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# 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 <prevector.h>
# 10 : : #include <primitives/transaction.h>
# 11 : : #include <script/script.h>
# 12 : : #include <serialize.h>
# 13 : : #include <span.h>
# 14 : :
# 15 : : /**
# 16 : : * This saves us from making many heap allocations when serializing
# 17 : : * and deserializing compressed scripts.
# 18 : : *
# 19 : : * This prevector size is determined by the largest .resize() in the
# 20 : : * CompressScript function. The largest compressed script format is a
# 21 : : * compressed public key, which is 33 bytes.
# 22 : : */
# 23 : : using CompressedScript = prevector<33, unsigned char>;
# 24 : :
# 25 : :
# 26 : : bool CompressScript(const CScript& script, CompressedScript& out);
# 27 : : unsigned int GetSpecialScriptSize(unsigned int nSize);
# 28 : : bool DecompressScript(CScript& script, unsigned int nSize, const CompressedScript& in);
# 29 : :
# 30 : : /**
# 31 : : * Compress amount.
# 32 : : *
# 33 : : * nAmount is of type uint64_t and thus cannot be negative. If you're passing in
# 34 : : * a CAmount (int64_t), make sure to properly handle the case where the amount
# 35 : : * is negative before calling CompressAmount(...).
# 36 : : *
# 37 : : * @pre Function defined only for 0 <= nAmount <= MAX_MONEY.
# 38 : : */
# 39 : : uint64_t CompressAmount(uint64_t nAmount);
# 40 : :
# 41 : : uint64_t DecompressAmount(uint64_t nAmount);
# 42 : :
# 43 : : /** Compact serializer for scripts.
# 44 : : *
# 45 : : * It detects common cases and encodes them much more efficiently.
# 46 : : * 3 special cases are defined:
# 47 : : * * Pay to pubkey hash (encoded as 21 bytes)
# 48 : : * * Pay to script hash (encoded as 21 bytes)
# 49 : : * * Pay to pubkey starting with 0x02, 0x03 or 0x04 (encoded as 33 bytes)
# 50 : : *
# 51 : : * Other scripts up to 121 bytes require 1 byte + script length. Above
# 52 : : * that, scripts up to 16505 bytes require 2 bytes + script length.
# 53 : : */
# 54 : : struct ScriptCompression
# 55 : : {
# 56 : : /**
# 57 : : * make this static for now (there are only 6 special scripts defined)
# 58 : : * this can potentially be extended together with a new nVersion for
# 59 : : * transactions, in which case this value becomes dependent on nVersion
# 60 : : * and nHeight of the enclosing transaction.
# 61 : : */
# 62 : : static const unsigned int nSpecialScripts = 6;
# 63 : :
# 64 : : template<typename Stream>
# 65 : 597712 : void Ser(Stream &s, const CScript& script) {
# 66 : 597712 : CompressedScript compr;
# 67 [ + + ][ + + ]: 597712 : if (CompressScript(script, compr)) {
# [ + + ][ + + ]
# 68 : 214479 : s << MakeSpan(compr);
# 69 : 214479 : return;
# 70 : 214479 : }
# 71 : 383233 : unsigned int nSize = script.size() + nSpecialScripts;
# 72 : 383233 : s << VARINT(nSize);
# 73 : 383233 : s << MakeSpan(script);
# 74 : 383233 : }
# 75 : :
# 76 : : template<typename Stream>
# 77 : 179974 : void Unser(Stream &s, CScript& script) {
# 78 : 179974 : unsigned int nSize = 0;
# 79 : 179974 : s >> VARINT(nSize);
# 80 [ + + ][ + - ]: 179974 : if (nSize < nSpecialScripts) {
# [ + + ]
# 81 : 24732 : CompressedScript vch(GetSpecialScriptSize(nSize), 0x00);
# 82 : 24732 : s >> MakeSpan(vch);
# 83 : 24732 : DecompressScript(script, nSize, vch);
# 84 : 24732 : return;
# 85 : 24732 : }
# 86 : 155242 : nSize -= nSpecialScripts;
# 87 [ + + ][ # # ]: 155242 : if (nSize > MAX_SCRIPT_SIZE) {
# [ - + ]
# 88 : : // Overly long script, replace with a short invalid one
# 89 : 2 : script << OP_RETURN;
# 90 : 2 : s.ignore(nSize);
# 91 : 155240 : } else {
# 92 : 155240 : script.resize(nSize);
# 93 : 155240 : s >> MakeSpan(script);
# 94 : 155240 : }
# 95 : 155242 : }
# 96 : : };
# 97 : :
# 98 : : struct AmountCompression
# 99 : : {
# 100 : : template<typename Stream, typename I> void Ser(Stream& s, I val)
# 101 : 597712 : {
# 102 : 597712 : s << VARINT(CompressAmount(val));
# 103 : 597712 : }
# 104 : : template<typename Stream, typename I> void Unser(Stream& s, I& val)
# 105 : 179974 : {
# 106 : 179974 : uint64_t v;
# 107 : 179974 : s >> VARINT(v);
# 108 : 179974 : val = DecompressAmount(v);
# 109 : 179974 : }
# 110 : : };
# 111 : :
# 112 : : /** wrapper for CTxOut that provides a more compact serialization */
# 113 : : struct TxOutCompression
# 114 : : {
# 115 : 777686 : FORMATTER_METHODS(CTxOut, obj) { READWRITE(Using<AmountCompression>(obj.nValue), Using<ScriptCompression>(obj.scriptPubKey)); }
# 116 : : };
# 117 : :
# 118 : : #endif // BITCOIN_COMPRESSOR_H
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