bitstream: Move VLC reading functions into the vlc.h header
[ffmpeg.git] / libavcodec / vlc.h
index 4ade824..8ac5238 100644 (file)
@@ -21,6 +21,8 @@
 
 #include <stdint.h>
 
+#include "bitstream.h"
+
 #define VLC_TYPE int16_t
 
 typedef struct VLC {
@@ -62,4 +64,76 @@ void ff_free_vlc(VLC *vlc);
         init_vlc(vlc, bits, a, b, c, d, e, f, g, INIT_VLC_USE_NEW_STATIC); \
     } while (0)
 
+/* Return the LUT element for the given bitstream configuration. */
+static inline int set_idx(BitstreamContext *bc, int code, int *n, int *nb_bits,
+                          VLC_TYPE (*table)[2])
+{
+    unsigned idx;
+
+    *nb_bits = -*n;
+    idx = bitstream_peek(bc, *nb_bits) + code;
+    *n = table[idx][1];
+
+    return table[idx][0];
+}
+
+/**
+ * Parse a VLC code.
+ * @param bits      is the number of bits which will be read at once, must be
+ *                  identical to nb_bits in init_vlc()
+ * @param max_depth is the number of times bits bits must be read to completely
+ *                  read the longest VLC code
+ *                  = (max_vlc_length + bits - 1) / bits
+ * If the VLC code is invalid and max_depth = 1, then no bits will be removed.
+ * If the VLC code is invalid and max_depth > 1, then the number of bits removed
+ * is undefined. */
+static inline int bitstream_read_vlc(BitstreamContext *bc, VLC_TYPE (*table)[2],
+                                     int bits, int max_depth)
+{
+    int nb_bits;
+    unsigned idx = bitstream_peek(bc, bits);
+    int code = table[idx][0];
+    int n    = table[idx][1];
+
+    if (max_depth > 1 && n < 0) {
+        skip_remaining(bc, bits);
+        code = set_idx(bc, code, &n, &nb_bits, table);
+        if (max_depth > 2 && n < 0) {
+            skip_remaining(bc, nb_bits);
+            code = set_idx(bc, code, &n, &nb_bits, table);
+        }
+    }
+    skip_remaining(bc, n);
+
+    return code;
+}
+
+#define BITSTREAM_RL_VLC(level, run, bc, table, bits, max_depth) \
+    do {                                                         \
+        int n, nb_bits;                                          \
+        unsigned index = bitstream_peek(bc, bits);               \
+        level = table[index].level;                              \
+        n     = table[index].len;                                \
+                                                                 \
+        if (max_depth > 1 && n < 0) {                            \
+            bitstream_skip(bc, bits);                            \
+                                                                 \
+            nb_bits = -n;                                        \
+                                                                 \
+            index = bitstream_peek(bc, nb_bits) + level;         \
+            level = table[index].level;                          \
+            n     = table[index].len;                            \
+            if (max_depth > 2 && n < 0) {                        \
+                bitstream_skip(bc, nb_bits);                     \
+                nb_bits = -n;                                    \
+                                                                 \
+                index = bitstream_peek(bc, nb_bits) + level;     \
+                level = table[index].level;                      \
+                n     = table[index].len;                        \
+            }                                                    \
+        }                                                        \
+        run = table[index].run;                                  \
+        bitstream_skip(bc, n);                                   \
+    } while (0)
+
 #endif /* AVCODEC_VLC_H */