// Package state defines how the beacon chain state for eth2
// functions in the running beacon node, using an advanced,
// immutable implementation of the state data structure.
//
// BeaconState getters may be accessed from inside or outside the package. To
// avoid duplicating locks, we have internal and external versions of the
// getter The external function carries out the short-circuit conditions,
// obtains a read lock, then calls the internal function.  The internal function
// carries out the short-circuit conditions and returns the required data
// without further locking, allowing it to be used by other package-level
// functions that already hold a lock. Hence the functions look something
// like this:
//
//  func (b *BeaconState) Foo() uint64 {
//    // Short-circuit conditions.
//    if !b.HasInnerState() {
//      return 0
//    }
//
//    // Read lock.
//    b.lock.RLock()
//    defer b.lock.RUnlock()
//
//    // Internal getter.
//    return b.foo()
//  }
//
//  func (b *BeaconState) foo() uint64 {
//    // Short-circuit conditions.
//    if !b.HasInnerState() {
//      return 0
//    }
//
//    return b.state.foo
//  }
//
// Although it is technically possible to remove the short-circuit conditions
// from the external function, that would require every read to obtain a lock
// even if the data was not present, leading to potential slowdowns.
package state