Merge #11058: Comments: More comments on functions/globals in standard.h.

360b464 Comments: More comments on functions/globals in standard.h. (Jim Posen)

Pull request description:

  I was confused about what "data carrier" meant, so I wanted to comment the `fAcceptDatacarrier` and `nMaxDatacarrierBytes` fields specifically. Then I figured I'd add docs for the rest of the functions.

Tree-SHA512: e6d0cfe6f4a2ab52ae76f984b1f5d8de371ae938e7832be8b02517d868f1caea62fec8888c917a2bd3d8ef74025de7f00dc96923fa56436dc6b190626652bf29

src/script/standard.cpp

@@ -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

src/script/standard.h

@@ -27,8 +27,19 @@ public:
     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. */
 extern unsigned nMaxDatacarrierBytes;
 
 /**
@@ -36,7 +47,7 @@ extern unsigned nMaxDatacarrierBytes;
  * 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.
  */
@@ -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,
 };
@@ -61,7 +72,7 @@ public:
     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
@@ -70,15 +81,58 @@ public:
  */
 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
+ * 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