kernel: add btck_block_tree_entry_equals

BlockTreeEntry objects are often compared. By exposing an equality
function, clients don't have to implement more expensive
comparisons based on height and block hash.

src/kernel/bitcoinkernel.cpp

@@ -1104,6 +1104,11 @@ const btck_BlockHash* btck_block_tree_entry_get_block_hash(const btck_BlockTreeE
     return btck_BlockHash::ref(btck_BlockTreeEntry::get(entry).phashBlock);
 }
 
+int btck_block_tree_entry_equals(const btck_BlockTreeEntry* entry1, const btck_BlockTreeEntry* entry2)
+{
+    return &btck_BlockTreeEntry::get(entry1) == &btck_BlockTreeEntry::get(entry2);
+}
+
 btck_BlockHash* btck_block_hash_create(const unsigned char block_hash[32])
 {
     return btck_BlockHash::create(std::span<const unsigned char>{block_hash, 32});

src/kernel/bitcoinkernel.h

@@ -922,6 +922,17 @@ BITCOINKERNEL_API int32_t BITCOINKERNEL_WARN_UNUSED_RESULT btck_block_tree_entry
 BITCOINKERNEL_API const btck_BlockHash* BITCOINKERNEL_WARN_UNUSED_RESULT btck_block_tree_entry_get_block_hash(
     const btck_BlockTreeEntry* block_tree_entry) BITCOINKERNEL_ARG_NONNULL(1);
 
+/**
+ * @brief Check if two block tree entries are equal. Two block tree entries are equal when they
+ * point to the same block.
+ *
+ * @param[in] entry1 Non-null.
+ * @param[in] entry2 Non-null.
+ * @return           1 if the block tree entries are equal, 0 otherwise.
+ */
+BITCOINKERNEL_API int BITCOINKERNEL_WARN_UNUSED_RESULT btck_block_tree_entry_equals(
+    const btck_BlockTreeEntry* entry1, const btck_BlockTreeEntry* entry2) BITCOINKERNEL_ARG_NONNULL(1, 2);
+
 ///@}
 
 /** @name ChainstateManagerOptions

src/kernel/bitcoinkernel_wrapper.h

@@ -786,6 +786,11 @@ public:
     {
     }
 
+    bool operator==(const BlockTreeEntry& other) const
+    {
+        return btck_block_tree_entry_equals(get(), other.get()) != 0;
+    }
+
     std::optional<BlockTreeEntry> GetPrevious() const
     {
         auto entry{btck_block_tree_entry_get_previous(get())};