hqx: Store shareable data in main decoder context

In preparation for multithreaded decoding.

libavcodec/hqx.h

@@ -22,6 +22,8 @@
 #define AVCODEC_HQX_H
 
 #include <stdint.h>
+
+#include "libavutil/frame.h"
 #include "libavutil/mem.h"
 #include "get_bits.h"
 #include "hqxdsp.h"
@@ -47,12 +49,23 @@ typedef struct HQXAC {
     const HQXLUT *lut;
 } HQXAC;
 
+struct HQXContext;
+
+typedef int (*mb_decode_func)(struct HQXContext *ctx, GetBitContext *gb, int x, int y);
+
 typedef struct HQXContext {
     HQXDSPContext hqxdsp;
 
+    AVFrame *pic;
+    mb_decode_func decode_func;
+
     int format, dcb, width, height;
     int interlaced;
 
+    uint8_t *src;
+    unsigned int data_size;
+    uint32_t slice_off[17];
+
     DECLARE_ALIGNED(16, int16_t, block)[16][64];
 
     VLC cbp_vlc;