Merge #8149: Segregated witness rebased

f852813 BIP9 parameters for testnet (Johnson Lau)
070dbc4 --- [SEGWIT] begin: deployment --- (Pieter Wuille)
fdb43df [qa] Add GetTransactionSigOpCost unit tests (Jonas Nick)
d846e02 [qa] script_tests: witness tests can specify tx amount (Suhas Daftuar)
330b0f3 [qa] p2p segwit tests (Suhas Daftuar)
4f7ff00 [qa] Add rpc test for segwit (Alex Morcos)
66cca79 [qa] Autogeneration support for witness in script_tests (Pieter Wuille)
06d3805 [qa] Add segwit support to script_tests (Pieter Wuille)
00f46cb [qa] Add transaction tests for segwit (NicolasDorier)
0aa9207 [qa] Witness version 0 signing unit tests (Pieter Wuille)
978e200 --- [SEGWIT] begin: tests --- (Pieter Wuille)
745eb67 [RPC] signrawtransaction can sign P2WSH (NicolasDorier)
f4691ab [RPC] Add wallet support for witness transactions (using P2SH) (Pieter Wuille)
605e847 BIP143: Signing logic (Pieter Wuille)
9757b57 --- [SEGWIT] begin: wallet --- (Pieter Wuille)
af87a67 Do not use compact blocks when segwit is enabled (Pieter Wuille)
6032f69 Add rewind logic to deal with post-fork software updates (Pieter Wuille)
b7dbeb2 [libconsensus] Script verification API with amounts (Thomas Kerin)
2b1f6f9 BIP141: Other consensus critical limits, and BIP145 (Pieter Wuille)
7c4bf77 [RPC] Return witness data in blockchain RPCs (Johnson Lau)
3dd4102 BIP143: Verification logic (Pieter Wuille)
0ef1dd3 Refactor script validation to observe amounts (Pieter Wuille)
b8a9749 BIP144: Handshake and relay (receiver side) (Pieter Wuille)
8b49040 BIP141: Commitment structure and deployment (Pieter Wuille)
449f9b8 BIP141: Witness program (Pieter Wuille)
7030d9e BIP144: Serialization, hashes, relay (sender side) (Pieter Wuille)
ecacfd9 --- [SEGWIT] begin: P2P/node/consensus --- (Pieter Wuille)

1 files changed, 166 insertions, 16 deletions

diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index 149816406a..e87ad90f0d 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -11,6 +11,10 @@
 #include "serialize.h"
 #include "uint256.h"
 
+static const int SERIALIZE_TRANSACTION_NO_WITNESS = 0x40000000;
+
+static const int WITNESS_SCALE_FACTOR = 4;
+
 /** An outpoint - a combination of a transaction hash and an index n into its vout */
 class COutPoint
 {
@@ -164,15 +168,30 @@ public:
         // which has units satoshis-per-kilobyte.
         // If you'd pay more than 1/3 in fees
         // to spend something, then we consider it dust.
-        // A typical spendable txout is 34 bytes big, and will
+        // A typical spendable non-segwit txout is 34 bytes big, and will
         // need a CTxIn of at least 148 bytes to spend:
         // so dust is a spendable txout less than
-        // 546*minRelayTxFee/1000 (in satoshis)
+        // 546*minRelayTxFee/1000 (in satoshis).
+        // A typical spendable segwit txout is 31 bytes big, and will
+        // need a CTxIn of at least 67 bytes to spend:
+        // so dust is a spendable txout less than
+        // 294*minRelayTxFee/1000 (in satoshis).
         if (scriptPubKey.IsUnspendable())
             return 0;
 
-        size_t nSize = GetSerializeSize(SER_DISK,0)+148u;
-        return 3*minRelayTxFee.GetFee(nSize);
+        size_t nSize = GetSerializeSize(SER_DISK, 0);
+        int witnessversion = 0;
+        std::vector<unsigned char> witnessprogram;
+
+        if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
+            // sum the sizes of the parts of a transaction input
+            // with 75% segwit discount applied to the script size.
+            nSize += (32 + 4 + 1 + (107 / WITNESS_SCALE_FACTOR) + 4);
+        } else {
+            nSize += (32 + 4 + 1 + 107 + 4); // the 148 mentioned above
+        }
+
+        return 3 * minRelayTxFee.GetFee(nSize);
     }
 
     bool IsDust(const CFeeRate &minRelayTxFee) const
@@ -194,8 +213,137 @@ public:
     std::string ToString() const;
 };
 
+class CTxinWitness
+{
+public:
+    CScriptWitness scriptWitness;
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion)
+    {
+        READWRITE(scriptWitness.stack);
+    }
+
+    bool IsNull() const { return scriptWitness.IsNull(); }
+
+    CTxinWitness() { }
+};
+
+class CTxWitness
+{
+public:
+    /** In case vtxinwit is missing, all entries are treated as if they were empty CTxInWitnesses */
+    std::vector<CTxinWitness> vtxinwit;
+
+    ADD_SERIALIZE_METHODS;
+
+    bool IsEmpty() const { return vtxinwit.empty(); }
+
+    bool IsNull() const
+    {
+        for (size_t n = 0; n < vtxinwit.size(); n++) {
+            if (!vtxinwit[n].IsNull()) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    void SetNull()
+    {
+        vtxinwit.clear();
+    }
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion)
+    {
+        for (size_t n = 0; n < vtxinwit.size(); n++) {
+            READWRITE(vtxinwit[n]);
+        }
+        if (IsNull()) {
+            /* It's illegal to encode a witness when all vtxinwit entries are empty. */
+            throw std::ios_base::failure("Superfluous witness record");
+        }
+    }
+};
+
 struct CMutableTransaction;
 
+/**
+ * Basic transaction serialization format:
+ * - int32_t nVersion
+ * - std::vector<CTxIn> vin
+ * - std::vector<CTxOut> vout
+ * - uint32_t nLockTime
+ *
+ * Extended transaction serialization format:
+ * - int32_t nVersion
+ * - unsigned char dummy = 0x00
+ * - unsigned char flags (!= 0)
+ * - std::vector<CTxIn> vin
+ * - std::vector<CTxOut> vout
+ * - if (flags & 1):
+ *   - CTxWitness wit;
+ * - uint32_t nLockTime
+ */
+template<typename Stream, typename Operation, typename TxType>
+inline void SerializeTransaction(TxType& tx, Stream& s, Operation ser_action, int nType, int nVersion) {
+    READWRITE(*const_cast<int32_t*>(&tx.nVersion));
+    unsigned char flags = 0;
+    if (ser_action.ForRead()) {
+        const_cast<std::vector<CTxIn>*>(&tx.vin)->clear();
+        const_cast<std::vector<CTxOut>*>(&tx.vout)->clear();
+        const_cast<CTxWitness*>(&tx.wit)->SetNull();
+        /* Try to read the vin. In case the dummy is there, this will be read as an empty vector. */
+        READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
+        if (tx.vin.size() == 0 && !(nVersion & SERIALIZE_TRANSACTION_NO_WITNESS)) {
+            /* We read a dummy or an empty vin. */
+            READWRITE(flags);
+            if (flags != 0) {
+                READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
+                READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
+            }
+        } else {
+            /* We read a non-empty vin. Assume a normal vout follows. */
+            READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
+        }
+        if ((flags & 1) && !(nVersion & SERIALIZE_TRANSACTION_NO_WITNESS)) {
+            /* The witness flag is present, and we support witnesses. */
+            flags ^= 1;
+            const_cast<CTxWitness*>(&tx.wit)->vtxinwit.resize(tx.vin.size());
+            READWRITE(tx.wit);
+        }
+        if (flags) {
+            /* Unknown flag in the serialization */
+            throw std::ios_base::failure("Unknown transaction optional data");
+        }
+    } else {
+        // Consistency check
+        assert(tx.wit.vtxinwit.size() <= tx.vin.size());
+        if (!(nVersion & SERIALIZE_TRANSACTION_NO_WITNESS)) {
+            /* Check whether witnesses need to be serialized. */
+            if (!tx.wit.IsNull()) {
+                flags |= 1;
+            }
+        }
+        if (flags) {
+            /* Use extended format in case witnesses are to be serialized. */
+            std::vector<CTxIn> vinDummy;
+            READWRITE(vinDummy);
+            READWRITE(flags);
+        }
+        READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
+        READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
+        if (flags & 1) {
+            const_cast<CTxWitness*>(&tx.wit)->vtxinwit.resize(tx.vin.size());
+            READWRITE(tx.wit);
+        }
+    }
+    READWRITE(*const_cast<uint32_t*>(&tx.nLockTime));
+}
+
 /** The basic transaction that is broadcasted on the network and contained in
  * blocks.  A transaction can contain multiple inputs and outputs.
  */
@@ -204,7 +352,6 @@ class CTransaction
 private:
     /** Memory only. */
     const uint256 hash;
-    void UpdateHash() const;
 
 public:
     // Default transaction version.
@@ -224,6 +371,7 @@ public:
     const int32_t nVersion;
     const std::vector<CTxIn> vin;
     const std::vector<CTxOut> vout;
+    CTxWitness wit; // Not const: can change without invalidating the txid cache
     const uint32_t nLockTime;
 
     /** Construct a CTransaction that qualifies as IsNull() */
@@ -238,13 +386,10 @@ public:
 
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion) {
-        READWRITE(*const_cast<int32_t*>(&this->nVersion));
-        nVersion = this->nVersion;
-        READWRITE(*const_cast<std::vector<CTxIn>*>(&vin));
-        READWRITE(*const_cast<std::vector<CTxOut>*>(&vout));
-        READWRITE(*const_cast<uint32_t*>(&nLockTime));
-        if (ser_action.ForRead())
+        SerializeTransaction(*this, s, ser_action, nType, nVersion);
+        if (ser_action.ForRead()) {
             UpdateHash();
+        }
     }
 
     bool IsNull() const {
@@ -255,6 +400,9 @@ public:
         return hash;
     }
 
+    // Compute a hash that includes both transaction and witness data
+    uint256 GetWitnessHash() const;
+
     // Return sum of txouts.
     CAmount GetValueOut() const;
     // GetValueIn() is a method on CCoinsViewCache, because
@@ -282,6 +430,8 @@ public:
     }
 
     std::string ToString() const;
+
+    void UpdateHash() const;
 };
 
 /** A mutable version of CTransaction. */
@@ -290,6 +440,7 @@ struct CMutableTransaction
     int32_t nVersion;
     std::vector<CTxIn> vin;
     std::vector<CTxOut> vout;
+    CTxWitness wit;
     uint32_t nLockTime;
 
     CMutableTransaction();
@@ -299,11 +450,7 @@ struct CMutableTransaction
 
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion) {
-        READWRITE(this->nVersion);
-        nVersion = this->nVersion;
-        READWRITE(vin);
-        READWRITE(vout);
-        READWRITE(nLockTime);
+        SerializeTransaction(*this, s, ser_action, nType, nVersion);
     }
 
     /** Compute the hash of this CMutableTransaction. This is computed on the
@@ -312,4 +459,7 @@ struct CMutableTransaction
     uint256 GetHash() const;
 };
 
+/** Compute the cost of a transaction, as defined by BIP 141 */
+int64_t GetTransactionCost(const CTransaction &tx);
+
 #endif // BITCOIN_PRIMITIVES_TRANSACTION_H