/*
  * Kega Game Video (KGV1) decoder
  * Copyright (c) 2010 Daniel Verkamp
  *
  * 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

  * Kega Game Video decoder
  */
 

 #include "libavutil/common.h"

 #include "libavutil/intreadwrite.h"

 #include "libavutil/imgutils.h"

 #include "avcodec.h"

 #include "internal.h"

 
 typedef struct {

     uint16_t *frame_buffer;
     uint16_t *last_frame_buffer;

 } KgvContext;
 

 static void decode_flush(AVCodecContext *avctx)
 {
     KgvContext * const c = avctx->priv_data;
 

     av_freep(&c->frame_buffer);
     av_freep(&c->last_frame_buffer);

 }
 

 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
                         AVPacket *avpkt)

 {

     AVFrame *frame = data;

     const uint8_t *buf = avpkt->data;
     const uint8_t *buf_end = buf + avpkt->size;
     KgvContext * const c = avctx->priv_data;

     int offsets[8];

     uint8_t *out, *prev;

     int outcnt = 0, maxcnt;

     int w, h, i, res;

 
     if (avpkt->size < 2)

         return AVERROR_INVALIDDATA;

 
     w = (buf[0] + 1) * 8;
     h = (buf[1] + 1) * 8;
     buf += 2;
 

     if (w != avctx->width || h != avctx->height) {

         av_freep(&c->frame_buffer);
         av_freep(&c->last_frame_buffer);

         if ((res = ff_set_dimensions(avctx, w, h)) < 0)
             return res;

     }

     if (!c->frame_buffer) {
         c->frame_buffer      = av_mallocz(avctx->width * avctx->height * 2);
         c->last_frame_buffer = av_mallocz(avctx->width * avctx->height * 2);
         if (!c->frame_buffer || !c->last_frame_buffer) {
             decode_flush(avctx);
             return AVERROR(ENOMEM);
         }
     }
 

     maxcnt = w * h;
 

     if ((res = ff_get_buffer(avctx, frame, 0)) < 0)

         return res;

     out  = c->frame_buffer;
     prev = c->last_frame_buffer;

     for (i = 0; i < 8; i++)

         offsets[i] = -1;
 

     while (outcnt < maxcnt && buf_end - 2 >= buf) {

         int code = AV_RL16(buf);
         buf += 2;
 
         if (!(code & 0x8000)) {

             AV_WN16A(&out[2 * outcnt], code); // rgb555 pixel coded directly
             outcnt++;

         } else {
             int count;
 
             if ((code & 0x6000) == 0x6000) {
                 // copy from previous frame
                 int oidx = (code >> 10) & 7;
                 int start;
 
                 count = (code & 0x3FF) + 3;
 
                 if (offsets[oidx] < 0) {
                     if (buf_end - 3 < buf)
                         break;
                     offsets[oidx] = AV_RL24(buf);
                     buf += 3;
                 }
 
                 start = (outcnt + offsets[oidx]) % maxcnt;
 

                 if (maxcnt - start < count || maxcnt - outcnt < count)

                     break;
 

                 if (!prev) {
                     av_log(avctx, AV_LOG_ERROR,
                            "Frame reference does not exist\n");
                     break;
                 }
 

                 memcpy(out + 2 * outcnt, prev + 2 * start, 2 * count);

             } else {
                 // copy from earlier in this frame
                 int offset = (code & 0x1FFF) + 1;
 
                 if (!(code & 0x6000)) {
                     count = 2;
                 } else if ((code & 0x6000) == 0x2000) {
                     count = 3;
                 } else {
                     if (buf_end - 1 < buf)
                         break;
                     count = 4 + *buf++;
                 }
 

                 if (outcnt < offset || maxcnt - outcnt < count)

                     break;
 

                 av_memcpy_backptr(out + 2 * outcnt, 2 * offset, 2 * count);

             }

             outcnt += count;

         }
     }
 
     if (outcnt - maxcnt)
         av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
 

     av_image_copy_plane(frame->data[0], frame->linesize[0],
                         (const uint8_t*)c->frame_buffer,  avctx->width * 2,
                         avctx->width * 2, avctx->height);
     FFSWAP(uint16_t *, c->frame_buffer, c->last_frame_buffer);

     *got_frame = 1;

 
     return avpkt->size;
 }
 
 static av_cold int decode_init(AVCodecContext *avctx)
 {

     avctx->pix_fmt = AV_PIX_FMT_RGB555;

 
     return 0;
 }
 

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

 AVCodec ff_kgv1_decoder = {

     .name           = "kgv1",

     .long_name      = NULL_IF_CONFIG_SMALL("Kega Game Video"),

     .type           = AVMEDIA_TYPE_VIDEO,

     .id             = AV_CODEC_ID_KGV1,

     .priv_data_size = sizeof(KgvContext),
     .init           = decode_init,

     .close          = decode_end,

     .decode         = decode_frame,

     .flush          = decode_flush,

     .capabilities   = CODEC_CAP_DR1,

 };