restore decompile

examples/decompile_smart_contract.nim

@@ -1,5 +1,5 @@
 # Nimbus
-# Copyright (c) 2018-2023 Status Research & Development GmbH
+# Copyright (c) 2018-2024 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)
@@ -8,9 +8,10 @@
 # at your option. This file may not be copied, modified, or distributed except
 # according to those terms.
 
-import ../nimbus/vm/code_bytes, strformat
+import ../nimbus/evm/code_stream, strformat
 
-var c = CodeBytes.fromHex("0x6003600202600055").expect("valid code")
+var c =
+  CodeStream.init(CodeBytesRef.fromHex("0x6003600202600055").expect("valid code"))
 
 let opcodes = c.decompile()
 for op in opcodes:

nimbus/evm/code_bytes.nim

@@ -30,7 +30,7 @@ func init*(T: type CodeBytesRef, bytes: openArray[byte]): CodeBytesRef =
 func init*(T: type CodeBytesRef, bytes: openArray[char]): CodeBytesRef =
   CodeBytesRef.init(bytes.toOpenArrayByte(0, bytes.high()))
 
-func fromHex*(T: type CodeBytesRef, hex: openArray[char]): Opt[CodeBytesRef] =
+func fromHex*(T: type CodeBytesRef, hex: string): Opt[CodeBytesRef] =
   try:
     Opt.some(CodeBytesRef.init(hexToSeqByte(hex)))
   except ValueError:

nimbus/evm/code_stream.nim

@@ -5,7 +5,8 @@
 #  * 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 chronicles, eth/common, ./interpreter/op_codes, ./code_bytes
+import
+  std/[sequtils, strutils], chronicles, eth/common, ./interpreter/op_codes, ./code_bytes
 
 export code_bytes
 
@@ -79,5 +80,24 @@ func isValidOpcode*(c: CodeStream, position: int): bool =
 func bytes*(c: CodeStream): lent seq[byte] =
   c.code.bytes()
 
+proc decompile*(original: CodeStream): seq[(int, Op, string)] =
+  # behave as https://etherscan.io/opcode-tool
+  var c = CodeStream.init(original.bytes)
+  while true:
+    var op = c.next
+    if op >= Push1 and op <= Push32:
+      result.add(
+        (
+          c.pc - 1,
+          op,
+          "0x" & c.read(op.int - 95).mapIt($(it.BiggestInt.toHex(2))).join(""),
+        )
+      )
+    elif op != Op.Stop:
+      result.add((c.pc - 1, op, ""))
+    else:
+      result.add((-1, Op.Stop, ""))
+      break
+
 func atEnd*(c: CodeStream): bool =
   c.pc >= c.code.bytes.len