Drop the chain argument to GetDifficulty

This removes the need to include rpc/blockchain.cpp in order to put
GetDifficulty under test. GetDifficulty was called in two ways:
* with a guaranteed non-null blockindex
* with no argument

Change the latter case to be provided chainActive.Tip() explicitly.

src/rpc/blockchain.cpp

@@ -6,7 +6,6 @@
 #include <rpc/blockchain.h>
 
 #include <amount.h>
-#include <chain.h>
 #include <chainparams.h>
 #include <checkpoints.h>
 #include <coins.h>
@@ -47,17 +46,13 @@ static std::mutex cs_blockchange;
 static std::condition_variable cond_blockchange;
 static CUpdatedBlock latestblock;
 
-/* Calculate the difficulty for a given block index,
+/* Calculate the difficulty for a given block index.
- * or the block index of the given chain.
  */
-double GetDifficulty(const CChain& chain, const CBlockIndex* blockindex)
+double GetDifficulty(const CBlockIndex* blockindex)
 {
     if (blockindex == nullptr)
     {
-        if (chain.Tip() == nullptr)
+        return 1.0;
-            return 1.0;
-        else
-            blockindex = chain.Tip();
     }
 
     int nShift = (blockindex->nBits >> 24) & 0xff;
@@ -78,11 +73,6 @@ double GetDifficulty(const CChain& chain, const CBlockIndex* blockindex)
     return dDiff;
 }
 
-double GetDifficulty(const CBlockIndex* blockindex)
-{
-    return GetDifficulty(chainActive, blockindex);
-}
-
 UniValue blockheaderToJSON(const CBlockIndex* blockindex)
 {
     AssertLockHeld(cs_main);
@@ -352,7 +342,7 @@ static UniValue getdifficulty(const JSONRPCRequest& request)
         );
 
     LOCK(cs_main);
-    return GetDifficulty();
+    return GetDifficulty(chainActive.Tip());
 }
 
 static std::string EntryDescriptionString()
@@ -1229,7 +1219,7 @@ UniValue getblockchaininfo(const JSONRPCRequest& request)
     obj.pushKV("blocks",                (int)chainActive.Height());
     obj.pushKV("headers",               pindexBestHeader ? pindexBestHeader->nHeight : -1);
     obj.pushKV("bestblockhash",         chainActive.Tip()->GetBlockHash().GetHex());
-    obj.pushKV("difficulty",            (double)GetDifficulty());
+    obj.pushKV("difficulty",            (double)GetDifficulty(chainActive.Tip()));
     obj.pushKV("mediantime",            (int64_t)chainActive.Tip()->GetMedianTimePast());
     obj.pushKV("verificationprogress",  GuessVerificationProgress(Params().TxData(), chainActive.Tip()));
     obj.pushKV("initialblockdownload",  IsInitialBlockDownload());

src/rpc/blockchain.h

@@ -16,7 +16,7 @@ class UniValue;
  * @return A floating point number that is a multiple of the main net minimum
  * difficulty (4295032833 hashes).
  */
-double GetDifficulty(const CBlockIndex* blockindex = nullptr);
+double GetDifficulty(const CBlockIndex* blockindex);
 
 /** Callback for when block tip changed. */
 void RPCNotifyBlockChange(bool ibd, const CBlockIndex *);
@@ -34,4 +34,3 @@ UniValue mempoolToJSON(bool fVerbose = false);
 UniValue blockheaderToJSON(const CBlockIndex* blockindex);
 
 #endif
-

src/rpc/mining.cpp

@@ -214,7 +214,7 @@ static UniValue getmininginfo(const JSONRPCRequest& request)
     obj.pushKV("blocks",           (int)chainActive.Height());
     obj.pushKV("currentblockweight", (uint64_t)nLastBlockWeight);
     obj.pushKV("currentblocktx",   (uint64_t)nLastBlockTx);
-    obj.pushKV("difficulty",       (double)GetDifficulty());
+    obj.pushKV("difficulty",       (double)GetDifficulty(chainActive.Tip()));
     obj.pushKV("networkhashps",    getnetworkhashps(request));
     obj.pushKV("pooledtx",         (uint64_t)mempool.size());
     obj.pushKV("chain",            Params().NetworkIDString());

src/test/blockchain_tests.cpp

@@ -2,7 +2,7 @@
 
 #include "stdlib.h"
 
-#include "rpc/blockchain.cpp"
+#include "rpc/blockchain.h"
 #include "test/test_bitcoin.h"
 
 /* Equality between doubles is imprecise. Comparison should be done
@@ -22,14 +22,6 @@ static CBlockIndex* CreateBlockIndexWithNbits(uint32_t nbits)
     return block_index;
 }
 
-static CChain CreateChainWithNbits(uint32_t nbits)
-{
-    CBlockIndex* block_index = CreateBlockIndexWithNbits(nbits);
-    CChain chain;
-    chain.SetTip(block_index);
-    return chain;
-}
-
 static void RejectDifficultyMismatch(double difficulty, double expected_difficulty) {
      BOOST_CHECK_MESSAGE(
         DoubleEquals(difficulty, expected_difficulty, 0.00001),
@@ -43,12 +35,7 @@ static void RejectDifficultyMismatch(double difficulty, double expected_difficul
 static void TestDifficulty(uint32_t nbits, double expected_difficulty)
 {
     CBlockIndex* block_index = CreateBlockIndexWithNbits(nbits);
-    /* Since we are passing in block index explicitly,
+    double difficulty = GetDifficulty(block_index);
-     * there is no need to set up anything within the chain itself.
-     */
-    CChain chain;
-
-    double difficulty = GetDifficulty(chain, block_index);
     delete block_index;
 
     RejectDifficultyMismatch(difficulty, expected_difficulty);
@@ -84,43 +71,8 @@ BOOST_AUTO_TEST_CASE(get_difficulty_for_very_high_target)
 // Verify that difficulty is 1.0 for an empty chain.
 BOOST_AUTO_TEST_CASE(get_difficulty_for_null_tip)
 {
-    CChain chain;
+    double difficulty = GetDifficulty(nullptr);
-    double difficulty = GetDifficulty(chain, nullptr);
     RejectDifficultyMismatch(difficulty, 1.0);
 }
 
-/* Verify that if difficulty is based upon the block index
- * in the chain, if no block index is explicitly specified.
- */
-BOOST_AUTO_TEST_CASE(get_difficulty_for_null_block_index)
-{
-    CChain chain = CreateChainWithNbits(0x1df88f6f);
-
-    double difficulty = GetDifficulty(chain, nullptr);
-    delete chain.Tip();
-
-    double expected_difficulty = 0.004023;
-
-    RejectDifficultyMismatch(difficulty, expected_difficulty);
-}
-
-/* Verify that difficulty is based upon the explicitly specified
- * block index rather than being taken from the provided chain,
- * when both are present.
- */
-BOOST_AUTO_TEST_CASE(get_difficulty_for_block_index_overrides_tip)
-{
-    CChain chain = CreateChainWithNbits(0x1df88f6f);
-    /* This block index's nbits should be used
-     * instead of the chain's when calculating difficulty.
-     */
-    CBlockIndex* override_block_index = CreateBlockIndexWithNbits(0x12345678);
-
-    double difficulty = GetDifficulty(chain, override_block_index);
-    delete chain.Tip();
-    delete override_block_index;
-
-    RejectDifficultyMismatch(difficulty, 5913134931067755359633408.0);
-}
-
 BOOST_AUTO_TEST_SUITE_END()