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4b9da8f919
7e9c7113afbed96cef80c327cc93e82000d6bb69 compressor: Make the domain of CompressAmount(...) explicit (practicalswift)
4a7fd7a7124f84e010b01d0769ef0572bf031ee8 tests: Add amount compression/decompression fuzzing to existing fuzzing harness: test compression round-trip (practicalswift)
Pull request description:
Small fuzzing improvement:
Add amount compression/decompression fuzzing to existing fuzzing harness: test compression round-trip (`DecompressAmount(CompressAmount(…))`).
Make the domain of `CompressAmount(…)` explicit.
Amount compression primer:
```
Compact serialization for amounts
Special serializer/deserializer for amount values. It is optimized for
values which have few non-zero digits in decimal representation. Most
amounts currently in the txout set take only 1 or 2 bytes to
represent.
```
**How to test this PR**
```
$ make distclean
$ ./autogen.sh
$ CC=clang CXX=clang++ ./configure --enable-fuzz \
--with-sanitizers=address,fuzzer,undefined
$ make
$ src/test/fuzz/integer
…
```
Top commit has no ACKs.
Tree-SHA512: 0f7c05b97012ccd5cd05a96c209e6b4d7d2fa73138bac9615cf531baa3f614f9003e29a198015bcc083af9f5bdc752bb52615b82c5df3c519b1a064bd4fc6664
107 lines
3.4 KiB
C++
107 lines
3.4 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2014 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_COMPRESSOR_H
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#define BITCOIN_COMPRESSOR_H
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#include <primitives/transaction.h>
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#include <script/script.h>
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#include <serialize.h>
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#include <span.h>
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bool CompressScript(const CScript& script, std::vector<unsigned char> &out);
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unsigned int GetSpecialScriptSize(unsigned int nSize);
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bool DecompressScript(CScript& script, unsigned int nSize, const std::vector<unsigned char> &out);
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/**
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* Compress amount.
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*
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* nAmount is of type uint64_t and thus cannot be negative. If you're passing in
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* a CAmount (int64_t), make sure to properly handle the case where the amount
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* is negative before calling CompressAmount(...).
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*
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* @pre Function defined only for 0 <= nAmount <= MAX_MONEY.
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*/
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uint64_t CompressAmount(uint64_t nAmount);
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uint64_t DecompressAmount(uint64_t nAmount);
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/** Compact serializer for scripts.
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*
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* It detects common cases and encodes them much more efficiently.
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* 3 special cases are defined:
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* * Pay to pubkey hash (encoded as 21 bytes)
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* * Pay to script hash (encoded as 21 bytes)
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* * Pay to pubkey starting with 0x02, 0x03 or 0x04 (encoded as 33 bytes)
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*
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* Other scripts up to 121 bytes require 1 byte + script length. Above
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* that, scripts up to 16505 bytes require 2 bytes + script length.
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*/
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struct ScriptCompression
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{
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/**
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* make this static for now (there are only 6 special scripts defined)
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* this can potentially be extended together with a new nVersion for
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* transactions, in which case this value becomes dependent on nVersion
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* and nHeight of the enclosing transaction.
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*/
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static const unsigned int nSpecialScripts = 6;
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template<typename Stream>
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void Ser(Stream &s, const CScript& script) {
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std::vector<unsigned char> compr;
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if (CompressScript(script, compr)) {
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s << MakeSpan(compr);
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return;
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}
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unsigned int nSize = script.size() + nSpecialScripts;
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s << VARINT(nSize);
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s << MakeSpan(script);
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}
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template<typename Stream>
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void Unser(Stream &s, CScript& script) {
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unsigned int nSize = 0;
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s >> VARINT(nSize);
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if (nSize < nSpecialScripts) {
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std::vector<unsigned char> vch(GetSpecialScriptSize(nSize), 0x00);
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s >> MakeSpan(vch);
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DecompressScript(script, nSize, vch);
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return;
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}
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nSize -= nSpecialScripts;
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if (nSize > MAX_SCRIPT_SIZE) {
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// Overly long script, replace with a short invalid one
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script << OP_RETURN;
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s.ignore(nSize);
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} else {
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script.resize(nSize);
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s >> MakeSpan(script);
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}
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}
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};
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struct AmountCompression
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{
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template<typename Stream, typename I> void Ser(Stream& s, I val)
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{
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s << VARINT(CompressAmount(val));
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}
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template<typename Stream, typename I> void Unser(Stream& s, I& val)
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{
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uint64_t v;
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s >> VARINT(v);
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val = DecompressAmount(v);
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}
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};
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/** wrapper for CTxOut that provides a more compact serialization */
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struct TxOutCompression
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{
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FORMATTER_METHODS(CTxOut, obj) { READWRITE(Using<AmountCompression>(obj.nValue), Using<ScriptCompression>(obj.scriptPubKey)); }
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};
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#endif // BITCOIN_COMPRESSOR_H
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