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dgb: SSOT think() Phase-2 verification-extension walk bounds + non-circular KAT
Lift the inline want/can/get walk-bound arithmetic from share_tracker.hpp think() Phase 2 into a header-only SSOT (think_p2_walk_bounds.hpp), sibling to the Phase-1 think_p1_walk_bounds.hpp landed in #353. Pins the three integer decisions per verified head against the p2pool data.py:2098-2103 oracle: want = max(CHAIN_LENGTH - head_height, 0) can = last_height if unrooted = max(last_height - 1 - CHAIN_LENGTH, 0) otherwise get = min(want, can) FENCED, additive: dgb/ tree-local only, header-only, share_tracker.hpp is NOT yet rewired (byte-identity delegation is the follow-on). Consensus- neutral pure arithmetic. KAT (4/4) hand-derives expectations from the oracle formula, not the subject. Registered in both the dir CMakeLists.txt and both build.yml --target allowlists (avoids #143 NOT_BUILT sentinel).
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Lines changed: 177 additions & 2 deletions

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‎.github/workflows/build.yml‎

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@@ -84,7 +84,7 @@ jobs:
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dgb_gentx_coinbase_test dgb_connection_coinbase_test dgb_pplns_payout_split_test nmc_auxpow_merkle_test nmc_template_builder_test nmc_auxpow_wire_test nmc_reconstruct_won_block_test dgb_gentx_share_path_test dgb_conn_pplns_producer_test dgb_other_tx_resolver_test \
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dgb_other_tx_assembler_test dgb_reconstruct_won_block_test dgb_reconstruct_closure_test dgb_gentx_unpack_test dgb_work_source_test dgb_template_builder_test dgb_embedded_coin_node_test dgb_embedded_tx_select_test dgb_template_other_txs_test dgb_coinbase_value_parity_test dgb_submit_classify_test dgb_aux_parent_coinbase_parity_test dgb_template_capture_test dgb_aux_doge_db_commitment_bind_test \
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rpc_request_test softfork_check_test genesis_check_test algo_select_test digishield_walk_test header_chain_test \
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dgb_coin_node_seam_test dgb_block_broadcast_test dgb_won_block_dispatch_test dgb_forced_won_share_dualpath_test dgb_scrypt_pow_test dgb_nonce_grinder_test dgb_regrind_block_test dgb_won_block_finalize_test dgb_share_target_genesis_test dgb_pool_msg_wire_test dgb_get_shares_walk_test dgb_download_stops_test dgb_think_p1_walk_bounds_test dgb_think_p1_desired_emit_test dgb_think_p6_desired_cutoff_test dgb_think_p4_head_keys_test v37_test \
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dgb_coin_node_seam_test dgb_block_broadcast_test dgb_won_block_dispatch_test dgb_forced_won_share_dualpath_test dgb_scrypt_pow_test dgb_nonce_grinder_test dgb_regrind_block_test dgb_won_block_finalize_test dgb_share_target_genesis_test dgb_pool_msg_wire_test dgb_get_shares_walk_test dgb_download_stops_test dgb_think_p1_walk_bounds_test dgb_think_p1_desired_emit_test dgb_think_p6_desired_cutoff_test dgb_think_p4_head_keys_test dgb_think_p2_walk_bounds_test v37_test \
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-j$(nproc)
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- name: Run tests
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dgb_gentx_coinbase_test dgb_connection_coinbase_test dgb_pplns_payout_split_test nmc_auxpow_merkle_test nmc_template_builder_test nmc_auxpow_wire_test nmc_reconstruct_won_block_test dgb_gentx_share_path_test dgb_conn_pplns_producer_test dgb_other_tx_resolver_test \
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dgb_other_tx_assembler_test dgb_reconstruct_won_block_test dgb_reconstruct_closure_test dgb_gentx_unpack_test dgb_work_source_test dgb_template_builder_test dgb_embedded_coin_node_test dgb_embedded_tx_select_test dgb_template_other_txs_test dgb_coinbase_value_parity_test dgb_submit_classify_test dgb_aux_parent_coinbase_parity_test dgb_template_capture_test dgb_aux_doge_db_commitment_bind_test \
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rpc_request_test softfork_check_test genesis_check_test algo_select_test digishield_walk_test header_chain_test \
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dgb_coin_node_seam_test dgb_block_broadcast_test dgb_won_block_dispatch_test dgb_forced_won_share_dualpath_test dgb_scrypt_pow_test dgb_nonce_grinder_test dgb_regrind_block_test dgb_won_block_finalize_test dgb_share_target_genesis_test dgb_pool_msg_wire_test dgb_get_shares_walk_test dgb_download_stops_test dgb_think_p1_walk_bounds_test dgb_think_p1_desired_emit_test dgb_think_p6_desired_cutoff_test dgb_think_p4_head_keys_test test_coin_broadcaster test_multiaddress_pplns test_pplns_stress \
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dgb_coin_node_seam_test dgb_block_broadcast_test dgb_won_block_dispatch_test dgb_forced_won_share_dualpath_test dgb_scrypt_pow_test dgb_nonce_grinder_test dgb_regrind_block_test dgb_won_block_finalize_test dgb_share_target_genesis_test dgb_pool_msg_wire_test dgb_get_shares_walk_test dgb_download_stops_test dgb_think_p1_walk_bounds_test dgb_think_p1_desired_emit_test dgb_think_p6_desired_cutoff_test dgb_think_p4_head_keys_test dgb_think_p2_walk_bounds_test test_coin_broadcaster test_multiaddress_pplns test_pplns_stress \
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v37_test \
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-j$(nproc)
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‎src/impl/dgb/test/CMakeLists.txt‎

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dgb_coin pool sharechain)
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gtest_add_tests(dgb_think_p4_head_keys_test "" AUTO)
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# dgb_think_p2_walk_bounds_test: FENCED, additive KAT pinning the think()
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# Phase-2 verification-extension walk bounds in think_p2_walk_bounds.hpp vs
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# the p2pool data.py:2098-2103 oracle (want=max(CL-h,0); can=last_height if
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# unrooted else max(last_height-1-CL,0); get=min(want,can)). Pure arithmetic
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# -> links only core. MUST also be in build.yml --target allowlist (#143).
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add_executable(dgb_think_p2_walk_bounds_test think_p2_walk_bounds_test.cpp)
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target_link_libraries(dgb_think_p2_walk_bounds_test PRIVATE
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GTest::gtest_main GTest::gtest
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core dgb
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c2pool_payout c2pool_merged_mining c2pool_hashrate c2pool_storage
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dgb_coin pool sharechain)
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gtest_add_tests(dgb_think_p2_walk_bounds_test "" AUTO)
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endif()

‎src/impl/dgb/test/think_p2_walk_bounds_test.cpp‎

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// dgb think() Phase-2 verification-extension walk BOUNDS conformance KAT.
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//
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// FENCED, additive (no production code touched this slice). Pins
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// src/impl/dgb/think_p2_walk_bounds.hpp against the p2pool data.py think()
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// Phase-2 oracle (data.py:2098-2103) for the three pure decisions per verified
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// head:
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// want = max(CHAIN_LENGTH - head_height, 0)
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// can = last_height if unrooted (no last_last)
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// = max(last_height - 1 - CHAIN_LENGTH, 0) otherwise
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// get = min(want, can)
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//
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// Expectations are HAND-DERIVED from the oracle formula, NOT read back from the
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// code under test — a conformance KAT that asks its subject for the answer
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// passes vacuously. Pure arithmetic: links only core (no chain standup). MUST
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// appear in BOTH this dir's CMakeLists.txt AND the build.yml --target allowlist,
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// or it becomes a #143 NOT_BUILT sentinel (compiled-out, silently "passing").
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#include <impl/dgb/think_p2_walk_bounds.hpp>
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#include <gtest/gtest.h>
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#include <cstdint>
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namespace {
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// ---- want = max(CHAIN_LENGTH - head_height, 0): floors at 0 above CL
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TEST(ThinkP2WalkBounds, WantFloorsAtZeroAboveChainLength)
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{
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constexpr int32_t CL = 10;
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// head below CL → positive remaining-to-verify count
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 0, false, CL).want, 10); // max(10,0)
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EXPECT_EQ(dgb::think_p2_walk_bounds(3, 0, false, CL).want, 7); // max(7,0)
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EXPECT_EQ(dgb::think_p2_walk_bounds(9, 0, false, CL).want, 1); // max(1,0)
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// head at/above CL → floored to 0
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EXPECT_EQ(dgb::think_p2_walk_bounds(10, 0, false, CL).want, 0); // boundary
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EXPECT_EQ(dgb::think_p2_walk_bounds(15, 0, false, CL).want, 0); // max(-5,0)
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}
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// ---- can, UNROOTED head (has_last == false) → full last_height
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TEST(ThinkP2WalkBounds, CanUnrootedIsFullLastHeight)
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{
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constexpr int32_t CL = 10;
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 0, false, CL).can, 0);
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 1, false, CL).can, 1);
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 50, false, CL).can, 50);
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// chain_length must not influence the unrooted `can`.
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 7, false, 9999).can, 7);
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}
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// ---- can, ROOTED head (has_last == true) → max(last_height - 1 - CL, 0)
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TEST(ThinkP2WalkBounds, CanRootedAppliesOffsetAndFloor)
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{
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constexpr int32_t CL = 10;
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// last_height - 1 - CL below 0 → floored to 0
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 10, true, CL).can, 0); // max(-1,0)
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 11, true, CL).can, 0); // max(0,0) boundary
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// above the offset → exact difference
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 12, true, CL).can, 1); // max(1,0)
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 20, true, CL).can, 9); // max(9,0)
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EXPECT_EQ(dgb::think_p2_walk_bounds(0, 100, true, CL).can, 89);
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}
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// ---- get = min(want, can): each side can dominate
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TEST(ThinkP2WalkBounds, GetIsMinOfWantAndCan)
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{
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constexpr int32_t CL = 10;
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// want dominates: head=2 → want=8; unrooted last_height=50 → can=50; get=8
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{
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auto b = dgb::think_p2_walk_bounds(2, 50, false, CL);
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EXPECT_EQ(b.want, 8);
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EXPECT_EQ(b.can, 50);
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EXPECT_EQ(b.get, 8);
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}
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// can dominates: head=0 → want=10; rooted last_height=14 → can=max(3,0)=3; get=3
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{
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auto b = dgb::think_p2_walk_bounds(0, 14, true, CL);
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EXPECT_EQ(b.want, 10);
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EXPECT_EQ(b.can, 3);
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EXPECT_EQ(b.get, 3);
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}
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// both zero → get=0 (head past CL, rooted tail under offset)
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{
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auto b = dgb::think_p2_walk_bounds(12, 11, true, CL);
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EXPECT_EQ(b.want, 0);
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EXPECT_EQ(b.can, 0);
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EXPECT_EQ(b.get, 0);
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}
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// equal want==can → get equals both
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{
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auto b = dgb::think_p2_walk_bounds(5, 5, false, CL); // want=5, can=5
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EXPECT_EQ(b.get, 5);
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}
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}
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} // namespace

‎src/impl/dgb/think_p2_walk_bounds.hpp‎

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#pragma once
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// SSOT for the think() Phase-2 verification-extension walk BOUNDS — the three
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// pure integer decisions that govern, per VERIFIED sharechain head, how many
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// shares think() Phase 2 walks backward attempting to extend verification:
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// want = how many shares below this head still need verifying,
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// can = how many the resolved segment actually permits fetching,
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// get = min(want, can) = the bounded walk count handed to get_chain().
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//
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// This formula is currently OPEN-CODED inline in share_tracker.hpp think()
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// Phase 2 (the want/can/get block just before the get_chain(last, to_get)
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// walk). A silent drift against the p2pool oracle — or against the sibling
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// Phase-1 walk-bounds SSOT (think_p1_walk_bounds.hpp) — would change how far a
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// c2pool-dgb node extends verification per think() cycle during sync, with NO
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// compile error. Lifting it to a single header-only SSOT lets a KAT pin the
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// exact arithmetic (want floor 0, the unrooted-vs-rooted `can` split, the
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// -1-CHAIN_LENGTH offset on the rooted branch, get = min).
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//
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// Oracle: p2pool data.py:2098-2103 OkayTracker.think(), per verified head:
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// want = max(self.net.CHAIN_LENGTH - head_height, 0)
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// can = max(last_height - 1 - self.net.CHAIN_LENGTH, 0)
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// if last_last_hash is not None else last_height
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// get = min(want, can)
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// (head_height = height of the verified head; last_height/last_last_hash =
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// the resolved tail segment's height and its parent, i.e. whether the
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// segment is rooted.)
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//
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// Per-coin isolation: dgb/ only. Header-only, additive; this slice does NOT yet
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// rewire share_tracker.hpp (that is the byte-identity-fenced delegation
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// follow-on) — it pins the bounds as a free function so the KAT exercises them
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// with no ShareTracker/NodeImpl standup. Consensus-neutral: pure arithmetic,
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// no value semantics changed. Sibling of think_p1_walk_bounds.hpp.
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#include <algorithm>
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#include <cstdint>
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namespace dgb {
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// The three Phase-2 walk-bound integers, returned together so the KAT (and the
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// eventual delegation) can pin each independently.
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struct ThinkP2WalkBounds {
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int32_t want; // shares still needing verification below this head
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int32_t can; // shares the resolved segment permits fetching
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int32_t get; // min(want, can) — the bounded count handed to get_chain()
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};
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// Compute the Phase-2 verification-extension walk bounds for one verified head.
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// head_height : accumulated height of the verified head.
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// last_height : height of the resolved tail segment (`last`).
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// has_last : whether the segment is rooted (last_last_hash is non-null).
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// false => `can` is the full last_height (unrooted: nothing
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// below has been settled away yet).
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// chain_length: net.CHAIN_LENGTH.
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inline ThinkP2WalkBounds think_p2_walk_bounds(int32_t head_height,
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int32_t last_height,
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bool has_last,
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int32_t chain_length)
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{
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int32_t want = std::max(chain_length - head_height, 0);
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int32_t can = has_last
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? std::max(last_height - 1 - chain_length, 0)
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: last_height;
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int32_t get = std::min(want, can);
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return {want, can, get};
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}
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} // namespace dgb

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