From 985c79552ceb6a5f5812d421dc5c86fa3b1cc41d Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Thu, 30 Nov 2017 16:48:38 -0800
Subject: [PATCH] Improve witness destination types and use them more

---
 src/script/standard.cpp | 11 +++--------
 src/script/standard.h   | 18 ++++++++++++++++--
 2 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/src/script/standard.cpp b/src/script/standard.cpp
index b7b33fade..0d9f6ae1f 100644
--- a/src/script/standard.cpp
+++ b/src/script/standard.cpp
@@ -348,19 +348,14 @@ CScript GetScriptForWitness(const CScript& redeemscript)
     std::vector<std::vector<unsigned char> > vSolutions;
     if (Solver(redeemscript, typ, vSolutions)) {
         if (typ == TX_PUBKEY) {
-            unsigned char h160[20];
-            CHash160().Write(&vSolutions[0][0], vSolutions[0].size()).Finalize(h160);
-            ret << OP_0 << std::vector<unsigned char>(&h160[0], &h160[20]);
-            return ret;
+            return GetScriptForDestination(WitnessV0KeyHash(Hash160(vSolutions[0].begin(), vSolutions[0].end())));
         } else if (typ == TX_PUBKEYHASH) {
-           ret << OP_0 << vSolutions[0];
-           return ret;
+            return GetScriptForDestination(WitnessV0KeyHash(vSolutions[0]));
         }
     }
     uint256 hash;
     CSHA256().Write(&redeemscript[0], redeemscript.size()).Finalize(hash.begin());
-    ret << OP_0 << ToByteVector(hash);
-    return ret;
+    return GetScriptForDestination(WitnessV0ScriptHash(hash));
 }
 
 bool IsValidDestination(const CTxDestination& dest) {
diff --git a/src/script/standard.h b/src/script/standard.h
index 3eeeabdc1..b1c314fa7 100644
--- a/src/script/standard.h
+++ b/src/script/standard.h
@@ -73,8 +73,19 @@ public:
     friend bool operator<(const CNoDestination &a, const CNoDestination &b) { return true; }
 };
 
-struct WitnessV0ScriptHash : public uint256 {};
-struct WitnessV0KeyHash : public uint160 {};
+struct WitnessV0ScriptHash : public uint256
+{
+    WitnessV0ScriptHash() : uint256() {}
+    explicit WitnessV0ScriptHash(const uint256& hash) : uint256(hash) {}
+    using uint256::uint256;
+};
+
+struct WitnessV0KeyHash : public uint160
+{
+    WitnessV0KeyHash() : uint160() {}
+    explicit WitnessV0KeyHash(const uint160& hash) : uint160(hash) {}
+    using uint160::uint160;
+};
 
 //! CTxDestination subtype to encode any future Witness version
 struct WitnessUnknown
@@ -164,6 +175,9 @@ CScript GetScriptForMultisig(int nRequired, const std::vector<CPubKey>& keys);
  * Generate a pay-to-witness script for the given redeem script. If the redeem
  * script is P2PK or P2PKH, this returns a P2WPKH script, otherwise it returns a
  * P2WSH script.
+ *
+ * TODO: replace calls to GetScriptForWitness with GetScriptForDestination using
+ * the various witness-specific CTxDestination subtypes.
  */
 CScript GetScriptForWitness(const CScript& redeemscript);