adding ffmpeg specific version

1 files changed, 61 insertions, 0 deletions

diff --git a/ffmpeg1/libavutil/rc4.c b/ffmpeg1/libavutil/rc4.c
new file mode 100644
index 0000000..4e52ba5
--- /dev/null
+++ b/ffmpeg1/libavutil/rc4.c
@@ -0,0 +1,61 @@
+/*
+ * RC4 encryption/decryption/pseudo-random number generator
+ * Copyright (c) 2007 Reimar Doeffinger
+ *
+ * loosely based on LibTomCrypt by Tom St Denis
+ *
+ * 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 "avutil.h"
+#include "common.h"
+#include "rc4.h"
+
+typedef struct AVRC4 AVRC4;
+
+int av_rc4_init(AVRC4 *r, const uint8_t *key, int key_bits, int decrypt) {
+    int i, j;
+    uint8_t y;
+    uint8_t *state = r->state;
+    int keylen = key_bits >> 3;
+    if (key_bits & 7)
+        return -1;
+    for (i = 0; i < 256; i++)
+        state[i] = i;
+    y = 0;
+    // j is i % keylen
+    for (j = 0, i = 0; i < 256; i++, j++) {
+        if (j == keylen) j = 0;
+        y += state[i] + key[j];
+        FFSWAP(uint8_t, state[i], state[y]);
+    }
+    r->x = 1;
+    r->y = state[1];
+    return 0;
+}
+
+void av_rc4_crypt(AVRC4 *r, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt) {
+    uint8_t x = r->x, y = r->y;
+    uint8_t *state = r->state;
+    while (count-- > 0) {
+        uint8_t sum = state[x] + state[y];
+        FFSWAP(uint8_t, state[x], state[y]);
+        *dst++ = src ? *src++ ^ state[sum] : state[sum];
+        x++;
+        y += state[x];
+    }
+    r->x = x; r->y = y;
+}