Simplify difficulty calculation API

src/rpc/blockchain.cpp

@@ -113,22 +113,11 @@ CBlockPolicyEstimator& EnsureAnyFeeEstimator(const std::any& context)
 
 /* Calculate the difficulty for a given block index.
  */
-double GetDifficulty(const CBlockIndex* tip, const CBlockIndex* blockindex)
+double GetDifficulty(const CBlockIndex* blockindex)
 {
-    unsigned int nBits;
-    unsigned int powLimit = InitialDifficulty(Params().GetConsensus());
-    if (blockindex == nullptr)
-    {
-        if (tip == nullptr)
-            nBits = powLimit;
-        else
-        {
-            // Vexta is SHA256D-only, so difficulty is based on the active chain tip.
-            nBits = tip->nBits;
-        }  
-    }
-    else
-        nBits = blockindex->nBits;
+    assert(blockindex != nullptr);
+
+    const unsigned int nBits = blockindex->nBits;
 
     int nShift = (nBits >> 24) & 0xff;
     double dDiff =
@@ -148,16 +137,11 @@ double GetDifficulty(const CBlockIndex* tip, const CBlockIndex* blockindex)
     return dDiff;
 }
 
-double GetDifficulty(const CBlockIndex* blockindex)
-{
-    return GetDifficulty(NULL, blockindex);
-}
-
 static double GetNextDifficulty(const CBlockIndex* tip, const Consensus::Params& consensusParams, int algo)
 {
     CBlockIndex next;
     next.nBits = GetNextWorkRequired(tip, nullptr, consensusParams, algo);
-    return GetDifficulty(nullptr, &next);
+    return GetDifficulty(&next);
 }
 
 static int ComputeNextBlockAndDepth(const CBlockIndex* tip, const CBlockIndex* blockindex, const CBlockIndex*& next)
@@ -215,7 +199,7 @@ UniValue blockheaderToJSON(const CBlockIndex* tip, const CBlockIndex* blockindex
     result.pushKV("mediantime", (int64_t)blockindex->GetMedianTimePast());
     result.pushKV("nonce", (uint64_t)blockindex->nNonce);
     result.pushKV("bits", strprintf("%08x", blockindex->nBits));
-    result.pushKV("difficulty", GetDifficulty(tip, blockindex));
+    result.pushKV("difficulty", GetDifficulty(blockindex));
     result.pushKV("chainwork", blockindex->nChainWork.GetHex());
     result.pushKV("nTx", (uint64_t)blockindex->nTx);
 

src/rpc/blockchain.h

@@ -29,12 +29,12 @@ struct NodeContext;
 static constexpr int NUM_GETBLOCKSTATS_PERCENTILES = 5;
 
 /**
- * Get the difficulty of the net wrt to the given block index.
+ * Get the difficulty represented by the given block index nBits.
  *
  * @return A floating point number that is a multiple of the main net minimum
  * difficulty (4295032833 hashes).
  */
-double GetDifficulty(const CBlockIndex* tip = NULL, const CBlockIndex* blockindex = nullptr);
+double GetDifficulty(const CBlockIndex* blockindex);
 
 /** Callback for when block tip changed. */
 void RPCNotifyBlockChange(const CBlockIndex*);

src/rpc/mining.cpp

@@ -665,9 +665,9 @@ static RPCHelpMan getmininginfo()
         GetNextWorkRequired(tip, nullptr, consensusParams, ALGO_RANDOMX);
 
     const double sha_difficulty =
-        GetDifficulty(nullptr, &sha_next);
+        GetDifficulty(&sha_next);
     const double randomx_difficulty =
-        GetDifficulty(nullptr, &randomx_next);
+        GetDifficulty(&randomx_next);
 
     difficulties.pushKV(
         GetMiningAlgoName(ALGO_SHA256D),

src/test/blockchain_tests.cpp

@@ -41,7 +41,7 @@ static void RejectDifficultyMismatch(double difficulty, double expected_difficul
 static void TestDifficulty(uint32_t nbits, double expected_difficulty)
 {
     CBlockIndex* block_index = CreateBlockIndexWithNbits(nbits);
-    double difficulty = GetDifficulty(NULL, block_index);
+    double difficulty = GetDifficulty(block_index);
     delete block_index;
 
     RejectDifficultyMismatch(difficulty, expected_difficulty);