From 2fdeefb545f034b290b366b20c8335389d3b270b Mon Sep 17 00:00:00 2001
From: sowle <crypto.sowle@gmail.com>
Date: Sat, 5 Jun 2021 03:36:58 +0300
Subject: [PATCH] crypto: scalar_vec_t, scalar_mat_t

---
 src/crypto/crypto-sugar.h | 147 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)

diff --git a/src/crypto/crypto-sugar.h b/src/crypto/crypto-sugar.h
index 30abccb9..1c1b1b9a 100644
--- a/src/crypto/crypto-sugar.h
+++ b/src/crypto/crypto-sugar.h
@@ -717,6 +717,146 @@ namespace crypto
   }; // struct point_g_t
 
 
+  //
+  // vector of scalars
+  //
+  struct scalar_vec_t : public std::vector<scalar_t>
+  {
+    typedef std::vector<scalar_t> super_t;
+
+    scalar_vec_t() {}
+    scalar_vec_t(size_t n) : super_t(n) {}
+    scalar_vec_t(std::initializer_list<scalar_t> init_list) : super_t(init_list) {}
+
+    bool is_reduced() const
+    {
+      for (auto& el : *this)
+        if (!el.is_reduced())
+          return false;
+      return true;
+    }
+
+    // add a scalar rhs to each element
+    scalar_vec_t operator+(const scalar_t& rhs) const
+    {
+      scalar_vec_t result(size());
+      for (size_t i = 0, n = size(); i < n; ++i)
+        result[i] = at(i) + rhs;
+      return result;
+    }
+
+    // subtract a scalar rhs to each element
+    scalar_vec_t operator-(const scalar_t& rhs) const
+    {
+      scalar_vec_t result(size());
+      for (size_t i = 0, n = size(); i < n; ++i)
+        result[i] = at(i) - rhs;
+      return result;
+    }
+
+    // multiply each element of the vector by a scalar
+    scalar_vec_t operator*(const scalar_t& rhs) const
+    {
+      scalar_vec_t result(size());
+      for (size_t i = 0, n = size(); i < n; ++i)
+        result[i] = at(i) * rhs;
+      return result;
+    }
+
+    // component-wise multiplication (a.k.a the Hadamard product) (only if their sizes match)
+    scalar_vec_t operator*(const scalar_vec_t& rhs) const
+    {
+      scalar_vec_t result;
+      const size_t n = size();
+      if (n != rhs.size())
+        return result;
+
+      result.resize(size());
+      for (size_t i = 0; i < n; ++i)
+        result[i] = at(i) * rhs[i];
+      return result;
+    }
+
+    // add each element of two vectors, but only if their sizes match
+    scalar_vec_t operator+(const scalar_vec_t& rhs) const
+    {
+      scalar_vec_t result;
+      const size_t n = size();
+      if (n != rhs.size())
+        return result;
+
+      result.resize(size());
+      for (size_t i = 0; i < n; ++i)
+        result[i] = at(i) + rhs[i];
+      return result;
+    }
+
+    // zeroes all elements
+    void zero()
+    {
+      size_t size_bytes = sizeof(scalar_t) * size();
+      memset(data(), 0, size_bytes);
+    }
+
+    // invert all elements in-place efficiently: 4*N muptiplications + 1 inversion
+    void invert()
+    {
+      // muls                    muls_rev
+      // 0:                      1 2 3 .. n-1  
+      // 1:   0                  2 3 .. n-1
+      // 2:   0 1                3 .. n-1
+      //
+      // n-1: 0 1 2 3 .. n-2     
+
+      const size_t size = this->size();
+
+      if (size < 2)
+      {
+        if (size == 1)
+          at(0) = at(0).reciprocal();
+        return;
+      }
+
+      scalar_vec_t muls(size), muls_rev(size);
+      muls[0] = 1;
+      for (size_t i = 0; i < size - 1; ++i)
+        muls[i + 1] = at(i) * muls[i];
+
+      muls_rev[size - 1] = 1;
+      for (size_t i = size - 1; i != 0; --i)
+        muls_rev[i - 1] = at(i) * muls_rev[i];
+
+      scalar_t inv = (muls[size - 1] * at(size - 1)).reciprocal();
+
+      for (size_t i = 0; i < size; ++i)
+        at(i) = muls[i] * inv * muls_rev[i];
+    }
+
+    scalar_t calc_hs() const;
+
+  }; // scalar_vec_t
+
+
+  // treats vector of scalars as an M x N matrix just for convenience
+  template<size_t N>
+  struct scalar_mat_t : public scalar_vec_t
+  {
+    typedef scalar_vec_t super_t;
+    static_assert(N > 0, "invalid N value");
+
+    scalar_mat_t() {}
+    scalar_mat_t(size_t n) : super_t(n) {}
+    scalar_mat_t(std::initializer_list<scalar_t> init_list) : super_t(init_list) {}
+
+    // matrix accessor M rows x N cols
+    scalar_t& operator()(size_t row, size_t col)
+    {
+      return at(row * N + col);
+    }
+  }; // scalar_mat_t
+
+
+
   //
   // Global constants
   //
@@ -908,4 +1048,11 @@ namespace crypto
   }; // hash_helper_t struct
 
 
+  inline scalar_t scalar_vec_t::calc_hs() const
+  {
+    // hs won't touch memory if size is 0, so it's safe
+    return hash_helper_t::hs(data(), sizeof(scalar_t) * size());
+  }
+
+
 } // namespace crypto