Added comments to wallet functions

src/wallet/wallet2.cpp

@@ -630,10 +630,17 @@ namespace
   }
 }
 //----------------------------------------------------------------------------------------------------
+// Select random input sources for transaction.
+// returns:
+//    direct return: amount of money found
+//    modified reference: selected_transfers, a list of iterators/indices of input sources
 uint64_t wallet2::select_transfers(uint64_t needed_money, bool add_dust, uint64_t dust, std::list<transfer_container::iterator>& selected_transfers)
 {
   std::vector<size_t> unused_transfers_indices;
   std::vector<size_t> unused_dust_indices;
+
+  // aggregate sources available for transfers
+  // if dust needed, take dust from only one source (so require source has at least dust amount)
   for (size_t i = 0; i < m_transfers.size(); ++i)
   {
     const transfer_details& td = m_transfers[i];

src/wallet/wallet2.h

@@ -304,9 +304,13 @@ namespace tools
     uint64_t unlock_time, uint64_t fee, const std::vector<uint8_t>& extra, T destination_split_strategy, const tx_dust_policy& dust_policy, cryptonote::transaction &tx)
   {
     using namespace cryptonote;
+    // throw if attempting a transaction with no destinations
     THROW_WALLET_EXCEPTION_IF(dsts.empty(), error::zero_destination);
 
     uint64_t needed_money = fee;
+
+    // calculate total amount being sent to all destinations
+    // throw if total amount overflows uint64_t
     BOOST_FOREACH(auto& dt, dsts)
     {
       THROW_WALLET_EXCEPTION_IF(0 == dt.amount, error::zero_destination);
@@ -314,6 +318,8 @@ namespace tools
       THROW_WALLET_EXCEPTION_IF(needed_money < dt.amount, error::tx_sum_overflow, dsts, fee);
     }
 
+    // randomly select inputs for transaction
+    // throw if requested send amount is greater than amount available to send
     std::list<transfer_container::iterator> selected_transfers;
     uint64_t found_money = select_transfers(needed_money, 0 == fake_outputs_count, dust_policy.dust_threshold, selected_transfers);
     THROW_WALLET_EXCEPTION_IF(found_money < needed_money, error::not_enough_money, found_money, needed_money - fee, fee);