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Aug 22, 2017
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Comments: More comments on functions/globals in standard.h. #11058

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3 changes: 0 additions & 3 deletions src/script/standard.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -34,9 +34,6 @@ const char* GetTxnOutputType(txnouttype t)
return nullptr;
}

/**
* Return public keys or hashes from scriptPubKey, for 'standard' transaction types.
*/
bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet)
{
// Templates
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62 changes: 58 additions & 4 deletions src/script/standard.h
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Expand Up @@ -27,16 +27,27 @@ class CScriptID : public uint160
CScriptID(const uint160& in) : uint160(in) {}
};

static const unsigned int MAX_OP_RETURN_RELAY = 83; //!< bytes (+1 for OP_RETURN, +2 for the pushdata opcodes)
/**
* Default setting for nMaxDatacarrierBytes. 80 bytes of data, +1 for OP_RETURN,
* +2 for the pushdata opcodes.
*/
static const unsigned int MAX_OP_RETURN_RELAY = 83;

/**
* A data carrying output is an unspendable output containing data. The script
* type is designated as TX_NULL_DATA.
*/
extern bool fAcceptDatacarrier;

/** Maximum size of TX_NULL_DATA scripts that this node considers standard. */
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(per transaction)

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I'm not sure if that's necessary to add here. This is the byte limit for OP_RETURN scripts, then IsStandardTx further restricts the number of OP_RETURN outputs per tx to 1. If this comment were to say per transaction it sort of implies that the data can be split across multiple OP_RETURN outputs as long as the limit is not exceeded.

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Ahh, missed that it was applied per-scriptPubKey and had an independant per-tx limit, yea, fine as-is.

extern unsigned nMaxDatacarrierBytes;

/**
* Mandatory script verification flags that all new blocks must comply with for
* them to be valid. (but old blocks may not comply with) Currently just P2SH,
* but in the future other flags may be added, such as a soft-fork to enforce
* strict DER encoding.
*
*
* Failing one of these tests may trigger a DoS ban - see CheckInputs() for
* details.
*/
Expand All @@ -50,7 +61,7 @@ enum txnouttype
TX_PUBKEYHASH,
TX_SCRIPTHASH,
TX_MULTISIG,
TX_NULL_DATA,
TX_NULL_DATA, //!< unspendable OP_RETURN script that carries data
TX_WITNESS_V0_SCRIPTHASH,
TX_WITNESS_V0_KEYHASH,
};
Expand All @@ -61,7 +72,7 @@ class CNoDestination {
friend bool operator<(const CNoDestination &a, const CNoDestination &b) { return true; }
};

/**
/**
* A txout script template with a specific destination. It is either:
* * CNoDestination: no destination set
* * CKeyID: TX_PUBKEYHASH destination
Expand All @@ -70,15 +81,58 @@ class CNoDestination {
*/
typedef boost::variant<CNoDestination, CKeyID, CScriptID> CTxDestination;

/** Get the name of a txnouttype as a C string, or nullptr if unknown. */
const char* GetTxnOutputType(txnouttype t);

/**
* Parse a scriptPubKey and identify script type for standard scripts. If
* successful, returns script type and parsed pubkeys or hashes, depending on
* the type. For example, for a P2SH script, vSolutionsRet will contain the
* script hash, for P2PKH it will contain the key hash, etc.
*
* @param[in] scriptPubKey Script to parse
* @param[out] typeRet The script type
* @param[out] vSolutionsRet Vector of parsed pubkeys and hashes
* @return True if script matches standard template
*/
bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet);

/**
* Parse a standard scriptPubKey for the destination address. Assigns result to
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Maybe note that this only works on some standard scriptPubKey types (eg currently does not work on segwit types, nor null_data, for obvious reasons).

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Happy to add if you prefer, but that seems like something that the implementation might change. Is it possible that a new CTxDestination for witness programs will be added? It's also interesting that this function does not return a CNoDestination for TX_NULL_DATA scripts.

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Sure, but we can also update the comment when the implementation changes to support more :)

* the addressRet parameter and returns true if successful. For multisig
* scripts, instead use ExtractDestinations. Currently only works for P2PK,
* P2PKH, and P2SH scripts.
*/
bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet);

/**
* Parse a standard scriptPubKey with one or more destination addresses. For
* multisig scripts, this populates the addressRet vector with the pubkey IDs
* and nRequiredRet with the n required to spend. For other destinations,
* addressRet is populated with a single value and nRequiredRet is set to 1.
* Returns true if successful. Currently does not extract address from
* pay-to-witness scripts.
*/
bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<CTxDestination>& addressRet, int& nRequiredRet);

/**
* Generate a Bitcoin scriptPubKey for the given CTxDestination. Returns a P2PKH
* script for a CKeyID destination, a P2SH script for a CScriptID, and an empty
* script for CNoDestination.
*/
CScript GetScriptForDestination(const CTxDestination& dest);

/** Generate a P2PK script for the given pubkey. */
CScript GetScriptForRawPubKey(const CPubKey& pubkey);

/** Generate a multisig script. */
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.
*/
CScript GetScriptForWitness(const CScript& redeemscript);

#endif // BITCOIN_SCRIPT_STANDARD_H