Fix #378, int to bytes32, LATEST_RANDAO_MIXES, get_seed, get_crosslink_committee, get_compact_committee_root (#380)

beacon_chain/spec/helpers.nim

@@ -7,7 +7,7 @@
 
 # Uncategorized helper functions from the spec
 
-import ./datatypes, ./digest, sequtils, math
+import ./datatypes, ./digest, sequtils, math, endians
 
 # https://github.com/ethereum/eth2.0-specs/blob/v0.8.3/specs/core/0_beacon-chain.md#integer_squareroot
 func integer_squareroot*(n: SomeInteger): SomeInteger =
@@ -102,9 +102,7 @@ func get_current_epoch*(state: BeaconState): Epoch =
 func get_randao_mix*(state: BeaconState,
                      epoch: Epoch): Eth2Digest =
     ## Returns the randao mix at a recent ``epoch``.
-    ## ``epoch`` expected to be between (current_epoch -
-    ## LATEST_RANDAO_MIXES_LENGTH, current_epoch].
-    state.randao_mixes[epoch mod LATEST_RANDAO_MIXES_LENGTH]
+    state.randao_mixes[epoch mod EPOCHS_PER_HISTORICAL_VECTOR]
 
 func bytes_to_int*(data: openarray[byte]): uint64 =
   doAssert data.len == 8
@@ -118,14 +116,12 @@ func bytes_to_int*(data: openarray[byte]): uint64 =
 func int_to_bytes32*(x: uint64): array[32, byte] =
   ## Little-endian data representation
   ## TODO remove uint64 when those callers fade away
-  for i in 0 ..< 8:
-    result[24 + i] = byte((x shr i*8) and 0xff)
+  littleEndian64(result[0].addr, x.unsafeAddr)
 
 func int_to_bytes32*(x: Epoch): array[32, byte] {.borrow.}
 
 func int_to_bytes8*(x: uint64): array[8, byte] =
-  for i in 0 ..< 8:
-    result[i] = byte((x shr i*8) and 0xff)
+  littleEndian64(result[0].addr, x.unsafeAddr)
 
 func int_to_bytes1*(x: int): array[1, byte] =
   doAssert x >= 0
@@ -175,11 +171,11 @@ func get_seed*(state: BeaconState, epoch: Epoch): Eth2Digest =
   var seed_input : array[32*3, byte]
 
   # Detect potential underflow
-  doAssert LATEST_RANDAO_MIXES_LENGTH >= MIN_SEED_LOOKAHEAD
+  doAssert EPOCHS_PER_HISTORICAL_VECTOR >= MIN_SEED_LOOKAHEAD
 
   seed_input[0..31] =
     get_randao_mix(state,
-      epoch + LATEST_RANDAO_MIXES_LENGTH - MIN_SEED_LOOKAHEAD - 1).data
+      epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD - 1).data
   seed_input[32..63] =
     state.active_index_roots[epoch mod EPOCHS_PER_HISTORICAL_VECTOR].data
   seed_input[64..95] = int_to_bytes32(epoch)

beacon_chain/spec/presets/mainnet.nim

@@ -136,7 +136,6 @@ const
   # State list lengths
   # ---------------------------------------------------------------
   # https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#state-list-lengths
-  LATEST_RANDAO_MIXES_LENGTH* = 8192
   EPOCHS_PER_HISTORICAL_VECTOR* = 65536
   EPOCHS_PER_SLASHINGS_VECTOR* = 8192
   HISTORICAL_ROOTS_LIMIT* = 16777216

beacon_chain/spec/presets/minimal.nim

@@ -99,7 +99,6 @@ const
   # https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#state-list-lengths
 
   # Changed
-  LATEST_RANDAO_MIXES_LENGTH* = 64
   EPOCHS_PER_HISTORICAL_VECTOR* = 64
   EPOCHS_PER_SLASHINGS_VECTOR* = 64
   HISTORICAL_ROOTS_LIMIT* = 16777216

beacon_chain/spec/state_transition_block.nim

@@ -90,11 +90,12 @@ proc processBlockHeader(
 
   true
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#randao
-proc processRandao(
+# https://github.com/ethereum/eth2.0-specs/blob/v0.8.3/specs/core/0_beacon-chain.md#randao
+proc process_randao(
     state: var BeaconState, body: BeaconBlockBody, flags: UpdateFlags,
     stateCache: var StateCache): bool =
   let
+    epoch = state.get_current_epoch()
     proposer_index = get_beacon_proposer_index(state, stateCache)
     proposer = addr state.validators[proposer_index]
 
@@ -102,23 +103,23 @@ proc processRandao(
   if skipValidation notin flags:
     if not bls_verify(
       proposer.pubkey,
-      hash_tree_root(get_current_epoch(state).uint64).data,
+      hash_tree_root(epoch.uint64).data,
       body.randao_reveal,
       get_domain(state, DOMAIN_RANDAO)):
 
       notice "Randao mismatch", proposer_pubkey = proposer.pubkey,
-                                message = get_current_epoch(state),
+                                message = epoch,
                                 signature = body.randao_reveal,
                                 slot = state.slot
       return false
 
   # Mix it in
   let
-    mix = get_current_epoch(state) mod LATEST_RANDAO_MIXES_LENGTH
+    mix = get_randao_mix(state, epoch)
     rr = eth2hash(body.randao_reveal.getBytes()).data
 
-  for i, b in state.randao_mixes[mix].data:
-    state.randao_mixes[mix].data[i] = b xor rr[i]
+  for i in 0 ..< mix.data.len:
+    state.randao_mixes[epoch mod EPOCHS_PER_HISTORICAL_VECTOR].data[i] = mix.data[i] xor rr[i]
 
   true
 

beacon_chain/spec/state_transition_epoch.nim

@@ -497,7 +497,7 @@ proc process_final_updates*(state: var BeaconState) =
   state.slashings[next_epoch mod EPOCHS_PER_SLASHINGS_VECTOR] = 0.Gwei
 
   # Set randao mix
-  state.randao_mixes[next_epoch mod LATEST_RANDAO_MIXES_LENGTH] =
+  state.randao_mixes[next_epoch mod EPOCHS_PER_HISTORICAL_VECTOR] =
     get_randao_mix(state, current_epoch)
 
   # Set historical root accumulator