/*

 * GIF decoder

 * Copyright (c) 2003 Fabrice Bellard

 * Copyright (c) 2006 Baptiste Coudurier

 * Copyright (c) 2012 Vitaliy E Sugrobov

 *

 * 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 "libavutil/mem.h"

#include "libavutil/opt.h"

#include "avcodec.h"

#include "bytestream.h"

#include "codec_internal.h"

#include "decode.h"

#include "lzw.h"

#include "gif.h"

/* This value is intentionally set to "transparent white" color.

 * It is much better to have white background instead of black

 * when gif image converted to format which not support transparency.

 */

#define GIF_TRANSPARENT_COLOR    0x00ffffff

typedef struct GifState {

    const AVClass *class;

    AVFrame *frame;

    int screen_width;

    int screen_height;

    int has_global_palette;

    int bits_per_pixel;

    uint32_t bg_color;

    int background_color_index;

    int transparent_color_index;

    int color_resolution;

    /* intermediate buffer for storing color indices

     * obtained from lzw-encoded data stream */

    uint8_t *idx_line;

    int idx_line_size;

    /* after the frame is displayed, the disposal method is used */

    int gce_prev_disposal;

    int gce_disposal;

    /* rectangle describing area that must be disposed */

    int gce_l, gce_t, gce_w, gce_h;

    /* depending on disposal method we store either part of the image

     * drawn on the canvas or background color that

     * should be used upon disposal */

    uint8_t *stored_img;

    int stored_img_size;

    int stored_bg_color;

    GetByteContext gb;

    LZWState *lzw;

    /* aux buffers */

    uint32_t global_palette[256];

    uint32_t local_palette[256];

    AVCodecContext *avctx;

    int keyframe;

    int keyframe_ok;

    int trans_color;    /**< color value that is used instead of transparent color */

} GifState;

static void gif_read_palette(GifState *s, uint32_t *pal, int nb)

{

    int i;

    for (i = 0; i < nb; i++, pal++)

        *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);

}

static void gif_fill(AVFrame *picture, uint32_t color)

{

    const ptrdiff_t linesize = picture->linesize[0];

    uint8_t *py = picture->data[0];

    const int w = picture->width;

    const int h = picture->height;

    for (int y = 0; y < h; y++) {

        uint32_t *px = (uint32_t *)py;

        for (int x = 0; x < w; x++)

            px[x] = color;

        py += linesize;

    }

}

static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)

{

    const ptrdiff_t linesize = picture->linesize[0];

    uint8_t *py = picture->data[0] + t * linesize;

    for (int y = 0; y < h; y++) {

        uint32_t *px = ((uint32_t *)py) + l;

        for (int x = 0; x < w; x++)

            px[x] = color;

        py += linesize;

    }

}

static void gif_copy_img_rect(const uint8_t *src, uint8_t *dst,

                              ptrdiff_t src_linesize,

                              ptrdiff_t dst_linesize,

                              int l, int t, int w, int h)

{

    const uint8_t *src_py = src;

    uint8_t *dst_py = dst;

    src_py += t * src_linesize;

    dst_py += t * dst_linesize;

    for (int y = 0; y < h; y++) {

        memcpy(dst_py + l * 4, src_py + l * 4, w * 4);

        src_py += src_linesize;

        dst_py += dst_linesize;

    }

}

static int gif_read_image(GifState *s, AVFrame *frame)

{

    int left, top, width, height, bits_per_pixel, code_size, flags, pw;

    int is_interleaved, has_local_palette, y, pass, y1, pal_size, lzwed_len;

    uint32_t *ptr, *pal, *px, *pr, *ptr1;

    ptrdiff_t linesize;

    int ret;

    uint8_t *idx;

    /* At least 9 bytes of Image Descriptor. */

    if (bytestream2_get_bytes_left(&s->gb) < 9)

        return AVERROR_INVALIDDATA;

    left   = bytestream2_get_le16u(&s->gb);

    top    = bytestream2_get_le16u(&s->gb);

    width  = bytestream2_get_le16u(&s->gb);

    height = bytestream2_get_le16u(&s->gb);

    flags  = bytestream2_get_byteu(&s->gb);

    is_interleaved = flags & 0x40;

    has_local_palette = flags & 0x80;

    bits_per_pixel = (flags & 0x07) + 1;

    ff_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);

    if (has_local_palette) {

        pal_size = 1 << bits_per_pixel;

        if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)

            return AVERROR_INVALIDDATA;

        gif_read_palette(s, s->local_palette, pal_size);

        pal = s->local_palette;

    } else {

        if (!s->has_global_palette) {

            av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");

            return AVERROR_INVALIDDATA;

        }

        pal = s->global_palette;

    }

    if (s->keyframe) {

        if (s->transparent_color_index == -1 && s->has_global_palette) {

            /* transparency wasn't set before the first frame, fill with background color */

            gif_fill(frame, s->bg_color);

        } else {

            /* otherwise fill with transparent color.

             * this is necessary since by default picture filled with 0x80808080. */

            gif_fill(frame, s->trans_color);

        }

    }

    /* verify that all the image is inside the screen dimensions */

    if (!width || width > s->screen_width) {

        av_log(s->avctx, AV_LOG_WARNING, "Invalid image width: %d, truncating.\n", width);

        width = s->screen_width;

    }

    if (left >= s->screen_width) {

        av_log(s->avctx, AV_LOG_ERROR, "Invalid left position: %d.\n", left);

        return AVERROR_INVALIDDATA;

    }

    if (!height || height > s->screen_height) {

        av_log(s->avctx, AV_LOG_WARNING, "Invalid image height: %d, truncating.\n", height);

        height = s->screen_height;

    }

    if (top >= s->screen_height) {

        av_log(s->avctx, AV_LOG_ERROR, "Invalid top position: %d.\n", top);

        return AVERROR_INVALIDDATA;

    }

    if (left + width > s->screen_width) {

        /* width must be kept around to avoid lzw vs line desync */

        pw = s->screen_width - left;

        av_log(s->avctx, AV_LOG_WARNING, "Image too wide by %d, truncating.\n",

               left + width - s->screen_width);

    } else {

        pw = width;

    }

    if (top + height > s->screen_height) {

        /* we don't care about the extra invisible lines */

        av_log(s->avctx, AV_LOG_WARNING, "Image too high by %d, truncating.\n",

               top + height - s->screen_height);

        height = s->screen_height - top;

    }

    /* process disposal method */

    if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {

        gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);

    } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {

        gif_copy_img_rect(s->stored_img, frame->data[0],

            FFABS(frame->linesize[0]), frame->linesize[0], s->gce_l, s->gce_t, s->gce_w, s->gce_h);

    }

    s->gce_prev_disposal = s->gce_disposal;

    if (s->gce_disposal != GCE_DISPOSAL_NONE) {

        s->gce_l = left;  s->gce_t = top;

        s->gce_w = pw;    s->gce_h = height;

        if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {

            if (s->transparent_color_index >= 0)

                s->stored_bg_color = s->trans_color;

            else

                s->stored_bg_color = s->bg_color;

        } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {

            av_fast_malloc(&s->stored_img, &s->stored_img_size, FFABS(frame->linesize[0]) * frame->height);

            if (!s->stored_img)

                return AVERROR(ENOMEM);

            gif_copy_img_rect(frame->data[0], s->stored_img,

                frame->linesize[0], FFABS(frame->linesize[0]), left, top, pw, height);

        }

    }

    /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */

    if (bytestream2_get_bytes_left(&s->gb) < 2)

        return AVERROR_INVALIDDATA;

    /* now get the image data */

    code_size = bytestream2_get_byteu(&s->gb);

    if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,

                                  bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {

        av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");

        return ret;

    }

    /* read all the image */

    linesize = frame->linesize[0];

    ptr1 = (uint32_t *)(frame->data[0] + top * linesize) + left;

    ptr = ptr1;

    pass = 0;

    y1 = 0;

    for (y = 0; y < height; y++) {

        int count = ff_lzw_decode(s->lzw, s->idx_line, width);

        if (count != width) {

            if (count)

                av_log(s->avctx, AV_LOG_ERROR, "LZW decode failed\n");

            goto decode_tail;

        }

        pr = ptr + pw;

        for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {

            if (*idx != s->transparent_color_index)

                *px = pal[*idx];

        }

        if (is_interleaved) {

            switch(pass) {

            default:

            case 0:

            case 1:

                y1 += 8;

                ptr += linesize * 2;

                break;

            case 2:

                y1 += 4;

                ptr += linesize * 1;

                break;

            case 3:

                y1 += 2;

                ptr += linesize / 2;

                break;

            }

            while (y1 >= height) {

                y1  = 4 >> pass;

                ptr = ptr1 + linesize / 4 * y1;

                pass++;

            }

        } else {

            ptr += linesize / 4;

        }

    }

 decode_tail:

    /* read the garbage data until end marker is found */

    lzwed_len = ff_lzw_decode_tail(s->lzw);

    bytestream2_skipu(&s->gb, lzwed_len);

    /* Graphic Control Extension's scope is single frame.

     * Remove its influence. */

    s->transparent_color_index = -1;

    s->gce_disposal = GCE_DISPOSAL_NONE;

    return 0;

}

static int gif_read_extension(GifState *s)

{

    int ext_code, ext_len, gce_flags, gce_transparent_index;

    /* There must be at least 2 bytes:

     * 1 for extension label and 1 for extension length. */

    if (bytestream2_get_bytes_left(&s->gb) < 2)

        return AVERROR_INVALIDDATA;

    ext_code = bytestream2_get_byteu(&s->gb);

    ext_len  = bytestream2_get_byteu(&s->gb);

    ff_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);

    switch(ext_code) {

    case GIF_GCE_EXT_LABEL:

        if (ext_len != 4)

            goto discard_ext;

        /* We need at least 5 bytes more: 4 is for extension body

         * and 1 for next block size. */

        if (bytestream2_get_bytes_left(&s->gb) < 5)

            return AVERROR_INVALIDDATA;

        gce_flags    = bytestream2_get_byteu(&s->gb);

        bytestream2_skipu(&s->gb, 2);    // delay during which the frame is shown

        gce_transparent_index = bytestream2_get_byteu(&s->gb);

        if (gce_flags & 0x01)

            s->transparent_color_index = gce_transparent_index;

        else

            s->transparent_color_index = -1;

        s->gce_disposal = (gce_flags >> 2) & 0x7;

        ff_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",

               gce_flags,

               s->transparent_color_index, s->gce_disposal);

        if (s->gce_disposal > 3) {

            s->gce_disposal = GCE_DISPOSAL_NONE;

            ff_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);

        }

        ext_len = bytestream2_get_byteu(&s->gb);

        break;

    }

    /* NOTE: many extension blocks can come after */

 discard_ext:

    while (ext_len) {

        /* There must be at least ext_len bytes and 1 for next block size byte. */

        if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)

            return AVERROR_INVALIDDATA;

        bytestream2_skipu(&s->gb, ext_len);

        ext_len = bytestream2_get_byteu(&s->gb);

        ff_dlog(s->avctx, "ext_len1=%d\n", ext_len);

    }

    return 0;

}

static int gif_read_header1(GifState *s)

{

    uint8_t sig[6];

    int v, n;

    int background_color_index;

    if (bytestream2_get_bytes_left(&s->gb) < 13)

        return AVERROR_INVALIDDATA;

    /* read gif signature */

    bytestream2_get_bufferu(&s->gb, sig, 6);

    if (memcmp(sig, gif87a_sig, 6) &&

        memcmp(sig, gif89a_sig, 6))

        return AVERROR_INVALIDDATA;

    /* read screen header */

    s->transparent_color_index = -1;

    s->screen_width  = bytestream2_get_le16u(&s->gb);

    s->screen_height = bytestream2_get_le16u(&s->gb);

    v = bytestream2_get_byteu(&s->gb);

    s->color_resolution = ((v & 0x70) >> 4) + 1;

    s->has_global_palette = (v & 0x80);

    s->bits_per_pixel = (v & 0x07) + 1;

    background_color_index = bytestream2_get_byteu(&s->gb);

    n = bytestream2_get_byteu(&s->gb);

    if (n) {

        s->avctx->sample_aspect_ratio.num = n + 15;

        s->avctx->sample_aspect_ratio.den = 64;

    }

    ff_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",

           s->screen_width, s->screen_height, s->bits_per_pixel,

           s->has_global_palette);

    if (s->has_global_palette) {

        s->background_color_index = background_color_index;

        n = 1 << s->bits_per_pixel;

        if (bytestream2_get_bytes_left(&s->gb) < n * 3)

            return AVERROR_INVALIDDATA;

        gif_read_palette(s, s->global_palette, n);

        s->bg_color = s->global_palette[s->background_color_index];

    } else

        s->background_color_index = -1;

    return 0;

}

static int gif_parse_next_image(GifState *s, AVFrame *frame)

{

    while (bytestream2_get_bytes_left(&s->gb) > 0) {

        int code = bytestream2_get_byte(&s->gb);

        int ret;

        av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);

        switch (code) {

        case GIF_IMAGE_SEPARATOR:

            return gif_read_image(s, frame);

        case GIF_EXTENSION_INTRODUCER:

            if ((ret = gif_read_extension(s)) < 0)

                return ret;

            break;

        case GIF_TRAILER:

            /* end of image */

            return AVERROR_EOF;

        default:

            /* erroneous block label */

            return AVERROR_INVALIDDATA;

        }

    }

    return AVERROR_EOF;

}

static av_cold int gif_decode_init(AVCodecContext *avctx)

{

    GifState *s = avctx->priv_data;

    s->avctx = avctx;

    avctx->pix_fmt = AV_PIX_FMT_RGB32;

    s->frame = av_frame_alloc();

    if (!s->frame)

        return AVERROR(ENOMEM);

    ff_lzw_decode_open(&s->lzw);

    if (!s->lzw)

        return AVERROR(ENOMEM);

    return 0;

}

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

                            int *got_frame, AVPacket *avpkt)

{

    GifState *s = avctx->priv_data;

    int ret;

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

    if (avpkt->size >= 6) {

        s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||

                      memcmp(avpkt->data, gif89a_sig, 6) == 0;

    } else {

        s->keyframe = 0;

    }

    if (s->keyframe) {

        s->keyframe_ok = 0;

        s->gce_prev_disposal = GCE_DISPOSAL_NONE;

        if ((ret = gif_read_header1(s)) < 0)

            return ret;

        if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)

            return ret;

        av_frame_unref(s->frame);

        av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);

        if (!s->idx_line)

            return AVERROR(ENOMEM);

    } else if (!s->keyframe_ok) {

        av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");

        return AVERROR_INVALIDDATA;

    }

    ret = ff_reget_buffer(avctx, s->frame, 0);

    if (ret < 0)

        return ret;

    ret = gif_parse_next_image(s, s->frame);

    if (ret < 0)

        return ret;

    if ((ret = av_frame_ref(rframe, s->frame)) < 0)

        return ret;

    rframe->pict_type = s->keyframe ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;

    rframe->flags     = AV_FRAME_FLAG_KEY * s->keyframe;

    s->keyframe_ok   |= !!s->keyframe;

    *got_frame = 1;

    return bytestream2_tell(&s->gb);

}

static av_cold int gif_decode_close(AVCodecContext *avctx)

{

    GifState *s = avctx->priv_data;

    ff_lzw_decode_close(&s->lzw);

    av_frame_free(&s->frame);

    av_freep(&s->idx_line);

    av_freep(&s->stored_img);

    return 0;

}

static const AVOption options[] = {

    { "trans_color", "color value (ARGB) that is used instead of transparent color",

      offsetof(GifState, trans_color), AV_OPT_TYPE_INT,

      {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,

      AV_OPT_FLAG_DECODING_PARAM|AV_OPT_FLAG_VIDEO_PARAM },

    { NULL },

};

static const AVClass decoder_class = {

    .class_name = "gif decoder",

    .item_name  = av_default_item_name,

    .option     = options,

    .version    = LIBAVUTIL_VERSION_INT,

    .category   = AV_CLASS_CATEGORY_DECODER,

};

const FFCodec ff_gif_decoder = {

    .p.name         = "gif",

    CODEC_LONG_NAME("GIF (Graphics Interchange Format)"),

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_GIF,

    .priv_data_size = sizeof(GifState),

    .init           = gif_decode_init,

    .close          = gif_decode_close,

    FF_CODEC_DECODE_CB(gif_decode_frame),

    .p.capabilities = AV_CODEC_CAP_DR1,

    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,

    .p.priv_class   = &decoder_class,

};