Avoid std parallel set_strong/unstrong, use variant events.

Makefile.am

@@ -45,6 +45,7 @@ src_libbitcoin_node_la_SOURCES = \
     src/chasers/chaser_check.cpp \
     src/chasers/chaser_confirm.cpp \
     src/chasers/chaser_header.cpp \
+    src/chasers/chaser_populate.cpp \
     src/chasers/chaser_snapshot.cpp \
     src/chasers/chaser_storage.cpp \
     src/chasers/chaser_template.cpp \
@@ -89,6 +90,7 @@ test_libbitcoin_node_test_SOURCES = \
     test/chasers/chaser_check.cpp \
     test/chasers/chaser_confirm.cpp \
     test/chasers/chaser_header.cpp \
+    test/chasers/chaser_populate.cpp \
     test/chasers/chaser_template.cpp \
     test/chasers/chaser_transaction.cpp \
     test/chasers/chaser_validate.cpp \
@@ -140,6 +142,7 @@ include_bitcoin_node_chasers_HEADERS = \
     include/bitcoin/node/chasers/chaser_confirm.hpp \
     include/bitcoin/node/chasers/chaser_header.hpp \
     include/bitcoin/node/chasers/chaser_organize.hpp \
+    include/bitcoin/node/chasers/chaser_populate.hpp \
     include/bitcoin/node/chasers/chaser_snapshot.hpp \
     include/bitcoin/node/chasers/chaser_storage.hpp \
     include/bitcoin/node/chasers/chaser_template.hpp \

builds/cmake/CMakeLists.txt

@@ -255,6 +255,7 @@ add_library( ${CANONICAL_LIB_NAME}
     "../../src/chasers/chaser_check.cpp"
     "../../src/chasers/chaser_confirm.cpp"
     "../../src/chasers/chaser_header.cpp"
+    "../../src/chasers/chaser_populate.cpp"
     "../../src/chasers/chaser_snapshot.cpp"
     "../../src/chasers/chaser_storage.cpp"
     "../../src/chasers/chaser_template.cpp"
@@ -329,6 +330,7 @@ if (with-tests)
         "../../test/chasers/chaser_check.cpp"
         "../../test/chasers/chaser_confirm.cpp"
         "../../test/chasers/chaser_header.cpp"
+        "../../test/chasers/chaser_populate.cpp"
         "../../test/chasers/chaser_template.cpp"
         "../../test/chasers/chaser_transaction.cpp"
         "../../test/chasers/chaser_validate.cpp"

builds/msvc/vs2022/libbitcoin-node-test/libbitcoin-node-test.vcxproj

@@ -75,6 +75,7 @@
     <ClCompile Include="..\..\..\..\test\chasers\chaser_check.cpp" />
     <ClCompile Include="..\..\..\..\test\chasers\chaser_confirm.cpp" />
     <ClCompile Include="..\..\..\..\test\chasers\chaser_header.cpp" />
+    <ClCompile Include="..\..\..\..\test\chasers\chaser_populate.cpp" />
     <ClCompile Include="..\..\..\..\test\chasers\chaser_template.cpp" />
     <ClCompile Include="..\..\..\..\test\chasers\chaser_transaction.cpp" />
     <ClCompile Include="..\..\..\..\test\chasers\chaser_validate.cpp" />

builds/msvc/vs2022/libbitcoin-node-test/libbitcoin-node-test.vcxproj.filters

@@ -36,6 +36,9 @@
     <ClCompile Include="..\..\..\..\test\chasers\chaser_header.cpp">
       <Filter>src\chasers</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\..\test\chasers\chaser_populate.cpp">
+      <Filter>src\chasers</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\..\..\test\chasers\chaser_template.cpp">
       <Filter>src\chasers</Filter>
     </ClCompile>

builds/msvc/vs2022/libbitcoin-node/libbitcoin-node.vcxproj

@@ -78,6 +78,7 @@
     <ClCompile Include="..\..\..\..\src\chasers\chaser_check.cpp" />
     <ClCompile Include="..\..\..\..\src\chasers\chaser_confirm.cpp" />
     <ClCompile Include="..\..\..\..\src\chasers\chaser_header.cpp" />
+    <ClCompile Include="..\..\..\..\src\chasers\chaser_populate.cpp" />
     <ClCompile Include="..\..\..\..\src\chasers\chaser_snapshot.cpp" />
     <ClCompile Include="..\..\..\..\src\chasers\chaser_storage.cpp" />
     <ClCompile Include="..\..\..\..\src\chasers\chaser_template.cpp" />
@@ -114,6 +115,7 @@
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_confirm.hpp" />
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_header.hpp" />
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_organize.hpp" />
+    <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_populate.hpp" />
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_snapshot.hpp" />
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_storage.hpp" />
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_template.hpp" />

builds/msvc/vs2022/libbitcoin-node/libbitcoin-node.vcxproj.filters

@@ -63,6 +63,9 @@
     <ClCompile Include="..\..\..\..\src\chasers\chaser_header.cpp">
       <Filter>src\chasers</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\..\src\chasers\chaser_populate.cpp">
+      <Filter>src\chasers</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\..\..\src\chasers\chaser_snapshot.cpp">
       <Filter>src\chasers</Filter>
     </ClCompile>
@@ -167,6 +170,9 @@
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_organize.hpp">
       <Filter>include\bitcoin\node\chasers</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_populate.hpp">
+      <Filter>include\bitcoin\node\chasers</Filter>
+    </ClInclude>
     <ClInclude Include="..\..\..\..\include\bitcoin\node\chasers\chaser_snapshot.hpp">
       <Filter>include\bitcoin\node\chasers</Filter>
     </ClInclude>

include/bitcoin/node.hpp

@@ -31,6 +31,7 @@
 #include <bitcoin/node/chasers/chaser_confirm.hpp>
 #include <bitcoin/node/chasers/chaser_header.hpp>
 #include <bitcoin/node/chasers/chaser_organize.hpp>
+#include <bitcoin/node/chasers/chaser_populate.hpp>
 #include <bitcoin/node/chasers/chaser_snapshot.hpp>
 #include <bitcoin/node/chasers/chaser_storage.hpp>
 #include <bitcoin/node/chasers/chaser_template.hpp>

include/bitcoin/node/chasers/chaser_block.hpp

@@ -41,33 +41,33 @@ class BCN_API chaser_block
 
 protected:
     /// Get header from Block instance.
-    virtual const system::chain::header& get_header(
-        const system::chain::block& block) const NOEXCEPT;
+    const system::chain::header& get_header(
+        const system::chain::block& block) const NOEXCEPT override;
 
     /// Query store for const pointer to Block instance by candidate height.
-    virtual bool get_block(system::chain::block::cptr& out,
-        size_t height) const NOEXCEPT;
+    bool get_block(system::chain::block::cptr& out,
+        size_t height) const NOEXCEPT override;
 
     /// Determine if Block is a duplicate (success for not duplicate).
-    virtual code duplicate(size_t& height,
-        const system::hash_digest& hash) const NOEXCEPT;
+    code duplicate(size_t& height,
+        const system::hash_digest& hash) const NOEXCEPT override;
 
     /// Determine if Block is valid.
-    virtual code validate(const system::chain::block& block,
-        const chain_state& state) const NOEXCEPT;
+    code validate(const system::chain::block& block,
+        const chain_state& state) const NOEXCEPT override;
 
     /// Notify check chaser to redownload the block (nop).
-    virtual void do_malleated(header_t link) NOEXCEPT;
+    void do_malleated(header_t link) NOEXCEPT override;
 
     /// Determine if state is top of a storable branch (always true).
-    virtual bool is_storable(const chain_state& state) const NOEXCEPT;
+    bool is_storable(const chain_state& state) const NOEXCEPT override;
 
     /// True if Block is on a milestone-covered branch.
-    virtual bool is_under_milestone(size_t height) const NOEXCEPT;
+    bool is_under_milestone(size_t height) const NOEXCEPT override;
 
     /// Milestone tracking.
-    virtual void update_milestone(const system::chain::header& header,
-        size_t height, size_t branch_point) NOEXCEPT;
+    void update_milestone(const system::chain::header& header,
+        size_t height, size_t branch_point) NOEXCEPT override;
 
 private:
     void set_prevout(const system::chain::input& input) const NOEXCEPT;

include/bitcoin/node/chasers/chaser_confirm.hpp

@@ -49,9 +49,7 @@ class BCN_API chaser_confirm
         event_value value) NOEXCEPT;
 
     virtual void do_validated(height_t height) NOEXCEPT;
-#if defined(SEQUENTIAL)
-    virtual void do_organize(size_t height) NOEXCEPT;
-#else
+    virtual void do_reorganize(size_t height) NOEXCEPT;
     virtual void do_organize(size_t height) NOEXCEPT;
     virtual bool enqueue_block(const database::header_link& link) NOEXCEPT;
     virtual void confirm_tx(const database::context& ctx,
@@ -63,17 +61,21 @@ class BCN_API chaser_confirm
     virtual void confirm_block(const code& ec,
         const database::header_link& link, size_t height) NOEXCEPT;
     virtual void next_block(size_t height) NOEXCEPT;
-#endif // SEQUENTIAL
 
 private:
+    void reset() NOEXCEPT;
+    bool busy() const NOEXCEPT;
+
     bool set_organized(const database::header_link& link,
         height_t height) NOEXCEPT;
     bool reset_organized(const database::header_link& link,
         height_t height) NOEXCEPT;
     bool set_reorganized(const database::header_link& link,
         height_t height) NOEXCEPT;
-    bool roll_back(header_links& popped, const database::header_link& link,
-        size_t fork_point, size_t top) NOEXCEPT;
+    bool roll_back(const header_links& popped, size_t fork_point,
+        size_t top) NOEXCEPT;
+    bool roll_back(const header_links& popped, size_t fork_point,
+        size_t top, const database::header_link& link) NOEXCEPT;
 
     bool get_fork_work(uint256_t& fork_work, header_links& fork,
         height_t fork_top) const NOEXCEPT;

include/bitcoin/node/chasers/chaser_header.hpp

@@ -44,33 +44,33 @@ class BCN_API chaser_header
 
 protected:
     /// Get header from Block instance.
-    virtual const system::chain::header& get_header(
-        const system::chain::header& header) const NOEXCEPT;
+    const system::chain::header& get_header(
+        const system::chain::header& header) const NOEXCEPT override;
 
     /// Query store for const pointer to Block instance by candidate height.
-    virtual bool get_block(system::chain::header::cptr& out,
-        size_t height) const NOEXCEPT;
+    bool get_block(system::chain::header::cptr& out,
+        size_t height) const NOEXCEPT override;
 
     /// Determine if Block is a duplicate (success for not duplicate).
-    virtual code duplicate(size_t& height,
-        const system::hash_digest& hash) const NOEXCEPT;
+    code duplicate(size_t& height,
+        const system::hash_digest& hash) const NOEXCEPT override;
 
     /// Determine if Block is valid.
-    virtual code validate(const system::chain::header& header,
-        const chain_state& state) const NOEXCEPT;
+    code validate(const system::chain::header& header,
+        const chain_state& state) const NOEXCEPT override;
 
     /// Notify check chaser to redownload the block.
-    virtual void do_malleated(header_t link) NOEXCEPT;
+    void do_malleated(header_t link) NOEXCEPT override;
 
     /// Determine if state is top of a storable branch.
-    virtual bool is_storable(const chain_state& state) const NOEXCEPT;
+    bool is_storable(const chain_state& state) const NOEXCEPT override;
 
     /// True if Block is on a milestone-covered branch.
-    virtual bool is_under_milestone(size_t height) const NOEXCEPT;
+    bool is_under_milestone(size_t height) const NOEXCEPT override;
 
     /// Milestone tracking.
-    virtual void update_milestone(const system::chain::header& header,
-        size_t height, size_t branch_point) NOEXCEPT;
+    void update_milestone(const system::chain::header& header,
+        size_t height, size_t branch_point) NOEXCEPT override;
 
 private:
     bool is_checkpoint(const chain_state& state) const NOEXCEPT;

include/bitcoin/node/chasers/chaser_populate.hpp

@@ -0,0 +1,55 @@
+/**
+ * Copyright (c) 2011-2023 libbitcoin developers (see AUTHORS)
+ *
+ * This file is part of libbitcoin.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef LIBBITCOIN_NODE_CHASERS_CHASER_POPULATE_HPP
+#define LIBBITCOIN_NODE_CHASERS_CHASER_POPULATE_HPP
+
+#include <bitcoin/node/chasers/chaser.hpp>
+#include <bitcoin/node/define.hpp>
+
+namespace libbitcoin {
+namespace node {
+
+class full_node;
+
+/// Order and populate downloaded non-bypass blocks for validation.
+class BCN_API chaser_populate
+  : public chaser
+{
+public:
+    DELETE_COPY_MOVE_DESTRUCT(chaser_populate);
+
+    chaser_populate(full_node& node) NOEXCEPT;
+
+    /// Initialize chaser state.
+    code start() NOEXCEPT override;
+
+protected:
+    virtual bool handle_event(const code& ec, chase event_,
+        event_value value) NOEXCEPT;
+
+    virtual void do_checked(height_t height) NOEXCEPT;
+
+private:
+    // TODO:
+};
+
+} // namespace node
+} // namespace libbitcoin
+
+#endif

include/bitcoin/node/chasers/chasers.hpp

@@ -25,10 +25,11 @@
 #include <bitcoin/node/chasers/chaser_confirm.hpp>
 #include <bitcoin/node/chasers/chaser_header.hpp>
 #include <bitcoin/node/chasers/chaser_organize.hpp>
-#include <bitcoin/node/chasers/chaser_validate.hpp>
+#include <bitcoin/node/chasers/chaser_populate.hpp>
 #include <bitcoin/node/chasers/chaser_snapshot.hpp>
 #include <bitcoin/node/chasers/chaser_storage.hpp>
 #include <bitcoin/node/chasers/chaser_template.hpp>
 #include <bitcoin/node/chasers/chaser_transaction.hpp>
+#include <bitcoin/node/chasers/chaser_validate.hpp>
 
 #endif

include/bitcoin/node/define.hpp

@@ -23,6 +23,7 @@
 #include <functional>
 #include <memory>
 #include <utility>
+#include <variant>
 
 /// Pulls in common /node headers (excluding settings/config/parser/full_node).
 #include <bitcoin/node/chase.hpp>
@@ -63,25 +64,51 @@ typedef std::shared_ptr<database::associations> map_ptr;
 typedef std::function<void(const code&, const map_ptr&,
     const job::ptr&)> map_handler;
 
-/// Node events.
-typedef uint64_t object_key;
-typedef uint64_t event_value;
-typedef network::desubscriber<object_key, chase, event_value> event_subscriber;
-typedef event_subscriber::handler event_notifier;
-typedef event_subscriber::completer event_completer;
+/// Event desubscriber key type.
+using object_key = uint64_t;
 
-/// Use for event_value variants (all unsigned integral integers).
-/// std::variant is inconsistent with interpretation of size_t as redundant or
-/// unique with respect to uint32_t and/or uint64_t (specifically macOS). So
-/// instead these are implicitly casted to event_value (uint64_t) and explicitly
-/// casted from event_value using system::possible_narrow_cast. This is no less
-/// type-safe as using std::variant in cases where the types are overloaded.
+/// Event value types.
 using count_t = size_t;
 using height_t = size_t;
 using channel_t = uint64_t;
 using object_t = object_key;
 using header_t = database::header_link::integer;
 using transaction_t = database::tx_link::integer;
+typedef system::chain::block::cptr block_t;
+////typedef struct
+////{
+////    size_t height;
+////    database::header_link link;
+////    system::chain::block::cptr block;
+////} xblock_t;
+
+/// std::variant types must be distinct, and xcode size_t is neither uint32_t 
+/// nor uint64_t, so this ensures we have the distinct set of necessary types.
+using event_value =
+    iif<is_same_type<std::size_t, uint64_t>,
+        std::variant<uint32_t, size_t, block_t>,
+        iif<is_same_type<std::size_t, uint32_t>,
+            std::variant<uint64_t, size_t, block_t>,
+                std::variant<uint64_t, uint32_t, size_t, block_t>>>;
+////using xevent_value =
+////    iif<is_same_type<std::size_t, uint64_t>,
+////        std::variant<uint32_t, size_t, xblock_t>,
+////        iif<is_same_type<std::size_t, uint32_t>,
+////            std::variant<uint64_t, size_t, xblock_t>,
+////                std::variant<uint64_t, uint32_t, size_t, xblock_t>>>;
+
+/// Event desubscriber.
+typedef network::desubscriber<object_key, chase, event_value> event_subscriber;
+////typedef network::desubscriber<object_key, chase, xevent_value> xevent_subscriber;
+typedef event_subscriber::handler event_notifier;
+typedef event_subscriber::completer event_completer;
+
+// NDEBUG MSVC
+////static_assert(sizeof(uint64_t) == 8u);
+////static_assert(sizeof(block_t) == 16u);
+////static_assert(sizeof(xblock_t) == 32u);
+////static_assert(sizeof(event_value) == 24u);
+////static_assert(sizeof(xevent_value) == 40u);
 
 } // namespace node
 } // namespace libbitcoin

include/bitcoin/node/impl/chasers/chaser_organize.ipp

@@ -96,13 +96,15 @@ bool CLASS::handle_event(const code&, chase event_, event_value value) NOEXCEPT
         case chase::unconfirmable:
         {
             // Roll back the candidate chain to confirmed top (via fork point).
-            POST(do_disorganize, possible_narrow_cast<header_t>(value));
+            BC_ASSERT(std::holds_alternative<header_t>(value));
+            POST(do_disorganize, std::get<header_t>(value));
             break;
         }
         case chase::malleated:
         {
             // Re-obtain the malleated block if it is still a candidate (virtual).
-            POST(do_malleated, possible_narrow_cast<header_t>(value));
+            BC_ASSERT(std::holds_alternative<header_t>(value));
+            POST(do_malleated, std::get<header_t>(value));
             break;
         }
         case chase::stop: