From 984d72ec659361d8c1a6f3c6864e839a807817a7 Mon Sep 17 00:00:00 2001
From: Ben Woosley <ben.woosley@gmail.com>
Date: Sun, 10 Jun 2018 22:19:07 -0700
Subject: Return the script type from Solver

Because false is synonymous with TX_NONSTANDARD, this conveys the same
information and makes the handling explicitly based on script type,
simplifying each call site.

Prior to this change it was common for the return value to be ignored,
or for the return value and TX_NONSTANDARD to be redundantly handled.
---
 src/script/standard.cpp | 57 ++++++++++++++++++-------------------------------
 1 file changed, 21 insertions(+), 36 deletions(-)

(limited to 'src/script/standard.cpp')

diff --git a/src/script/standard.cpp b/src/script/standard.cpp
index d7b1724790..d309420d35 100644
--- a/src/script/standard.cpp
+++ b/src/script/standard.cpp
@@ -87,7 +87,7 @@ static bool MatchMultisig(const CScript& script, unsigned int& required, std::ve
     return (it + 1 == script.end());
 }
 
-bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet)
+txnouttype Solver(const CScript& scriptPubKey, std::vector<std::vector<unsigned char>>& vSolutionsRet)
 {
     vSolutionsRet.clear();
 
@@ -95,33 +95,28 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::v
     // it is always OP_HASH160 20 [20 byte hash] OP_EQUAL
     if (scriptPubKey.IsPayToScriptHash())
     {
-        typeRet = TX_SCRIPTHASH;
         std::vector<unsigned char> hashBytes(scriptPubKey.begin()+2, scriptPubKey.begin()+22);
         vSolutionsRet.push_back(hashBytes);
-        return true;
+        return TX_SCRIPTHASH;
     }
 
     int witnessversion;
     std::vector<unsigned char> witnessprogram;
     if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
         if (witnessversion == 0 && witnessprogram.size() == WITNESS_V0_KEYHASH_SIZE) {
-            typeRet = TX_WITNESS_V0_KEYHASH;
             vSolutionsRet.push_back(witnessprogram);
-            return true;
+            return TX_WITNESS_V0_KEYHASH;
         }
         if (witnessversion == 0 && witnessprogram.size() == WITNESS_V0_SCRIPTHASH_SIZE) {
-            typeRet = TX_WITNESS_V0_SCRIPTHASH;
             vSolutionsRet.push_back(witnessprogram);
-            return true;
+            return TX_WITNESS_V0_SCRIPTHASH;
         }
         if (witnessversion != 0) {
-            typeRet = TX_WITNESS_UNKNOWN;
             vSolutionsRet.push_back(std::vector<unsigned char>{(unsigned char)witnessversion});
             vSolutionsRet.push_back(std::move(witnessprogram));
-            return true;
+            return TX_WITNESS_UNKNOWN;
         }
-        typeRet = TX_NONSTANDARD;
-        return false;
+        return TX_NONSTANDARD;
     }
 
     // Provably prunable, data-carrying output
@@ -130,47 +125,39 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::v
     // byte passes the IsPushOnly() test we don't care what exactly is in the
     // script.
     if (scriptPubKey.size() >= 1 && scriptPubKey[0] == OP_RETURN && scriptPubKey.IsPushOnly(scriptPubKey.begin()+1)) {
-        typeRet = TX_NULL_DATA;
-        return true;
+        return TX_NULL_DATA;
     }
 
     std::vector<unsigned char> data;
     if (MatchPayToPubkey(scriptPubKey, data)) {
-        typeRet = TX_PUBKEY;
         vSolutionsRet.push_back(std::move(data));
-        return true;
+        return TX_PUBKEY;
     }
 
     if (MatchPayToPubkeyHash(scriptPubKey, data)) {
-        typeRet = TX_PUBKEYHASH;
         vSolutionsRet.push_back(std::move(data));
-        return true;
+        return TX_PUBKEYHASH;
     }
 
     unsigned int required;
     std::vector<std::vector<unsigned char>> keys;
     if (MatchMultisig(scriptPubKey, required, keys)) {
-        typeRet = TX_MULTISIG;
         vSolutionsRet.push_back({static_cast<unsigned char>(required)}); // safe as required is in range 1..16
         vSolutionsRet.insert(vSolutionsRet.end(), keys.begin(), keys.end());
         vSolutionsRet.push_back({static_cast<unsigned char>(keys.size())}); // safe as size is in range 1..16
-        return true;
+        return TX_MULTISIG;
     }
 
     vSolutionsRet.clear();
-    typeRet = TX_NONSTANDARD;
-    return false;
+    return TX_NONSTANDARD;
 }
 
 bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
 {
     std::vector<valtype> vSolutions;
-    txnouttype whichType;
-    if (!Solver(scriptPubKey, whichType, vSolutions))
-        return false;
+    txnouttype whichType = Solver(scriptPubKey, vSolutions);
 
-    if (whichType == TX_PUBKEY)
-    {
+    if (whichType == TX_PUBKEY) {
         CPubKey pubKey(vSolutions[0]);
         if (!pubKey.IsValid())
             return false;
@@ -212,11 +199,11 @@ bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
 bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<CTxDestination>& addressRet, int& nRequiredRet)
 {
     addressRet.clear();
-    typeRet = TX_NONSTANDARD;
     std::vector<valtype> vSolutions;
-    if (!Solver(scriptPubKey, typeRet, vSolutions))
+    typeRet = Solver(scriptPubKey, vSolutions);
+    if (typeRet == TX_NONSTANDARD) {
         return false;
-    if (typeRet == TX_NULL_DATA){
+    } else if (typeRet == TX_NULL_DATA) {
         // This is data, not addresses
         return false;
     }
@@ -324,14 +311,12 @@ CScript GetScriptForMultisig(int nRequired, const std::vector<CPubKey>& keys)
 
 CScript GetScriptForWitness(const CScript& redeemscript)
 {
-    txnouttype typ;
     std::vector<std::vector<unsigned char> > vSolutions;
-    if (Solver(redeemscript, typ, vSolutions)) {
-        if (typ == TX_PUBKEY) {
-            return GetScriptForDestination(WitnessV0KeyHash(Hash160(vSolutions[0].begin(), vSolutions[0].end())));
-        } else if (typ == TX_PUBKEYHASH) {
-            return GetScriptForDestination(WitnessV0KeyHash(vSolutions[0]));
-        }
+    txnouttype typ = Solver(redeemscript, vSolutions);
+    if (typ == TX_PUBKEY) {
+        return GetScriptForDestination(WitnessV0KeyHash(Hash160(vSolutions[0].begin(), vSolutions[0].end())));
+    } else if (typ == TX_PUBKEYHASH) {
+        return GetScriptForDestination(WitnessV0KeyHash(vSolutions[0]));
     }
     return GetScriptForDestination(WitnessV0ScriptHash(redeemscript));
 }
-- 
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