Refactor some things into more composable (smaller) functions

This commit refactors some of the rpc-related functions in the
Blockchain class to be more composable.  This change was made
in order to make implementing the new zmq rpc easier without
trampling on the old rpc.

New functions:
  Blockchain::get_num_mature_outputs
  Blockchain::get_random_outputs
  Blockchain::get_output_key
  Blockchain::get_output_key_mask_unlocked

  Blockchain::find_blockchain_supplement (overload)

functions which previously had this functionality inline now call these
functions as necessary.

src/cryptonote_core/blockchain.cpp

@@ -1571,6 +1571,98 @@ void Blockchain::add_out_to_get_random_outs(COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_A
   output_data_t data = m_db->get_output_key(amount, i);
   oen.out_key = data.pubkey;
 }
+
+uint64_t Blockchain::get_num_mature_outputs(uint64_t amount) const
+{
+  auto num_outs = m_db->get_num_outputs(amount);
+  // ensure we don't include outputs that aren't yet eligible to be used
+  // outpouts are sorted by height
+  while (num_outs > 0)
+  {
+    const tx_out_index toi = m_db->get_output_tx_and_index(amount, num_outs - 1);
+    const uint64_t height = m_db->get_tx_block_height(toi.first);
+    if (height + CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE <= m_db->height())
+      break;
+    --num_outs;
+  }
+
+  return num_outs;
+}
+
+std::vector<uint64_t> Blockchain::get_random_outputs(uint64_t amount, uint64_t count) const
+{
+  uint64_t num_outs = get_num_mature_outputs(amount);
+
+  std::vector<uint64_t> indices;
+
+  std::unordered_set<uint64_t> seen_indices;
+
+  // if there aren't enough outputs to mix with (or just enough),
+  // use all of them.  Eventually this should become impossible.
+  if (num_outs <= count)
+  {
+    for (uint64_t i = 0; i < num_outs; i++)
+    {
+      // get tx_hash, tx_out_index from DB
+      tx_out_index toi = m_db->get_output_tx_and_index(amount, i);
+
+      // if tx is unlocked, add output to indices
+      if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
+      {
+        indices.push_back(i);
+      }
+    }
+  }
+  else
+  {
+    // while we still need more mixins
+    while (indices.size() < count)
+    {
+      // if we've gone through every possible output, we've gotten all we can
+      if (seen_indices.size() == num_outs)
+      {
+        break;
+      }
+
+      // get a random output index from the DB.  If we've already seen it,
+      // return to the top of the loop and try again, otherwise add it to the
+      // list of output indices we've seen.
+
+      // triangular distribution over [a,b) with a=0, mode c=b=up_index_limit
+      uint64_t r = crypto::rand<uint64_t>() % ((uint64_t)1 << 53);
+      double frac = std::sqrt((double)r / ((uint64_t)1 << 53));
+      uint64_t i = (uint64_t)(frac*num_outs);
+      // just in case rounding up to 1 occurs after sqrt
+      if (i == num_outs)
+        --i;
+
+      if (seen_indices.count(i))
+      {
+        continue;
+      }
+      seen_indices.emplace(i);
+
+      // get tx_hash, tx_out_index from DB
+      tx_out_index toi = m_db->get_output_tx_and_index(amount, i);
+
+      // if the output's transaction is unlocked, add the output's index to
+      // our list.
+      if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
+      {
+        indices.push_back(i);
+      }
+    }
+  }
+
+  return indices;
+}
+
+crypto::public_key Blockchain::get_output_key(uint64_t amount, uint64_t global_index) const
+{
+  output_data_t data = m_db->get_output_key(amount, global_index);
+  return data.pubkey;
+}
+
 //------------------------------------------------------------------
 // This function takes an RPC request for mixins and creates an RPC response
 // with the requested mixins.
@@ -1585,80 +1677,18 @@ bool Blockchain::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUT
   // from BlockchainDB where <n> is req.outs_count (number of mixins).
   for (uint64_t amount : req.amounts)
   {
-    auto num_outs = m_db->get_num_outputs(amount);
-    // ensure we don't include outputs that aren't yet eligible to be used
-    // outpouts are sorted by height
-    while (num_outs > 0)
-    {
-      const tx_out_index toi = m_db->get_output_tx_and_index(amount, num_outs - 1);
-      const uint64_t height = m_db->get_tx_block_height(toi.first);
-      if (height + CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE <= m_db->height())
-        break;
-      --num_outs;
-    }
-
     // create outs_for_amount struct and populate amount field
     COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::outs_for_amount& result_outs = *res.outs.insert(res.outs.end(), COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::outs_for_amount());
     result_outs.amount = amount;
 
-    std::unordered_set<uint64_t> seen_indices;
+    std::vector<uint64_t> indices = get_random_outputs(amount, req.outs_count);
 
-    // if there aren't enough outputs to mix with (or just enough),
+    for (auto i : indices)
-    // use all of them.  Eventually this should become impossible.
-    if (num_outs <= req.outs_count)
     {
-      for (uint64_t i = 0; i < num_outs; i++)
+      COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::out_entry& oe = *result_outs.outs.insert(result_outs.outs.end(), COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::out_entry());
-      {
-        // get tx_hash, tx_out_index from DB
-        tx_out_index toi = m_db->get_output_tx_and_index(amount, i);
 
-        // if tx is unlocked, add output to result_outs
+      oe.global_amount_index = i;
-        if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
+      oe.out_key = get_output_key(amount, i);
-        {
-          add_out_to_get_random_outs(result_outs, amount, i);
-        }
-
-      }
-    }
-    else
-    {
-      // while we still need more mixins
-      while (result_outs.outs.size() < req.outs_count)
-      {
-        // if we've gone through every possible output, we've gotten all we can
-        if (seen_indices.size() == num_outs)
-        {
-          break;
-        }
-
-        // get a random output index from the DB.  If we've already seen it,
-        // return to the top of the loop and try again, otherwise add it to the
-        // list of output indices we've seen.
-
-        // triangular distribution over [a,b) with a=0, mode c=b=up_index_limit
-        uint64_t r = crypto::rand<uint64_t>() % ((uint64_t)1 << 53);
-        double frac = std::sqrt((double)r / ((uint64_t)1 << 53));
-        uint64_t i = (uint64_t)(frac*num_outs);
-        // just in case rounding up to 1 occurs after sqrt
-        if (i == num_outs)
-          --i;
-
-        if (seen_indices.count(i))
-        {
-          continue;
-        }
-        seen_indices.emplace(i);
-
-        // get tx_hash, tx_out_index from DB
-        tx_out_index toi = m_db->get_output_tx_and_index(amount, i);
-
-        // if the output's transaction is unlocked, add the output's index to
-        // our list.
-        if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
-        {
-          add_out_to_get_random_outs(result_outs, amount, i);
-        }
-      }
     }
   }
   return true;
@@ -1816,6 +1846,15 @@ bool Blockchain::get_outs(const COMMAND_RPC_GET_OUTPUTS_BIN::request& req, COMMA
   return true;
 }
 //------------------------------------------------------------------
+void Blockchain::get_output_key_mask_unlocked(const uint64_t& amount, const uint64_t& index, crypto::public_key& key, rct::key& mask, bool& unlocked) const
+{
+  const auto o_data = m_db->get_output_key(amount, index);
+  key = o_data.pubkey;
+  mask = o_data.commitment;
+  tx_out_index toi = m_db->get_output_tx_and_index(amount, index);
+  unlocked = is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first));
+}
+//------------------------------------------------------------------
 // This function takes a list of block hashes from another node
 // on the network to find where the split point is between us and them.
 // This is used to see what to send another node that needs to sync.
@@ -2025,28 +2064,39 @@ void Blockchain::print_blockchain_outs(const std::string& file) const
 // Find the split point between us and foreign blockchain and return
 // (by reference) the most recent common block hash along with up to
 // BLOCKS_IDS_SYNCHRONIZING_DEFAULT_COUNT additional (more recent) hashes.
-bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp) const
+bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, std::list<crypto::hash>& hashes, uint64_t& start_height, uint64_t& current_height) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
 
   // if we can't find the split point, return false
-  if(!find_blockchain_supplement(qblock_ids, resp.start_height))
+  if(!find_blockchain_supplement(qblock_ids, start_height))
   {
     return false;
   }
 
   m_db->block_txn_start(true);
-  resp.total_height = get_current_blockchain_height();
+  current_height = get_current_blockchain_height();
   size_t count = 0;
-  for(size_t i = resp.start_height; i < resp.total_height && count < BLOCKS_IDS_SYNCHRONIZING_DEFAULT_COUNT; i++, count++)
+  for(size_t i = start_height; i < current_height && count < BLOCKS_IDS_SYNCHRONIZING_DEFAULT_COUNT; i++, count++)
   {
-    resp.m_block_ids.push_back(m_db->get_block_hash_from_height(i));
+    hashes.push_back(m_db->get_block_hash_from_height(i));
   }
-  resp.cumulative_difficulty = m_db->get_block_cumulative_difficulty(m_db->height() - 1);
+
   m_db->block_txn_stop();
   return true;
 }
+
+bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp) const
+{
+  LOG_PRINT_L3("Blockchain::" << __func__);
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  bool result = find_blockchain_supplement(qblock_ids, resp.m_block_ids, resp.start_height, resp.total_height);
+  resp.cumulative_difficulty = m_db->get_block_cumulative_difficulty(m_db->height() - 1);
+
+  return result;
+}
 //------------------------------------------------------------------
 //FIXME: change argument to std::vector, low priority
 // find split point between ours and foreign blockchain (or start at

src/cryptonote_core/blockchain.h

@@ -366,6 +366,22 @@ namespace cryptonote
      */
     bool get_short_chain_history(std::list<crypto::hash>& ids) const;
 
+    /**
+     * @brief get recent block hashes for a foreign chain
+     *
+     * Find the split point between us and foreign blockchain and return
+     * (by reference) the most recent common block hash along with up to
+     * BLOCKS_IDS_SYNCHRONIZING_DEFAULT_COUNT additional (more recent) hashes.
+     *
+     * @param qblock_ids the foreign chain's "short history" (see get_short_chain_history)
+     * @param hashes the hashes to be returned, return-by-reference
+     * @param start_height the start height, return-by-reference
+     * @param current_height the current blockchain height, return-by-reference
+     *
+     * @return true if a block found in common, else false
+     */
+    bool find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, std::list<crypto::hash>& hashes, uint64_t& start_height, uint64_t& current_height) const;
+
     /**
      * @brief get recent block hashes for a foreign chain
      *
@@ -426,6 +442,35 @@ namespace cryptonote
      */
     bool handle_get_objects(NOTIFY_REQUEST_GET_OBJECTS::request& arg, NOTIFY_RESPONSE_GET_OBJECTS::request& rsp);
 
+    /**
+     * @brief get number of outputs of an amount past the minimum spendable age
+     *
+     * @param amount the output amount
+     *
+     * @return the number of mature outputs
+     */
+    uint64_t get_num_mature_outputs(uint64_t amount) const;
+
+    /**
+     * @brief get random outputs (indices) for an amount
+     *
+     * @param amount the amount
+     * @param count the number of random outputs to choose
+     *
+     * @return the outputs' amount-global indices
+     */
+    std::vector<uint64_t> get_random_outputs(uint64_t amount, uint64_t count) const;
+
+    /**
+     * @brief get the public key for an output
+     *
+     * @param amount the output amount
+     * @param global_index the output amount-global index
+     *
+     * @return the public key
+     */
+    crypto::public_key get_output_key(uint64_t amount, uint64_t global_index) const;
+
     /**
      * @brief gets random outputs to mix with
      *
@@ -457,6 +502,17 @@ namespace cryptonote
      */
     bool get_outs(const COMMAND_RPC_GET_OUTPUTS_BIN::request& req, COMMAND_RPC_GET_OUTPUTS_BIN::response& res) const;
 
+    /**
+     * @brief gets an output's key and unlocked state
+     *
+     * @param amount in - the output amount
+     * @param index in - the output global amount index
+     * @param mask out - the output's RingCT mask
+     * @param key out - the output's key
+     * @param unlocked out - the output's unlocked state
+     */
+    void get_output_key_mask_unlocked(const uint64_t& amount, const uint64_t& index, crypto::public_key& key, rct::key& mask, bool& unlocked) const;
+
     /**
      * @brief gets random ringct outputs to mix with
      *