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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2018 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 <primitives/transaction.h>
#include <script/script.h>
#include <serialize.h>
#include <span.h>
class CKeyID;
class CPubKey;
class CScriptID;
bool CompressScript(const CScript& script, std::vector<unsigned char> &out);
unsigned int GetSpecialScriptSize(unsigned int nSize);
bool DecompressScript(CScript& script, unsigned int nSize, const std::vector<unsigned char> &out);
/**
* Compress amount.
*
* nAmount is of type uint64_t and thus cannot be negative. If you're passing in
* a CAmount (int64_t), make sure to properly handle the case where the amount
* is negative before calling CompressAmount(...).
*
* @pre Function defined only for 0 <= nAmount <= MAX_MONEY.
*/
uint64_t CompressAmount(uint64_t nAmount);
uint64_t DecompressAmount(uint64_t nAmount);
/** Compact serializer for scripts.
*
* It detects common cases and encodes them much more efficiently.
* 3 special cases are defined:
* * Pay to pubkey hash (encoded as 21 bytes)
* * Pay to script hash (encoded as 21 bytes)
* * Pay to pubkey starting with 0x02, 0x03 or 0x04 (encoded as 33 bytes)
*
* Other scripts up to 121 bytes require 1 byte + script length. Above
* that, scripts up to 16505 bytes require 2 bytes + script length.
*/
class CScriptCompressor
{
private:
/**
* make this static for now (there are only 6 special scripts defined)
* this can potentially be extended together with a new nVersion for
* transactions, in which case this value becomes dependent on nVersion
* and nHeight of the enclosing transaction.
*/
static const unsigned int nSpecialScripts = 6;
CScript &script;
public:
explicit CScriptCompressor(CScript &scriptIn) : script(scriptIn) { }
template<typename Stream>
void Serialize(Stream &s) const {
std::vector<unsigned char> compr;
if (CompressScript(script, compr)) {
s << MakeSpan(compr);
return;
}
unsigned int nSize = script.size() + nSpecialScripts;
s << VARINT(nSize);
s << MakeSpan(script);
}
template<typename Stream>
void Unserialize(Stream &s) {
unsigned int nSize = 0;
s >> VARINT(nSize);
if (nSize < nSpecialScripts) {
std::vector<unsigned char> vch(GetSpecialScriptSize(nSize), 0x00);
s >> MakeSpan(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 >> MakeSpan(script);
}
}
};
/** wrapper for CTxOut that provides a more compact serialization */
class CTxOutCompressor
{
private:
CTxOut &txout;
public:
explicit CTxOutCompressor(CTxOut &txoutIn) : txout(txoutIn) { }
ADD_SERIALIZE_METHODS;
template <typename Stream, typename Operation>
inline void SerializationOp(Stream& s, Operation ser_action) {
if (!ser_action.ForRead()) {
uint64_t nVal = CompressAmount(txout.nValue);
READWRITE(VARINT(nVal));
} else {
uint64_t nVal = 0;
READWRITE(VARINT(nVal));
txout.nValue = DecompressAmount(nVal);
}
CScriptCompressor cscript(REF(txout.scriptPubKey));
READWRITE(cscript);
}
};
#endif // BITCOIN_COMPRESSOR_H
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