refactor: Unify asmap version calculation and naming

Calculate the asmap version only in one place: A dedicated function in util/asmap.

The version was also referred to as asmap checksum in several places. To avoid confusion call it asmap version everywhere.

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();
+}

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