script: (refactor) prepare for introducing sighash midstate cache

sipa · sipa · commit 8f3ddb0bcceb · 2025-08-06T09:33:17.000-04:00
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
@@ -1569,6 +1569,18 @@ uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn
 {
     assert(nIn < txTo.vin.size());
 
+    if (sigversion != SigVersion::WITNESS_V0) {
+        // Check for invalid use of SIGHASH_SINGLE
+        if ((nHashType & 0x1f) == SIGHASH_SINGLE) {
+            if (nIn >= txTo.vout.size()) {
+                //  nOut out of range
+                return uint256::ONE;
+            }
+        }
+    }
+
+    HashWriter ss{};
+
     if (sigversion == SigVersion::WITNESS_V0) {
         uint256 hashPrevouts;
         uint256 hashSequence;
@@ -1583,16 +1595,14 @@ uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn
             hashSequence = cacheready ? cache->hashSequence : SHA256Uint256(GetSequencesSHA256(txTo));
         }
 
-
         if ((nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
             hashOutputs = cacheready ? cache->hashOutputs : SHA256Uint256(GetOutputsSHA256(txTo));
         } else if ((nHashType & 0x1f) == SIGHASH_SINGLE && nIn < txTo.vout.size()) {
-            HashWriter ss{};
-            ss << txTo.vout[nIn];
-            hashOutputs = ss.GetHash();
+            HashWriter inner_ss{};
+            inner_ss << txTo.vout[nIn];
+            hashOutputs = inner_ss.GetHash();
         }
 
-        HashWriter ss{};
         // Version
         ss << txTo.version;
         // Input prevouts/nSequence (none/all, depending on flags)
@@ -1609,26 +1619,16 @@ uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn
         ss << hashOutputs;
         // Locktime
         ss << txTo.nLockTime;
-        // Sighash type
-        ss << nHashType;
-
-        return ss.GetHash();
-    }
+    } else {
+        // Wrapper to serialize only the necessary parts of the transaction being signed
+        CTransactionSignatureSerializer<T> txTmp(txTo, scriptCode, nIn, nHashType);
 
-    // Check for invalid use of SIGHASH_SINGLE
-    if ((nHashType & 0x1f) == SIGHASH_SINGLE) {
-        if (nIn >= txTo.vout.size()) {
-            //  nOut out of range
-            return uint256::ONE;
-        }
+        // Serialize
+        ss << txTmp;
     }
 
-    // Wrapper to serialize only the necessary parts of the transaction being signed
-    CTransactionSignatureSerializer<T> txTmp(txTo, scriptCode, nIn, nHashType);
-
-    // Serialize and hash
-    HashWriter ss{};
-    ss << txTmp << nHashType;
+    // Add sighash type and hash.
+    ss << nHashType;
     return ss.GetHash();
 }
 
