Line data    Source code

       1             : // Copyright (c) 2009-2010 Satoshi Nakamoto
       2             : // Copyright (c) 2009-2020 The Bitcoin Core developers
       3             : // Distributed under the MIT software license, see the accompanying
       4             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       5             : 
       6             : #ifndef BITCOIN_COMPRESSOR_H
       7             : #define BITCOIN_COMPRESSOR_H
       8             : 
       9             : #include <primitives/transaction.h>
      10             : #include <script/script.h>
      11             : #include <serialize.h>
      12             : #include <span.h>
      13             : 
      14             : bool CompressScript(const CScript& script, std::vector<unsigned char> &out);
      15             : unsigned int GetSpecialScriptSize(unsigned int nSize);
      16             : bool DecompressScript(CScript& script, unsigned int nSize, const std::vector<unsigned char> &out);
      17             : 
      18             : /**
      19             :  * Compress amount.
      20             :  *
      21             :  * nAmount is of type uint64_t and thus cannot be negative. If you're passing in
      22             :  * a CAmount (int64_t), make sure to properly handle the case where the amount
      23             :  * is negative before calling CompressAmount(...).
      24             :  *
      25             :  * @pre Function defined only for 0 <= nAmount <= MAX_MONEY.
      26             :  */
      27             : uint64_t CompressAmount(uint64_t nAmount);
      28             : 
      29             : uint64_t DecompressAmount(uint64_t nAmount);
      30             : 
      31             : /** Compact serializer for scripts.
      32             :  *
      33             :  *  It detects common cases and encodes them much more efficiently.
      34             :  *  3 special cases are defined:
      35             :  *  * Pay to pubkey hash (encoded as 21 bytes)
      36             :  *  * Pay to script hash (encoded as 21 bytes)
      37             :  *  * Pay to pubkey starting with 0x02, 0x03 or 0x04 (encoded as 33 bytes)
      38             :  *
      39             :  *  Other scripts up to 121 bytes require 1 byte + script length. Above
      40             :  *  that, scripts up to 16505 bytes require 2 bytes + script length.
      41             :  */
      42             : struct ScriptCompression
      43             : {
      44             :     /**
      45             :      * make this static for now (there are only 6 special scripts defined)
      46             :      * this can potentially be extended together with a new nVersion for
      47             :      * transactions, in which case this value becomes dependent on nVersion
      48             :      * and nHeight of the enclosing transaction.
      49             :      */
      50             :     static const unsigned int nSpecialScripts = 6;
      51             : 
      52             :     template<typename Stream>
      53      435753 :     void Ser(Stream &s, const CScript& script) {
      54      435753 :         std::vector<unsigned char> compr;
      55      435753 :         if (CompressScript(script, compr)) {
      56      185015 :             s << MakeSpan(compr);
      57      185015 :             return;
      58             :         }
      59      250738 :         unsigned int nSize = script.size() + nSpecialScripts;
      60      250738 :         s << VARINT(nSize);
      61      250738 :         s << MakeSpan(script);
      62      435753 :     }
      63             : 
      64             :     template<typename Stream>
      65      114583 :     void Unser(Stream &s, CScript& script) {
      66      114583 :         unsigned int nSize = 0;
      67      114583 :         s >> VARINT(nSize);
      68      114583 :         if (nSize < nSpecialScripts) {
      69       19078 :             std::vector<unsigned char> vch(GetSpecialScriptSize(nSize), 0x00);
      70       19078 :             s >> MakeSpan(vch);
      71       19078 :             DecompressScript(script, nSize, vch);
      72             :             return;
      73       19078 :         }
      74       95505 :         nSize -= nSpecialScripts;
      75       95505 :         if (nSize > MAX_SCRIPT_SIZE) {
      76             :             // Overly long script, replace with a short invalid one
      77           1 :             script << OP_RETURN;
      78           1 :             s.ignore(nSize);
      79           1 :         } else {
      80       95504 :             script.resize(nSize);
      81       95504 :             s >> MakeSpan(script);
      82             :         }
      83      114581 :     }
      84             : };
      85             : 
      86             : struct AmountCompression
      87             : {
      88      435753 :     template<typename Stream, typename I> void Ser(Stream& s, I val)
      89             :     {
      90      435753 :         s << VARINT(CompressAmount(val));
      91      435753 :     }
      92      114583 :     template<typename Stream, typename I> void Unser(Stream& s, I& val)
      93             :     {
      94      114583 :         uint64_t v;
      95      114583 :         s >> VARINT(v);
      96      114583 :         val = DecompressAmount(v);
      97      114583 :     }
      98             : };
      99             : 
     100             : /** wrapper for CTxOut that provides a more compact serialization */
     101             : struct TxOutCompression
     102             : {
     103     1100672 :     FORMATTER_METHODS(CTxOut, obj) { READWRITE(Using<AmountCompression>(obj.nValue), Using<ScriptCompression>(obj.scriptPubKey)); }
     104             : };
     105             : 
     106             : #endif // BITCOIN_COMPRESSOR_H