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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2013 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef H_BITCOIN_SCRIPT_COMPRESSOR
#define H_BITCOIN_SCRIPT_COMPRESSOR
#include "script/script.h"
/** 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<unsigned char> &out) const;
unsigned int GetSpecialSize(unsigned int nSize) const;
bool Decompress(unsigned int nSize, const std::vector<unsigned char> &out);
public:
CScriptCompressor(CScript &scriptIn) : script(scriptIn) { }
unsigned int GetSerializeSize(int nType, int nVersion) const {
std::vector<unsigned char> compr;
if (Compress(compr))
return compr.size();
unsigned int nSize = script.size() + nSpecialScripts;
return script.size() + VARINT(nSize).GetSerializeSize(nType, nVersion);
}
template<typename Stream>
void Serialize(Stream &s, int nType, int nVersion) const {
std::vector<unsigned char> 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, int nType, int nVersion) {
unsigned int nSize = 0;
s >> VARINT(nSize);
if (nSize < nSpecialScripts) {
std::vector<unsigned char> vch(GetSpecialSize(nSize), 0x00);
s >> REF(CFlatData(vch));
Decompress(nSize, vch);
return;
}
nSize -= nSpecialScripts;
script.resize(nSize);
s >> REF(CFlatData(script));
}
};
#endif
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