Revert "Merge pull request #200 from sigp/new-structure"

This reverts commit d7a3545be1, reversing
changes made to 1da06c156c.

beacon_node/beacon_chain/src/checkpoint.rs

@@ -0,0 +1,43 @@
+use serde_derive::Serialize;
+use types::{BeaconBlock, BeaconState, Hash256};
+
+/// Represents some block and it's associated state. Generally, this will be used for tracking the
+/// head, justified head and finalized head.
+#[derive(PartialEq, Clone, Serialize)]
+pub struct CheckPoint {
+    pub beacon_block: BeaconBlock,
+    pub beacon_block_root: Hash256,
+    pub beacon_state: BeaconState,
+    pub beacon_state_root: Hash256,
+}
+
+impl CheckPoint {
+    /// Create a new checkpoint.
+    pub fn new(
+        beacon_block: BeaconBlock,
+        beacon_block_root: Hash256,
+        beacon_state: BeaconState,
+        beacon_state_root: Hash256,
+    ) -> Self {
+        Self {
+            beacon_block,
+            beacon_block_root,
+            beacon_state,
+            beacon_state_root,
+        }
+    }
+
+    /// Update all fields of the checkpoint.
+    pub fn update(
+        &mut self,
+        beacon_block: BeaconBlock,
+        beacon_block_root: Hash256,
+        beacon_state: BeaconState,
+        beacon_state_root: Hash256,
+    ) {
+        self.beacon_block = beacon_block;
+        self.beacon_block_root = beacon_block_root;
+        self.beacon_state = beacon_state;
+        self.beacon_state_root = beacon_state_root;
+    }
+}