/*
  * Wing Commander/Xan Video Decoder
  * Copyright (C) 2011 Konstantin Shishkov
  * based on work by Mike Melanson
  *
  * 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
  */
 
 #include "avcodec.h"
 #include "libavutil/intreadwrite.h"

 #include "libavutil/mem.h"

 #include "bytestream.h"

 #define BITSTREAM_READER_LE

 #include "get_bits.h"

 #include "internal.h"

 
 typedef struct XanContext {
     AVCodecContext *avctx;

     AVFrame *pic;

 
     uint8_t *y_buffer;
     uint8_t *scratch_buffer;
     int     buffer_size;

     GetByteContext gb;

 } XanContext;
 

 static av_cold int xan_decode_end(AVCodecContext *avctx)
 {
     XanContext *s = avctx->priv_data;
 
     av_frame_free(&s->pic);
 
     av_freep(&s->y_buffer);
     av_freep(&s->scratch_buffer);
 
     return 0;
 }

 static av_cold int xan_decode_init(AVCodecContext *avctx)
 {
     XanContext *s = avctx->priv_data;
 
     s->avctx = avctx;
 

     avctx->pix_fmt = AV_PIX_FMT_YUV420P;

     if (avctx->height < 8) {
         av_log(avctx, AV_LOG_ERROR, "Invalid frame height: %d.\n", avctx->height);
         return AVERROR(EINVAL);
     }

     if (avctx->width & 1) {
         av_log(avctx, AV_LOG_ERROR, "Invalid frame width: %d.\n", avctx->width);
         return AVERROR(EINVAL);
     }

     s->buffer_size = avctx->width * avctx->height;
     s->y_buffer = av_malloc(s->buffer_size);
     if (!s->y_buffer)
         return AVERROR(ENOMEM);
     s->scratch_buffer = av_malloc(s->buffer_size + 130);
     if (!s->scratch_buffer) {

         xan_decode_end(avctx);
         return AVERROR(ENOMEM);
     }
 
     s->pic = av_frame_alloc();
     if (!s->pic) {
         xan_decode_end(avctx);

         return AVERROR(ENOMEM);
     }
 
     return 0;
 }
 

 static int xan_unpack_luma(XanContext *s,

                            uint8_t *dst, const int dst_size)
 {

     int tree_size, eof;
     int bits, mask;
     int tree_root, node;
     const uint8_t *dst_end = dst + dst_size;
     GetByteContext tree = s->gb;
     int start_off = bytestream2_tell(&tree);

     tree_size = bytestream2_get_byte(&s->gb);
     eof       = bytestream2_get_byte(&s->gb);
     tree_root = eof + tree_size;
     bytestream2_skip(&s->gb, tree_size * 2);

     node = tree_root;
     bits = bytestream2_get_byte(&s->gb);
     mask = 0x80;
     for (;;) {
         int bit = !!(bits & mask);
         mask >>= 1;
         bytestream2_seek(&tree, start_off + node*2 + bit - eof * 2, SEEK_SET);
         node = bytestream2_get_byte(&tree);
         if (node == eof)
             break;
         if (node < eof) {
             *dst++ = node;
             if (dst > dst_end)
                 break;
             node = tree_root;
         }
         if (!mask) {
             if (bytestream2_get_bytes_left(&s->gb) <= 0)
                 break;
             bits = bytestream2_get_byteu(&s->gb);
             mask = 0x80;
         }
     }
     return dst != dst_end ? AVERROR_INVALIDDATA : 0;

 }
 
 /* almost the same as in xan_wc3 decoder */

 static int xan_unpack(XanContext *s,
                       uint8_t *dest, const int dest_len)

 {
     uint8_t opcode;
     int size;
     uint8_t *orig_dest = dest;
     const uint8_t *dest_end = dest + dest_len;
 
     while (dest < dest_end) {

         if (bytestream2_get_bytes_left(&s->gb) <= 0)
             return AVERROR_INVALIDDATA;
 
         opcode = bytestream2_get_byteu(&s->gb);

 
         if (opcode < 0xe0) {
             int size2, back;
             if ((opcode & 0x80) == 0) {
                 size  = opcode & 3;

                 back  = ((opcode & 0x60) << 3) + bytestream2_get_byte(&s->gb) + 1;

                 size2 = ((opcode & 0x1c) >> 2) + 3;
             } else if ((opcode & 0x40) == 0) {

                 size  = bytestream2_peek_byte(&s->gb) >> 6;
                 back  = (bytestream2_get_be16(&s->gb) & 0x3fff) + 1;

                 size2 = (opcode & 0x3f) + 4;
             } else {
                 size  = opcode & 3;

                 back  = ((opcode & 0x10) << 12) + bytestream2_get_be16(&s->gb) + 1;
                 size2 = ((opcode & 0x0c) <<  6) + bytestream2_get_byte(&s->gb) + 5;

                 if (size + size2 > dest_end - dest)
                     break;
             }

             if (dest + size + size2 > dest_end ||

                 dest - orig_dest + size < back)

                 return AVERROR_INVALIDDATA;

             bytestream2_get_buffer(&s->gb, dest, size);

             dest += size;
             av_memcpy_backptr(dest, back, size2);
             dest += size2;
         } else {
             int finish = opcode >= 0xfc;
 
             size = finish ? opcode & 3 : ((opcode & 0x1f) << 2) + 4;

             if (dest_end - dest < size)

                 return AVERROR_INVALIDDATA;

             bytestream2_get_buffer(&s->gb, dest, size);

             dest += size;
             if (finish)
                 break;
         }
     }
     return dest - orig_dest;
 }
 

 static int xan_decode_chroma(AVCodecContext *avctx, unsigned chroma_off)

 {
     XanContext *s = avctx->priv_data;
     uint8_t *U, *V;
     int val, uval, vval;
     int i, j;
     const uint8_t *src, *src_end;
     const uint8_t *table;

     int mode, offset, dec_size, table_size;

 
     if (!chroma_off)
         return 0;

     if (chroma_off + 4 >= bytestream2_get_bytes_left(&s->gb)) {

         av_log(avctx, AV_LOG_ERROR, "Invalid chroma block position\n");

         return AVERROR_INVALIDDATA;

     }

     bytestream2_seek(&s->gb, chroma_off + 4, SEEK_SET);

     mode        = bytestream2_get_le16(&s->gb);
     table       = s->gb.buffer;
     table_size  = bytestream2_get_le16(&s->gb);
     offset      = table_size * 2;
     table_size += 1;

     if (offset >= bytestream2_get_bytes_left(&s->gb)) {

         av_log(avctx, AV_LOG_ERROR, "Invalid chroma block offset\n");

         return AVERROR_INVALIDDATA;

     }
 

     bytestream2_skip(&s->gb, offset);

     memset(s->scratch_buffer, 0, s->buffer_size);

     dec_size = xan_unpack(s, s->scratch_buffer, s->buffer_size);

     if (dec_size < 0) {
         av_log(avctx, AV_LOG_ERROR, "Chroma unpacking failed\n");

         return dec_size;

     }
 

     U = s->pic->data[1];
     V = s->pic->data[2];

     src     = s->scratch_buffer;
     src_end = src + dec_size;
     if (mode) {
         for (j = 0; j < avctx->height >> 1; j++) {
             for (i = 0; i < avctx->width >> 1; i++) {

                 if (src_end - src < 1)
                     return 0;

                 val = *src++;
                 if (val) {

                     if (val >= table_size)

                         return AVERROR_INVALIDDATA;

                     val  = AV_RL16(table + (val << 1));
                     uval = (val >> 3) & 0xF8;
                     vval = (val >> 8) & 0xF8;
                     U[i] = uval | (uval >> 5);
                     V[i] = vval | (vval >> 5);
                 }
             }

             U += s->pic->linesize[1];
             V += s->pic->linesize[2];

         }

         if (avctx->height & 1) {

             memcpy(U, U - s->pic->linesize[1], avctx->width >> 1);
             memcpy(V, V - s->pic->linesize[2], avctx->width >> 1);

         }

     } else {

         uint8_t *U2 = U + s->pic->linesize[1];
         uint8_t *V2 = V + s->pic->linesize[2];

 
         for (j = 0; j < avctx->height >> 2; j++) {
             for (i = 0; i < avctx->width >> 1; i += 2) {

                 if (src_end - src < 1)
                     return 0;

                 val = *src++;
                 if (val) {

                     if (val >= table_size)

                         return AVERROR_INVALIDDATA;

                     val  = AV_RL16(table + (val << 1));
                     uval = (val >> 3) & 0xF8;
                     vval = (val >> 8) & 0xF8;
                     U[i] = U[i+1] = U2[i] = U2[i+1] = uval | (uval >> 5);
                     V[i] = V[i+1] = V2[i] = V2[i+1] = vval | (vval >> 5);
                 }
             }

             U  += s->pic->linesize[1] * 2;
             V  += s->pic->linesize[2] * 2;
             U2 += s->pic->linesize[1] * 2;
             V2 += s->pic->linesize[2] * 2;

         }

         if (avctx->height & 3) {
             int lines = ((avctx->height + 1) >> 1) - (avctx->height >> 2) * 2;
 

             memcpy(U, U - lines * s->pic->linesize[1], lines * s->pic->linesize[1]);
             memcpy(V, V - lines * s->pic->linesize[2], lines * s->pic->linesize[2]);

         }

     }
 
     return 0;
 }
 

 static int xan_decode_frame_type0(AVCodecContext *avctx)

 {
     XanContext *s = avctx->priv_data;
     uint8_t *ybuf, *prev_buf, *src = s->scratch_buffer;
     unsigned  chroma_off, corr_off;

     int cur, last;

     int i, j;
     int ret;
 

     chroma_off = bytestream2_get_le32(&s->gb);
     corr_off   = bytestream2_get_le32(&s->gb);

     if ((ret = xan_decode_chroma(avctx, chroma_off)) != 0)

         return ret;
 

     if (corr_off >= bytestream2_size(&s->gb)) {

         av_log(avctx, AV_LOG_WARNING, "Ignoring invalid correction block position\n");
         corr_off = 0;
     }

     bytestream2_seek(&s->gb, 12, SEEK_SET);
     ret = xan_unpack_luma(s, src, s->buffer_size >> 1);

     if (ret) {
         av_log(avctx, AV_LOG_ERROR, "Luma decoding failed\n");
         return ret;
     }
 
     ybuf = s->y_buffer;
     last = *src++;
     ybuf[0] = last << 1;
     for (j = 1; j < avctx->width - 1; j += 2) {
         cur = (last + *src++) & 0x1F;
         ybuf[j]   = last + cur;
         ybuf[j+1] = cur << 1;
         last = cur;
     }

     ybuf[j]  = last << 1;

     prev_buf = ybuf;
     ybuf += avctx->width;
 
     for (i = 1; i < avctx->height; i++) {
         last = ((prev_buf[0] >> 1) + *src++) & 0x1F;
         ybuf[0] = last << 1;
         for (j = 1; j < avctx->width - 1; j += 2) {
             cur = ((prev_buf[j + 1] >> 1) + *src++) & 0x1F;
             ybuf[j]   = last + cur;
             ybuf[j+1] = cur << 1;
             last = cur;
         }

         ybuf[j] = last << 1;

         prev_buf = ybuf;
         ybuf += avctx->width;
     }
 
     if (corr_off) {

         int dec_size;

         bytestream2_seek(&s->gb, 8 + corr_off, SEEK_SET);

         dec_size = xan_unpack(s, s->scratch_buffer, s->buffer_size / 2);

         if (dec_size < 0)
             dec_size = 0;

         else
             dec_size = FFMIN(dec_size, s->buffer_size/2 - 1);
 

         for (i = 0; i < dec_size; i++)
             s->y_buffer[i*2+1] = (s->y_buffer[i*2+1] + (s->scratch_buffer[i] << 1)) & 0x3F;
     }
 
     src  = s->y_buffer;

     ybuf = s->pic->data[0];

     for (j = 0; j < avctx->height; j++) {
         for (i = 0; i < avctx->width; i++)
             ybuf[i] = (src[i] << 2) | (src[i] >> 3);
         src  += avctx->width;

         ybuf += s->pic->linesize[0];

     }
 
     return 0;
 }
 

 static int xan_decode_frame_type1(AVCodecContext *avctx)

 {
     XanContext *s = avctx->priv_data;
     uint8_t *ybuf, *src = s->scratch_buffer;
     int cur, last;
     int i, j;
     int ret;
 

     if ((ret = xan_decode_chroma(avctx, bytestream2_get_le32(&s->gb))) != 0)

         return ret;
 

     bytestream2_seek(&s->gb, 16, SEEK_SET);
     ret = xan_unpack_luma(s, src,

                           s->buffer_size >> 1);
     if (ret) {
         av_log(avctx, AV_LOG_ERROR, "Luma decoding failed\n");
         return ret;
     }
 
     ybuf = s->y_buffer;
     for (i = 0; i < avctx->height; i++) {
         last = (ybuf[0] + (*src++ << 1)) & 0x3F;
         ybuf[0] = last;
         for (j = 1; j < avctx->width - 1; j += 2) {
             cur = (ybuf[j + 1] + (*src++ << 1)) & 0x3F;
             ybuf[j]   = (last + cur) >> 1;
             ybuf[j+1] = cur;
             last = cur;
         }

         ybuf[j] = last;

         ybuf += avctx->width;
     }
 
     src = s->y_buffer;

     ybuf = s->pic->data[0];

     for (j = 0; j < avctx->height; j++) {
         for (i = 0; i < avctx->width; i++)
             ybuf[i] = (src[i] << 2) | (src[i] >> 3);
         src  += avctx->width;

         ybuf += s->pic->linesize[0];

     }
 
     return 0;
 }
 
 static int xan_decode_frame(AVCodecContext *avctx,

                             void *data, int *got_frame,

                             AVPacket *avpkt)
 {
     XanContext *s = avctx->priv_data;
     int ftype;
     int ret;
 

     if ((ret = ff_reget_buffer(avctx, s->pic)) < 0)

         return ret;
 

     bytestream2_init(&s->gb, avpkt->data, avpkt->size);
     ftype = bytestream2_get_le32(&s->gb);

     switch (ftype) {
     case 0:

         ret = xan_decode_frame_type0(avctx);

         break;
     case 1:

         ret = xan_decode_frame_type1(avctx);

         break;
     default:
         av_log(avctx, AV_LOG_ERROR, "Unknown frame type %d\n", ftype);

         return AVERROR_INVALIDDATA;

     }
     if (ret)
         return ret;
 

     if ((ret = av_frame_ref(data, s->pic)) < 0)

         return ret;
 

     *got_frame = 1;

 
     return avpkt->size;
 }
 
 AVCodec ff_xan_wc4_decoder = {

     .name           = "xan_wc4",

     .long_name      = NULL_IF_CONFIG_SMALL("Wing Commander IV / Xxan"),

     .type           = AVMEDIA_TYPE_VIDEO,

     .id             = AV_CODEC_ID_XAN_WC4,

     .priv_data_size = sizeof(XanContext),
     .init           = xan_decode_init,
     .close          = xan_decode_end,
     .decode         = xan_decode_frame,
     .capabilities   = CODEC_CAP_DR1,

 };