add top height to get_output_distribution, and cache it for rct

This should cache the vast majority of calls for long running wallets

src/rpc/core_rpc_server.cpp

@@ -2083,6 +2083,22 @@ namespace cryptonote
     {
       for (uint64_t amount: req.amounts)
       {
+        static struct D
+        {
+          boost::mutex mutex;
+          std::vector<uint64_t> cached_distribution;
+          uint64_t cached_from, cached_to, cached_start_height, cached_base;
+          bool cached;
+          D(): cached_from(0), cached_to(0), cached_start_height(0), cached_base(0), cached(false) {}
+        } d;
+        boost::unique_lock<boost::mutex> lock(d.mutex);
+
+        if (d.cached && amount == 0 && d.cached_from == req.from_height && d.cached_to == req.to_height)
+        {
+          res.distributions.push_back({amount, d.cached_start_height, d.cached_distribution, d.cached_base});
+          continue;
+        }
+
         std::vector<uint64_t> distribution;
         uint64_t start_height, base;
         if (!m_core.get_output_distribution(amount, req.from_height, start_height, distribution, base))
@@ -2091,12 +2107,29 @@ namespace cryptonote
           error_resp.message = "Failed to get rct distribution";
           return false;
         }
+        if (req.to_height > 0 && req.to_height >= req.from_height)
+        {
+          uint64_t offset = std::max(req.from_height, start_height);
+          if (offset <= req.to_height && req.to_height - offset + 1 < distribution.size())
+            distribution.resize(req.to_height - offset + 1);
+        }
         if (req.cumulative)
         {
           distribution[0] += base;
           for (size_t n = 1; n < distribution.size(); ++n)
             distribution[n] += distribution[n-1];
         }
+
+        if (amount == 0)
+        {
+          d.cached_from = req.from_height;
+          d.cached_to = req.to_height;
+          d.cached_distribution = distribution;
+          d.cached_start_height = start_height;
+          d.cached_base = base;
+          d.cached = true;
+        }
+
         res.distributions.push_back({amount, start_height, std::move(distribution), base});
       }
     }

src/rpc/core_rpc_server_commands_defs.h

@@ -2210,11 +2210,13 @@ namespace cryptonote
     {
       std::vector<uint64_t> amounts;
       uint64_t from_height;
+      uint64_t to_height;
       bool cumulative;
 
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE(amounts)
         KV_SERIALIZE_OPT(from_height, (uint64_t)0)
+        KV_SERIALIZE_OPT(to_height, (uint64_t)0)
         KV_SERIALIZE_OPT(cumulative, false)
       END_KV_SERIALIZE_MAP()
     };

src/wallet/wallet2.cpp

@@ -5874,6 +5874,7 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
       auto end = std::unique(req_t.amounts.begin(), req_t.amounts.end());
       req_t.amounts.resize(std::distance(req_t.amounts.begin(), end));
       req_t.from_height = std::max<uint64_t>(segregation_fork_height, RECENT_OUTPUT_BLOCKS) - RECENT_OUTPUT_BLOCKS;
+      req_t.to_height = segregation_fork_height + 1;
       req_t.cumulative = true;
       m_daemon_rpc_mutex.lock();
       bool r = net_utils::invoke_http_json_rpc("/json_rpc", "get_output_distribution", req_t, resp_t, m_http_client, rpc_timeout);
@@ -5893,6 +5894,7 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
           {
             THROW_WALLET_EXCEPTION_IF(d.start_height > segregation_fork_height, error::get_output_distribution, "Distribution start_height too high");
             THROW_WALLET_EXCEPTION_IF(segregation_fork_height - d.start_height >= d.distribution.size(), error::get_output_distribution, "Distribution size too small");
+            THROW_WALLET_EXCEPTION_IF(segregation_fork_height - RECENT_OUTPUT_BLOCKS - d.start_height >= d.distribution.size(), error::get_output_distribution, "Distribution size too small");
             THROW_WALLET_EXCEPTION_IF(segregation_fork_height <= RECENT_OUTPUT_BLOCKS, error::wallet_internal_error, "Fork height too low");
             THROW_WALLET_EXCEPTION_IF(segregation_fork_height - RECENT_OUTPUT_BLOCKS < d.start_height, error::get_output_distribution, "Bad start height");
             uint64_t till_fork = d.distribution[segregation_fork_height - d.start_height];