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Compact serialization for scripts

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Special serializers for script which detect common cases and encode
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.
This commit is contained in:
Pieter Wuille 2012-06-15 18:52:19 +02:00
parent 4d6144f97f
commit 69fc8047a9
5 changed files with 213 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/key.cpp
View File

@ -120,9 +120,9 @@ err:
return ret;
}
void CKey::SetCompressedPubKey()
void CKey::SetCompressedPubKey(bool fCompressed)
{
EC_KEY_set_conv_form(pkey, POINT_CONVERSION_COMPRESSED);
EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
fCompressedPubKey = true;
}

3
src/key.h
View File

@ -113,9 +113,8 @@ protected:
bool fSet;
bool fCompressedPubKey;
void SetCompressedPubKey();
public:
void SetCompressedPubKey(bool fCompressed = true);
void Reset();

14
src/main.h
View File

@ -647,6 +647,20 @@ protected:
const CTxOut& GetOutputFor(const CTxIn& input, const MapPrevTx& inputs) const;
};
/** wrapper for CTxOut that provides a more compact serialization */
class CTxOutCompressor
{
private:
CTxOut &txout;
public:
CTxOutCompressor(CTxOut &txoutIn) : txout(txoutIn) { }
IMPLEMENT_SERIALIZE(
READWRITE(VARINT(txout.nValue));
CScriptCompressor cscript(REF(txout.scriptPubKey));
READWRITE(cscript);
)
};

125
src/script.cpp
View File

@ -1951,3 +1951,128 @@ void CScript::SetMultisig(int nRequired, const std::vector<CKey>& keys)
*this << key.GetPubKey();
*this << EncodeOP_N(keys.size()) << OP_CHECKMULTISIG;
}
bool CScriptCompressor::IsToKeyID(CKeyID &hash) const
{
if (script.size() == 25 && script[0] == OP_DUP && script[1] == OP_HASH160
&& script[2] == 20 && script[23] == OP_EQUALVERIFY
&& script[24] == OP_CHECKSIG) {
memcpy(&hash, &script[3], 20);
return true;
}
return false;
}
bool CScriptCompressor::IsToScriptID(CScriptID &hash) const
{
if (script.size() == 23 && script[0] == OP_HASH160 && script[1] == 20
&& script[22] == OP_EQUAL) {
memcpy(&hash, &script[2], 20);
return true;
}
return false;
}
bool CScriptCompressor::IsToPubKey(std::vector<unsigned char> &pubkey) const
{
if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG
&& (script[1] == 0x02 || script[1] == 0x03)) {
pubkey.resize(33);
memcpy(&pubkey[0], &script[1], 33);
return true;
}
if (script.size() == 67 && script[0] == 65 && script[66] == OP_CHECKSIG
&& script[1] == 0x04) {
pubkey.resize(65);
memcpy(&pubkey[0], &script[1], 65);
CKey key;
return (key.SetPubKey(CPubKey(pubkey))); // SetPubKey fails if this is not a valid public key, a case that would not be compressible
}
return false;
}
bool CScriptCompressor::Compress(std::vector<unsigned char> &out) const
{
CKeyID keyID;
if (IsToKeyID(keyID)) {
out.resize(21);
out[0] = 0x00;
memcpy(&out[1], &keyID, 20);
return true;
}
CScriptID scriptID;
if (IsToScriptID(scriptID)) {
out.resize(21);
out[0] = 0x01;
memcpy(&out[1], &scriptID, 20);
return true;
}
std::vector<unsigned char> pubkey;
if (IsToPubKey(pubkey)) {
out.resize(33);
memcpy(&out[1], &pubkey[1], 32);
if (pubkey[0] == 0x02 || pubkey[0] == 0x03) {
out[0] = pubkey[0];
return true;
} else if (pubkey[0] == 0x04) {
out[0] = 0x04 | (pubkey[64] & 0x01);
return true;
}
}
return false;
}
unsigned int CScriptCompressor::GetSpecialSize(unsigned int nSize) const
{
if (nSize == 0 || nSize == 1)
return 20;
if (nSize == 2 || nSize == 3 || nSize == 4 || nSize == 5)
return 32;
return 0;
}
bool CScriptCompressor::Decompress(unsigned int nSize, const std::vector<unsigned char> &in)
{
switch(nSize) {
case 0x00:
script.resize(25);
script[0] = OP_DUP;
script[1] = OP_HASH160;
script[2] = 20;
memcpy(&script[3], &in[0], 20);
script[23] = OP_EQUALVERIFY;
script[24] = OP_CHECKSIG;
return true;
case 0x01:
script.resize(23);
script[0] = OP_HASH160;
script[1] = 20;
memcpy(&script[2], &in[0], 20);
script[22] = OP_EQUAL;
return true;
case 0x02:
case 0x03:
script.resize(35);
script[0] = 33;
script[1] = nSize;
memcpy(&script[2], &in[0], 32);
script[34] = OP_CHECKSIG;
return true;
case 0x04:
case 0x05:
std::vector<unsigned char> vch(33, 0x00);
vch[0] = nSize - 2;
memcpy(&vch[1], &in[0], 32);
CKey key;
if (!key.SetPubKey(CPubKey(vch)))
return false;
key.SetCompressedPubKey(false); // Decompress public key
CPubKey pubkey = key.GetPubKey();
script.resize(67);
script[0] = 65;
memcpy(&script[1], &pubkey.Raw()[0], 65);
script[66] = OP_CHECKSIG;
return true;
}
return false;
}

71
src/script.h
View File

@ -579,7 +579,78 @@ public:
}
};
/** 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(std::vector<unsigned char> &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[0], &compr[compr.size()]);
return;
}
unsigned int nSize = script.size() + nSpecialScripts;
s << VARINT(nSize);
s << CFlatData(&script[0], &script[script.size()]);
}
template<typename Stream>
void Unserialize(Stream &s, int nType, int nVersion) {
unsigned int nSize;
s >> VARINT(nSize);
if (nSize < nSpecialScripts) {
std::vector<unsigned char> vch(GetSpecialSize(nSize), 0x00);
s >> REF(CFlatData(&vch[0], &vch[vch.size()]));
Decompress(nSize, vch);
return;
}
nSize -= nSpecialScripts;
script.resize(nSize);
s >> REF(CFlatData(&script[0], &script[script.size()]));
}
};
bool IsCanonicalPubKey(const std::vector<unsigned char> &vchPubKey);
bool IsCanonicalSignature(const std::vector<unsigned char> &vchSig);