Merge branch 't/libao'

[paraslash.git] / bitstream.c

diff --git a/bitstream.c b/bitstream.c
index dedcdead5bc77bb12880ec9342dc95a39e6cd615..1139edc0d01dfe3668906f747809e0bfb055c18e 100644 (file)
--- a/bitstream.c
+++ b/bitstream.c
@@ -132,10 +132,11 @@ static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
 /**
  * Build VLC decoding tables suitable for use with get_vlc().
  *
- * \param nb_bits Set the decoding table size (2^nb_bits)
- * entries. The bigger it is, the faster is the decoding. But
- * it should not be too big to save memory and L1 cache. '9'
- * is a good compromise.
+ * \param vlc The structure to be initialized.
+ *
+ * \param nb_bits Set the decoding table size (2^nb_bits) entries. The bigger
+ * it is, the faster is the decoding. But it should not be too big to save
+ * memory and L1 cache. '9' is a good compromise.
  *
  * \param nb_codes Number of vlcs codes.
  *
@@ -163,3 +164,44 @@ void free_vlc(struct vlc *vlc)
 {
        freep(&vlc->table);
 }
+
+/**
+ * Parse a vlc code.
+ *
+ * \param gbc The getbit context structure.
+ *
+ * \param table The vlc tables to use.
+ *
+ * \param bits The number of bits which will be read at once, must be
+ * identical to nb_bits in init_vlc().
+ *
+ * \param max_depth The number of times bits bits must be read to completely
+ * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
+ *
+ * \return The vlc code.
+ */
+int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
+               int max_depth)
+{
+       int n, idx, nb_bits, code;
+
+       idx = show_bits(gbc, bits);
+       code = table[idx][0];
+       n = table[idx][1];
+       if (max_depth > 1 && n < 0) {
+               skip_bits(gbc, bits);
+               nb_bits = -n;
+               idx = show_bits(gbc, nb_bits) + code;
+               code = table[idx][0];
+               n = table[idx][1];
+               if (max_depth > 2 && n < 0) {
+                       skip_bits(gbc, nb_bits);
+                       nb_bits = -n;
+                       idx = show_bits(gbc, nb_bits) + code;
+                       code = table[idx][0];
+                       n = table[idx][1];
+               }
+       }
+       skip_bits(gbc, n);
+       return code >= 0? code : -E_VLC;
+}