/*
  * Escape 124 Video Decoder
  * Copyright (C) 2008 Eli Friedman (eli.friedman@gmail.com)
  *
  * 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 "internal.h"

 #define BITSTREAM_READER_LE

 #include "get_bits.h"

 
 typedef union MacroBlock {
     uint16_t pixels[4];
     uint32_t pixels32[2];
 } MacroBlock;
 
 typedef union SuperBlock {
     uint16_t pixels[64];
     uint32_t pixels32[32];
 } SuperBlock;
 
 typedef struct CodeBook {
     unsigned depth;
     unsigned size;

     MacroBlock* blocks;

 } CodeBook;
 
 typedef struct Escape124Context {

     AVFrame *frame;

 
     unsigned num_superblocks;
 

     CodeBook codebooks[3];

 } Escape124Context;
 
 /**
  * Initialize the decoder
  * @param avctx decoder context
  * @return 0 success, negative on error
  */
 static av_cold int escape124_decode_init(AVCodecContext *avctx)
 {
     Escape124Context *s = avctx->priv_data;
 

     avctx->pix_fmt = AV_PIX_FMT_RGB555;

 
     s->num_superblocks = ((unsigned)avctx->width / 8) *
                          ((unsigned)avctx->height / 8);
 

     s->frame = av_frame_alloc();
     if (!s->frame)
         return AVERROR(ENOMEM);
 

     return 0;
 }
 
 static av_cold int escape124_decode_close(AVCodecContext *avctx)
 {
     unsigned i;
     Escape124Context *s = avctx->priv_data;
 
     for (i = 0; i < 3; i++)

         av_free(s->codebooks[i].blocks);

     av_frame_free(&s->frame);

 
     return 0;
 }
 

 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,

                                  unsigned size)
 {
     unsigned i, j;

     CodeBook cb = { 0 };

     if (size >= INT_MAX / 34 || get_bits_left(gb) < size * 34)

         return cb;

     if (size >= INT_MAX / sizeof(MacroBlock))
         return cb;
     cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
     if (!cb.blocks)
         return cb;

     cb.depth = depth;
     cb.size = size;

     for (i = 0; i < size; i++) {
         unsigned mask_bits = get_bits(gb, 4);
         unsigned color0 = get_bits(gb, 15);
         unsigned color1 = get_bits(gb, 15);
 
         for (j = 0; j < 4; j++) {
             if (mask_bits & (1 << j))

                 cb.blocks[i].pixels[j] = color1;

             else

                 cb.blocks[i].pixels[j] = color0;

         }
     }
     return cb;
 }
 
 static unsigned decode_skip_count(GetBitContext* gb)
 {
     unsigned value;
     // This function reads a maximum of 23 bits,
     // which is within the padding space

     if (get_bits_left(gb) < 1)

         return -1;
     value = get_bits1(gb);
     if (!value)
         return value;
 
     value += get_bits(gb, 3);
     if (value != (1 + ((1 << 3) - 1)))
         return value;
 
     value += get_bits(gb, 7);
     if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
         return value;
 
     return value + get_bits(gb, 12);
 }
 
 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
                                     int* codebook_index, int superblock_index)
 {
     // This function reads a maximum of 22 bits; the callers
     // guard this function appropriately
     unsigned block_index, depth;
 
     if (get_bits1(gb)) {
         static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
         *codebook_index = transitions[*codebook_index][get_bits1(gb)];
     }
 

     depth = s->codebooks[*codebook_index].depth;

 
     // depth = 0 means that this shouldn't read any bits;
     // in theory, this is the same as get_bits(gb, 0), but
     // that doesn't actually work.
     block_index = depth ? get_bits(gb, depth) : 0;
 
     if (*codebook_index == 1) {

         block_index += superblock_index << s->codebooks[1].depth;

     }
 
     // This condition can occur with invalid bitstreams and
     // *codebook_index == 2

     if (block_index >= s->codebooks[*codebook_index].size)

         return (MacroBlock) { { 0 } };
 

     return s->codebooks[*codebook_index].blocks[block_index];

 }
 
 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
    // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
    uint32_t *dst = sb->pixels32 + index + (index & -4);
 
    // This technically violates C99 aliasing rules, but it should be safe.
    dst[0] = mb.pixels32[0];
    dst[4] = mb.pixels32[1];
 }
 
 static void copy_superblock(uint16_t* dest, unsigned dest_stride,
                             uint16_t* src, unsigned src_stride)
 {
     unsigned y;
     if (src)
         for (y = 0; y < 8; y++)
             memcpy(dest + y * dest_stride, src + y * src_stride,
                    sizeof(uint16_t) * 8);
     else
         for (y = 0; y < 8; y++)
             memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
 }
 
 static const uint16_t mask_matrix[] = {0x1,   0x2,   0x10,   0x20,
                                        0x4,   0x8,   0x40,   0x80,
                                        0x100, 0x200, 0x1000, 0x2000,
                                        0x400, 0x800, 0x4000, 0x8000};
 
 static int escape124_decode_frame(AVCodecContext *avctx,

                                   void *data, int *got_frame,

                                   AVPacket *avpkt)

 {

     int buf_size = avpkt->size;

     Escape124Context *s = avctx->priv_data;

     AVFrame *frame = data;

 
     GetBitContext gb;
     unsigned frame_flags, frame_size;
     unsigned i;
 
     unsigned superblock_index, cb_index = 1,
              superblock_col_index = 0,
              superblocks_per_row = avctx->width / 8, skip = -1;
 
     uint16_t* old_frame_data, *new_frame_data;
     unsigned old_stride, new_stride;
 

     int ret;

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

 
     // This call also guards the potential depth reads for the
     // codebook unpacking.

     if (get_bits_left(&gb) < 64)

         return -1;
 
     frame_flags = get_bits_long(&gb, 32);
     frame_size  = get_bits_long(&gb, 32);
 
     // Leave last frame unchanged
     // FIXME: Is this necessary?  I haven't seen it in any real samples
     if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {

         if (!s->frame->data[0])

             return AVERROR_INVALIDDATA;
 

         av_log(avctx, AV_LOG_DEBUG, "Skipping frame\n");

         *got_frame = 1;

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

             return ret;

 
         return frame_size;
     }
 
     for (i = 0; i < 3; i++) {
         if (frame_flags & (1 << (17 + i))) {
             unsigned cb_depth, cb_size;
             if (i == 2) {
                 // This codebook can be cut off at places other than
                 // powers of 2, leaving some of the entries undefined.
                 cb_size = get_bits_long(&gb, 20);
                 cb_depth = av_log2(cb_size - 1) + 1;
             } else {
                 cb_depth = get_bits(&gb, 4);
                 if (i == 0) {
                     // This is the most basic codebook: pow(2,depth) entries
                     // for a depth-length key
                     cb_size = 1 << cb_depth;
                 } else {
                     // This codebook varies per superblock
                     // FIXME: I don't think this handles integer overflow
                     // properly
                     cb_size = s->num_superblocks << cb_depth;
                 }
             }

             av_free(s->codebooks[i].blocks);

             s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);

             if (!s->codebooks[i].blocks)

                 return -1;
         }
     }
 

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

         return ret;

     new_frame_data = (uint16_t*)frame->data[0];
     new_stride = frame->linesize[0] / 2;

     old_frame_data = (uint16_t*)s->frame->data[0];
     old_stride = s->frame->linesize[0] / 2;

 
     for (superblock_index = 0; superblock_index < s->num_superblocks;
          superblock_index++) {
         MacroBlock mb;
         SuperBlock sb;
         unsigned multi_mask = 0;
 
         if (skip == -1) {
             // Note that this call will make us skip the rest of the blocks
             // if the frame prematurely ends
             skip = decode_skip_count(&gb);
         }
 
         if (skip) {
             copy_superblock(new_frame_data, new_stride,
                             old_frame_data, old_stride);
         } else {
             copy_superblock(sb.pixels, 8,
                             old_frame_data, old_stride);
 

             while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {

                 unsigned mask;
                 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
                 mask = get_bits(&gb, 16);
                 multi_mask |= mask;
                 for (i = 0; i < 16; i++) {
                     if (mask & mask_matrix[i]) {
                         insert_mb_into_sb(&sb, mb, i);
                     }
                 }
             }
 

             if (!get_bits1(&gb)) {

                 unsigned inv_mask = get_bits(&gb, 4);
                 for (i = 0; i < 4; i++) {
                     if (inv_mask & (1 << i)) {
                         multi_mask ^= 0xF << i*4;
                     } else {
                         multi_mask ^= get_bits(&gb, 4) << i*4;
                     }
                 }
 
                 for (i = 0; i < 16; i++) {
                     if (multi_mask & mask_matrix[i]) {
                         mb = decode_macroblock(s, &gb, &cb_index,
                                                superblock_index);
                         insert_mb_into_sb(&sb, mb, i);
                     }
                 }
             } else if (frame_flags & (1 << 16)) {

                 while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {

                     mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
                     insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
                 }
             }
 
             copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
         }
 
         superblock_col_index++;
         new_frame_data += 8;
         if (old_frame_data)
             old_frame_data += 8;
         if (superblock_col_index == superblocks_per_row) {
             new_frame_data += new_stride * 8 - superblocks_per_row * 8;
             if (old_frame_data)
                 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
             superblock_col_index = 0;
         }
         skip--;
     }
 

     av_log(avctx, AV_LOG_DEBUG,

            "Escape sizes: %i, %i, %i\n",
            frame_size, buf_size, get_bits_count(&gb) / 8);
 

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

         return ret;

     *got_frame = 1;

 
     return frame_size;
 }
 
 

 AVCodec ff_escape124_decoder = {

     .name           = "escape124",

     .long_name      = NULL_IF_CONFIG_SMALL("Escape 124"),

     .type           = AVMEDIA_TYPE_VIDEO,

     .id             = AV_CODEC_ID_ESCAPE124,

     .priv_data_size = sizeof(Escape124Context),
     .init           = escape124_decode_init,
     .close          = escape124_decode_close,
     .decode         = escape124_decode_frame,
     .capabilities   = CODEC_CAP_DR1,

 };