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Merge pull request #835 from frstrtr/btc/gentx-coinbase-ssot
btc(#744): gentx_coinbase SSOT assembler -- reconstructor slice 2/7
2 parents cb4ba26 + c46d7e7 commit 3fc1213

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‎src/impl/btc/coin/gentx_coinbase.hpp‎

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// SPDX-License-Identifier: AGPL-3.0-or-later
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#pragma once
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// ============================================================================
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// gentx_coinbase.hpp — SSOT non-witness coinbase (gentx) assembler.
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//
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// Single source of the p2pool coinbase wire layout. Consumed by:
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// - share_check.hpp generate_share_transaction() (the verification SSOT)
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// - share_check.hpp create_local_share() (the "same format as" smell)
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// - won-block reconstruction (as_block framing)
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// so that emission and verification can never diverge on a byte.
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//
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// Produces the NON-WITNESS serialization and its double-SHA256 txid
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// (== p2pool gentx_hash). Byte layout mirrors
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// frstrtr/p2pool-merged-v36 data.py (BTC parent) generate_transaction():
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//
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// version(4 LE = 1)
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// vin_count(varint = 1)
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// vin[0] = prev_hash(32 zero) | prev_idx(0xffffffff) | script(VarStr) | seq(0xffffffff)
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// vout_count(varint)
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// vouts: [segwit_commitment?] ++ payout_outputs ++ donation ++ op_return_commitment
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// each vout = value(8 LE) | script(VarStr)
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// lock_time(4 = 0)
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//
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// Pure: takes already-built script/amount inputs (no tracker, no share template
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// dependency) so it is directly KAT-able against a canonical oracle vector.
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// ============================================================================
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#include <core/pack.hpp>
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#include <core/pack_types.hpp>
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#include <core/hash.hpp>
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#include <core/uint256.hpp>
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#include <cstdint>
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#include <optional>
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#include <span>
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#include <utility>
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#include <vector>
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namespace btc::coin
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{
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struct GentxCoinbase
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{
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std::vector<unsigned char> bytes; // non-witness serialization
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uint256 txid; // double-SHA256(bytes) == gentx_hash
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};
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// payout_outputs: (scriptPubKey, value) pairs in final consensus order.
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// segwit_commitment_script / segwit absent -> no witness-commitment vout.
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inline GentxCoinbase assemble_gentx_coinbase(
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const std::vector<unsigned char>& coinbase_script,
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const std::optional<std::vector<unsigned char>>& segwit_commitment_script,
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const std::vector<std::pair<std::vector<unsigned char>, uint64_t>>& payout_outputs,
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uint64_t donation_amount,
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const std::vector<unsigned char>& donation_script,
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const std::vector<unsigned char>& op_return_script)
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{
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PackStream tx;
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// tx version = 1
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uint32_t tx_version = 1;
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&tx_version), 4));
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// vin count = 1
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{
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unsigned char one = 1;
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&one), 1));
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}
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// vin[0]: prev_output = 0...0:ffffffff, script = coinbase, sequence = 0xffffffff
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{
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uint256 zero_hash;
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tx << zero_hash;
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uint32_t prev_idx = 0xffffffff;
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&prev_idx), 4));
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BaseScript cb; cb.m_data = coinbase_script;
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tx << cb;
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uint32_t seq = 0xffffffff;
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&seq), 4));
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}
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// vout count
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size_t n_outs = payout_outputs.size() + 1 /* donation */ + 1 /* OP_RETURN */
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+ (segwit_commitment_script.has_value() ? 1 : 0);
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if (n_outs < 253)
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{
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uint8_t cnt = static_cast<uint8_t>(n_outs);
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&cnt), 1));
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}
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else
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{
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uint8_t marker = 0xfd;
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&marker), 1));
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uint16_t cnt = static_cast<uint16_t>(n_outs);
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&cnt), 2));
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}
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auto write_txout = [&](uint64_t value, const std::vector<unsigned char>& script) {
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&value), 8));
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BaseScript bs; bs.m_data = script;
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tx << bs;
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};
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// segwit witness-commitment vout (value 0)
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if (segwit_commitment_script.has_value())
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write_txout(0, segwit_commitment_script.value());
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// PPLNS payout outputs (caller supplies final sorted order)
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for (auto& [script, amount] : payout_outputs)
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write_txout(amount, script);
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// donation output
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write_txout(donation_amount, donation_script);
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// OP_RETURN ref commitment (value 0)
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write_txout(0, op_return_script);
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// lock_time = 0
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{
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uint32_t locktime = 0;
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tx.write(std::span<const std::byte>(reinterpret_cast<const std::byte*>(&locktime), 4));
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}
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GentxCoinbase out;
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out.bytes.assign(reinterpret_cast<const unsigned char*>(tx.data()),
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reinterpret_cast<const unsigned char*>(tx.data()) + tx.size());
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auto sp = std::span<const unsigned char>(out.bytes.data(), out.bytes.size());
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out.txid = Hash(sp);
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return out;
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}
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} // namespace btc::coin

‎src/impl/btc/test/CMakeLists.txt‎

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if (BUILD_TESTING AND GTest_FOUND)
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# btc twin of ltc share_test — uniquely named to avoid the CMP0002 target
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# collision with src/impl/ltc/test (both subdirs build in the same tree).
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add_executable(btc_share_test share_test.cpp f11_donation_invariance_test.cpp f10b_version_punish_removal_test.cpp g01_share_format_parity_test.cpp auto_ratchet_sim_test.cpp block_broadcast_guard_test.cpp block_broadcast_connect_test.cpp regtest_sharechain_isolation_test.cpp stratum_merkle_branch_test.cpp witness_commitment_merkle_test.cpp finder_fee_integer_exact_test.cpp rpc_conf_test.cpp genesis_check_test.cpp won_share_dualpath_test.cpp gentx_unpack_test.cpp)
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add_executable(btc_share_test share_test.cpp f11_donation_invariance_test.cpp f10b_version_punish_removal_test.cpp g01_share_format_parity_test.cpp auto_ratchet_sim_test.cpp block_broadcast_guard_test.cpp block_broadcast_connect_test.cpp regtest_sharechain_isolation_test.cpp stratum_merkle_branch_test.cpp witness_commitment_merkle_test.cpp finder_fee_integer_exact_test.cpp rpc_conf_test.cpp genesis_check_test.cpp won_share_dualpath_test.cpp gentx_unpack_test.cpp gentx_coinbase_test.cpp)
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target_link_libraries(btc_share_test PRIVATE
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GTest::gtest_main GTest::gtest
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core btc

‎src/impl/btc/test/gentx_coinbase_test.cpp‎

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// SPDX-License-Identifier: AGPL-3.0-or-later
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// BTC (#744 reconstructor slice 2/7) — SSOT non-witness coinbase (gentx) assembler KAT.
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//
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// Locks btc::coin::assemble_gentx_coinbase() (coin/gentx_coinbase.hpp) — the
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// single coinbase wire-layout extracted from generate_share_transaction()
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// (share_check.hpp:965, the verification SSOT) — against GROUND-TRUTH vectors
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// derived from the canonical oracle frstrtr/p2pool-dgb-scrypt
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// (util/pack.py byte logic + bitcoin/data.py tx_id_type; donation script
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// 4104ffd0...ac). The vectors are NOT self-generated from this builder: they
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// are the oracle serializer's output, so a PASS proves emission==oracle, not
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// merely self-consistency.
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//
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// Asserts, for both the no-segwit and witness-commitment-first layouts:
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// build -> non-witness serialize == oracle BYTES
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// double-SHA256(bytes) (GetHex display) == oracle TXID
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// Per-coin isolation: the only BTC<->DGB divergence is the segwit predicate at
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// serialize time (witness vout present-or-absent), exercised by both cases.
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#include <gtest/gtest.h>
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#include <impl/btc/coin/gentx_coinbase.hpp>
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#include <optional>
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#include <string>
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#include <utility>
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#include <vector>
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namespace {
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std::vector<unsigned char> unhex(const std::string& h) {
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std::vector<unsigned char> v; v.reserve(h.size() / 2);
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auto nyb = [](char c) -> int { return (c <= '9') ? c - '0' : (c | 0x20) - 'a' + 10; };
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for (size_t i = 0; i + 1 < h.size(); i += 2)
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v.push_back(static_cast<unsigned char>((nyb(h[i]) << 4) | nyb(h[i + 1])));
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return v;
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}
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std::string tohex(const std::vector<unsigned char>& v) {
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static const char* H = "0123456789abcdef";
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std::string s; s.reserve(v.size() * 2);
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for (unsigned char b : v) { s.push_back(H[b >> 4]); s.push_back(H[b & 0xf]); }
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return s;
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}
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// --- fixed inputs shared verbatim with the oracle generator ----------------
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const std::vector<unsigned char> CB = unhex("03a1b2c3041122334455667788");
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const std::vector<unsigned char> P1 = unhex(std::string("76a914") + std::string(40, '1') + "88ac");
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const std::vector<unsigned char> P2 = unhex(std::string("76a914") + std::string(40, '2') + "88ac");
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const std::vector<unsigned char> DON = unhex("4104ffd03de44a6e11b9917f3a29f9443283d9871c9d743ef30d5eddcd37094b64d1b3d8090496b53256786bf5c82932ec23c3b74d9f05a6f95a8b5529352656664bac");
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const std::vector<std::pair<std::vector<unsigned char>, uint64_t>> PAYOUTS = {
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{P1, 5000000000ull},
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{P2, 2500000000ull},
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};
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// Ground truth from the oracle serializer (see file header).
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const std::string NOSEG_BYTES =
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"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";
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const std::string NOSEG_TXID =
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"c5734775c1521b216e0e1bca506e4d15755cf55125caf56b7e0728a6d54a9b59";
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const std::string SEG_BYTES =
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"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";
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const std::string SEG_TXID =
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"4b66aabff52ca1336b52688815cece123075856880aaf6e77cb44f0d477b6162";
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} // namespace
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// op_return / wc literals: build them explicitly to avoid std::string surprises.
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static std::vector<unsigned char> make_opret() {
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auto v = unhex("6a28");
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for (int i = 0; i < 32; ++i) v.push_back(0xab);
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const unsigned char nonce[8] = {0x08, 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01};
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for (unsigned char b : nonce) v.push_back(b);
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return v;
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}
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static std::vector<unsigned char> make_wc() {
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auto v = unhex("6a24aa21a9ed");
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for (int i = 0; i < 32; ++i) v.push_back(0xcd);
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return v;
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}
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TEST(BTC_gentx_coinbase, NoSegwitOracleVector) {
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auto opret = make_opret();
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auto g = btc::coin::assemble_gentx_coinbase(
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CB, std::nullopt, PAYOUTS, /*donation_amount=*/1, DON, opret);
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EXPECT_EQ(tohex(g.bytes), NOSEG_BYTES);
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EXPECT_EQ(g.txid.GetHex(), NOSEG_TXID);
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}
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TEST(BTC_gentx_coinbase, SegwitCommitmentFirstOracleVector) {
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auto opret = make_opret();
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auto wc = make_wc();
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auto g = btc::coin::assemble_gentx_coinbase(
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CB, std::optional<std::vector<unsigned char>>(wc), PAYOUTS,
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/*donation_amount=*/1, DON, opret);
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EXPECT_EQ(tohex(g.bytes), SEG_BYTES);
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EXPECT_EQ(g.txid.GetHex(), SEG_TXID);
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}
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// Guard the per-coin isolation invariant: toggling only the segwit predicate
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// changes vout-count + prepends exactly one 0-value commitment vout, nothing
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// else — the divergence is gated, not a forked framer.
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TEST(BTC_gentx_coinbase, SegwitPredicateIsTheOnlyDivergence) {
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EXPECT_NE(NOSEG_BYTES, SEG_BYTES);
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// both share the identical coinbase-script vin prefix and donation/op_return tail
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EXPECT_EQ(NOSEG_BYTES.substr(0, 90), SEG_BYTES.substr(0, 90));
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}

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