/*

  * Go2Webinar / Go2Meeting decoder

  * Copyright (c) 2012 Konstantin Shishkov

  * Copyright (c) 2013 Maxim Poliakovski

  *

  * This file is part of FFmpeg.

  *

  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *

  * FFmpeg is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**
  * @file

  * Go2Webinar / Go2Meeting decoder

  */
 

 #include <inttypes.h>

 #include <zlib.h>
 

 #include "libavutil/imgutils.h"

 #include "libavutil/intreadwrite.h"

 #include "avcodec.h"

 #include "blockdsp.h"

 #include "bytestream.h"

 #include "elsdec.h"

 #include "get_bits.h"

 #include "idctdsp.h"

 #include "internal.h"

 #include "jpegtables.h"

 #include "mjpeg.h"
 

 #define EPIC_PIX_STACK_SIZE 1024
 #define EPIC_PIX_STACK_MAX  (EPIC_PIX_STACK_SIZE - 1)
 

 enum ChunkType {

     DISPLAY_INFO = 0xC8,

     TILE_DATA,
     CURSOR_POS,
     CURSOR_SHAPE,
     CHUNK_CC,
     CHUNK_CD
 };
 
 enum Compression {
     COMPR_EPIC_J_B = 2,
     COMPR_KEMPF_J_B,
 };
 
 static const uint8_t luma_quant[64] = {
      8,  6,  5,  8, 12, 20, 26, 31,
      6,  6,  7, 10, 13, 29, 30, 28,
      7,  7,  8, 12, 20, 29, 35, 28,
      7,  9, 11, 15, 26, 44, 40, 31,
      9, 11, 19, 28, 34, 55, 52, 39,
     12, 18, 28, 32, 41, 52, 57, 46,
     25, 32, 39, 44, 52, 61, 60, 51,
     36, 46, 48, 49, 56, 50, 52, 50
 };
 
 static const uint8_t chroma_quant[64] = {
      9,  9, 12, 24, 50, 50, 50, 50,
      9, 11, 13, 33, 50, 50, 50, 50,
     12, 13, 28, 50, 50, 50, 50, 50,
     24, 33, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
 };
 

 typedef struct ePICPixListElem {
     struct ePICPixListElem *next;
     uint32_t               pixel;
     uint8_t                rung;
 } ePICPixListElem;
 
 typedef struct ePICPixHashElem {
     uint32_t                pix_id;
     struct ePICPixListElem  *list;
 } ePICPixHashElem;
 
 #define EPIC_HASH_SIZE 256
 typedef struct ePICPixHash {
     ePICPixHashElem *bucket[EPIC_HASH_SIZE];
     int              bucket_size[EPIC_HASH_SIZE];
     int              bucket_fill[EPIC_HASH_SIZE];
 } ePICPixHash;
 
 typedef struct ePICContext {
     ElsDecCtx        els_ctx;
     int              next_run_pos;
     ElsUnsignedRung  unsigned_rung;
     uint8_t          W_flag_rung;
     uint8_t          N_flag_rung;
     uint8_t          W_ctx_rung[256];
     uint8_t          N_ctx_rung[512];
     uint8_t          nw_pred_rung[256];
     uint8_t          ne_pred_rung[256];
     uint8_t          prev_row_rung[14];
     uint8_t          runlen_zeroes[14];
     uint8_t          runlen_one;
     int              stack_pos;
     uint32_t         stack[EPIC_PIX_STACK_SIZE];
     ePICPixHash      hash;
 } ePICContext;
 

 typedef struct JPGContext {

     BlockDSPContext bdsp;

     IDCTDSPContext idsp;

     ScanTable  scantable;
 
     VLC        dc_vlc[2], ac_vlc[2];
     int        prev_dc[3];

     DECLARE_ALIGNED(32, int16_t, block)[6][64];

 
     uint8_t    *buf;
 } JPGContext;
 
 typedef struct G2MContext {

     ePICContext ec;

     JPGContext jc;

     int        version;
 
     int        compression;
     int        width, height, bpp;

     int        orig_width, orig_height;

     int        tile_width, tile_height;
     int        tiles_x, tiles_y, tile_x, tile_y;
 
     int        got_header;
 
     uint8_t    *framebuf;
     int        framebuf_stride, old_width, old_height;
 

     uint8_t    *synth_tile, *jpeg_tile, *epic_buf, *epic_buf_base;
     int        tile_stride, epic_buf_stride, old_tile_w, old_tile_h;
     int        swapuv;

 
     uint8_t    *kempf_buf, *kempf_flags;
 
     uint8_t    *cursor;
     int        cursor_stride;
     int        cursor_fmt;
     int        cursor_w, cursor_h, cursor_x, cursor_y;
     int        cursor_hot_x, cursor_hot_y;
 } G2MContext;
 
 static av_cold int build_vlc(VLC *vlc, const uint8_t *bits_table,
                              const uint8_t *val_table, int nb_codes,
                              int is_ac)
 {
     uint8_t  huff_size[256] = { 0 };
     uint16_t huff_code[256];
     uint16_t huff_sym[256];
     int i;
 
     ff_mjpeg_build_huffman_codes(huff_size, huff_code, bits_table, val_table);
 
     for (i = 0; i < 256; i++)
         huff_sym[i] = i + 16 * is_ac;
 
     if (is_ac)
         huff_sym[0] = 16 * 256;
 
     return ff_init_vlc_sparse(vlc, 9, nb_codes, huff_size, 1, 1,
                               huff_code, 2, 2, huff_sym, 2, 2, 0);
 }
 
 static av_cold int jpg_init(AVCodecContext *avctx, JPGContext *c)
 {
     int ret;
 
     ret = build_vlc(&c->dc_vlc[0], avpriv_mjpeg_bits_dc_luminance,
                     avpriv_mjpeg_val_dc, 12, 0);
     if (ret)
         return ret;
     ret = build_vlc(&c->dc_vlc[1], avpriv_mjpeg_bits_dc_chrominance,
                     avpriv_mjpeg_val_dc, 12, 0);
     if (ret)
         return ret;
     ret = build_vlc(&c->ac_vlc[0], avpriv_mjpeg_bits_ac_luminance,
                     avpriv_mjpeg_val_ac_luminance, 251, 1);
     if (ret)
         return ret;
     ret = build_vlc(&c->ac_vlc[1], avpriv_mjpeg_bits_ac_chrominance,
                     avpriv_mjpeg_val_ac_chrominance, 251, 1);
     if (ret)
         return ret;
 

     ff_blockdsp_init(&c->bdsp, avctx);

     ff_idctdsp_init(&c->idsp, avctx);
     ff_init_scantable(c->idsp.idct_permutation, &c->scantable,

                       ff_zigzag_direct);
 
     return 0;
 }
 
 static av_cold void jpg_free_context(JPGContext *ctx)
 {
     int i;
 
     for (i = 0; i < 2; i++) {
         ff_free_vlc(&ctx->dc_vlc[i]);
         ff_free_vlc(&ctx->ac_vlc[i]);
     }
 
     av_freep(&ctx->buf);
 }
 
 static void jpg_unescape(const uint8_t *src, int src_size,
                          uint8_t *dst, int *dst_size)
 {
     const uint8_t *src_end = src + src_size;
     uint8_t *dst_start = dst;
 
     while (src < src_end) {
         uint8_t x = *src++;
 
         *dst++ = x;
 
         if (x == 0xFF && !*src)
             src++;
     }
     *dst_size = dst - dst_start;
 }
 
 static int jpg_decode_block(JPGContext *c, GetBitContext *gb,
                             int plane, int16_t *block)
 {
     int dc, val, pos;
     const int is_chroma = !!plane;
     const uint8_t *qmat = is_chroma ? chroma_quant : luma_quant;
 

     c->bdsp.clear_block(block);

     dc = get_vlc2(gb, c->dc_vlc[is_chroma].table, 9, 3);
     if (dc < 0)
         return AVERROR_INVALIDDATA;
     if (dc)
         dc = get_xbits(gb, dc);

     dc                = dc * qmat[0] + c->prev_dc[plane];
     block[0]          = dc;

     c->prev_dc[plane] = dc;
 
     pos = 0;
     while (pos < 63) {
         val = get_vlc2(gb, c->ac_vlc[is_chroma].table, 9, 3);
         if (val < 0)
             return AVERROR_INVALIDDATA;
         pos += val >> 4;
         val &= 0xF;
         if (pos > 63)
             return val ? AVERROR_INVALIDDATA : 0;
         if (val) {
             int nbits = val;
 

             val                                 = get_xbits(gb, nbits);
             val                                *= qmat[ff_zigzag_direct[pos]];

             block[c->scantable.permutated[pos]] = val;
         }
     }
     return 0;
 }
 

 static inline void yuv2rgb(uint8_t *out, int ridx, int Y, int U, int V)

 {

     out[ridx]     = av_clip_uint8(Y +              (91881 * V + 32768 >> 16));
     out[1]        = av_clip_uint8(Y + (-22554 * U - 46802 * V + 32768 >> 16));
     out[2 - ridx] = av_clip_uint8(Y + (116130 * U             + 32768 >> 16));

 }
 
 static int jpg_decode_data(JPGContext *c, int width, int height,
                            const uint8_t *src, int src_size,
                            uint8_t *dst, int dst_stride,
                            const uint8_t *mask, int mask_stride, int num_mbs,
                            int swapuv)
 {
     GetBitContext gb;
     int mb_w, mb_h, mb_x, mb_y, i, j;
     int bx, by;
     int unesc_size;
     int ret;

     const int ridx = swapuv ? 2 : 0;

     if ((ret = av_reallocp(&c->buf,

                            src_size + AV_INPUT_BUFFER_PADDING_SIZE)) < 0)

         return ret;

     jpg_unescape(src, src_size, c->buf, &unesc_size);

     memset(c->buf + unesc_size, 0, AV_INPUT_BUFFER_PADDING_SIZE);

     if((ret = init_get_bits8(&gb, c->buf, unesc_size)) < 0)
         return ret;

 
     width = FFALIGN(width, 16);
     mb_w  =  width        >> 4;
     mb_h  = (height + 15) >> 4;
 
     if (!num_mbs)

         num_mbs = mb_w * mb_h * 4;

 
     for (i = 0; i < 3; i++)
         c->prev_dc[i] = 1024;

     bx =
     by = 0;

     c->bdsp.clear_blocks(c->block[0]);

     for (mb_y = 0; mb_y < mb_h; mb_y++) {
         for (mb_x = 0; mb_x < mb_w; mb_x++) {

             if (mask && !mask[mb_x * 2] && !mask[mb_x * 2 + 1] &&
                 !mask[mb_x * 2 +     mask_stride] &&
                 !mask[mb_x * 2 + 1 + mask_stride]) {

                 bx += 16;
                 continue;
             }
             for (j = 0; j < 2; j++) {
                 for (i = 0; i < 2; i++) {

                     if (mask && !mask[mb_x * 2 + i + j * mask_stride])
                         continue;
                     num_mbs--;

                     if ((ret = jpg_decode_block(c, &gb, 0,
                                                 c->block[i + j * 2])) != 0)
                         return ret;

                     c->idsp.idct(c->block[i + j * 2]);

                 }
             }
             for (i = 1; i < 3; i++) {
                 if ((ret = jpg_decode_block(c, &gb, i, c->block[i + 3])) != 0)
                     return ret;

                 c->idsp.idct(c->block[i + 3]);

             }
 
             for (j = 0; j < 16; j++) {
                 uint8_t *out = dst + bx * 3 + (by + j) * dst_stride;
                 for (i = 0; i < 16; i++) {
                     int Y, U, V;
 
                     Y = c->block[(j >> 3) * 2 + (i >> 3)][(i & 7) + (j & 7) * 8];

                     U = c->block[4][(i >> 1) + (j >> 1) * 8] - 128;
                     V = c->block[5][(i >> 1) + (j >> 1) * 8] - 128;
                     yuv2rgb(out + i * 3, ridx, Y, U, V);

                 }
             }
 

             if (!num_mbs)

                 return 0;
             bx += 16;
         }
         bx  = 0;
         by += 16;
         if (mask)

             mask += mask_stride * 2;

     }
 
     return 0;
 }
 

 #define LOAD_NEIGHBOURS(x)      \
     W   = curr_row[(x)   - 1];  \
     N   = above_row[(x)];       \
     WW  = curr_row[(x)   - 2];  \
     NW  = above_row[(x)  - 1];  \
     NE  = above_row[(x)  + 1];  \
     NN  = above2_row[(x)];      \
     NNW = above2_row[(x) - 1];  \
     NWW = above_row[(x)  - 2];  \
     NNE = above2_row[(x) + 1]
 
 #define UPDATE_NEIGHBOURS(x)    \
     NNW = NN;                   \
     NN  = NNE;                  \
     NWW = NW;                   \
     NW  = N;                    \
     N   = NE;                   \
     NE  = above_row[(x)  + 1];  \
     NNE = above2_row[(x) + 1]
 
 #define R_shift 16
 #define G_shift  8
 #define B_shift  0
 
 /* improved djb2 hash from http://www.cse.yorku.ca/~oz/hash.html */
 static int djb2_hash(uint32_t key)
 {

     uint32_t h = 5381;

 
     h = (h * 33) ^ ((key >> 24) & 0xFF); // xxx: probably not needed at all
     h = (h * 33) ^ ((key >> 16) & 0xFF);
     h = (h * 33) ^ ((key >>  8) & 0xFF);
     h = (h * 33) ^  (key        & 0xFF);
 
     return h & (EPIC_HASH_SIZE - 1);
 }
 
 static void epic_hash_init(ePICPixHash *hash)
 {
     memset(hash, 0, sizeof(*hash));
 }
 
 static ePICPixHashElem *epic_hash_find(const ePICPixHash *hash, uint32_t key)
 {
     int i, idx = djb2_hash(key);
     ePICPixHashElem *bucket = hash->bucket[idx];
 
     for (i = 0; i < hash->bucket_fill[idx]; i++)
         if (bucket[i].pix_id == key)
             return &bucket[i];
 
     return NULL;
 }
 
 static ePICPixHashElem *epic_hash_add(ePICPixHash *hash, uint32_t key)
 {
     ePICPixHashElem *bucket, *ret;
     int idx = djb2_hash(key);
 
     if (hash->bucket_size[idx] > INT_MAX / sizeof(**hash->bucket))
         return NULL;
 
     if (!(hash->bucket_fill[idx] < hash->bucket_size[idx])) {
         int new_size = hash->bucket_size[idx] + 16;
         bucket = av_realloc(hash->bucket[idx], new_size * sizeof(*bucket));
         if (!bucket)
             return NULL;
         hash->bucket[idx]      = bucket;
         hash->bucket_size[idx] = new_size;
     }
 
     ret = &hash->bucket[idx][hash->bucket_fill[idx]++];
     memset(ret, 0, sizeof(*ret));
     ret->pix_id = key;
     return ret;
 }
 
 static int epic_add_pixel_to_cache(ePICPixHash *hash, uint32_t key, uint32_t pix)
 {
     ePICPixListElem *new_elem;
     ePICPixHashElem *hash_elem = epic_hash_find(hash, key);
 
     if (!hash_elem) {
         if (!(hash_elem = epic_hash_add(hash, key)))
             return AVERROR(ENOMEM);
     }
 
     new_elem = av_mallocz(sizeof(*new_elem));
     if (!new_elem)
         return AVERROR(ENOMEM);
 
     new_elem->pixel = pix;
     new_elem->next  = hash_elem->list;
     hash_elem->list = new_elem;
 
     return 0;
 }
 
 static inline int epic_cache_entries_for_pixel(const ePICPixHash *hash,
                                                uint32_t pix)
 {
     ePICPixHashElem *hash_elem = epic_hash_find(hash, pix);
 
     if (hash_elem != NULL && hash_elem->list != NULL)
         return 1;
 
     return 0;
 }
 
 static void epic_free_pixel_cache(ePICPixHash *hash)
 {
     int i, j;
 
     for (i = 0; i < EPIC_HASH_SIZE; i++) {
         for (j = 0; j < hash->bucket_fill[i]; j++) {
             ePICPixListElem *list_elem = hash->bucket[i][j].list;
             while (list_elem) {
                 ePICPixListElem *tmp = list_elem->next;
                 av_free(list_elem);
                 list_elem = tmp;
             }
         }
         av_freep(&hash->bucket[i]);
         hash->bucket_size[i] =
         hash->bucket_fill[i] = 0;
     }
 }
 
 static inline int is_pixel_on_stack(const ePICContext *dc, uint32_t pix)
 {
     int i;
 
     for (i = 0; i < dc->stack_pos; i++)
         if (dc->stack[i] == pix)
             break;
 
     return i != dc->stack_pos;
 }
 
 #define TOSIGNED(val) (((val) >> 1) ^ -((val) & 1))
 
 static inline int epic_decode_component_pred(ePICContext *dc,
                                              int N, int W, int NW)
 {
     unsigned delta = ff_els_decode_unsigned(&dc->els_ctx, &dc->unsigned_rung);
     return mid_pred(N, N + W - NW, W) - TOSIGNED(delta);
 }
 
 static uint32_t epic_decode_pixel_pred(ePICContext *dc, int x, int y,
                                        const uint32_t *curr_row,
                                        const uint32_t *above_row)
 {
     uint32_t N, W, NW, pred;
     unsigned delta;
     int GN, GW, GNW, R, G, B;
 
     if (x && y) {
         W  = curr_row[x  - 1];
         N  = above_row[x];
         NW = above_row[x - 1];
 
         GN  = (N  >> G_shift) & 0xFF;
         GW  = (W  >> G_shift) & 0xFF;
         GNW = (NW >> G_shift) & 0xFF;
 
         G = epic_decode_component_pred(dc, GN, GW, GNW);
 
         R = G + epic_decode_component_pred(dc,
                                            ((N  >> R_shift) & 0xFF) - GN,
                                            ((W  >> R_shift) & 0xFF) - GW,
                                            ((NW >> R_shift) & 0xFF) - GNW);
 
         B = G + epic_decode_component_pred(dc,
                                            ((N  >> B_shift) & 0xFF) - GN,
                                            ((W  >> B_shift) & 0xFF) - GW,
                                            ((NW >> B_shift) & 0xFF) - GNW);
     } else {
         if (x)
             pred = curr_row[x - 1];
         else
             pred = above_row[x];
 
         delta = ff_els_decode_unsigned(&dc->els_ctx, &dc->unsigned_rung);
         R     = ((pred >> R_shift) & 0xFF) - TOSIGNED(delta);
 
         delta = ff_els_decode_unsigned(&dc->els_ctx, &dc->unsigned_rung);
         G     = ((pred >> G_shift) & 0xFF) - TOSIGNED(delta);
 
         delta = ff_els_decode_unsigned(&dc->els_ctx, &dc->unsigned_rung);
         B     = ((pred >> B_shift) & 0xFF) - TOSIGNED(delta);
     }
 

     if (R<0 || G<0 || B<0) {
         av_log(NULL, AV_LOG_ERROR, "RGB %d %d %d is out of range\n", R, G, B);
         return 0;
     }
 

     return (R << R_shift) | (G << G_shift) | (B << B_shift);
 }
 
 static int epic_predict_pixel(ePICContext *dc, uint8_t *rung,
                               uint32_t *pPix, uint32_t pix)
 {
     if (!ff_els_decode_bit(&dc->els_ctx, rung)) {
         *pPix = pix;
         return 1;
     }
     dc->stack[dc->stack_pos++ & EPIC_PIX_STACK_MAX] = pix;
     return 0;
 }
 
 static int epic_handle_edges(ePICContext *dc, int x, int y,
                              const uint32_t *curr_row,
                              const uint32_t *above_row, uint32_t *pPix)
 {
     uint32_t pix;
 
     if (!x && !y) { /* special case: top-left pixel */
         /* the top-left pixel is coded independently with 3 unsigned numbers */
         *pPix = (ff_els_decode_unsigned(&dc->els_ctx, &dc->unsigned_rung) << R_shift) |
                 (ff_els_decode_unsigned(&dc->els_ctx, &dc->unsigned_rung) << G_shift) |
                 (ff_els_decode_unsigned(&dc->els_ctx, &dc->unsigned_rung) << B_shift);
         return 1;
     }
 
     if (x) { /* predict from W first */
         pix = curr_row[x - 1];
         if (epic_predict_pixel(dc, &dc->W_flag_rung, pPix, pix))
             return 1;
     }
 
     if (y) { /* then try to predict from N */
         pix = above_row[x];
         if (!dc->stack_pos || dc->stack[0] != pix) {
             if (epic_predict_pixel(dc, &dc->N_flag_rung, pPix, pix))
                 return 1;
         }
     }
 
     return 0;
 }
 
 static int epic_decode_run_length(ePICContext *dc, int x, int y, int tile_width,
                                   const uint32_t *curr_row,
                                   const uint32_t *above_row,
                                   const uint32_t *above2_row,
                                   uint32_t *pPix, int *pRun)
 {
     int idx, got_pixel = 0, WWneW, old_WWneW = 0;
     uint32_t W, WW, N, NN, NW, NE, NWW, NNW, NNE;
 
     *pRun = 0;
 
     LOAD_NEIGHBOURS(x);
 
     if (dc->next_run_pos == x) {
         /* can't reuse W for the new pixel in this case */
         WWneW = 1;
     } else {
         idx = (WW  != W)  << 7 |
               (NW  != W)  << 6 |
               (N   != NE) << 5 |
               (NW  != N)  << 4 |
               (NWW != NW) << 3 |
               (NNE != NE) << 2 |
               (NN  != N)  << 1 |
               (NNW != NW);
         WWneW = ff_els_decode_bit(&dc->els_ctx, &dc->W_ctx_rung[idx]);

         if (WWneW < 0)
             return WWneW;

     }
 
     if (WWneW)
         dc->stack[dc->stack_pos++ & EPIC_PIX_STACK_MAX] = W;
     else {
         *pPix     = W;
         got_pixel = 1;
     }
 
     do {
         int NWneW = 1;
         if (got_pixel) // pixel value already known (derived from either W or N)
             NWneW = *pPix != N;
         else { // pixel value is unknown and will be decoded later
             NWneW = *pRun ? NWneW : NW != W;
 
             /* TODO: RFC this mess! */
             switch (((NW != N) << 2) | (NWneW << 1) | WWneW) {
             case 0:
                 break; // do nothing here
             case 3:
             case 5:
             case 6:
             case 7:
                 if (!is_pixel_on_stack(dc, N)) {
                     idx = WWneW       << 8 |
                           (*pRun ? old_WWneW : WW != W) << 7 |
                           NWneW       << 6 |
                           (N   != NE) << 5 |
                           (NW  != N)  << 4 |
                           (NWW != NW) << 3 |
                           (NNE != NE) << 2 |
                           (NN  != N)  << 1 |
                           (NNW != NW);
                     if (!ff_els_decode_bit(&dc->els_ctx, &dc->N_ctx_rung[idx])) {
                         NWneW = 0;
                         *pPix = N;
                         got_pixel = 1;
                         break;
                     }
                 }
                 /* fall through */
             default:
                 NWneW = 1;
                 old_WWneW = WWneW;
                 if (!is_pixel_on_stack(dc, N))
                     dc->stack[dc->stack_pos++ & EPIC_PIX_STACK_MAX] = N;
             }
         }
 
         (*pRun)++;
         if (x + *pRun >= tile_width - 1)
             break;
 
         UPDATE_NEIGHBOURS(x + *pRun);
 
         if (!NWneW && NW == N && N == NE) {
             int pos, run, rle;
             int start_pos = x + *pRun;
 
             /* scan for a run of pix in the line above */
             uint32_t pix = above_row[start_pos + 1];
             for (pos = start_pos + 2; pos < tile_width; pos++)
                 if (!(above_row[pos] == pix))
                     break;
             run = pos - start_pos - 1;

             idx = av_ceil_log2(run);

             if (ff_els_decode_bit(&dc->els_ctx, &dc->prev_row_rung[idx]))
                 *pRun += run;
             else {
                 int flag;
                 /* run-length is coded as plain binary number of idx - 1 bits */
                 for (pos = idx - 1, rle = 0, flag = 0; pos >= 0; pos--) {
                     if ((1 << pos) + rle < run &&
                         ff_els_decode_bit(&dc->els_ctx,
                                           flag ? &dc->runlen_one
                                                : &dc->runlen_zeroes[pos])) {
                         flag = 1;
                         rle |= 1 << pos;
                     }
                 }
                 *pRun += rle;
                 break; // return immediately
             }
             if (x + *pRun >= tile_width - 1)
                 break;
 
             LOAD_NEIGHBOURS(x + *pRun);
             WWneW = 0;
             NWneW = 0;
         }
 
         idx = WWneW       << 7 |
               NWneW       << 6 |
               (N   != NE) << 5 |
               (NW  != N)  << 4 |
               (NWW != NW) << 3 |
               (NNE != NE) << 2 |
               (NN  != N)  << 1 |
               (NNW != NW);
         WWneW = ff_els_decode_bit(&dc->els_ctx, &dc->W_ctx_rung[idx]);
     } while (!WWneW);
 
     dc->next_run_pos = x + *pRun;
     return got_pixel;
 }
 
 static int epic_predict_pixel2(ePICContext *dc, uint8_t *rung,
                                uint32_t *pPix, uint32_t pix)
 {
     if (ff_els_decode_bit(&dc->els_ctx, rung)) {
         *pPix = pix;
         return 1;
     }
     dc->stack[dc->stack_pos++ & EPIC_PIX_STACK_MAX] = pix;
     return 0;
 }
 
 static int epic_predict_from_NW_NE(ePICContext *dc, int x, int y, int run,
                                    int tile_width, const uint32_t *curr_row,
                                    const uint32_t *above_row, uint32_t *pPix)
 {
     int pos;
 
     /* try to reuse the NW pixel first */
     if (x && y) {
         uint32_t NW = above_row[x - 1];
         if (NW != curr_row[x - 1] && NW != above_row[x] && !is_pixel_on_stack(dc, NW)) {
             if (epic_predict_pixel2(dc, &dc->nw_pred_rung[NW & 0xFF], pPix, NW))
                 return 1;
         }
     }
 
     /* try to reuse the NE[x + run, y] pixel */
     pos = x + run - 1;
     if (pos < tile_width - 1 && y) {
         uint32_t NE = above_row[pos + 1];
         if (NE != above_row[pos] && !is_pixel_on_stack(dc, NE)) {
             if (epic_predict_pixel2(dc, &dc->ne_pred_rung[NE & 0xFF], pPix, NE))
                 return 1;
         }
     }
 
     return 0;
 }
 
 static int epic_decode_from_cache(ePICContext *dc, uint32_t W, uint32_t *pPix)
 {
     ePICPixListElem *list, *prev = NULL;
     ePICPixHashElem *hash_elem = epic_hash_find(&dc->hash, W);
 
     if (!hash_elem || !hash_elem->list)
         return 0;
 
     list = hash_elem->list;
     while (list) {
         if (!is_pixel_on_stack(dc, list->pixel)) {
             if (ff_els_decode_bit(&dc->els_ctx, &list->rung)) {
                 *pPix = list->pixel;
                 if (list != hash_elem->list) {
                     prev->next      = list->next;
                     list->next      = hash_elem->list;
                     hash_elem->list = list;
                 }
                 return 1;
             }
             dc->stack[dc->stack_pos++ & EPIC_PIX_STACK_MAX] = list->pixel;
         }
         prev = list;
         list = list->next;
     }
 
     return 0;
 }
 
 static int epic_decode_tile(ePICContext *dc, uint8_t *out, int tile_height,
                             int tile_width, int stride)
 {
     int x, y;
     uint32_t pix;
     uint32_t *curr_row = NULL, *above_row = NULL, *above2_row;
 
     for (y = 0; y < tile_height; y++, out += stride) {
         above2_row = above_row;
         above_row  = curr_row;
         curr_row   = (uint32_t *) out;
 
         for (x = 0, dc->next_run_pos = 0; x < tile_width;) {
             if (dc->els_ctx.err)
                 return AVERROR_INVALIDDATA; // bail out in the case of ELS overflow
 
             pix = curr_row[x - 1]; // get W pixel
 
             if (y >= 1 && x >= 2 &&
                 pix != curr_row[x - 2]  && pix != above_row[x - 1] &&
                 pix != above_row[x - 2] && pix != above_row[x] &&
                 !epic_cache_entries_for_pixel(&dc->hash, pix)) {
                 curr_row[x] = epic_decode_pixel_pred(dc, x, y, curr_row, above_row);
                 x++;
             } else {
                 int got_pixel, run;
                 dc->stack_pos = 0; // empty stack
 
                 if (y < 2 || x < 2 || x == tile_width - 1) {
                     run       = 1;
                     got_pixel = epic_handle_edges(dc, x, y, curr_row, above_row, &pix);

                 } else {

                     got_pixel = epic_decode_run_length(dc, x, y, tile_width,
                                                        curr_row, above_row,
                                                        above2_row, &pix, &run);

                     if (got_pixel < 0)
                         return got_pixel;
                 }

 
                 if (!got_pixel && !epic_predict_from_NW_NE(dc, x, y, run,
                                                            tile_width, curr_row,
                                                            above_row, &pix)) {
                     uint32_t ref_pix = curr_row[x - 1];
                     if (!x || !epic_decode_from_cache(dc, ref_pix, &pix)) {
                         pix = epic_decode_pixel_pred(dc, x, y, curr_row, above_row);
                         if (x) {
                             int ret = epic_add_pixel_to_cache(&dc->hash,
                                                               ref_pix,
                                                               pix);
                             if (ret)
                                 return ret;
                         }
                     }
                 }
                 for (; run > 0; x++, run--)
                     curr_row[x] = pix;
             }
         }
     }
 
     return 0;
 }
 
 static int epic_jb_decode_tile(G2MContext *c, int tile_x, int tile_y,
                                const uint8_t *src, size_t src_size,
                                AVCodecContext *avctx)
 {
     uint8_t prefix, mask = 0x80;
     int extrabytes, tile_width, tile_height, awidth, aheight;
     size_t els_dsize;
     uint8_t *dst;
 
     if (!src_size)
         return 0;
 
     /* get data size of the ELS partition as unsigned variable-length integer */
     prefix = *src++;
     src_size--;
     for (extrabytes = 0; (prefix & mask) && (extrabytes < 7); extrabytes++)
         mask >>= 1;
     if (extrabytes > 3 || src_size < extrabytes) {
         av_log(avctx, AV_LOG_ERROR, "ePIC: invalid data size VLI\n");
         return AVERROR_INVALIDDATA;
     }
 
     els_dsize = prefix & ((0x80 >> extrabytes) - 1); // mask out the length prefix
     while (extrabytes-- > 0) {
         els_dsize = (els_dsize << 8) | *src++;
         src_size--;
     }
 
     if (src_size < els_dsize) {

         av_log(avctx, AV_LOG_ERROR, "ePIC: data too short, needed %"SIZE_SPECIFIER", got %"SIZE_SPECIFIER"\n",

                els_dsize, src_size);
         return AVERROR_INVALIDDATA;
     }
 
     tile_width  = FFMIN(c->width  - tile_x * c->tile_width,  c->tile_width);
     tile_height = FFMIN(c->height - tile_y * c->tile_height, c->tile_height);
     awidth      = FFALIGN(tile_width,  16);
     aheight     = FFALIGN(tile_height, 16);
 
     if (els_dsize) {
         int ret, i, j, k;
         uint8_t tr_r, tr_g, tr_b, *buf;
         uint32_t *in;
         /* ELS decoder initializations */
         memset(&c->ec, 0, sizeof(c->ec));
         ff_els_decoder_init(&c->ec.els_ctx, src, els_dsize);
         epic_hash_init(&c->ec.hash);
 
         /* decode transparent pixel value */
         tr_r = ff_els_decode_unsigned(&c->ec.els_ctx, &c->ec.unsigned_rung);
         tr_g = ff_els_decode_unsigned(&c->ec.els_ctx, &c->ec.unsigned_rung);
         tr_b = ff_els_decode_unsigned(&c->ec.els_ctx, &c->ec.unsigned_rung);
         if (c->ec.els_ctx.err != 0) {
             av_log(avctx, AV_LOG_ERROR,
                    "ePIC: couldn't decode transparency pixel!\n");
             return AVERROR_INVALIDDATA;
         }
 
         ret = epic_decode_tile(&c->ec, c->epic_buf, tile_height, tile_width,
                                c->epic_buf_stride);
 
         epic_free_pixel_cache(&c->ec.hash);
         ff_els_decoder_uninit(&c->ec.unsigned_rung);
 
         if (ret) {
             av_log(avctx, AV_LOG_ERROR,
                    "ePIC: tile decoding failed, frame=%d, tile_x=%d, tile_y=%d\n",
                    avctx->frame_number, tile_x, tile_y);
             return AVERROR_INVALIDDATA;
         }
 
         buf = c->epic_buf;
         dst = c->framebuf + tile_x * c->tile_width * 3 +
               tile_y * c->tile_height * c->framebuf_stride;
 
         for (j = 0; j < tile_height; j++) {
             uint8_t *out = dst;
             in  = (uint32_t *) buf;
             for (i = 0; i < tile_width; i++) {
                 out[0] = (in[i] >> R_shift) & 0xFF;
                 out[1] = (in[i] >> G_shift) & 0xFF;
                 out[2] = (in[i] >> B_shift) & 0xFF;
                 out   += 3;
             }
             buf += c->epic_buf_stride;
             dst += c->framebuf_stride;
         }
 
         if (src_size > els_dsize) {
             uint8_t *jpg;
             uint32_t tr;
             int bstride = FFALIGN(tile_width, 16) >> 3;
             int nblocks = 0;
             int estride = c->epic_buf_stride >> 2;
 
             src      += els_dsize;
             src_size -= els_dsize;
 
             in = (uint32_t *) c->epic_buf;
             tr = (tr_r << R_shift) | (tr_g << G_shift) | (tr_b << B_shift);
 
             memset(c->kempf_flags, 0,
                    (aheight >> 3) * bstride * sizeof(*c->kempf_flags));
             for (j = 0; j < tile_height; j += 8) {
                 for (i = 0; i < tile_width; i += 8) {
                     c->kempf_flags[(i >> 3) + (j >> 3) * bstride] = 0;
                     for (k = 0; k < 8 * 8; k++) {
                         if (in[i + (k & 7) + (k >> 3) * estride] == tr) {
                             c->kempf_flags[(i >> 3) + (j >> 3) * bstride] = 1;
                             nblocks++;
                             break;
                         }
                     }
                 }
                 in += 8 * estride;
             }
 
             memset(c->jpeg_tile, 0, c->tile_stride * aheight);
             jpg_decode_data(&c->jc, awidth, aheight, src, src_size,
                             c->jpeg_tile, c->tile_stride,
                             c->kempf_flags, bstride, nblocks, c->swapuv);
 
             in  = (uint32_t *) c->epic_buf;
             dst = c->framebuf + tile_x * c->tile_width * 3 +
                   tile_y * c->tile_height * c->framebuf_stride;
             jpg = c->jpeg_tile;
             for (j = 0; j < tile_height; j++) {
                 for (i = 0; i < tile_width; i++)
                     if (in[i] == tr)
                         memcpy(dst + i * 3, jpg + i * 3, 3);
                 in  += c->epic_buf_stride >> 2;
                 dst += c->framebuf_stride;
                 jpg += c->tile_stride;
             }
         }
     } else {
         dst = c->framebuf + tile_x * c->tile_width * 3 +
               tile_y * c->tile_height * c->framebuf_stride;
         return jpg_decode_data(&c->jc, tile_width, tile_height, src, src_size,
                                dst, c->framebuf_stride, NULL, 0, 0, c->swapuv);
     }
 
     return 0;
 }
 

 static int kempf_restore_buf(const uint8_t *src, int len,

                               uint8_t *dst, int stride,
                               const uint8_t *jpeg_tile, int tile_stride,
                               int width, int height,
                               const uint8_t *pal, int npal, int tidx)
 {
     GetBitContext gb;
     int i, j, nb, col;

     int ret;

     int align_width = FFALIGN(width, 16);

     if ((ret = init_get_bits8(&gb, src, len)) < 0)
         return ret;

 
     if (npal <= 2)       nb = 1;
     else if (npal <= 4)  nb = 2;
     else if (npal <= 16) nb = 4;
     else                 nb = 8;
 
     for (j = 0; j < height; j++, dst += stride, jpeg_tile += tile_stride) {
         if (get_bits(&gb, 8))
             continue;
         for (i = 0; i < width; i++) {
             col = get_bits(&gb, nb);
             if (col != tidx)
                 memcpy(dst + i * 3, pal + col * 3, 3);
             else
                 memcpy(dst + i * 3, jpeg_tile + i * 3, 3);
         }

         skip_bits_long(&gb, nb * (align_width - width));

     }

 
     return 0;

 }
 
 static int kempf_decode_tile(G2MContext *c, int tile_x, int tile_y,
                              const uint8_t *src, int src_size)
 {
     int width, height;
     int hdr, zsize, npal, tidx = -1, ret;
     int i, j;
     const uint8_t *src_end = src + src_size;
     uint8_t pal[768], transp[3];
     uLongf dlen = (c->tile_width + 1) * c->tile_height;
     int sub_type;
     int nblocks, cblocks, bstride;
     int bits, bitbuf, coded;
     uint8_t *dst = c->framebuf + tile_x * c->tile_width * 3 +
                    tile_y * c->tile_height * c->framebuf_stride;
 
     if (src_size < 2)
         return AVERROR_INVALIDDATA;
 
     width  = FFMIN(c->width  - tile_x * c->tile_width,  c->tile_width);
     height = FFMIN(c->height - tile_y * c->tile_height, c->tile_height);
 

     hdr      = *src++;

     sub_type = hdr >> 5;
     if (sub_type == 0) {
         int j;
         memcpy(transp, src, 3);
         src += 3;
         for (j = 0; j < height; j++, dst += c->framebuf_stride)
             for (i = 0; i < width; i++)
                 memcpy(dst + i * 3, transp, 3);
         return 0;
     } else if (sub_type == 1) {
         return jpg_decode_data(&c->jc, width, height, src, src_end - src,
                                dst, c->framebuf_stride, NULL, 0, 0, 0);
     }
 
     if (sub_type != 2) {
         memcpy(transp, src, 3);
         src += 3;
     }
     npal = *src++ + 1;

     if (src_end - src < npal * 3)
         return AVERROR_INVALIDDATA;

     memcpy(pal, src, npal * 3);
     src += npal * 3;

     if (sub_type != 2) {
         for (i = 0; i < npal; i++) {
             if (!memcmp(pal + i * 3, transp, 3)) {

                 tidx = i;
                 break;

             }
         }
     }
 
     if (src_end - src < 2)
         return 0;

     zsize = (src[0] << 8) | src[1];
     src  += 2;

     if (src_end - src < zsize + (sub_type != 2))

         return AVERROR_INVALIDDATA;
 
     ret = uncompress(c->kempf_buf, &dlen, src, zsize);
     if (ret)
         return AVERROR_INVALIDDATA;
     src += zsize;
 
     if (sub_type == 2) {
         kempf_restore_buf(c->kempf_buf, dlen, dst, c->framebuf_stride,
                           NULL, 0, width, height, pal, npal, tidx);
         return 0;
     }
 
     nblocks = *src++ + 1;
     cblocks = 0;

     bstride = FFALIGN(width, 16) >> 3;

     // blocks are coded LSB and we need normal bitreader for JPEG data
     bits = 0;
     for (i = 0; i < (FFALIGN(height, 16) >> 4); i++) {
         for (j = 0; j < (FFALIGN(width, 16) >> 4); j++) {
             if (!bits) {

                 if (src >= src_end)
                     return AVERROR_INVALIDDATA;

                 bitbuf = *src++;
                 bits   = 8;
             }
             coded = bitbuf & 1;
             bits--;
             bitbuf >>= 1;
             cblocks += coded;
             if (cblocks > nblocks)
                 return AVERROR_INVALIDDATA;

             c->kempf_flags[j * 2 +      i * 2      * bstride] =
             c->kempf_flags[j * 2 + 1 +  i * 2      * bstride] =
             c->kempf_flags[j * 2 +     (i * 2 + 1) * bstride] =
             c->kempf_flags[j * 2 + 1 + (i * 2 + 1) * bstride] = coded;

         }
     }
 
     memset(c->jpeg_tile, 0, c->tile_stride * height);
     jpg_decode_data(&c->jc, width, height, src, src_end - src,
                     c->jpeg_tile, c->tile_stride,

                     c->kempf_flags, bstride, nblocks * 4, 0);

 
     kempf_restore_buf(c->kempf_buf, dlen, dst, c->framebuf_stride,
                       c->jpeg_tile, c->tile_stride,
                       width, height, pal, npal, tidx);
 
     return 0;
 }
 
 static int g2m_init_buffers(G2MContext *c)
 {
     int aligned_height;
 

     if (!c->framebuf || c->old_width < c->width || c->old_height < c->height) {

         c->framebuf_stride = FFALIGN(c->width + 15, 16) * 3;
         aligned_height     = c->height + 15;

         av_free(c->framebuf);

         c->framebuf = av_mallocz_array(c->framebuf_stride, aligned_height);

         if (!c->framebuf)
             return AVERROR(ENOMEM);
     }
     if (!c->synth_tile || !c->jpeg_tile ||

         (c->compression == 2 && !c->epic_buf_base) ||

         c->old_tile_w < c->tile_width ||
         c->old_tile_h < c->tile_height) {

         c->tile_stride     = FFALIGN(c->tile_width, 16) * 3;

         c->epic_buf_stride = FFALIGN(c->tile_width * 4, 16);
         aligned_height     = FFALIGN(c->tile_height,    16);

         av_freep(&c->synth_tile);
         av_freep(&c->jpeg_tile);
         av_freep(&c->kempf_buf);
         av_freep(&c->kempf_flags);
         av_freep(&c->epic_buf_base);
         c->epic_buf    = NULL;

         c->synth_tile  = av_mallocz(c->tile_stride      * aligned_height);
         c->jpeg_tile   = av_mallocz(c->tile_stride      * aligned_height);

         c->kempf_buf   = av_mallocz((c->tile_width + 1) * aligned_height +

                                     AV_INPUT_BUFFER_PADDING_SIZE);

         c->kempf_flags = av_mallocz(c->tile_width       * aligned_height);

         if (!c->synth_tile || !c->jpeg_tile ||
             !c->kempf_buf || !c->kempf_flags)
             return AVERROR(ENOMEM);

         if (c->compression == 2) {
             c->epic_buf_base = av_mallocz(c->epic_buf_stride * aligned_height + 4);
             if (!c->epic_buf_base)
                 return AVERROR(ENOMEM);
             c->epic_buf = c->epic_buf_base + 4;
         }

     }
 
     return 0;
 }
 

 static int g2m_load_cursor(AVCodecContext *avctx, G2MContext *c,
                            GetByteContext *gb)

 {
     int i, j, k;
     uint8_t *dst;
     uint32_t bits;

     uint32_t cur_size, cursor_w, cursor_h, cursor_stride;
     uint32_t cursor_hot_x, cursor_hot_y;

     int cursor_fmt, err;

     cur_size     = bytestream2_get_be32(gb);
     cursor_w     = bytestream2_get_byte(gb);
     cursor_h     = bytestream2_get_byte(gb);
     cursor_hot_x = bytestream2_get_byte(gb);
     cursor_hot_y = bytestream2_get_byte(gb);
     cursor_fmt   = bytestream2_get_byte(gb);

     cursor_stride = FFALIGN(cursor_w, cursor_fmt==1 ? 32 : 1) * 4;

 
     if (cursor_w < 1 || cursor_w > 256 ||
         cursor_h < 1 || cursor_h > 256) {

         av_log(avctx, AV_LOG_ERROR, "Invalid cursor dimensions %"PRIu32"x%"PRIu32"\n",

                cursor_w, cursor_h);
         return AVERROR_INVALIDDATA;
     }
     if (cursor_hot_x > cursor_w || cursor_hot_y > cursor_h) {

         av_log(avctx, AV_LOG_WARNING, "Invalid hotspot position %"PRIu32",%"PRIu32"\n",

                cursor_hot_x, cursor_hot_y);
         cursor_hot_x = FFMIN(cursor_hot_x, cursor_w - 1);
         cursor_hot_y = FFMIN(cursor_hot_y, cursor_h - 1);
     }
     if (cur_size - 9 > bytestream2_get_bytes_left(gb) ||
         c->cursor_w * c->cursor_h / 4 > cur_size) {

         av_log(avctx, AV_LOG_ERROR, "Invalid cursor data size %"PRIu32"/%u\n",

                cur_size, bytestream2_get_bytes_left(gb));
         return AVERROR_INVALIDDATA;
     }
     if (cursor_fmt != 1 && cursor_fmt != 32) {
         avpriv_report_missing_feature(avctx, "Cursor format %d",
                                       cursor_fmt);
         return AVERROR_PATCHWELCOME;
     }
 

     if ((err = av_reallocp(&c->cursor, cursor_stride * cursor_h)) < 0) {

         av_log(avctx, AV_LOG_ERROR, "Cannot allocate cursor buffer\n");

         return err;

     }
 
     c->cursor_w      = cursor_w;
     c->cursor_h      = cursor_h;
     c->cursor_hot_x  = cursor_hot_x;
     c->cursor_hot_y  = cursor_hot_y;
     c->cursor_fmt    = cursor_fmt;
     c->cursor_stride = cursor_stride;

 
     dst = c->cursor;
     switch (c->cursor_fmt) {
     case 1: // old monochrome
         for (j = 0; j < c->cursor_h; j++) {
             for (i = 0; i < c->cursor_w; i += 32) {
                 bits = bytestream2_get_be32(gb);
                 for (k = 0; k < 32; k++) {
                     dst[0] = !!(bits & 0x80000000);

                     dst   += 4;

                     bits <<= 1;
                 }
             }
         }
 
         dst = c->cursor;
         for (j = 0; j < c->cursor_h; j++) {
             for (i = 0; i < c->cursor_w; i += 32) {
                 bits = bytestream2_get_be32(gb);
                 for (k = 0; k < 32; k++) {
                     int mask_bit = !!(bits & 0x80000000);
                     switch (dst[0] * 2 + mask_bit) {
                     case 0:

                         dst[0] = 0xFF;
                         dst[1] = 0x00;
                         dst[2] = 0x00;
                         dst[3] = 0x00;

                         break;
                     case 1:

                         dst[0] = 0xFF;
                         dst[1] = 0xFF;
                         dst[2] = 0xFF;
                         dst[3] = 0xFF;

                         break;
                     default:

                         dst[0] = 0x00;
                         dst[1] = 0x00;
                         dst[2] = 0x00;
                         dst[3] = 0x00;

                     }

                     dst   += 4;

                     bits <<= 1;
                 }
             }
         }
         break;
     case 32: // full colour
         /* skip monochrome version of the cursor and decode RGBA instead */
         bytestream2_skip(gb, c->cursor_h * (FFALIGN(c->cursor_w, 32) >> 3));
         for (j = 0; j < c->cursor_h; j++) {
             for (i = 0; i < c->cursor_w; i++) {
                 int val = bytestream2_get_be32(gb);
                 *dst++ = val >>  0;
                 *dst++ = val >>  8;
                 *dst++ = val >> 16;
                 *dst++ = val >> 24;
             }
         }
         break;
     default:
         return AVERROR_PATCHWELCOME;
     }
     return 0;
 }
 
 #define APPLY_ALPHA(src, new, alpha) \
     src = (src * (256 - alpha) + new * alpha) >> 8
 
 static void g2m_paint_cursor(G2MContext *c, uint8_t *dst, int stride)
 {
     int i, j;
     int x, y, w, h;
     const uint8_t *cursor;
 
     if (!c->cursor)
         return;
 
     x = c->cursor_x - c->cursor_hot_x;
     y = c->cursor_y - c->cursor_hot_y;
 
     cursor = c->cursor;
     w      = c->cursor_w;
     h      = c->cursor_h;
 
     if (x + w > c->width)
         w = c->width - x;
     if (y + h > c->height)
         h = c->height - y;
     if (x < 0) {
         w      +=  x;
         cursor += -x * 4;
     } else {
         dst    +=  x * 3;
     }
     if (y < 0) {
         h      +=  y;
         cursor += -y * c->cursor_stride;
     } else {
         dst    +=  y * stride;
     }
     if (w < 0 || h < 0)
         return;
 
     for (j = 0; j < h; j++) {
         for (i = 0; i < w; i++) {
             uint8_t alpha = cursor[i * 4];
             APPLY_ALPHA(dst[i * 3 + 0], cursor[i * 4 + 1], alpha);
             APPLY_ALPHA(dst[i * 3 + 1], cursor[i * 4 + 2], alpha);
             APPLY_ALPHA(dst[i * 3 + 2], cursor[i * 4 + 3], alpha);
         }
         dst    += stride;
         cursor += c->cursor_stride;
     }
 }
 
 static int g2m_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_picture_ptr, AVPacket *avpkt)
 {
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     G2MContext *c = avctx->priv_data;
     AVFrame *pic = data;
     GetByteContext bc, tbc;
     int magic;
     int got_header = 0;

     uint32_t chunk_size, r_mask, g_mask, b_mask;

     int chunk_type, chunk_start;

     int i;
     int ret;
 
     if (buf_size < 12) {
         av_log(avctx, AV_LOG_ERROR,
                "Frame should have at least 12 bytes, got %d instead\n",
                buf_size);
         return AVERROR_INVALIDDATA;
     }
 
     bytestream2_init(&bc, buf, buf_size);
 
     magic = bytestream2_get_be32(&bc);
     if ((magic & ~0xF) != MKBETAG('G', '2', 'M', '0') ||

         (magic & 0xF) < 2 || (magic & 0xF) > 5) {

         av_log(avctx, AV_LOG_ERROR, "Wrong magic %08X\n", magic);
         return AVERROR_INVALIDDATA;
     }
 

     c->swapuv = magic == MKBETAG('G', '2', 'M', '2');

 
     while (bytestream2_get_bytes_left(&bc) > 5) {

         chunk_size  = bytestream2_get_le32(&bc) - 1;
         chunk_type  = bytestream2_get_byte(&bc);
         chunk_start = bytestream2_tell(&bc);

         if (chunk_size > bytestream2_get_bytes_left(&bc)) {

             av_log(avctx, AV_LOG_ERROR, "Invalid chunk size %"PRIu32" type %02X\n",

                    chunk_size, chunk_type);
             break;
         }
         switch (chunk_type) {

         case DISPLAY_INFO:

             got_header =

             c->got_header = 0;
             if (chunk_size < 21) {

                 av_log(avctx, AV_LOG_ERROR, "Invalid display info size %"PRIu32"\n",

                        chunk_size);
                 break;
             }
             c->width  = bytestream2_get_be32(&bc);
             c->height = bytestream2_get_be32(&bc);

             if (c->width < 16 || c->height < 16) {

                 av_log(avctx, AV_LOG_ERROR,
                        "Invalid frame dimensions %dx%d\n",
                        c->width, c->height);

                 ret = AVERROR_INVALIDDATA;
                 goto header_fail;

             }

             if (c->width != avctx->width || c->height != avctx->height) {
                 ret = ff_set_dimensions(avctx, c->width, c->height);
                 if (ret < 0)
                     goto header_fail;
             }

             c->compression = bytestream2_get_be32(&bc);
             if (c->compression != 2 && c->compression != 3) {

                 avpriv_report_missing_feature(avctx, "Compression method %d",
                                               c->compression);

                 ret = AVERROR_PATCHWELCOME;
                 goto header_fail;

             }
             c->tile_width  = bytestream2_get_be32(&bc);
             c->tile_height = bytestream2_get_be32(&bc);

             if (c->tile_width <= 0 || c->tile_height <= 0 ||
                 ((c->tile_width | c->tile_height) & 0xF) ||

                 c->tile_width * (uint64_t)c->tile_height >= INT_MAX / 4 ||
                 av_image_check_size2(c->tile_width, c->tile_height, avctx->max_pixels, avctx->pix_fmt, 0, avctx) < 0

             ) {

                 av_log(avctx, AV_LOG_ERROR,
                        "Invalid tile dimensions %dx%d\n",
                        c->tile_width, c->tile_height);

                 ret = AVERROR_INVALIDDATA;
                 goto header_fail;

             }
             c->tiles_x = (c->width  + c->tile_width  - 1) / c->tile_width;
             c->tiles_y = (c->height + c->tile_height - 1) / c->tile_height;

             c->bpp     = bytestream2_get_byte(&bc);

             if (c->bpp == 32) {

                 if (bytestream2_get_bytes_left(&bc) < 16 ||

                     (chunk_size - 21) < 16) {

                     av_log(avctx, AV_LOG_ERROR,
                            "Display info: missing bitmasks!\n");

                     ret = AVERROR_INVALIDDATA;
                     goto header_fail;

                 }
                 r_mask = bytestream2_get_be32(&bc);
                 g_mask = bytestream2_get_be32(&bc);
                 b_mask = bytestream2_get_be32(&bc);
                 if (r_mask != 0xFF0000 || g_mask != 0xFF00 || b_mask != 0xFF) {

                     avpriv_report_missing_feature(avctx,
                                                   "Bitmasks: R=%"PRIX32", G=%"PRIX32", B=%"PRIX32,
                                                   r_mask, g_mask, b_mask);

                     ret = AVERROR_PATCHWELCOME;
                     goto header_fail;

                 }
             } else {

                 avpriv_request_sample(avctx, "bpp=%d", c->bpp);

                 ret = AVERROR_PATCHWELCOME;
                 goto header_fail;

             }

             if (g2m_init_buffers(c)) {
                 ret = AVERROR(ENOMEM);
                 goto header_fail;
             }

             got_header = 1;
             break;
         case TILE_DATA:
             if (!c->tiles_x || !c->tiles_y) {
                 av_log(avctx, AV_LOG_WARNING,

                        "No display info - skipping tile\n");

                 break;
             }
             if (chunk_size < 2) {

                 av_log(avctx, AV_LOG_ERROR, "Invalid tile data size %"PRIu32"\n",

                        chunk_size);
                 break;
             }
             c->tile_x = bytestream2_get_byte(&bc);
             c->tile_y = bytestream2_get_byte(&bc);
             if (c->tile_x >= c->tiles_x || c->tile_y >= c->tiles_y) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Invalid tile pos %d,%d (in %dx%d grid)\n",
                        c->tile_x, c->tile_y, c->tiles_x, c->tiles_y);
                 break;
             }
             ret = 0;
             switch (c->compression) {
             case COMPR_EPIC_J_B:

                 ret = epic_jb_decode_tile(c, c->tile_x, c->tile_y,
                                           buf + bytestream2_tell(&bc),
                                           chunk_size - 2, avctx);
                 break;

             case COMPR_KEMPF_J_B:
                 ret = kempf_decode_tile(c, c->tile_x, c->tile_y,
                                         buf + bytestream2_tell(&bc),

                                         chunk_size - 2);

                 break;
             }
             if (ret && c->framebuf)
                 av_log(avctx, AV_LOG_ERROR, "Error decoding tile %d,%d\n",
                        c->tile_x, c->tile_y);
             break;
         case CURSOR_POS:
             if (chunk_size < 5) {

                 av_log(avctx, AV_LOG_ERROR, "Invalid cursor pos size %"PRIu32"\n",

                        chunk_size);
                 break;
             }
             c->cursor_x = bytestream2_get_be16(&bc);
             c->cursor_y = bytestream2_get_be16(&bc);
             break;
         case CURSOR_SHAPE:
             if (chunk_size < 8) {

                 av_log(avctx, AV_LOG_ERROR, "Invalid cursor data size %"PRIu32"\n",

                        chunk_size);
                 break;
             }
             bytestream2_init(&tbc, buf + bytestream2_tell(&bc),
                              chunk_size - 4);

             g2m_load_cursor(avctx, c, &tbc);

             break;
         case CHUNK_CC:
         case CHUNK_CD:
             break;
         default:

             av_log(avctx, AV_LOG_WARNING, "Skipping chunk type %02d\n",

                    chunk_type);
         }

 
         /* navigate to next chunk */
         bytestream2_skip(&bc, chunk_start + chunk_size - bytestream2_tell(&bc));

     }
     if (got_header)
         c->got_header = 1;
 

     if (c->width && c->height && c->framebuf) {

         if ((ret = ff_get_buffer(avctx, pic, 0)) < 0)

             return ret;
 
         pic->key_frame = got_header;
         pic->pict_type = got_header ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
 
         for (i = 0; i < avctx->height; i++)
             memcpy(pic->data[0] + i * pic->linesize[0],

                    c->framebuf + i * c->framebuf_stride,

                    c->width * 3);
         g2m_paint_cursor(c, pic->data[0], pic->linesize[0]);
 
         *got_picture_ptr = 1;
     }
 
     return buf_size;

 header_fail:

     c->width   =
     c->height  = 0;
     c->tiles_x =
     c->tiles_y = 0;

     c->tile_width =
     c->tile_height = 0;

     return ret;

 }
 
 static av_cold int g2m_decode_init(AVCodecContext *avctx)
 {

     G2MContext *const c = avctx->priv_data;

     int ret;
 
     if ((ret = jpg_init(avctx, &c->jc)) != 0) {
         av_log(avctx, AV_LOG_ERROR, "Cannot initialise VLCs\n");
         jpg_free_context(&c->jc);
         return AVERROR(ENOMEM);
     }
 

     avctx->pix_fmt = AV_PIX_FMT_RGB24;

     // store original sizes and check against those if resize happens
     c->orig_width  = avctx->width;
     c->orig_height = avctx->height;
 

     return 0;
 }
 
 static av_cold int g2m_decode_end(AVCodecContext *avctx)
 {

     G2MContext *const c = avctx->priv_data;

 
     jpg_free_context(&c->jc);
 

     av_freep(&c->epic_buf_base);

     c->epic_buf = NULL;

     av_freep(&c->kempf_buf);
     av_freep(&c->kempf_flags);
     av_freep(&c->synth_tile);
     av_freep(&c->jpeg_tile);
     av_freep(&c->cursor);
     av_freep(&c->framebuf);
 
     return 0;
 }
 
 AVCodec ff_g2m_decoder = {
     .name           = "g2m",
     .long_name      = NULL_IF_CONFIG_SMALL("Go2Meeting"),
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_G2M,
     .priv_data_size = sizeof(G2MContext),
     .init           = g2m_decode_init,
     .close          = g2m_decode_end,
     .decode         = g2m_decode_frame,

     .capabilities   = AV_CODEC_CAP_DR1,

     .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,

 };