/*
  * 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/imgutils.h"

 #include "libavutil/opt.h"

 #include "avcodec.h"
 #include "bytestream.h"

 #include "internal.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 */
     uint32_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)
 {
     uint32_t *p = (uint32_t *)picture->data[0];
     uint32_t *p_end = p + (picture->linesize[0] / sizeof(uint32_t)) * picture->height;
 
     for (; p < p_end; p++)
         *p = color;
 }
 
 static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
 {
     const int linesize = picture->linesize[0] / sizeof(uint32_t);
     const uint32_t *py = (uint32_t *)picture->data[0] + t * linesize;

     const uint32_t *pr, *pb = py + h * linesize;

     uint32_t *px;
 
     for (; py < pb; py += linesize) {
         px = (uint32_t *)py + l;
         pr = px + w;
 
         for (; px < pr; px++)
             *px = color;
     }
 }
 
 static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst,
                               int linesize, int l, int t, int w, int h)
 {
     const int y_start = t * linesize;

     const uint32_t *src_px,

                    *src_py = src + y_start,
                    *dst_py = dst + y_start;

     const uint32_t *src_pb = src_py + h * linesize;

     uint32_t *dst_px;
 
     for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
         src_px = src_py + l;
         dst_px = (uint32_t *)dst_py + l;
 

         memcpy(dst_px, src_px, w * sizeof(uint32_t));

     }
 }

 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, linesize, pal_size, lzwed_len;

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

     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 || left >= s->screen_width) {
         av_log(s->avctx, AV_LOG_ERROR, "Invalid image width.\n");

         return AVERROR_INVALIDDATA;

     }

     if (!height || height > s->screen_height || top >= s->screen_height) {
         av_log(s->avctx, AV_LOG_ERROR, "Invalid image height.\n");

         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, (uint32_t *)frame->data[0],
             frame->linesize[0] / sizeof(uint32_t), 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, frame->linesize[0] * frame->height);

             if (!s->stored_img)
                 return AVERROR(ENOMEM);

             gif_copy_img_rect((uint32_t *)frame->data[0], s->stored_img,

                 frame->linesize[0] / sizeof(uint32_t), 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] / sizeof(uint32_t);
     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 * 8;
                 break;
             case 2:
                 y1 += 4;
                 ptr += linesize * 4;
                 break;
             case 3:
                 y1 += 2;
                 ptr += linesize * 2;
                 break;
             }

             while (y1 >= height) {

                 y1  = 4 >> pass;

                 ptr = ptr1 + linesize * y1;
                 pass++;
             }

         } else {
             ptr += linesize;
         }
     }

 
  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);

     return 0;
 }
 

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

 {
     GifState *s = avctx->priv_data;
     int ret;
 

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

     s->frame->pts     = avpkt->pts;

 #if FF_API_PKT_PTS
 FF_DISABLE_DEPRECATION_WARNINGS

     s->frame->pkt_pts = avpkt->pts;

 FF_ENABLE_DEPRECATION_WARNINGS
 #endif

     s->frame->pkt_dts = avpkt->dts;
     av_frame_set_pkt_duration(s->frame, avpkt->duration);

     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);

         if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)

             return ret;
 

         av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
         if (!s->idx_line)
             return AVERROR(ENOMEM);
 

         s->frame->pict_type = AV_PICTURE_TYPE_I;
         s->frame->key_frame = 1;

         s->keyframe_ok = 1;

     } else {

         if (!s->keyframe_ok) {
             av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
             return AVERROR_INVALIDDATA;
         }
 

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

             return ret;
 

         s->frame->pict_type = AV_PICTURE_TYPE_P;
         s->frame->key_frame = 0;

     }

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

     if (ret < 0)
         return ret;

     if ((ret = av_frame_ref(data, s->frame)) < 0)
         return ret;

     *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,
 };
 

 AVCodec ff_gif_decoder = {

     .name           = "gif",

     .long_name      = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),

     .type           = AVMEDIA_TYPE_VIDEO,

     .id             = AV_CODEC_ID_GIF,

     .priv_data_size = sizeof(GifState),
     .init           = gif_decode_init,
     .close          = gif_decode_close,
     .decode         = gif_decode_frame,

     .capabilities   = AV_CODEC_CAP_DR1,

     .priv_class     = &decoder_class,

 };