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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 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"
class CKeyID;
class CPubKey;
class CScriptID;
/**
* 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;
protected:
/**
* These check for scripts for which a special case with a shorter encoding
* is defined. They are implemented separately from the CScript test, as
* these test for exact byte sequence correspondences, and are more strict.
* For example, IsToPubKey also verifies whether the public key is valid (as
* invalid ones cannot be represented in compressed form).
*/
bool IsToKeyID(CKeyID &hash) const;
bool IsToScriptID(CScriptID &hash) const;
bool IsToPubKey(CPubKey &pubkey) const;
bool Compress(std::vector<uint8_t> &out) const;
unsigned int GetSpecialSize(unsigned int nSize) const;
bool Decompress(unsigned int nSize, const std::vector<uint8_t> &out);
public:
CScriptCompressor(CScript &scriptIn) : script(scriptIn) {}
template <typename Stream> void Serialize(Stream &s) const {
std::vector<uint8_t> compr;
if (Compress(compr)) {
s << CFlatData(compr);
return;
}
unsigned int nSize = script.size() + nSpecialScripts;
s << VARINT(nSize);
s << CFlatData(script);
}
template <typename Stream> void Unserialize(Stream &s) {
unsigned int nSize = 0;
s >> VARINT(nSize);
if (nSize < nSpecialScripts) {
std::vector<uint8_t> vch(GetSpecialSize(nSize), 0x00);
s >> REF(CFlatData(vch));
Decompress(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 >> REF(CFlatData(script));
}
}
};
/** wrapper for CTxOut that provides a more compact serialization */
class CTxOutCompressor {
private:
CTxOut &txout;
public:
static uint64_t CompressAmount(Amount nAmount);
static Amount DecompressAmount(uint64_t nAmount);
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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