compressor.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2021 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef BITCOIN_COMPRESSOR_H
#define BITCOIN_COMPRESSOR_H
 
#include <prevector.h>
#include <primitives/transaction.h>
#include <script/script.h>
#include <serialize.h>
#include <span.h>
 
using CompressedScript = prevector<33, unsigned char>;
 
 
bool CompressScript(const CScript& script, CompressedScript& out);
unsigned int GetSpecialScriptSize(unsigned int nSize);
bool DecompressScript(CScript& script, unsigned int nSize, const CompressedScript& in);
 
uint64_t CompressAmount(uint64_t nAmount);
 
uint64_t DecompressAmount(uint64_t nAmount);
 
struct ScriptCompression
{
    static const unsigned int nSpecialScripts = 6;
 
    template<typename Stream>
    void Ser(Stream &s, const CScript& script) {
        CompressedScript compr;
        if (CompressScript(script, compr)) {
            s << Span{compr};
            return;
        }
        unsigned int nSize = script.size() + nSpecialScripts;
        s << VARINT(nSize);
        s << Span{script};
    }
 
    template<typename Stream>
    void Unser(Stream &s, CScript& script) {
        unsigned int nSize = 0;
        s >> VARINT(nSize);
        if (nSize < nSpecialScripts) {
            CompressedScript vch(GetSpecialScriptSize(nSize), 0x00);
            s >> Span{vch};
            DecompressScript(script, nSize, vch);
            return;
        }
        nSize -= nSpecialScripts;
        if (nSize > MAX_SCRIPT_SIZE) {
            // Overly long script, replace with a short invalid one
            script << OP_RETURN;
            s.ignore(nSize);
        } else {
            script.resize(nSize);
            s >> Span{script};
        }
    }
};
 
struct AmountCompression
{
    template<typename Stream, typename I> void Ser(Stream& s, I val)
    {
        s << VARINT(CompressAmount(val));
    }
    template<typename Stream, typename I> void Unser(Stream& s, I& val)
    {
        uint64_t v;
        s >> VARINT(v);
        val = DecompressAmount(v);
    }
};
 
struct TxOutCompression
{
    FORMATTER_METHODS(CTxOut, obj) { READWRITE(Using<AmountCompression>(obj.nValue), Using<ScriptCompression>(obj.scriptPubKey)); }
};
 
#endif // BITCOIN_COMPRESSOR_H