add --regtest and --fixed-difficulty for regression testing

on_generateblocks RPC call combines functionality from the on_getblocktemplate and on_submitblock RPC calls to allow rapid block creation. Difficulty is set permanently to 1 for regtest.
Makes use of FAKECHAIN network type, but takes hard fork heights from mainchain
Default reserve_size in generate_blocks RPC call is now 1. If it is 0, the following error occurs 'Failed to calculate offset for'.
Queries hard fork heights info of other network types

src/cryptonote_core/blockchain.cpp

@@ -329,7 +329,7 @@ uint64_t Blockchain::get_current_blockchain_height() const
 //------------------------------------------------------------------
 //FIXME: possibly move this into the constructor, to avoid accidentally
 //       dereferencing a null BlockchainDB pointer
-bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline, const cryptonote::test_options *test_options)
+bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline, const cryptonote::test_options *test_options, difficulty_type fixed_difficulty)
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_tx_pool);
@@ -351,6 +351,7 @@ bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline
 
   m_nettype = test_options != NULL ? FAKECHAIN : nettype;
   m_offline = offline;
+  m_fixed_difficulty = fixed_difficulty;
   if (m_hardfork == nullptr)
   {
     if (m_nettype ==  FAKECHAIN || m_nettype == STAGENET)
@@ -805,6 +806,11 @@ bool Blockchain::get_block_by_hash(const crypto::hash &h, block &blk, bool *orph
 // less blocks than desired if there aren't enough.
 difficulty_type Blockchain::get_difficulty_for_next_block()
 {
+  if (m_fixed_difficulty)
+  {
+    return m_db->height() ? m_fixed_difficulty : 1;
+  }
+
   LOG_PRINT_L3("Blockchain::" << __func__);
 
   CRITICAL_REGION_LOCAL(m_difficulty_lock);
@@ -1007,6 +1013,11 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
 // an alternate chain.
 difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std::list<blocks_ext_by_hash::iterator>& alt_chain, block_extended_info& bei) const
 {
+  if (m_fixed_difficulty)
+  {
+    return m_db->height() ? m_fixed_difficulty : 1;
+  }
+
   LOG_PRINT_L3("Blockchain::" << __func__);
   std::vector<uint64_t> timestamps;
   std::vector<difficulty_type> cumulative_difficulties;
@@ -4374,6 +4385,39 @@ HardFork::State Blockchain::get_hard_fork_state() const
   return m_hardfork->get_state();
 }
 
+const std::vector<HardFork::Params>& Blockchain::get_hard_fork_heights(network_type nettype)
+{
+  static const std::vector<HardFork::Params> mainnet_heights = []()
+  {
+    std::vector<HardFork::Params> heights;
+    for (const auto& i : mainnet_hard_forks)
+      heights.emplace_back(i.version, i.height, i.threshold, i.time);
+    return heights;
+  }();
+  static const std::vector<HardFork::Params> testnet_heights = []()
+  {
+    std::vector<HardFork::Params> heights;
+    for (const auto& i : testnet_hard_forks)
+      heights.emplace_back(i.version, i.height, i.threshold, i.time);
+    return heights;
+  }();
+  static const std::vector<HardFork::Params> stagenet_heights = []()
+  {
+    std::vector<HardFork::Params> heights;
+    for (const auto& i : stagenet_hard_forks)
+      heights.emplace_back(i.version, i.height, i.threshold, i.time);
+    return heights;
+  }();
+  static const std::vector<HardFork::Params> dummy;
+  switch (nettype)
+  {
+    case MAINNET: return mainnet_heights;
+    case TESTNET: return testnet_heights;
+    case STAGENET: return stagenet_heights;
+    default: return dummy;
+  }
+}
+
 bool Blockchain::get_hard_fork_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint64_t &earliest_height, uint8_t &voting) const
 {
   return m_hardfork->get_voting_info(version, window, votes, threshold, earliest_height, voting);

src/cryptonote_core/blockchain.h

@@ -114,10 +114,11 @@ namespace cryptonote
      * @param nettype network type
      * @param offline true if running offline, else false
      * @param test_options test parameters
+     * @param fixed_difficulty fixed difficulty for testing purposes; 0 means disabled
      *
      * @return true on success, false if any initialization steps fail
      */
-    bool init(BlockchainDB* db, const network_type nettype = MAINNET, bool offline = false, const cryptonote::test_options *test_options = NULL);
+    bool init(BlockchainDB* db, const network_type nettype = MAINNET, bool offline = false, const cryptonote::test_options *test_options = NULL, difficulty_type fixed_difficulty = 0);
 
     /**
      * @brief Initialize the Blockchain state
@@ -754,6 +755,13 @@ namespace cryptonote
      */
     HardFork::State get_hard_fork_state() const;
 
+    /**
+     * @brief gets the hardfork heights of given network
+     *
+     * @return the HardFork object
+     */
+    static const std::vector<HardFork::Params>& get_hard_fork_heights(network_type nettype);
+
     /**
      * @brief gets the current hardfork version in use/voted for
      *
@@ -1033,6 +1041,7 @@ namespace cryptonote
 
     network_type m_nettype;
     bool m_offline;
+    difficulty_type m_fixed_difficulty;
 
     std::atomic<bool> m_cancel;
 

src/cryptonote_core/cryptonote_core.cpp

@@ -76,6 +76,16 @@ namespace cryptonote
   , "Run on stagenet. The wallet must be launched with --stagenet flag."
   , false
   };
+  const command_line::arg_descriptor<bool> arg_regtest_on  = {
+    "regtest"
+  , "Run in a regression testing mode."
+  , false
+  };
+  const command_line::arg_descriptor<difficulty_type> arg_fixed_difficulty  = {
+    "fixed-difficulty"
+  , "Fixed difficulty used for testing."
+  , 0
+  };
   const command_line::arg_descriptor<std::string, false, true, 2> arg_data_dir = {
     "data-dir"
   , "Specify data directory"
@@ -252,6 +262,8 @@ namespace cryptonote
 
     command_line::add_arg(desc, arg_testnet_on);
     command_line::add_arg(desc, arg_stagenet_on);
+    command_line::add_arg(desc, arg_regtest_on);
+    command_line::add_arg(desc, arg_fixed_difficulty);
     command_line::add_arg(desc, arg_dns_checkpoints);
     command_line::add_arg(desc, arg_prep_blocks_threads);
     command_line::add_arg(desc, arg_fast_block_sync);
@@ -374,7 +386,8 @@ namespace cryptonote
   {
     start_time = std::time(nullptr);
 
-    if (test_options != NULL)
+    const bool regtest = command_line::get_arg(vm, arg_regtest_on);
+    if (test_options != NULL || regtest)
     {
       m_nettype = FAKECHAIN;
     }
@@ -431,6 +444,16 @@ namespace cryptonote
     blockchain_db_sync_mode sync_mode = db_defaultsync;
     uint64_t blocks_per_sync = 1;
 
+    if (m_nettype == FAKECHAIN)
+    {
+      // reset the db by removing the database file before opening it
+      if (!db->remove_data_file(filename))
+      {
+        MERROR("Failed to remove data file in " << filename);
+        return false;
+      }
+    }
+
     try
     {
       uint64_t db_flags = 0;
@@ -508,7 +531,12 @@ namespace cryptonote
     m_blockchain_storage.set_user_options(blocks_threads,
         blocks_per_sync, sync_mode, fast_sync);
 
-    r = m_blockchain_storage.init(db.release(), m_nettype, m_offline, test_options);
+    const std::pair<uint8_t, uint64_t> regtest_hard_forks[3] = {std::make_pair(1, 0), std::make_pair(Blockchain::get_hard_fork_heights(MAINNET).back().version, 1), std::make_pair(0, 0)};
+    const cryptonote::test_options regtest_test_options = {
+      regtest_hard_forks
+    };
+    const difficulty_type fixed_difficulty = command_line::get_arg(vm, arg_fixed_difficulty);
+    r = m_blockchain_storage.init(db.release(), m_nettype, m_offline, regtest ? &regtest_test_options : test_options, fixed_difficulty);
 
     r = m_mempool.init(max_txpool_size);
     CHECK_AND_ASSERT_MES(r, false, "Failed to initialize memory pool");

src/cryptonote_core/cryptonote_core.h

@@ -61,6 +61,8 @@ namespace cryptonote
   extern const command_line::arg_descriptor<std::string, false, true, 2> arg_data_dir;
   extern const command_line::arg_descriptor<bool, false> arg_testnet_on;
   extern const command_line::arg_descriptor<bool, false> arg_stagenet_on;
+  extern const command_line::arg_descriptor<bool, false> arg_regtest_on;
+  extern const command_line::arg_descriptor<difficulty_type> arg_fixed_difficulty;
   extern const command_line::arg_descriptor<bool> arg_offline;
 
   /************************************************************************/