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-rw-r--r--src/script/compressor.h84
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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