Loading and saving ledger and lcl consensus. (#51)

* Ledger saving, loading, consensus with ledger sequence number.
* std terminate exception handler.

src/cons/ledger_handler.cpp

@@ -0,0 +1,108 @@
+
+#include <flatbuffers/flatbuffers.h>
+#include <iostream>
+#include <fstream>
+#include <boost/filesystem.hpp>
+#include "../conf.hpp"
+#include "../crypto.hpp"
+#include "../p2p/p2p.hpp"
+#include "../fbschema/ledger_helpers.hpp"
+#include "ledger_handler.hpp"
+
+namespace cons
+{
+
+const std::string save_ledger(const p2p::proposal &proposal, const uint64_t led_seq_no)
+{
+    //Serialize lcl using flatbuffer ledger schema.
+    flatbuffers::FlatBufferBuilder builder(1024);
+    const std::string_view ledger_str = fbschema::ledger::create_ledger_from_proposal(builder, proposal);
+
+    //Get binary hash of the the serialized lcl.
+    const std::string lcl = crypto::get_hash(ledger_str);
+
+    //Get hex from binary hash
+    std::string lcl_hash;
+    util::bin2hex(lcl_hash,
+                  reinterpret_cast<const unsigned char *>(lcl.data()),
+                  lcl.size());
+
+    //create file path to save lcl.
+    //file name -> [ledger sequnce numer]-[lcl hex]
+    std::string path;
+    std::string seq_no = std::to_string(led_seq_no);
+    path.reserve(conf::ctx.histDir.size() + lcl_hash.size() + seq_no.size() + 6);
+    path.append(conf::ctx.histDir);
+    path.append("/");
+    path.append(seq_no);
+    path.append("-");
+    path.append(lcl_hash);
+    path.append(".lcl");
+
+    //write lcl to file system
+    std::ofstream ofs(std::move(path));
+    ofs.write(ledger_str.data(), ledger_str.size());
+    ofs.close();
+
+    return (lcl_hash);
+}
+
+const ledger_history load_ledger()
+{
+    ledger_history ldg_hist;
+    ldg_hist.led_seq_no = 0;
+    // might need to load history in order to request response lcl history
+    //std::unordered_map<std::string, std::string_view> lcl_history_files;
+
+    //Get all records at lcl history direcory and find the last closed ledger.
+    std::string latest_file_name;
+    std::string::size_type latest_pos = 0;
+    for (auto &entry : boost::filesystem::directory_iterator(conf::ctx.histDir))
+    {
+        const boost::filesystem::path file_path = entry.path();
+        const std::string file_name = entry.path().filename().string();
+
+        if (boost::filesystem::is_directory(file_path))
+        {
+            LOG_ERR << "Found directory " << file_name << " in " << conf::ctx.histDir << ". There should be no folders in this directory";
+        }
+        else if (file_path.extension() != ".lcl")
+        {
+            LOG_ERR << "Found invalid file extension: " << file_path.extension() << " for lcl file " << file_name << " in " << conf::ctx.histDir;
+        }
+        else
+        {
+            std::string::size_type pos = file_name.find("-");
+            uint64_t seq_no;
+
+            if (pos != std::string::npos)
+            {
+                seq_no = std::stoull(file_name.substr(0, pos));
+            }
+            else
+            {
+                //lcl records should follow [ledger sequnce numer]-lcl[lcl hex] format.
+                LOG_ERR << "Invalid file name: " << file_name;
+            }
+
+            if (seq_no > ldg_hist.led_seq_no)
+            {
+                ldg_hist.led_seq_no = seq_no;
+                latest_pos = pos;
+                latest_file_name = file_name;
+            }
+        }
+    }
+    
+    //check if there is a saved lcl file -> if no send genesis lcl.
+    if (latest_file_name.empty())
+        ldg_hist.lcl = "genesis";
+    else if ((latest_file_name.size() - 6) > latest_pos) //validation to check position is not the end of the file name.
+        ldg_hist.lcl = latest_file_name.substr(latest_pos + 1, (latest_file_name.size() - 6));
+    else
+        LOG_ERR << "Invalid latest file name: " << latest_file_name;
+
+    return ldg_hist;
+}
+
+} // namespace cons