Add some world defs

src/world.rs

@@ -0,0 +1,28 @@
+use fnv::FnvHashMap;
+
+type ChunkPosScalar = i16;
+
+#[derive(Hash)]
+struct ChunkPos {
+    x: ChunkPosScalar,
+    y: ChunkPosScalar,
+}
+
+pub struct World {
+    chunks: FnvHashMap<ChunkPos, Chunk>,
+}
+
+const CHUNK_EXTENT: u16 = 256;
+const CHUNK_N_BLOCKS: usize = CHUNK_EXTENT as usize * CHUNK_EXTENT as usize;
+
+type ChunkBlocks = [Block; CHUNK_N_BLOCKS];
+
+pub struct Chunk {
+    blocks: ChunkBlocks,
+}
+
+type BlockId = u16;
+
+pub struct Block {
+    id: BlockId,
+}