Chunk chunk = world.getChunkFromBlockCoords(x, z);
int cX = x & 15, cZ = z & 15;
for (int y = yS; y <= yL; ++y) {
boolean v = meta == -1 || chunk.getBlockMetadata(cX, y, cZ) == meta;
if (v && chunk.getBlock(cX, y, cZ) == block) {
if (chunk.func_150807_a(cX, y, cZ, Blocks.air, 0)) {
set.add(chunk);
}
}
}
}