    }
+
+    if (!sha) {
+        uint32_t seed = 0;
+        int j;
+        // Unable to allocate an sha context, just xor the buffer together
+        // to create something hopefully unique.
+        for (j = 0; j < 512; j++)
+            seed ^= buffer[j];
+        return seed;
+    }
+    av_sha_init(sha, 160);
+    av_sha_update(sha, (const uint8_t *) buffer, sizeof(buffer));
+    av_sha_final(sha, digest);
+    av_free(sha);
+    return AV_RB32(digest) + AV_RB32(digest + 16);
+}
+
+uint32_t av_get_random_seed(void)
+{
+    uint32_t seed;
+
+#if HAVE_CRYPTGENRANDOM
+    HCRYPTPROV provider;
+    if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
+                            CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
+        BOOL ret = CryptGenRandom(provider, sizeof(seed), (PBYTE) &seed);
+        CryptReleaseContext(provider, 0);
+        if (ret)
+            return seed;
+    }
+#endif
+
+    if (read_random(&seed, "/dev/urandom") == sizeof(seed))
+        return seed;
+    if (read_random(&seed, "/dev/random")  == sizeof(seed))
+        return seed;
+    return get_generic_seed();
+}