Rename script/standard.{cpp/h} to script/solver.{cpp/h}

Since script/standard only contains things that are used by the Solver
and its callers, rename the files to script/solver.

1 files changed, 223 insertions, 0 deletions

diff --git a/src/script/solver.cpp b/src/script/solver.cpp
new file mode 100644
index 0000000000..1cd388b061
--- /dev/null
+++ b/src/script/solver.cpp
@@ -0,0 +1,223 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <script/solver.h>
+#include <pubkey.h>
+#include <script/interpreter.h>
+#include <script/script.h>
+#include <span.h>
+
+#include <string>
+#include <algorithm>
+
+typedef std::vector<unsigned char> valtype;
+
+std::string GetTxnOutputType(TxoutType t)
+{
+    switch (t) {
+    case TxoutType::NONSTANDARD: return "nonstandard";
+    case TxoutType::PUBKEY: return "pubkey";
+    case TxoutType::PUBKEYHASH: return "pubkeyhash";
+    case TxoutType::SCRIPTHASH: return "scripthash";
+    case TxoutType::MULTISIG: return "multisig";
+    case TxoutType::NULL_DATA: return "nulldata";
+    case TxoutType::WITNESS_V0_KEYHASH: return "witness_v0_keyhash";
+    case TxoutType::WITNESS_V0_SCRIPTHASH: return "witness_v0_scripthash";
+    case TxoutType::WITNESS_V1_TAPROOT: return "witness_v1_taproot";
+    case TxoutType::WITNESS_UNKNOWN: return "witness_unknown";
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
+}
+
+static bool MatchPayToPubkey(const CScript& script, valtype& pubkey)
+{
+    if (script.size() == CPubKey::SIZE + 2 && script[0] == CPubKey::SIZE && script.back() == OP_CHECKSIG) {
+        pubkey = valtype(script.begin() + 1, script.begin() + CPubKey::SIZE + 1);
+        return CPubKey::ValidSize(pubkey);
+    }
+    if (script.size() == CPubKey::COMPRESSED_SIZE + 2 && script[0] == CPubKey::COMPRESSED_SIZE && script.back() == OP_CHECKSIG) {
+        pubkey = valtype(script.begin() + 1, script.begin() + CPubKey::COMPRESSED_SIZE + 1);
+        return CPubKey::ValidSize(pubkey);
+    }
+    return false;
+}
+
+static bool MatchPayToPubkeyHash(const CScript& script, valtype& pubkeyhash)
+{
+    if (script.size() == 25 && script[0] == OP_DUP && script[1] == OP_HASH160 && script[2] == 20 && script[23] == OP_EQUALVERIFY && script[24] == OP_CHECKSIG) {
+        pubkeyhash = valtype(script.begin () + 3, script.begin() + 23);
+        return true;
+    }
+    return false;
+}
+
+/** Test for "small positive integer" script opcodes - OP_1 through OP_16. */
+static constexpr bool IsSmallInteger(opcodetype opcode)
+{
+    return opcode >= OP_1 && opcode <= OP_16;
+}
+
+/** Retrieve a minimally-encoded number in range [min,max] from an (opcode, data) pair,
+ *  whether it's OP_n or through a push. */
+static std::optional<int> GetScriptNumber(opcodetype opcode, valtype data, int min, int max)
+{
+    int count;
+    if (IsSmallInteger(opcode)) {
+        count = CScript::DecodeOP_N(opcode);
+    } else if (IsPushdataOp(opcode)) {
+        if (!CheckMinimalPush(data, opcode)) return {};
+        try {
+            count = CScriptNum(data, /* fRequireMinimal = */ true).getint();
+        } catch (const scriptnum_error&) {
+            return {};
+        }
+    } else {
+        return {};
+    }
+    if (count < min || count > max) return {};
+    return count;
+}
+
+static bool MatchMultisig(const CScript& script, int& required_sigs, std::vector<valtype>& pubkeys)
+{
+    opcodetype opcode;
+    valtype data;
+
+    CScript::const_iterator it = script.begin();
+    if (script.size() < 1 || script.back() != OP_CHECKMULTISIG) return false;
+
+    if (!script.GetOp(it, opcode, data)) return false;
+    auto req_sigs = GetScriptNumber(opcode, data, 1, MAX_PUBKEYS_PER_MULTISIG);
+    if (!req_sigs) return false;
+    required_sigs = *req_sigs;
+    while (script.GetOp(it, opcode, data) && CPubKey::ValidSize(data)) {
+        pubkeys.emplace_back(std::move(data));
+    }
+    auto num_keys = GetScriptNumber(opcode, data, required_sigs, MAX_PUBKEYS_PER_MULTISIG);
+    if (!num_keys) return false;
+    if (pubkeys.size() != static_cast<unsigned long>(*num_keys)) return false;
+
+    return (it + 1 == script.end());
+}
+
+std::optional<std::pair<int, std::vector<Span<const unsigned char>>>> MatchMultiA(const CScript& script)
+{
+    std::vector<Span<const unsigned char>> keyspans;
+
+    // Redundant, but very fast and selective test.
+    if (script.size() == 0 || script[0] != 32 || script.back() != OP_NUMEQUAL) return {};
+
+    // Parse keys
+    auto it = script.begin();
+    while (script.end() - it >= 34) {
+        if (*it != 32) return {};
+        ++it;
+        keyspans.emplace_back(&*it, 32);
+        it += 32;
+        if (*it != (keyspans.size() == 1 ? OP_CHECKSIG : OP_CHECKSIGADD)) return {};
+        ++it;
+    }
+    if (keyspans.size() == 0 || keyspans.size() > MAX_PUBKEYS_PER_MULTI_A) return {};
+
+    // Parse threshold.
+    opcodetype opcode;
+    std::vector<unsigned char> data;
+    if (!script.GetOp(it, opcode, data)) return {};
+    if (it == script.end()) return {};
+    if (*it != OP_NUMEQUAL) return {};
+    ++it;
+    if (it != script.end()) return {};
+    auto threshold = GetScriptNumber(opcode, data, 1, (int)keyspans.size());
+    if (!threshold) return {};
+
+    // Construct result.
+    return std::pair{*threshold, std::move(keyspans)};
+}
+
+TxoutType Solver(const CScript& scriptPubKey, std::vector<std::vector<unsigned char>>& vSolutionsRet)
+{
+    vSolutionsRet.clear();
+
+    // Shortcut for pay-to-script-hash, which are more constrained than the other types:
+    // it is always OP_HASH160 20 [20 byte hash] OP_EQUAL
+    if (scriptPubKey.IsPayToScriptHash())
+    {
+        std::vector<unsigned char> hashBytes(scriptPubKey.begin()+2, scriptPubKey.begin()+22);
+        vSolutionsRet.push_back(hashBytes);
+        return TxoutType::SCRIPTHASH;
+    }
+
+    int witnessversion;
+    std::vector<unsigned char> witnessprogram;
+    if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
+        if (witnessversion == 0 && witnessprogram.size() == WITNESS_V0_KEYHASH_SIZE) {
+            vSolutionsRet.push_back(std::move(witnessprogram));
+            return TxoutType::WITNESS_V0_KEYHASH;
+        }
+        if (witnessversion == 0 && witnessprogram.size() == WITNESS_V0_SCRIPTHASH_SIZE) {
+            vSolutionsRet.push_back(std::move(witnessprogram));
+            return TxoutType::WITNESS_V0_SCRIPTHASH;
+        }
+        if (witnessversion == 1 && witnessprogram.size() == WITNESS_V1_TAPROOT_SIZE) {
+            vSolutionsRet.push_back(std::move(witnessprogram));
+            return TxoutType::WITNESS_V1_TAPROOT;
+        }
+        if (witnessversion != 0) {
+            vSolutionsRet.push_back(std::vector<unsigned char>{(unsigned char)witnessversion});
+            vSolutionsRet.push_back(std::move(witnessprogram));
+            return TxoutType::WITNESS_UNKNOWN;
+        }
+        return TxoutType::NONSTANDARD;
+    }
+
+    // Provably prunable, data-carrying output
+    //
+    // So long as script passes the IsUnspendable() test and all but the first
+    // 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)) {
+        return TxoutType::NULL_DATA;
+    }
+
+    std::vector<unsigned char> data;
+    if (MatchPayToPubkey(scriptPubKey, data)) {
+        vSolutionsRet.push_back(std::move(data));
+        return TxoutType::PUBKEY;
+    }
+
+    if (MatchPayToPubkeyHash(scriptPubKey, data)) {
+        vSolutionsRet.push_back(std::move(data));
+        return TxoutType::PUBKEYHASH;
+    }
+
+    int required;
+    std::vector<std::vector<unsigned char>> keys;
+    if (MatchMultisig(scriptPubKey, required, keys)) {
+        vSolutionsRet.push_back({static_cast<unsigned char>(required)}); // safe as required is in range 1..20
+        vSolutionsRet.insert(vSolutionsRet.end(), keys.begin(), keys.end());
+        vSolutionsRet.push_back({static_cast<unsigned char>(keys.size())}); // safe as size is in range 1..20
+        return TxoutType::MULTISIG;
+    }
+
+    vSolutionsRet.clear();
+    return TxoutType::NONSTANDARD;
+}
+
+CScript GetScriptForRawPubKey(const CPubKey& pubKey)
+{
+    return CScript() << std::vector<unsigned char>(pubKey.begin(), pubKey.end()) << OP_CHECKSIG;
+}
+
+CScript GetScriptForMultisig(int nRequired, const std::vector<CPubKey>& keys)
+{
+    CScript script;
+
+    script << nRequired;
+    for (const CPubKey& key : keys)
+        script << ToByteVector(key);
+    script << keys.size() << OP_CHECKMULTISIG;
+
+    return script;
+}