/*

 * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder

 * Copyright (c) 2012 Konstantin Shishkov

 *

 * 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

 * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder

 */

#include "avcodec.h"

#include "codec_internal.h"

#include "decode.h"

#include "mss12.h"

typedef struct MSS1Context {

    MSS12Context   ctx;

    AVFrame       *pic;

    SliceContext   sc;

} MSS1Context;

static void arith_normalise(ArithCoder *c)

{

    for (;;) {

        if (c->high >= 0x8000) {

            if (c->low < 0x8000) {

                if (c->low >= 0x4000 && c->high < 0xC000) {

                    c->value -= 0x4000;

                    c->low   -= 0x4000;

                    c->high  -= 0x4000;

                } else {

                    return;

                }

            } else {

                c->value -= 0x8000;

                c->low   -= 0x8000;

                c->high  -= 0x8000;

            }

        }

        c->value <<= 1;

        c->low   <<= 1;

        c->high  <<= 1;

        c->high   |= 1;

        if (get_bits_left(c->gbc.gb) < 1)

            c->overread++;

        c->value  |= get_bits1(c->gbc.gb);

    }

}

ARITH_GET_BIT(arith)

static int arith_get_bits(ArithCoder *c, int bits)

{

    int range = c->high - c->low + 1;

    int val   = (((c->value - c->low + 1) << bits) - 1) / range;

    int prob  = range * val;

    c->high   = ((prob + range) >> bits) + c->low - 1;

    c->low   += prob >> bits;

    arith_normalise(c);

    return val;

}

static int arith_get_number(ArithCoder *c, int mod_val)

{

    int range = c->high - c->low + 1;

    int val   = ((c->value - c->low + 1) * mod_val - 1) / range;

    int prob  = range * val;

    c->high   = (prob + range) / mod_val + c->low - 1;

    c->low   += prob / mod_val;

    arith_normalise(c);

    return val;

}

static int arith_get_prob(ArithCoder *c, int16_t *probs)

{

    int range = c->high - c->low + 1;

    int val   = ((c->value - c->low + 1) * probs[0] - 1) / range;

    int sym   = 1;

    while (probs[sym] > val)

        sym++;

    c->high = range * probs[sym - 1] / probs[0] + c->low - 1;

    c->low += range * probs[sym]     / probs[0];

    return sym;

}

ARITH_GET_MODEL_SYM(arith)

static void arith_init(ArithCoder *c, GetBitContext *gb)

{

    c->low           = 0;

    c->high          = 0xFFFF;

    c->value         = get_bits(gb, 16);

    c->overread      = 0;

    c->gbc.gb        = gb;

    c->get_model_sym = arith_get_model_sym;

    c->get_number    = arith_get_number;

}

static void decode_pal(MSS12Context *ctx, ArithCoder *acoder)

{

    int i, ncol, r, g, b;

    uint32_t *pal = ctx->pal + 256 - ctx->free_colours;

    if (!ctx->free_colours)

        return;

    ncol = arith_get_number(acoder, ctx->free_colours + 1);

    for (i = 0; i < ncol; i++) {

        r = arith_get_bits(acoder, 8);

        g = arith_get_bits(acoder, 8);

        b = arith_get_bits(acoder, 8);

        *pal++ = (0xFFU << 24) | (r << 16) | (g << 8) | b;

    }

}

static int mss1_decode_frame(AVCodecContext *avctx, AVFrame *rframe,

                             int *got_frame, AVPacket *avpkt)

{

    MSS1Context *ctx = avctx->priv_data;

    MSS12Context *c = &ctx->ctx;

    GetBitContext gb;

    ArithCoder acoder;

    int ret;

    if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)

        return ret;

    arith_init(&acoder, &gb);

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

        return ret;

    c->pal_pic    =  ctx->pic->data[0] + ctx->pic->linesize[0] * (avctx->height - 1);

    c->pal_stride = -ctx->pic->linesize[0];

    c->keyframe   = !arith_get_bit(&acoder);

    if (c->keyframe) {

        c->corrupted = 0;

        ff_mss12_slicecontext_reset(&ctx->sc);

        decode_pal(c, &acoder);

        ctx->pic->flags |= AV_FRAME_FLAG_KEY;

        ctx->pic->pict_type = AV_PICTURE_TYPE_I;

    } else {

        if (c->corrupted)

            return AVERROR_INVALIDDATA;

        ctx->pic->flags &= ~AV_FRAME_FLAG_KEY;

        ctx->pic->pict_type = AV_PICTURE_TYPE_P;

    }

    c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0,

                                        avctx->width, avctx->height);

    if (c->corrupted)

        return AVERROR_INVALIDDATA;

    memcpy(ctx->pic->data[1], c->pal, AVPALETTE_SIZE);

    if ((ret = av_frame_ref(rframe, ctx->pic)) < 0)

        return ret;

    *got_frame      = 1;

    /* always report that the buffer was completely consumed */

    return avpkt->size;

}

static av_cold int mss1_decode_init(AVCodecContext *avctx)

{

    MSS1Context * const c = avctx->priv_data;

    int ret;

    c->ctx.avctx       = avctx;

    c->pic = av_frame_alloc();

    if (!c->pic)

        return AVERROR(ENOMEM);

    ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL);

    if (ret < 0)

        return ret;

    avctx->pix_fmt = AV_PIX_FMT_PAL8;

    return ret;

}

static av_cold int mss1_decode_end(AVCodecContext *avctx)

{

    MSS1Context * const ctx = avctx->priv_data;

    av_frame_free(&ctx->pic);

    ff_mss12_decode_end(&ctx->ctx);

    return 0;

}

const FFCodec ff_mss1_decoder = {

    .p.name         = "mss1",

    CODEC_LONG_NAME("MS Screen 1"),

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_MSS1,

    .priv_data_size = sizeof(MSS1Context),

    .init           = mss1_decode_init,

    .close          = mss1_decode_end,

    FF_CODEC_DECODE_CB(mss1_decode_frame),

    .p.capabilities = AV_CODEC_CAP_DR1,

    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,

};