Added Capella Epoch Processing Logic (#3666)

consensus/state_processing/src/common/mod.rs

@@ -4,6 +4,7 @@ mod get_attesting_indices;
 mod get_indexed_attestation;
 mod initiate_validator_exit;
 mod slash_validator;
+mod withdraw_balance;
 
 pub mod altair;
 pub mod base;
@@ -14,6 +15,7 @@ pub use get_attesting_indices::{get_attesting_indices, get_attesting_indices_fro
 pub use get_indexed_attestation::get_indexed_attestation;
 pub use initiate_validator_exit::initiate_validator_exit;
 pub use slash_validator::slash_validator;
+pub use withdraw_balance::withdraw_balance;
 
 use safe_arith::SafeArith;
 use types::{BeaconState, BeaconStateError, EthSpec};

consensus/state_processing/src/common/withdraw_balance.rs

@@ -0,0 +1,28 @@
+use crate::common::decrease_balance;
+use safe_arith::SafeArith;
+use types::{BeaconStateError as Error, *};
+
+pub fn withdraw_balance<T: EthSpec>(
+    state: &mut BeaconState<T>,
+    validator_index: usize,
+    amount: u64,
+) -> Result<(), Error> {
+    decrease_balance(state, validator_index as usize, amount)?;
+
+    let withdrawal_address = Address::from_slice(
+        &state
+            .get_validator(validator_index)?
+            .withdrawal_credentials
+            .as_bytes()[12..],
+    );
+    let withdrawal = Withdrawal {
+        index: *state.next_withdrawal_index()?,
+        validator_index: validator_index as u64,
+        address: withdrawal_address,
+        amount,
+    };
+    state.next_withdrawal_index_mut()?.safe_add_assign(1)?;
+    state.withdrawal_queue_mut()?.push(withdrawal)?;
+
+    Ok(())
+}