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;
int value = get_bits1(gb);
if (value) {
static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
value = get_bits1(gb);
*codebook_index = transitions[*codebook_index][value];
}
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 = get_bitsz(gb, depth);
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 av_always_inline int get_tail(GetBitContext *gb, int k)
{
int p, e, res;
if (k < 1)
return 0;
p = av_log2(k);
e = (1 << (p + 1)) - k - 1;
res = get_bitsz(gb, p);
if (res >= e)
res = (res << 1) - e + get_bits1(gb);
return res;
}
static int build_huffman(AVCodecContext *avctx, GetBitContext *gbit, int max)
{
MagicYUVContext *s = avctx->priv_data;
int i = 0, j = 0, k;
memset(s->len, 0, sizeof(s->len));
while (get_bits_left(gbit) >= 8) {
int b = get_bits(gbit, 1);
int x = get_bits(gbit, 7);
int l = get_bitsz(gbit, b * 8) + 1;
for (k = 0; k < l; k++)
if (j + k < max)
s->len[i][j + k] = x;
j += l;
if (j == max) {
j = 0;
if (s->huff_build(&s->vlc[i], s->len[i])) {
av_log(avctx, AV_LOG_ERROR, "Cannot build Huffman codes\n");
return AVERROR_INVALIDDATA;
}
i++;
if (i == s->planes) {
break;
}
} else if (j > max) {
av_log(avctx, AV_LOG_ERROR, "Invalid Huffman codes\n");
return AVERROR_INVALIDDATA;
}
}
if (i != s->planes) {
av_log(avctx, AV_LOG_ERROR, "Huffman tables too short\n");
return AVERROR_INVALIDDATA;
}
return 0;
}
