X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=bitstream.c;h=1139edc0d01dfe3668906f747809e0bfb055c18e;hp=e6360e6a92848db1ef41e7a57483c950140d84d6;hb=ab273892c54e29087d2a6b0d52de8081be1b905f;hpb=3231d60840731fa0197e765a5e0dfa707ec3746a

diff --git a/bitstream.c b/bitstream.c
index e6360e6a..1139edc0 100644
--- a/bitstream.c
+++ b/bitstream.c
@@ -83,29 +83,29 @@ static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
 		/* if code matches the prefix, it is in the table */
 		n -= n_prefix;
 		code_prefix2 = code >> n;
-		if (n > 0 && code_prefix2 == code_prefix) {
-			if (n <= table_nb_bits) {
-				/* no need to add another table */
-				j = (code << (table_nb_bits - n)) & (table_size - 1);
-				nb = 1 << (table_nb_bits - n);
-				for (k = 0; k < nb; k++) {
-					if (table[j][1] /* bits */ != 0) {
-						PARA_EMERG_LOG("detected incorrect code\n");
-						exit(EXIT_FAILURE);
-					}
-					table[j][1] = n;	//bits
-					table[j][0] = symbol;
-					j++;
+		if (n <= 0 || code_prefix2 != code_prefix)
+			continue;
+		if (n <= table_nb_bits) {
+			/* no need to add another table */
+			j = (code << (table_nb_bits - n)) & (table_size - 1);
+			nb = 1 << (table_nb_bits - n);
+			for (k = 0; k < nb; k++) {
+				if (table[j][1] /* bits */ != 0) {
+					PARA_EMERG_LOG("incorrect code\n");
+					exit(EXIT_FAILURE);
 				}
-			} else {
-				n -= table_nb_bits;
-				j = (code >> n) & ((1 << table_nb_bits) - 1);
-				/* compute table size */
-				n1 = -table[j][1];	//bits
-				if (n > n1)
-					n1 = n;
-				table[j][1] = -n1;	//bits
+				table[j][1] = n;	//bits
+				table[j][0] = symbol;
+				j++;
 			}
+		} else {
+			n -= table_nb_bits;
+			j = (code >> n) & ((1 << table_nb_bits) - 1);
+			/* compute table size */
+			n1 = -table[j][1];	//bits
+			if (n > n1)
+				n1 = n;
+			table[j][1] = -n1;	//bits
 		}
 	}
 
@@ -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.
  *
@@ -156,11 +157,51 @@ void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
 	vlc->table = NULL;
 	vlc->table_allocated = 0;
 	vlc->table_size = 0;
-	build_table(vlc, nb_bits, nb_codes, bits,
-		codes, codes_size, 0, 0);
+	build_table(vlc, nb_bits, nb_codes, bits, codes, codes_size, 0, 0);
 }
 
 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;
+}