forked from such-gitea/wownero-lws
89 lines
3.7 KiB
C++
89 lines
3.7 KiB
C++
// Copyright (c) 2019-2020, The Monero Project
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include <cstdint>
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#include <random>
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#include <vector>
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namespace lws
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{
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//! Select outputs using a gamma distribution with Sarang's output-lineup method
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class gamma_picker
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{
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std::vector<uint64_t> rct_offsets;
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std::gamma_distribution<double> gamma;
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double outputs_per_second;
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gamma_picker(const gamma_picker&) = default; // force explicit usage of `clone()` to copy.
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public:
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//! \post `!is_valid()` since the chain of offsets is empty.
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gamma_picker()
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: gamma_picker(std::vector<std::uint64_t>{})
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{}
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//! Use default (recommended) gamma parameters with `rct_offsets`.
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explicit gamma_picker(std::vector<std::uint64_t> rct_offsets);
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explicit gamma_picker(std::vector<std::uint64_t> rct_offsets, double shape, double scale);
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//! \post Source of move `!is_valid()`.
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gamma_picker(gamma_picker&&) = default;
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//! \post Source of move `!is_valid()`.
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gamma_picker& operator=(gamma_picker&&) = default;
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//! \return A copy of `this`.
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gamma_picker clone() const { return gamma_picker{*this}; }
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//! \return `is_valid()`.
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explicit operator bool() const noexcept { return is_valid(); }
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//! \return True if `operator()()` can pick an output using `offsets()`.
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bool is_valid() const noexcept;
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//! \return An upper-bound on the number of unlocked/spendable outputs based on block age.
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std::uint64_t spendable_upper_bound() const noexcept;
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/*!
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Select a random output index for use in a ring. Outputs in the unspendable
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range (too new) and older than the chain (too old) are filtered out by
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retrying the gamma distribution.
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\throw std::logic_error if `!is_valid()` - considered unrecoverable.
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\throw std::runtiime_error if no output within spendable range was selected
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after 100 attempts.
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\return Selected output using gamma distribution.
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*/
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std::uint64_t operator()();
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//! \return Current ringct distribution used for `operator()()` output selection.
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const std::vector<std::uint64_t>& offsets() const noexcept { return rct_offsets; }
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//! \return Ownership of `offsets()` by move. \post `!is_valid()`
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std::vector<std::uint64_t> take_offsets();
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};
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} // lws
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