The current code contains a rather complex script template matching engine, which is only used for 3 particular script types (P2PK, P2PKH, multisig). The first two of these are trivial to match for otherwise, and a specialized matcher for multisig is both more compact and more efficient than a generic one.
The goal is being more flexible, so that for example larger standard multisigs inside SegWit outputs are easier to implement.
As a side-effect, it also gets rid of the pseudo opcodes hack.
185- // template matching params
186- OP_SMALLINTEGER = 0xfa,
187- OP_PUBKEYS = 0xfb,
188- OP_PUBKEYHASH = 0xfd,
189- OP_PUBKEY = 0xfe,
190-
73+ opcodetype opcode;
74+ valtype data;
75+ CScript::const_iterator it = script.begin();
76+ if (script.size() < 1 || script.back() != OP_CHECKMULTISIG) return false;
77+
78+ if (!script.GetOp(it, opcode, data) || (opcode != OP_0 && (opcode < OP_1 || opcode > OP_16))) return false;
78+ if (!script.GetOp(it, opcode, data) || (opcode != OP_0 && (opcode < OP_1 || opcode > OP_16))) return false;
79+ required = CScript::DecodeOP_N(opcode);
80+ while (script.GetOp(it, opcode, data) && CPubKey::ValidSize(data)) {
81+ pubkeys.emplace_back(std::move(data));
82 }
83+ if (opcode != OP_0 && (opcode < OP_1 || opcode > OP_16)) return false;
opcode < OP_0 || opcode > OP_16?
IsSmallInteger function for this (which would be distinct from IsOP_N by not accepting OP_1NEGATE).
44- {
45- // Standard tx, sender provides pubkey, receiver adds signature
46- mTemplates.insert(std::make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));
47+ if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG) {
48+ pubkey = valtype(script.begin() + 1, script.begin() + 34);
49+ return CPubKey::ValidSize(pubkey);
CpubKey::ValidSize checks the data-dependent size (depending on what the first byte is).
48+ pubkey = valtype(script.begin() + 1, script.begin() + 34);
49+ return CPubKey::ValidSize(pubkey);
50+ }
51+ if (script.size() == 67 && script[0] == 65 && script[66] == OP_CHECKSIG) {
52+ pubkey = valtype(script.begin() + 1, script.begin() + 66);
53+ return CPubKey::ValidSize(pubkey);
75+ CScript::const_iterator it = script.begin();
76+ if (script.size() < 1 || script.back() != OP_CHECKMULTISIG) return false;
77+
78+ if (!script.GetOp(it, opcode, data) || (opcode != OP_0 && (opcode < OP_1 || opcode > OP_16))) return false;
79+ required = CScript::DecodeOP_N(opcode);
80+ while (script.GetOp(it, opcode, data) && CPubKey::ValidSize(data)) {
CPubKey::ValidSize rejects empty data.
46- mTemplates.insert(std::make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));
47+ if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG) {
48+ pubkey = valtype(script.begin() + 1, script.begin() + 34);
49+ return CPubKey::ValidSize(pubkey);
50+ }
51+ if (script.size() == 67 && script[0] == 65 && script[66] == OP_CHECKSIG) {
42- static std::multimap<txnouttype, CScript> mTemplates;
43- if (mTemplates.empty())
44- {
45- // Standard tx, sender provides pubkey, receiver adds signature
46- mTemplates.insert(std::make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));
47+ if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG) {
53+ return CPubKey::ValidSize(pubkey);
54+ }
55+ return false;
56+}
57+
58+static bool MatchPayToPubkeyHash(const CScript& script, valtype& pubkeyhash)
See also IsToKeyID in compressor.cpp, which looks equivalent.
Could split this up as CScript::IsPayToPubkeyHash, and do the unpacking in Solver, ala IsPayToScriptHash. Would make the case handling more consistent in Solver.
34@@ -35,22 +35,55 @@ const char* GetTxnOutputType(txnouttype t)
35 return nullptr;
36 }
37
38-bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet)
39+static bool MatchPayToPubkey(const CScript& script, valtype& pubkey)
IsToPubKey in compressor, which looks equivalent.
86+ while (script.GetOp(it, opcode, data) && CPubKey::ValidSize(data)) {
87+ pubkeys.emplace_back(std::move(data));
88 }
89+ if (!IsSmallInteger(opcode)) return false;
90+ unsigned int keys = CScript::DecodeOP_N(opcode);
91+ if (pubkeys.size() != keys || required == 0 || keys < required) return false;
required == 0 check could be an earlier return
221+ std::vector<std::vector<unsigned char>> keys;
222+ if (MatchMultisig(scriptPubKey, required, keys)) {
223+ typeRet = TX_MULTISIG;
224+ vSolutionsRet.push_back({static_cast<unsigned char>(required)});
225+ vSolutionsRet.insert(vSolutionsRet.end(), keys.begin(), keys.end());
226+ vSolutionsRet.push_back({static_cast<unsigned char>(keys.size())});
88+ pubkeys.emplace_back(std::move(data));
89 }
90+ if (!IsSmallInteger(opcode)) return false;
91+ unsigned int keys = CScript::DecodeOP_N(opcode);
92+ if (pubkeys.size() != keys || keys < required) return false;
93+ if (it + 1 != script.end()) return false;
nit
0return it + 1 == script.end();
42- static std::multimap<txnouttype, CScript> mTemplates;
43- if (mTemplates.empty())
44- {
45- // Standard tx, sender provides pubkey, receiver adds signature
46- mTemplates.insert(std::make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));
47+ if (script.size() == CPubKey::PUBLIC_KEY_SIZE + 2 && script[0] == CPubKey::PUBLIC_KEY_SIZE && script[CPubKey::PUBLIC_KEY_SIZE + 1] == OP_CHECKSIG) {
script.back() == OP_CHECKSIG?
The current code contains a rather complex script template matching engine,
which is only used for 3 particular script types (P2PK, P2PKH, multisig).
The first two of these are trivial to match for otherwise, and a specialized
matcher for multisig is both more compact and more efficient than a generic
one.
The goal is being more flexible, so that for example larger standard multisigs
inside SegWit outputs are more easy to implement.
As a side-effect, it also gets rid of the pseudo opcodes hack.
67+}
68+
69+/** Test for "small integer" script opcodes - OP_0 through OP_16. */
70+static constexpr bool IsSmallInteger(opcodetype opcode)
71+{
72+ return opcode == OP_0 || (opcode >= OP_1 && opcode <= OP_16);
opcode == OP_0 here, you can remove if (required == 0) return false; below