implement txparse tool and add make target for txparse

Makefile

@@ -260,6 +260,10 @@ evmstate: | build deps
 evmstate_test: | build deps evmstate
 	$(ENV_SCRIPT) nim c -r $(NIM_PARAMS) "tools/evmstate/$@.nim"
 
+# builds txparse tool
+txparse: | build deps
+	$(ENV_SCRIPT) nim c $(NIM_PARAMS) "tools/txparse/$@.nim"
+
 # usual cleaning
 clean: | clean-common
 	rm -rf build/{nimbus,fluffy,nimbus_verified_proxy,$(TOOLS_CSV),all_tests,test_kvstore_rocksdb,test_rpc,all_fluffy_tests,all_fluffy_portal_spec_tests,test_portal_testnet,portalcli,blockwalk,eth_data_exporter,utp_test_app,utp_test,*.dSYM}

tools/txparse/readme.md

@@ -0,0 +1,43 @@
+## Tx parser (`txparse`)
+
+This is a very simple utility, which reads line by line from standard input.
+For each line, it tries to interpret it as hexadecimal data, and the data as
+an Ethereum transaction.
+
+If all goes well, it outputs a line containing the `address` of the sender.
+Otherwise, it outputs `err: ` and a suitable error message.
+
+### Build instructions
+
+There are few options to build `txparse` tool like any other nimbus tools.
+
+1. Use nimble to install dependencies and your system Nim compiler(version <= 1.6.0).
+    ```
+    $> nimble install -y --depsOnly
+    $> nim c -d:release tools/txparse/txparse
+    ```
+2. Use nimbus shipped Nim compiler and dependencies.
+    ```
+    $> make update
+    $> ./env.sh nim c tools/txparse/txparse
+    ```
+3. Use nimbus makefile.
+    ```
+    $> make update
+    $> make txparse
+    ```
+
+Example:
+
+```
+$ cat ./sample.input | ./txparse
+err: t is not a hexadecimal character
+err: m is not a hexadecimal character
+err: hex string must have even length
+err:   is not a hexadecimal character
+err: Read past the end of the RLP stream
+err: The RLP contains a larger than expected Int value
+0xd02d72e067e77158444ef2020ff2d325f929b363
+0xd02d72e067e77158444ef2020ff2d325f929b363
+err: hex string must have even length
+```

tools/txparse/sample.input

@@ -0,0 +1,9 @@
+test
+monkey
+0x1
+0x112391201239129312392139123 123 12 312 312 3
+0xdead
+0xf8d2b86702f864010180820fa08284d09411111111111111111111111111111111111111118080c001a0b7dfab36232379bb3d1497a4f91c1966b1f932eae3ade107bf5d723b9cb474e0a06261c359a10f2132f126d250485b90cf20f30340801244a08ef6142ab33d1904b86702f864010280820fa08284d09411111111111111111111111111111111111111118080c080a0d4ec563b6568cd42d998fc4134b36933c6568d01533b5adf08769270243c6c7fa072bf7c21eac6bbeae5143371eef26d5e279637f3bd73482b55979d76d935b1e9
+02f864010180820fa08284d09411111111111111111111111111111111111111118080c001a0b7dfab36232379bb3d1497a4f91c1966b1f932eae3ade107bf5d723b9cb474e0a06261c359a10f2132f126d250485b90cf20f30340801244a08ef6142ab33d1904
+0x02f864010180820fa08284d09411111111111111111111111111111111111111118080c001a0b7dfab36232379bb3d1497a4f91c1966b1f932eae3ade107bf5d723b9cb474e0a06261c359a10f2132f126d250485b90cf20f30340801244a08ef6142ab33d1904
+deadest

tools/txparse/txparse.nim

@@ -0,0 +1,37 @@
+# Nimbus
+# Copyright (c) 2022 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+#    http://www.apache.org/licenses/LICENSE-2.0)
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+#    http://opensource.org/licenses/MIT)
+# at your option. This file may not be copied, modified, or distributed except
+# according to those terms.
+
+import
+  eth/[common, rlp],
+  stew/byteutils,
+  ../../nimbus/transaction
+
+proc parseTx(hexLine: string) =
+  try:
+    let
+      bytes = hexToSeqByte(hexLine)
+      tx = rlp.decode(bytes, Transaction)
+      address = tx.getSender()
+
+    # everything ok
+    echo "0x", address.toHex
+
+  except RlpError as ex:
+    echo "err: ", ex.msg
+  except ValueError as ex:
+    echo "err: ", ex.msg
+  except ValidationError as ex:
+    echo "err: ", ex.msg
+
+proc main() =
+  for hexLine in stdin.lines:
+    parseTx(hexLine)
+
+main()