Add --block-number option to blockchain_import

This enables the importer to stop after reaching a specified block
number (zero-based index), before reaching the end of the source
blockchain.

src/blockchain_converter/blockchain_import.cpp

@@ -169,7 +169,7 @@ int pop_blocks(FakeCore& simple_core, int num_blocks)
 }
 
 template <typename FakeCore>
-int import_from_file(FakeCore& simple_core, std::string& import_file_path)
+int import_from_file(FakeCore& simple_core, std::string& import_file_path, uint64_t stop_height=0)
 {
 #if !defined(BLOCKCHAIN_DB)
   static_assert(std::is_same<fake_core_memory, FakeCore>::value || std::is_same<fake_core_lmdb, FakeCore>::value,
@@ -230,9 +230,10 @@ int import_from_file(FakeCore& simple_core, std::string& import_file_path)
   // Note that a new blockchain will start with block number 0 (total blocks: 1)
   // due to genesis block being added at initialization.
 
-  // CONFIG
-  // TODO: can expand on this, e.g. with --block-number option
-  uint64_t stop_height = total_source_blocks - 1;
+  if (! stop_height)
+  {
+    stop_height = total_source_blocks - 1;
+  }
 
   // These are what we'll try to use, and they don't have to be a determination
   // from source and destination blockchains, but those are the defaults.
@@ -530,6 +531,7 @@ int main(int argc, char* argv[])
 
   uint32_t log_level = LOG_LEVEL_0;
   uint64_t num_blocks = 0;
+  uint64_t block_height = 0;
   std::string dirname;
   std::string db_arg_str;
 
@@ -539,6 +541,7 @@ int main(int argc, char* argv[])
   po::options_description desc_cmd_only("Command line options");
   po::options_description desc_cmd_sett("Command line options and settings options");
   const command_line::arg_descriptor<uint32_t> arg_log_level   =  {"log-level",  "", log_level};
+  const command_line::arg_descriptor<uint64_t> arg_block_height = {"block-number", "stop at block number", block_height};
   const command_line::arg_descriptor<uint64_t> arg_batch_size  =  {"batch-size", "", db_batch_size};
   const command_line::arg_descriptor<uint64_t> arg_pop_blocks  =  {"pop-blocks", "", num_blocks};
   const command_line::arg_descriptor<bool>     arg_testnet_on  = {
@@ -565,6 +568,7 @@ int main(int argc, char* argv[])
   command_line::add_arg(desc_cmd_sett, command_line::arg_data_dir, default_data_path.string());
   command_line::add_arg(desc_cmd_sett, command_line::arg_testnet_data_dir, default_testnet_data_path.string());
   command_line::add_arg(desc_cmd_sett, arg_log_level);
+  command_line::add_arg(desc_cmd_sett, arg_block_height);
   command_line::add_arg(desc_cmd_sett, arg_batch_size);
   command_line::add_arg(desc_cmd_sett, arg_pop_blocks);
   command_line::add_arg(desc_cmd_sett, arg_testnet_on);
@@ -598,6 +602,7 @@ int main(int argc, char* argv[])
   opt_verify    = command_line::get_arg(vm, arg_verify);
   opt_batch     = command_line::get_arg(vm, arg_batch);
   opt_resume    = command_line::get_arg(vm, arg_resume);
+  block_height  = command_line::get_arg(vm, arg_block_height);
   db_batch_size = command_line::get_arg(vm, arg_batch_size);
 
   if (command_line::get_arg(vm, command_line::arg_help))
@@ -629,6 +634,11 @@ int main(int argc, char* argv[])
       db_batch_size = db_batch_size_verify;
     }
   }
+  uint64_t stop_height = 0;
+  if (! vm["block-number"].defaulted())
+  {
+    stop_height = block_height;
+  }
 
   std::vector<std::string> db_engines {"memory", "lmdb"};
 
@@ -702,12 +712,12 @@ int main(int argc, char* argv[])
   if (db_engine == "lmdb")
   {
     fake_core_lmdb simple_core(dirname, opt_testnet, opt_batch, mdb_flags);
-    import_from_file(simple_core, import_file_path);
+    import_from_file(simple_core, import_file_path, stop_height);
   }
   else if (db_engine == "memory")
   {
     fake_core_memory simple_core(dirname, opt_testnet);
-    import_from_file(simple_core, import_file_path);
+    import_from_file(simple_core, import_file_path, stop_height);
   }
   else
   {
@@ -737,7 +747,7 @@ int main(int argc, char* argv[])
     exit(0);
   }
 
-  import_from_file(simple_core, import_file_path);
+  import_from_file(simple_core, import_file_path, stop_height);
 #endif
 
   }