Abstract out IsSegWitOutput from utxoupdatepsbt

This is not a pure refactor; additional functionality is added in
IsSegWitOutput which lets it recurse into P2SH when a
SigningProvider is provided that knows about the inner script.

2 files changed, 19 insertions, 0 deletions

diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 36dd68a3d..5320dc087 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -505,3 +505,19 @@ FlatSigningProvider Merge(const FlatSigningProvider& a, const FlatSigningProvide
     ret.origins.insert(b.origins.begin(), b.origins.end());
     return ret;
 }
+
+bool IsSegWitOutput(const SigningProvider& provider, const CScript& script)
+{
+    std::vector<valtype> solutions;
+    auto whichtype = Solver(script, solutions);
+    if (whichtype == TX_WITNESS_V0_SCRIPTHASH || whichtype == TX_WITNESS_V0_KEYHASH || whichtype == TX_WITNESS_UNKNOWN) return true;
+    if (whichtype == TX_SCRIPTHASH) {
+        auto h160 = uint160(solutions[0]);
+        CScript subscript;
+        if (provider.GetCScript(h160, subscript)) {
+            whichtype = Solver(subscript, solutions);
+            if (whichtype == TX_WITNESS_V0_SCRIPTHASH || whichtype == TX_WITNESS_V0_KEYHASH || whichtype == TX_WITNESS_UNKNOWN) return true;
+        }
+    }
+    return false;
+}
diff --git a/src/script/sign.h b/src/script/sign.h
index f746325b9..e5c0329a6 100644
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -232,4 +232,7 @@ void UpdateInput(CTxIn& input, const SignatureData& data);
  * Solvability is unrelated to whether we consider this output to be ours. */
 bool IsSolvable(const SigningProvider& provider, const CScript& script);
 
+/** Check whether a scriptPubKey is known to be segwit. */
+bool IsSegWitOutput(const SigningProvider& provider, const CScript& script);
+
 #endif // BITCOIN_SCRIPT_SIGN_H