X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=bitstream.c;h=ddad67bb177211b3909f88d3be9dcb3d5c381238;hp=dedcdead5bc77bb12880ec9342dc95a39e6cd615;hb=bd10c0f46e0b7eadfb8c6d5cd45581cec253d775;hpb=d06e0fc014b8557556951a78ae4c07b5bba2052f

diff --git a/bitstream.c b/bitstream.c
index dedcdead..ddad67bb 100644
--- a/bitstream.c
+++ b/bitstream.c
@@ -27,6 +27,7 @@
 #include "wma.h"
 #include "bitstream.h"
 
+/** Read an 8, 16, or 32 bit entity from a VLC table. */
 #define GET_DATA(v, table, i, size) \
 {\
 	const uint8_t *ptr = (const uint8_t *)table + i * size; \
@@ -132,10 +133,11 @@ 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.
  *
@@ -159,7 +161,56 @@ void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
 	build_table(vlc, nb_bits, nb_codes, bits, codes, codes_size, 0, 0);
 }
 
+/**
+ * Deallocate all resources of a VLC table.
+ *
+ * \param vlc Pointer to an initialized vlc structure.
+ *
+ * The table given by \a vlc must have been initialized earlier via \ref
+ * init_vlc().
+ */
 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;
+}