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tdfec/td/fec/online/Rfc.h

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+/*
+    This file is part of TON Blockchain Library.
+
+    TON Blockchain Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    TON Blockchain Library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2017-2019 Telegram Systems LLP
+*/
+#pragma once
+#include <random>
+#include <algorithm>
+
+#include "td/utils/Status.h"
+#include "td/utils/Span.h"
+#include "td/utils/Random.h"
+
+namespace td {
+namespace online_code {
+template <class Random>
+class UniformDistributionSimple {
+ public:
+  UniformDistributionSimple(uint32 L, uint32 R) : L_(L), R_(R) {
+  }
+  void set_random(Random *random) {
+    random_ = random;
+  }
+  uint32 operator()() {
+    return static_cast<uint32>((*random_)() % (R_ - L_ + 1)) + L_;
+  }
+
+ private:
+  Random *random_{nullptr};
+  uint32 L_;
+  uint32 R_;
+};
+
+using Random = Random::Xorshift128plus;
+using UniformDistribution = UniformDistributionSimple<Random>;
+
+class Rfc {
+ public:
+  class Parameters {
+   public:
+    Parameters(size_t source_blocks, double epsilon, uint32 quality);
+    size_t source_blocks_count() const;
+    size_t outer_encoding_blocks_count() const;
+    size_t estimated_packets() const;
+
+    template <class F>
+    void outer_encoding_for_each(F &&f) const {
+      Random r(static_cast<uint32>(1));
+      outer_distribution_.set_random(&r);
+
+      for (uint32 j = 0; j < outer_encoding_blocks_count(); j++) {
+        f(j, uint32(source_blocks_count() + j));
+      }
+      for (uint32 i = 0; i < source_blocks_count(); i++) {
+        for (uint32 j = 0; j < quality_; j++) {
+          f(outer_distribution_(), i);
+        }
+      }
+    }
+
+    Span<uint32> get_inner_encoding_row(size_t row_id) const;
+
+   private:
+    struct DegreeDistribution {
+     public:
+      DegreeDistribution(double epsilon);
+
+      uint32 get_degree(double x) const;
+
+      size_t get_max_degree() const;
+
+     private:
+      std::vector<double> p_;
+    };
+
+    uint32 source_blocks_;
+    double epsilon_;
+    uint32 quality_;
+    DegreeDistribution degree_distribution_;
+    size_t outer_encoding_blocks_count_;
+    mutable std::vector<uint32> row_buffer_ = std::vector<uint32>(degree_distribution_.get_max_degree(), 0);
+
+    mutable UniformDistribution outer_distribution_{0, static_cast<uint32>(outer_encoding_blocks_count()) - 1};
+    mutable UniformDistribution inner_distribution_{
+        0, static_cast<uint32>(outer_encoding_blocks_count() + source_blocks_count()) - 1};
+  };
+  static Result<Parameters> get_parameters(size_t K);
+};
+}  // namespace online_code
+}  // namespace td