static int get_bits(Jpeg2000DecoderContext *s, int n) { int res = 0; if (s->buf_end - s->buf < ((n - s->bit_index) >> 8)) return AVERROR_INVALIDDATA; while (--n >= 0) { res <<= 1; if (s->bit_index == 0) { s->bit_index = 7 + (*s->buf != 0xff); s->buf++; } s->bit_index--; res |= (*s->buf >> s->bit_index) & 1; } return res; }