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/*

 * 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 {

    AVFrame *prev;

} KgvContext;

static void decode_flush(AVCodecContext *avctx)

{

    KgvContext * const c = avctx->priv_data;

    av_frame_unref(c->prev);

}

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 ((res = av_image_check_size(w, h, 0, avctx)) < 0)

        return res;

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

        av_frame_unref(c->prev);

        avcodec_set_dimensions(avctx, w, h);

    }

    maxcnt = w * h;

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

        return res;

    out  = frame->data[0];

    if (c->prev->data[0]) {

        prev = c->prev->data[0];

    } else {

        prev = NULL;

    }

    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_frame_unref(c->prev);

    if ((res = av_frame_ref(c->prev, frame)) < 0)

        return res;

    *got_frame = 1;

    return avpkt->size;

}

static av_cold int decode_init(AVCodecContext *avctx)

{

    KgvContext * const c = avctx->priv_data;

    avctx->pix_fmt = AV_PIX_FMT_RGB555;

    avctx->flags  |= CODEC_FLAG_EMU_EDGE;

    c->prev = av_frame_alloc();

    if (!c->prev)

        return AVERROR(ENOMEM);

    return 0;

}

static av_cold int decode_end(AVCodecContext *avctx)

{

    KgvContext * const c = avctx->priv_data;

    av_frame_free(&c->prev);

    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,

};