wallet RPC converted to use new transaction semantics

wallet RPC now uses wallet2::create_transactions and wallet2::commit_tx instead
of wallet2::transfer.  This made it possible to add the RPC call /transfer_split, which
will split transactions automatically if they are too large.  The old call to
/transfer will return an error stating to use /transfer_split if multiple
transactions are needed to fulfill the request.

src/wallet/wallet2.cpp

@@ -43,6 +43,9 @@ void do_prepare_file_names(const std::string& file_path, std::string& keys_file,
 
 namespace tools
 {
+// for now, limit to 30 attempts.  TODO: discuss a good number to limit to.
+const size_t MAX_SPLIT_ATTEMPTS = 30;
+
 //----------------------------------------------------------------------------------------------------
 void wallet2::init(const std::string& daemon_address, uint64_t upper_transaction_size_limit)
 {
@@ -697,6 +700,56 @@ void wallet2::transfer(const std::vector<cryptonote::tx_destination_entry>& dsts
   pending_tx ptx;
   transfer(dsts, fake_outputs_count, unlock_time, fee, extra, tx, ptx);
 }
+
+namespace {
+// split_amounts(vector<cryptonote::tx_destination_entry> dsts, size_t num_splits)
+//
+// split amount for each dst in dsts into num_splits parts
+// and make num_splits new vector<crypt...> instances to hold these new amounts
+std::vector<std::vector<cryptonote::tx_destination_entry>> split_amounts(
+    std::vector<cryptonote::tx_destination_entry> dsts, size_t num_splits)
+{
+  std::vector<std::vector<cryptonote::tx_destination_entry>> retVal;
+
+  if (num_splits <= 1)
+  {
+    retVal.push_back(dsts);
+    return retVal;
+  }
+
+  // for each split required
+  for (size_t i=0; i < num_splits; i++)
+  {
+    std::vector<cryptonote::tx_destination_entry> new_dsts;
+
+    // for each destination
+    for (size_t j=0; j < dsts.size(); j++)
+    {
+      cryptonote::tx_destination_entry de;
+      uint64_t amount;
+
+      amount = dsts[j].amount;
+      amount = amount / num_splits;
+
+      // if last split, add remainder
+      if (i + 1 == num_splits)
+      {
+        amount += dsts[j].amount % num_splits;
+      }
+      
+      de.addr = dsts[j].addr;
+      de.amount = amount;
+
+      new_dsts.push_back(de);
+    }
+
+    retVal.push_back(new_dsts);
+  }
+
+  return retVal;
+}
+} // anonymous namespace
+
 //----------------------------------------------------------------------------------------------------
 // take a pending tx and actually send it to the daemon
 void wallet2::commit_tx(pending_tx& ptx)
@@ -718,10 +771,105 @@ void wallet2::commit_tx(pending_tx& ptx)
     it->m_spent = true;
 
   LOG_PRINT_L0("Transaction successfully sent. <" << get_transaction_hash(ptx.tx) << ">" << ENDL
-                << "Commission: " << print_money(ptx.fee+ptx.dust) << " (dust: " << print_money(ptx.dust) << ")" << ENDL
-                << "Balance: " << print_money(balance()) << ENDL
-                << "Unlocked: " << print_money(unlocked_balance()) << ENDL
-                << "Please, wait for confirmation for your balance to be unlocked.");
+            << "Commission: " << print_money(ptx.fee+ptx.dust) << " (dust: " << print_money(ptx.dust) << ")" << ENDL
+            << "Balance: " << print_money(balance()) << ENDL
+            << "Unlocked: " << print_money(unlocked_balance()) << ENDL
+            << "Please, wait for confirmation for your balance to be unlocked.");
 }
 
+void wallet2::commit_tx(std::vector<pending_tx>& ptx_vector)
+{
+  for (auto & ptx : ptx_vector)
+  {
+    commit_tx(ptx);
+  }
+}
+
+//----------------------------------------------------------------------------------------------------
+// separated the call(s) to wallet2::transfer into their own function
+//
+// this function will make multiple calls to wallet2::transfer if multiple
+// transactions will be required
+std::vector<wallet2::pending_tx> wallet2::create_transactions(std::vector<cryptonote::tx_destination_entry> dsts, const size_t fake_outs_count, const uint64_t unlock_time, const uint64_t fee, const std::vector<uint8_t> extra)
+{
+
+  // failsafe split attempt counter
+  size_t attempt_count = 0;
+
+  for(attempt_count = 1; ;attempt_count++)
+  {
+    auto split_values = split_amounts(dsts, attempt_count);
+
+    // Throw if split_amounts comes back with a vector of size different than it should
+    if (split_values.size() != attempt_count)
+    {
+      throw std::runtime_error("Splitting transactions returned a number of potential tx not equal to what was requested");
+    }
+
+    std::vector<pending_tx> ptx_vector;
+    try
+    {
+      // for each new destination vector (i.e. for each new tx)
+      for (auto & dst_vector : split_values)
+      {
+        cryptonote::transaction tx;
+        pending_tx ptx;
+        transfer(dst_vector, fake_outs_count, unlock_time, fee, extra, tx, ptx);
+        ptx_vector.push_back(ptx);
+
+        // mark transfers to be used as "spent"
+        BOOST_FOREACH(transfer_container::iterator it, ptx.selected_transfers)
+          it->m_spent = true;
+      }
+
+      // if we made it this far, we've selected our transactions.  committing them will mark them spent,
+      // so this is a failsafe in case they don't go through
+      // unmark pending tx transfers as spent
+      for (auto & ptx : ptx_vector)
+      {
+        // mark transfers to be used as not spent
+        BOOST_FOREACH(transfer_container::iterator it2, ptx.selected_transfers)
+          it2->m_spent = false;
+
+      }
+
+      // if we made it this far, we're OK to actually send the transactions
+      return ptx_vector;
+
+    }
+    // only catch this here, other exceptions need to pass through to the calling function
+    catch (const tools::error::tx_too_big& e)
+    {
+
+      // unmark pending tx transfers as spent
+      for (auto & ptx : ptx_vector)
+      {
+        // mark transfers to be used as not spent
+        BOOST_FOREACH(transfer_container::iterator it2, ptx.selected_transfers)
+          it2->m_spent = false;
+
+      }
+
+      if (attempt_count >= MAX_SPLIT_ATTEMPTS)
+      {
+        throw;
+      }
+    }
+    catch (...)
+    {
+      // in case of some other exception, make sure any tx in queue are marked unspent again
+
+      // unmark pending tx transfers as spent
+      for (auto & ptx : ptx_vector)
+      {
+        // mark transfers to be used as not spent
+        BOOST_FOREACH(transfer_container::iterator it2, ptx.selected_transfers)
+          it2->m_spent = false;
+
+      }
+
+      throw;
+    }
+  }
+}
 }