Initial revision

Originally committed as revision 5 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 77 insertions, 0 deletions

diff --git a/libavcodec/libac3/bitstream.c b/libavcodec/libac3/bitstream.c
new file mode 100644
index 0000000000..7e9bd1f66a
--- /dev/null
+++ b/libavcodec/libac3/bitstream.c
@@ -0,0 +1,77 @@
+/* 
+ *  bitstream.c
+ *
+ *	Copyright (C) Aaron Holtzman - Dec 1999
+ *
+ *  This file is part of ac3dec, a free AC-3 audio decoder
+ *	
+ *  ac3dec is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2, or (at your option)
+ *  any later version.
+ *   
+ *  ac3dec 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 General Public License for more details.
+ *   
+ *  You should have received a copy of the GNU General Public License
+ *  along with GNU Make; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
+ *
+ */
+
+#include <inttypes.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "ac3.h"
+#include "ac3_internal.h"
+#include "bitstream.h"
+
+#define BUFFER_SIZE 4096
+
+static uint8_t *buffer_start;
+
+uint32_t bits_left;
+uint32_t current_word;
+
+void bitstream_set_ptr (uint8_t * buf)
+{
+    buffer_start = buf;
+    bits_left = 0;
+}
+
+static inline void
+bitstream_fill_current()
+{
+    current_word = *((uint32_t*)buffer_start)++;
+    current_word = swab32(current_word);
+}
+
+//
+// The fast paths for _get is in the
+// bitstream.h header file so it can be inlined.
+//
+// The "bottom half" of this routine is suffixed _bh
+//
+// -ah
+//
+
+uint32_t
+bitstream_get_bh(uint32_t num_bits)
+{
+    uint32_t result;
+
+    num_bits -= bits_left;
+    result = (current_word << (32 - bits_left)) >> (32 - bits_left);
+
+    bitstream_fill_current();
+
+    if(num_bits != 0)
+	result = (result << num_bits) | (current_word >> (32 - num_bits));
+	
+    bits_left = 32 - num_bits;
+
+    return result;
+}