Balance is 128-bit value.

polkadot/primitives/src/lib.rs

@@ -50,7 +50,8 @@ pub use primitives::block::Id as BlockId;
 pub use primitives::block::Log as Log;
 
 /// An index to a block.
-pub type BlockNumber = u64;
+/// 32-bits will allow for 136 years of blocks assuming 1 block per second.
+pub type BlockNumber = u32;
 
 /// Alias to Ed25519 pubkey that identifies an account on the relay chain. This will almost
 /// certainly continue to be the same as the substrate's `AuthorityId`.
@@ -60,11 +61,11 @@ pub type AccountId = primitives::AuthorityId;
 /// exactly equivalent to what the substrate calls an "authority".
 pub type SessionKey = primitives::AuthorityId;
 
-/// Indentifier for a chain.
-pub type ChainId = u64;
+/// Indentifier for a chain. 32-bit should be plenty.
+pub type ChainId = u32;
 
-/// Index of a transaction in the relay chain.
-pub type Index = u64;
+/// Index of a transaction in the relay chain. 32-bit should be plenty.
+pub type Index = u32;
 
 /// A hash of some data used by the relay chain.
 pub type Hash = primitives::H256;
@@ -76,4 +77,10 @@ pub type Signature = runtime_primitives::Ed25519Signature;
 pub type Timestamp = u64;
 
 /// The balance of an account.
-pub type Balance = u64;
+/// 128-bits (or 38 significant decimal figures) will allow for 10m currency (10^7) at a resolution
+/// to all for one second's worth of an annualised 50% reward be paid to a unit holder (10^11 unit
+/// denomination), or 10^18 total atomic units, to grow at 50%/year for 51 years (10^9 multiplier)
+/// for an eventual total of 10^27 units (27 significant decimal figures).
+/// We round denomination to 10^12 (12 sdf), and leave the other redundancy at the upper end so
+/// that 32 bits may be multiplied with a balance in 128 bits without worrying about overflow.
+pub type Balance = u128;

substrate/codec/src/slicable.rs

@@ -344,7 +344,7 @@ macro_rules! impl_non_endians {
  )* }
 }
 
-impl_endians!(u16, u32, u64, usize, i16, i32, i64, isize);
+impl_endians!(u16, u32, u64, u128, usize, i16, i32, i64, i128, isize);
 impl_non_endians!(i8, [u8; 1], [u8; 2], [u8; 3], [u8; 4], [u8; 5], [u8; 6], [u8; 7], [u8; 8],
  [u8; 10], [u8; 12], [u8; 14], [u8; 16], [u8; 20], [u8; 24], [u8; 28], [u8; 32], [u8; 40],
  [u8; 48], [u8; 56], [u8; 64], [u8; 80], [u8; 96], [u8; 112], [u8; 128], bool);

substrate/runtime/primitives/src/traits.rs

@@ -61,7 +61,7 @@ pub trait As<T> {
 macro_rules! impl_numerics {
  ( $( $t:ty ),* ) => {
  $(
- impl_numerics!($t: u8, u16, u32, u64, usize, i8, i16, i32, i64, isize,);
+ impl_numerics!($t: u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize,);
  )*
  };
  ( $f:ty : $t:ty, $( $rest:ty, )* ) => {
@@ -74,7 +74,7 @@ macro_rules! impl_numerics {
  ( $f:ty : ) => {}
 }
 
-impl_numerics!(u8, u16, u32, u64, usize, i8, i16, i32, i64, isize);
+impl_numerics!(u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);
 
 pub struct Identity;
 impl<T> Convert<T, T> for Identity {