Add arraymap.reset().

Author: evoskuil

include/bitcoin/database/impl/primitives/arrayhead.ipp

@@ -77,8 +77,10 @@ bool CLASS::clear() NOEXCEPT
     if (!ptr)
         return false;
 
-    // std::memset/fill_n have identical performance (on win32).
-    ////std::memset(ptr->data(), system::bit_all<uint8_t>, size());
+    // Retains head size, since head is array not map, and resets body logical
+    // count to zero, which is picked up in arraymap::reset(). Body file size
+    // remains unchanged and subject to initialization size at each startup. So
+    // there is no reduction until restart, which can include config change.
     std::fill_n(ptr->data(), size(), system::bit_all<uint8_t>);
     return set_body_count(zero);
 }

include/bitcoin/database/impl/primitives/arraymap.ipp

@@ -49,6 +49,14 @@ bool CLASS::close() NOEXCEPT
     return head_.set_body_count(body_.count());
 }
 
+TEMPLATE
+bool CLASS::reset() NOEXCEPT
+{
+    Link count{};
+    return head_.clear() && head_.get_body_count(count) &&
+        body_.truncate(count);
+}
+
 TEMPLATE
 bool CLASS::backup() NOEXCEPT
 {

include/bitcoin/database/primitives/arraymap.hpp

@@ -50,6 +50,7 @@ class arraymap
 
     bool create() NOEXCEPT;
     bool close() NOEXCEPT;
+    bool reset() NOEXCEPT;
     bool backup() NOEXCEPT;
     bool restore() NOEXCEPT;
     bool verify() const NOEXCEPT;

test/primitives/arrayhead.cpp

@@ -88,7 +88,7 @@ BOOST_AUTO_TEST_CASE(arrayhead__get_body_count__created__zero)
     BOOST_REQUIRE_EQUAL(count, zero);
 }
 
-BOOST_AUTO_TEST_CASE(arrayhead__set_body_count__get__expected)
+BOOST_AUTO_TEST_CASE(arrayhead__set_body_count__get_body_count__expected)
 {
     data_chunk data;
     test::chunk_storage store{ data };
@@ -103,6 +103,25 @@ BOOST_AUTO_TEST_CASE(arrayhead__set_body_count__get__expected)
     BOOST_REQUIRE_EQUAL(count, expected);
 }
 
+BOOST_AUTO_TEST_CASE(arrayhead__clear__get_body_count__zero)
+{
+    data_chunk data;
+    test::chunk_storage store{ data };
+    test_header head{ store, buckets };
+    BOOST_REQUIRE(head.create());
+
+    constexpr auto expected = 42u;
+    BOOST_REQUIRE(head.set_body_count(expected));
+
+    link count{};
+    BOOST_REQUIRE(head.get_body_count(count));
+    BOOST_REQUIRE_EQUAL(count, expected);
+
+    BOOST_REQUIRE(head.clear());
+    BOOST_REQUIRE(head.get_body_count(count));
+    BOOST_REQUIRE_EQUAL(count, zero);
+}
+
 BOOST_AUTO_TEST_CASE(arrayhead__at__key__terminal)
 {
     test::chunk_storage store;

test/primitives/arraymap.cpp

@@ -855,6 +855,19 @@ BOOST_AUTO_TEST_CASE(arraymap__record_body_count__nine_close__nine)
     BOOST_REQUIRE(!instance.get_fault());
 }
 
+BOOST_AUTO_TEST_CASE(arraymap__reset__nine_close__zero)
+{
+    test::chunk_storage head_store{};
+    test::chunk_storage body_store{};
+    record_table instance{ head_store, body_store, initial_buckets };
+    BOOST_REQUIRE(instance.create());
+    body_store.buffer() = base16_chunk("112233441122334411223344112233441122334411223344112233441122334411223344");
+    BOOST_REQUIRE(instance.reset());
+    BOOST_REQUIRE(instance.close());
+    BOOST_REQUIRE_EQUAL(head_store.buffer(), base16_chunk("000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"));
+    BOOST_REQUIRE(!instance.get_fault());
+}
+
 BOOST_AUTO_TEST_CASE(arraymap__record_body_count__nine_backup__nine)
 {
     test::chunk_storage head_store{};