Proper Uint256 parser for JSON genesis (#1071)

* Update exception tracinig

* Use lazy JSON parser

why:
  Uint246 type is not directly supported by the JSON serializer

* Json parser update for stringified UInt256 integers

why:
  Now available

* update sub-module branch reference

nimbus/chain_config.nim

@@ -17,6 +17,8 @@ import
   json_serialization/lexer,
   "."/[forks, genesis_alloc]
 
+{.push raises: [Defect].}
+
 type
   CliqueOptions = object
     epoch : Option[int]
@@ -135,60 +137,102 @@ const
   GoerliNet*  = 5.NetworkId
   KovanNet*   = 42.NetworkId
 
-proc read(rlp: var Rlp, x: var AddressBalance, _: type EthAddress): EthAddress {.inline.} =
+proc read(rlp: var Rlp, x: var AddressBalance, _: type EthAddress): EthAddress
+    {.gcsafe, raises: [Defect,RlpError].} =
   let val = rlp.read(UInt256).toByteArrayBE()
   result[0 .. ^1] = val.toOpenArray(12, val.high)
 
-proc read(rlp: var Rlp, x: var AddressBalance, _: type GenesisAccount): GenesisAccount {.inline.} =
+proc read(rlp: var Rlp, x: var AddressBalance, _: type GenesisAccount): GenesisAccount
+    {.gcsafe, raises: [Defect,RlpError].} =
   GenesisAccount(balance: rlp.read(UInt256))
 
-func decodePrealloc*(data: seq[byte]): GenesisAlloc =
+func decodePrealloc*(data: seq[byte]): GenesisAlloc
+    {.gcsafe, raises: [Defect,RlpError].} =
   for tup in rlp.decode(data, seq[AddressBalance]):
     result[tup.address] = tup.account
 
-proc readValue(reader: var JsonReader, value: var UInt256) =
+# borrowed from `lexer.hexCharValue()` :)
+proc fromHex(c: char): int =
+  case c
+  of '0'..'9': ord(c) - ord('0')
+  of 'a'..'f': ord(c) - ord('a') + 10
+  of 'A'..'F': ord(c) - ord('A') + 10
+  else: -1
+
+proc readValue(reader: var JsonReader, value: var UInt256)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   ## Mixin for `Json.loadFile()`. Note that this driver applies the same
   ## to `BlockNumber` fields as well as generic `UInt265` fields like the
   ## account `balance`.
-  let tok = reader.lexer.tok
-  if tok == tkInt:
-    value = reader.lexer.absIntVal.u256
-    reader.lexer.next()
-  elif tok == tkString:
-    # Make sure that "0x11" decodes to 17, "b" and "11" decode to 11.
-    if reader.lexer.strVal.filterIt(it.isDigit.not).len == 0:
-      try:    value = reader.lexer.strVal.parse(UInt256, radix = 10)
-      except: reader.raiseUnexpectedValue("int string overflow")
-    else:
-      # note that radix is static, so 16 (or 10) cannot be a variable
-      try:    value = reader.lexer.strVal.parse(UInt256, radix = 16)
-      except: reader.raiseUnexpectedValue("hex string parse error")
-    reader.lexer.next()
+  var (accu, ok) = (0.u256, true)
+  if reader.lexer.lazyTok == tkNumeric:
+    try:
+      reader.lexer.customIntValueIt:
+        accu = accu * 10 + it.u256
+      ok = reader.lexer.lazyTok == tkExInt # non-negative wanted
+    except:
+      ok = false
+  elif reader.lexer.lazyTok == tkQuoted:
+    try:
+      var (sLen, base) = (0, 10)
+      reader.lexer.customTextValueIt:
+        if ok:
+          var num = it.fromHex
+          if base <= num:
+            ok = false # cannot be larger than base
+          elif sLen < 2:
+            if 0 <= num:
+              accu = accu * base.u256 + num.u256
+            elif sLen == 1 and it in {'x', 'X'}:
+              base = 16 # handle "0x" prefix
+            else:
+              ok = false
+            sLen.inc
+          elif num < 0:
+            ok = false # not a hex digit
+          elif base == 10:
+            accu = accu * 10 + num.u256
+          else:
+            accu = accu * 16 + num.u256
+    except:
+      reader.raiseUnexpectedValue("numeric string parse error")
   else:
     reader.raiseUnexpectedValue("expect int or hex/int string")
+  if not ok:
+    reader.raiseUnexpectedValue("Uint256 parse error")
+  value = accu
+  reader.lexer.next()
 
-proc readValue(reader: var JsonReader, value: var ChainId) =
+proc readValue(reader: var JsonReader, value: var ChainId)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = reader.readValue(int).ChainId
 
-proc readValue(reader: var JsonReader, value: var Hash256) =
+proc readValue(reader: var JsonReader, value: var Hash256)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = Hash256.fromHex(reader.readValue(string))
 
-proc readValue(reader: var JsonReader, value: var BlockNonce) =
+proc readValue(reader: var JsonReader, value: var BlockNonce)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = fromHex[uint64](reader.readValue(string)).toBlockNonce
 
-proc readValue(reader: var JsonReader, value: var EthTime) =
+proc readValue(reader: var JsonReader, value: var EthTime)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = fromHex[int64](reader.readValue(string)).fromUnix
 
-proc readValue(reader: var JsonReader, value: var seq[byte]) =
+proc readValue(reader: var JsonReader, value: var seq[byte])
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = hexToSeqByte(reader.readValue(string))
 
-proc readValue(reader: var JsonReader, value: var GasInt) =
+proc readValue(reader: var JsonReader, value: var GasInt)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = fromHex[GasInt](reader.readValue(string))
 
-proc readValue(reader: var JsonReader, value: var EthAddress) =
+proc readValue(reader: var JsonReader, value: var EthAddress)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = parseAddress(reader.readValue(string))
 
-proc readValue(reader: var JsonReader, value: var AccountNonce) =
+proc readValue(reader: var JsonReader, value: var AccountNonce)
+    {.gcsafe, raises: [Defect,CatchableError].} =
   value = fromHex[uint64](reader.readValue(string))
 
 template to(a: string, b: type EthAddress): EthAddress =
@@ -199,9 +243,7 @@ template to(a: string, b: type UInt256): UInt256 =
   # json_serialization decode table stuff
   UInt256.fromHex(a)
 
-proc loadNetworkParams*(cc: CustomChain, cg: var NetworkParams):
-    bool {.raises: [Defect].} =
-
+proc loadNetworkParams*(cc: CustomChain, cg: var NetworkParams): bool =
   cg.genesis               = cc.genesis
   cg.config.chainId        = cc.config.chainId
   cg.config.daoForkSupport = cc.config.daoForkSupport
@@ -265,7 +307,7 @@ proc loadNetworkParams*(cc: CustomChain, cg: var NetworkParams):
   return true
 
 proc loadNetworkParams*(fileName: string, cg: var NetworkParams):
-    bool {.raises: [Defect].} =
+    bool {.raises: [Defect,SerializationError].} =
   var cc: CustomChain
   try:
     cc = Json.loadFile(fileName, CustomChain, allowUnknownFields = true)
@@ -275,15 +317,14 @@ proc loadNetworkParams*(fileName: string, cg: var NetworkParams):
   except JsonReaderError as e:
     error "Invalid network params file format", fileName, msg=e.formatMsg("")
     return false
-  except:
-    var msg = getCurrentExceptionMsg()
-    error "Error loading network params file", fileName, msg
+  except Exception as e:
+    error "Error loading network params file",
+      fileName, exception = e.name, msg = e.msg
     return false
 
   loadNetworkParams(cc, cg)
 
-proc decodeNetworkParams*(jsonString: string, cg: var NetworkParams):
-    bool {.raises: [Defect].} =
+proc decodeNetworkParams*(jsonString: string, cg: var NetworkParams): bool =
 
   var cc: CustomChain
   try:
@@ -298,7 +339,8 @@ proc decodeNetworkParams*(jsonString: string, cg: var NetworkParams):
 
   loadNetworkParams(cc, cg)
 
-proc parseGenesisAlloc*(data: string, ga: var GenesisAlloc): bool =
+proc parseGenesisAlloc*(data: string, ga: var GenesisAlloc): bool
+    {.gcsafe, raises: [Defect,CatchableError].} =
   try:
     ga = Json.decode(data, GenesisAlloc, allowUnknownFields = true)
   except JsonReaderError as e:
@@ -414,7 +456,8 @@ proc chainConfigForNetwork(id: NetworkId): ChainConfig =
   else:
     ChainConfig()
 
-proc genesisBlockForNetwork(id: NetworkId): Genesis =
+proc genesisBlockForNetwork(id: NetworkId): Genesis
+    {.gcsafe, raises: [Defect,CatchableError].} =
   result = case id
   of MainNet:
     Genesis(
@@ -453,6 +496,7 @@ proc genesisBlockForNetwork(id: NetworkId): Genesis =
   else:
     Genesis()
 
-proc networkParams*(id: NetworkId): NetworkParams =
+proc networkParams*(id: NetworkId): NetworkParams
+    {.gcsafe, raises: [Defect,CatchableError].} =
   result.genesis = genesisBlockForNetwork(id)
   result.config  = chainConfigForNetwork(id)

tests/test_genesis.nim

@@ -76,9 +76,22 @@ proc customGenesisTest() =
       check h.blockHash == genesisHash
       check cg.config.poaEngine == false
 
+    test "Mainnet shadow fork 1":
+      var cg: NetworkParams
+      check loadNetworkParams("mainshadow1.json".findFilePath, cg)
+      let h = cg.toGenesisHeader
+      let stateRoot = "d7f8974fb5ac78d9ac099b9ad5018bedc2ce0a72dad1827a1709da30580f0544".toDigest
+      let genesisHash = "d4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3".toDigest
+      let ttd = "46_089_003_871_917_200_000_000".parse(Uint256)
+      check h.stateRoot == stateRoot
+      check h.blockHash == genesisHash
+      check cg.config.terminalTotalDifficulty.get == ttd
+      check cg.config.poaEngine == false
+
 proc genesisMain*() =
   genesisTest()
   customGenesisTest()
 
 when isMainModule:
-  genesisMain()
+  genesisTest()
+  customGenesisTest()

vendor/nim-json-serialization

@@ -1 +1 @@
-Subproject commit c5f0e2465e8375dfc7aa0f56ccef67cb680bc6b0
+Subproject commit 3509706517f3562cbcbe9d94988eccdd80474ab8

vendor/nim-serialization

@@ -1 +1 @@
-Subproject commit fcd0eadadde0ee000a63df8ab21dc4e9f015a790
+Subproject commit 9631fbd1c81c8b25ff8740df440ca7ba87fa6131