Enable OP_CAT in script debugger

Author: vostrnad

src/lib/utils/bitcoin/script/interpreter.ts

@@ -133,6 +133,7 @@ import {
   bytesToHex,
   bytesToIntLE,
   bytesToUIntLE,
+  concatBytes,
   intLEToBytes,
   uint8ArrayEqual,
 } from '$lib/utils/uintarray'
@@ -188,6 +189,7 @@ enum ScriptWarning {
   codeseparator,
   mixedCheckMultisigAndCheckSigAdd,
   nonMinimalIf,
+  cat,
 }
 
 const warningMessageMap: Record<ScriptWarning, string> = {
@@ -201,6 +203,7 @@ const warningMessageMap: Record<ScriptWarning, string> = {
   [ScriptWarning.mixedCheckMultisigAndCheckSigAdd]:
     'OP_CHECKMULTISIG and OP_CHECKSIGADD cannot be used in the same script',
   [ScriptWarning.nonMinimalIf]: 'argument of OP_IF/NOTIF is not minimal',
+  [ScriptWarning.cat]: 'OP_CAT is only available on signet',
 }
 
 type ScriptErrorCode = keyof typeof errorMessageMap
@@ -417,7 +420,7 @@ export const evalScript = (
     const opcode = reader.readByte()
 
     if (
-      opcode === OP_CAT ||
+      // opcode === OP_CAT ||
       opcode === OP_SUBSTR ||
       opcode === OP_LEFT ||
       opcode === OP_RIGHT ||
@@ -823,6 +826,23 @@ export const evalScript = (
         }
         break
 
+      case OP_CAT:
+        {
+          if (stack.length < 2) {
+            return setStackSizeError(2)
+          }
+          const vch1 = stacktop(-2)!
+          const vch2 = stacktop(-1)!
+          if (vch1.length + vch2.length > MAX_SCRIPT_ELEMENT_SIZE) {
+            return setError(SCRIPT_ERR_PUSH_SIZE)
+          }
+          popstack()
+          popstack()
+          stack.push(concatBytes([vch1, vch2]))
+          loopHighlight = { count: 1, color: 'success' }
+        }
+        break
+
       case OP_SIZE:
         // (in -- in size)
         if (stack.length === 0) {

tests/script/interpreter.test.ts

@@ -16,6 +16,7 @@ import {
   OP_ADD,
   OP_BOOLAND,
   OP_BOOLOR,
+  OP_CAT,
   OP_CHECKLOCKTIMEVERIFY,
   OP_CHECKMULTISIG,
   OP_CHECKMULTISIGVERIFY,
@@ -165,8 +166,8 @@ describe('evalScript', () => {
 
   test('should return error for incorrect scripts', () => {
     const testcases: Array<[string, string[], number]> = [
-      // disabled opcode OP_CAT
-      ['7e', [], 16],
+      // disabled opcode OP_SUBSTR
+      ['7f', [], 16],
       // incomplete push
       ['01', [], 15],
       ['4c', [], 15],
@@ -211,6 +212,7 @@ describe('evalScript', () => {
       [OP_SWAP, 2],
       [OP_TUCK, 2],
 
+      [OP_CAT, 2],
       [OP_SIZE, 1],
 
       [OP_EQUAL, 2],