1 files changed, 144 insertions, 0 deletions
diff --git a/src/gallium/auxiliary/vl/vl_bitstream_parser.c b/src/gallium/auxiliary/vl/vl_bitstream_parser.c
new file mode 100644
index 0000000000..356faa1348
--- /dev/null
+++ b/src/gallium/auxiliary/vl/vl_bitstream_parser.c
@@ -0,0 +1,144 @@
+#include "vl_bitstream_parser.h"
+#include <assert.h>
+#include <limits.h>
+#include <util/u_memory.h>
+
+static unsigned
+grab_bits(unsigned cursor, unsigned how_many_bits, unsigned bitstream_elt)
+{
+   unsigned excess_bits = sizeof(unsigned) * CHAR_BIT - how_many_bits - cursor;
+	
+   assert(cursor < sizeof(unsigned) * CHAR_BIT);
+   assert(how_many_bits > 0 && how_many_bits <= sizeof(unsigned) * CHAR_BIT);
+   assert(cursor + how_many_bits <= sizeof(unsigned) * CHAR_BIT);
+
+   return (bitstream_elt << excess_bits) >> (excess_bits + cursor);
+}
+
+static unsigned
+show_bits(unsigned cursor, unsigned how_many_bits, const unsigned *bitstream)
+{	
+   unsigned cur_int = cursor / (sizeof(unsigned) * CHAR_BIT);
+   unsigned cur_bit = cursor % (sizeof(unsigned) * CHAR_BIT);
+	
+   assert(bitstream);
+	
+   if (cur_bit + how_many_bits > sizeof(unsigned) * CHAR_BIT)
+   {
+      return grab_bits(cur_bit, sizeof(unsigned) * CHAR_BIT - cur_bit,
+                       bitstream[cur_int]) |
+             grab_bits(0, cur_bit + how_many_bits - sizeof(unsigned) * CHAR_BIT,
+                       bitstream[cur_int + 1]) << (sizeof(unsigned) * CHAR_BIT - cur_bit);
+   }
+   else
+      return grab_bits(cur_bit, how_many_bits, bitstream[cur_int]);
+}
+
+bool vl_bitstream_parser_init(struct vl_bitstream_parser *parser,
+                              unsigned num_bitstreams,
+                              const void **bitstreams,
+                              const unsigned *sizes)
+{
+   assert(parser);
+   assert(num_bitstreams);
+   assert(bitstreams);
+   assert(sizes);
+
+   parser->num_bitstreams = num_bitstreams;
+   parser->bitstreams = (const unsigned**)bitstreams;
+   parser->sizes = sizes;
+   parser->cur_bitstream = 0;
+   parser->cursor = 0;
+
+   return true;
+}
+
+void vl_bitstream_parser_cleanup(struct vl_bitstream_parser *parser)
+{
+   assert(parser);
+}
+
+unsigned
+vl_bitstream_parser_get_bits(struct vl_bitstream_parser *parser,
+                             unsigned how_many_bits)
+{
+   unsigned bits;
+
+   assert(parser);
+
+   bits = vl_bitstream_parser_show_bits(parser, how_many_bits);
+
+   vl_bitstream_parser_forward(parser, how_many_bits);
+
+   return bits;
+}
+
+unsigned
+vl_bitstream_parser_show_bits(struct vl_bitstream_parser *parser,
+                              unsigned how_many_bits)
+{	
+   unsigned bits = 0;
+   unsigned shift = 0;
+   unsigned cursor;
+   unsigned cur_bitstream;
+
+   assert(parser);
+
+   cursor = parser->cursor;
+   cur_bitstream = parser->cur_bitstream;
+
+   while (1)
+   {
+      unsigned bits_left = parser->sizes[cur_bitstream] * CHAR_BIT - cursor;
+      unsigned bits_to_show = how_many_bits > bits_left ? bits_left : how_many_bits;
+
+      bits |= show_bits(cursor, bits_to_show,
+                        parser->bitstreams[cur_bitstream]) << shift;
+		
+      if (how_many_bits > bits_to_show)
+      {
+         how_many_bits -= bits_to_show;
+         cursor = 0;
+         ++cur_bitstream;
+         shift += bits_to_show;
+      }
+      else
+         break;
+   }
+
+   return bits;
+}
+
+void vl_bitstream_parser_forward(struct vl_bitstream_parser *parser,
+                                 unsigned how_many_bits)
+{
+   assert(parser);
+   assert(how_many_bits);
+
+   parser->cursor += how_many_bits;
+
+   while (parser->cursor > parser->sizes[parser->cur_bitstream] * CHAR_BIT)
+   {
+      parser->cursor -= parser->sizes[parser->cur_bitstream++] * CHAR_BIT;
+      assert(parser->cur_bitstream < parser->num_bitstreams);
+   }
+}
+
+void vl_bitstream_parser_rewind(struct vl_bitstream_parser *parser,
+                                unsigned how_many_bits)
+{
+   signed c;
+	
+   assert(parser);
+   assert(how_many_bits);
+	
+   c = parser->cursor - how_many_bits;
+
+   while (c < 0)
+   {
+      c += parser->sizes[parser->cur_bitstream--] * CHAR_BIT;
+      assert(parser->cur_bitstream < parser->num_bitstreams);
+   }
+
+   parser->cursor = (unsigned)c;
+}