Initial working base separated from top-level monero project

src/util/random_outputs.h

@@ -0,0 +1,92 @@
+// Copyright (c) 2018-2019, The Monero Project
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+
+#include <cstdint>
+#include <functional>
+#include <vector>
+
+#include "common/expect.h"            // monero/src
+#include "rpc/message_data_structs.h" // monero/src
+#include "span.h"                     // monero/src
+#include "util/fwd.h"
+
+namespace lws
+{
+    using histogram = cryptonote::rpc::output_amount_count;
+    using output_ref = cryptonote::rpc::output_amount_and_index;
+    using output_keys = cryptonote::rpc::output_key_mask_unlocked;
+
+    struct random_output
+    {
+        output_keys keys;
+        std::uint64_t index;
+    };
+
+    struct random_ring
+    {
+        std::vector<random_output> ring;
+        std::uint64_t amount;
+    };
+
+    using key_fetcher = expect<std::vector<output_keys>>(std::vector<output_ref>);
+
+    /*!
+        Selects random outputs for use in a ring signature. `amounts` of `0`
+        use a gamma distribution algorithm and all other amounts use a
+        triangular distribution.
+
+        \param mixin The number of dummy outputs per ring.
+        \param amounts The amounts that need dummy outputs to be selected.
+        \param pick_rct Ring-ct distribution from the daemon
+        \param histograms A histogram from the daemon foreach non-zero value
+            in `amounts`.
+        \param fetch A function that can retrieve the keys for the randomly
+            selected outputs.
+
+        \note `histograms` is modified - the list is sorted by amount.
+
+        \note This currenty leaks the real outputs to `fetch`, because the
+            real output is not provided alongside the dummy outputs. This is a
+            limitation of the current openmonero/mymonero API. When this is
+            resolved, this function can possibly be moved outside of the `lws`
+            namespace for use by simple wallet.
+
+        \return Randomly selected outputs in rings of size `mixin`, one for
+            each element in `amounts`. Amounts with less than `mixin` available
+            are not returned. All outputs are unlocked.
+    */
+    expect<std::vector<random_ring>> pick_random_outputs(
+        std::uint32_t mixin,
+        epee::span<const std::uint64_t> amounts,
+        gamma_picker& pick_rct,
+        epee::span<histogram> histograms,
+        std::function<key_fetcher> fetch
+    );
+}
+