Separate CScriptCompressor

1 files changed, 84 insertions, 0 deletions

diff --git a/src/script/compressor.h b/src/script/compressor.h
new file mode 100644
index 0000000000..f0a3754f02
--- /dev/null
+++ b/src/script/compressor.h
@@ -0,0 +1,84 @@
+// 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