secp256r1_fixed_base.hpp

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#pragma once
 
#include "./types.hpp"
#include "barretenberg/common/assert.hpp"
#include "barretenberg/ecc/curves/secp256r1/secp256r1.hpp"
#include <array>
#include <mutex>
#include <utility>
 
namespace bb::plookup::secp256r1_fixed_base {
 
// Inherits all layout numerics (NUM_WINDOWS*, WINDOW_BITS_*, TABLE_SIZE_*, NUM_AXES, LO_TAIL_WINDOW,
// HI_TAIL_WINDOW, and the `window_bits` / `table_size` helpers) from Secp256r1FixedBaseParams. They live
// in `secp256r1_fixed_base_params.hpp` so the enum in `types.hpp` can reach them without a cycle.
class table : public Secp256r1FixedBaseParams {
  public:
    using G1 = bb::secp256r1::g1;
    using Element = G1::element;
    using AffineElement = G1::affine_element;
 
    enum AxisIndex : size_t {
        AXIS_XLO = 0,
        AXIS_XHI = 1,
        AXIS_YLO = 2,
        AXIS_YHI = 3,
    };
 
    static constexpr BasicTableId axis_start_id(AxisIndex axis)
    {
        switch (axis) {
        case AXIS_XLO:
            return SECP256R1_FIXED_BASE_XLO_0;
        case AXIS_XHI:
            return SECP256R1_FIXED_BASE_XHI_0;
        case AXIS_YLO:
            return SECP256R1_FIXED_BASE_YLO_0;
        case AXIS_YHI:
            return SECP256R1_FIXED_BASE_YHI_0;
        }
        return SECP256R1_FIXED_BASE_XLO_0; // unreachable
    }
 
    static void init_tables();
 
    static AffineElement total_offset();
 
    template <AxisIndex axis, size_t window_idx> static std::array<bb::fr, 2> get_values(std::array<uint64_t, 2> key);
 
    template <AxisIndex axis, size_t window_idx>
    static BasicTable generate_basic_table(BasicTableId id, size_t table_index);
 
    template <AxisIndex axis>
    static BasicTable generate_basic_table_runtime(BasicTableId id, size_t window_idx, size_t table_index);
 
    static MultiTable get_multitable(MultiTableId id, AxisIndex axis, bool is_lo);
 
    static const AffineElement& get_entry(size_t window_idx, size_t k)
    {
        init_tables();
        BB_ASSERT_LT(window_idx, NUM_WINDOWS);
        BB_ASSERT_LT(k, table_size(window_idx));
        return native_table[window_idx][k];
    }
 
    static std::array<bb::fr, 2> extract_axis(const AffineElement& point, AxisIndex axis);
 
  private:
    // Precomputed entries: native_table[w][k] = k · 2^(bit_offset(w)) · G + 2^w · H. The array is sized
    // to the big-window table size (128); tail windows only populate the first table_size(w) entries
    // (8 for the lo tail, 2 for the hi tail), and the trailing slots are unused.
    static std::array<std::array<AffineElement, TABLE_SIZE_BIG>, NUM_WINDOWS> native_table;
    static AffineElement cached_total_offset;
    static std::once_flag init_flag;
};
 
} // namespace bb::plookup::secp256r1_fixed_base