refactor: Unify asmap version calculation and naming

diff --git a/src/addrman.cpp b/src/addrman.cpp
index 206b5411..2e514909 100644
--- a/src/addrman.cpp
+++ b/src/addrman.cpp
@@ -156,7 +156,7 @@ void AddrManImpl::Serialize(Stream& s_) const
      * * for each new bucket:
      *   * number of elements
      *   * for each element: index in the serialized "all new addresses"
-     * * asmap checksum
+     * * asmap version
      *
      * 2**30 is xorred with the number of buckets to make addrman deserializer v0 detect it
      * as incompatible. This is necessary because it did not check the version number on
@@ -222,9 +222,9 @@ void AddrManImpl::Serialize(Stream& s_) const
             }
         }
     }
-    // Store asmap checksum after bucket entries so that it
+    // Store asmap version after bucket entries so that it
     // can be ignored by older clients for backward compatibility.
-    s << m_netgroupman.GetAsmapChecksum();
+    s << m_netgroupman.GetAsmapVersion();
 }
 
 template <typename Stream>
@@ -330,16 +330,16 @@ void AddrManImpl::Unserialize(Stream& s_)
         }
     }
 
-    // If the bucket count and asmap checksum haven't changed, then attempt
+    // If the bucket count and asmap version haven't changed, then attempt
     // to restore the entries to the buckets/positions they were in before
     // serialization.
-    uint256 supplied_asmap_checksum{m_netgroupman.GetAsmapChecksum()};
-    uint256 serialized_asmap_checksum;
+    uint256 supplied_asmap_version{m_netgroupman.GetAsmapVersion()};
+    uint256 serialized_asmap_version;
     if (format >= Format::V2_ASMAP) {
-        s >> serialized_asmap_checksum;
+        s >> serialized_asmap_version;
     }
     const bool restore_bucketing{nUBuckets == ADDRMAN_NEW_BUCKET_COUNT &&
-        serialized_asmap_checksum == supplied_asmap_checksum};
+        serialized_asmap_version == supplied_asmap_version};
 
     if (!restore_bucketing) {
         LogDebug(BCLog::ADDRMAN, "Bucketing method was updated, re-bucketing addrman entries from disk\n");
diff --git a/src/init.cpp b/src/init.cpp
index 6c14f501..198c07ae 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1581,7 +1581,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
                 InitError(strprintf(_("Could not parse asmap file %s"), fs::quoted(fs::PathToString(asmap_path))));
                 return false;
             }
-            const uint256 asmap_version = (HashWriter{} << asmap).GetHash();
+            const uint256 asmap_version = AsmapVersion(asmap);;
             LogInfo("Using asmap version %s for IP bucketing", asmap_version.ToString());
         } else {
             LogInfo("Using /16 prefix for IP bucketing");
diff --git a/src/netgroup.cpp b/src/netgroup.cpp
index 970aa2b4..5a81cd6b 100644
--- a/src/netgroup.cpp
+++ b/src/netgroup.cpp
@@ -10,11 +10,9 @@
 
 #include <cstddef>
 
-uint256 NetGroupManager::GetAsmapChecksum() const
+uint256 NetGroupManager::GetAsmapVersion() const
 {
-    if (!m_asmap.size()) return {};
-
-    return (HashWriter{} << m_asmap).GetHash();
+    return AsmapVersion(m_asmap);
 }
 
 std::vector<unsigned char> NetGroupManager::GetGroup(const CNetAddr& address) const
diff --git a/src/netgroup.h b/src/netgroup.h
index 399876e5..7f08fef7 100644
--- a/src/netgroup.h
+++ b/src/netgroup.h
@@ -20,8 +20,8 @@ public:
         : m_asmap{std::move(asmap)}
     {}
 
-    /** Get a checksum identifying the asmap being used. */
-    uint256 GetAsmapChecksum() const;
+    /** Get the asmap version, a checksum identifying the asmap being used. */
+    uint256 GetAsmapVersion() const;
 
     /**
      * Get the canonical identifier of the network group for address.
diff --git a/src/util/asmap.cpp b/src/util/asmap.cpp
index 23cf6d16..1993103a 100644
--- a/src/util/asmap.cpp
+++ b/src/util/asmap.cpp
@@ -5,9 +5,11 @@
 #include <util/asmap.h>
 
 #include <clientversion.h>
+#include <hash.h>
 #include <logging.h>
 #include <serialize.h>
 #include <streams.h>
+#include <uint256.h>
 #include <util/fs.h>
 
 #include <algorithm>
@@ -223,3 +225,12 @@ std::vector<std::byte> DecodeAsmap(fs::path path)
 
     return buffer;
 }
+
+uint256 AsmapVersion(const std::vector<std::byte>& data)
+{
+    if (data.empty()) return {};
+
+    HashWriter asmap_hasher;
+    asmap_hasher << data;
+    return asmap_hasher.GetHash();
+}
diff --git a/src/util/asmap.h b/src/util/asmap.h
index b107ad25..722aeec7 100644
--- a/src/util/asmap.h
+++ b/src/util/asmap.h
@@ -5,6 +5,7 @@
 #ifndef BITCOIN_UTIL_ASMAP_H
 #define BITCOIN_UTIL_ASMAP_H
 
+#include <uint256.h>
 #include <util/fs.h>
 
 #include <cstddef>
@@ -17,5 +18,7 @@ bool SanityCheckASMap(const std::vector<std::byte>& asmap, int bits);
 
 /** Read asmap from provided binary file */
 std::vector<std::byte> DecodeAsmap(fs::path path);
+/** Calculate the asmap version, a checksum identifying the asmap being used. */
+uint256 AsmapVersion(const std::vector<std::byte>& data);
 
 #endif // BITCOIN_UTIL_ASMAP_H