bar_gadget.tcc

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/** @file
 *****************************************************************************
 
 Implementation of interfaces for an auxiliary gadget for the FOORAM CPU.
 
 See bar_gadget.hpp .
 
 *****************************************************************************
 * @author     This file is part of libsnark, developed by SCIPR Lab
 *             and contributors (see AUTHORS).
 * @copyright  MIT license (see LICENSE file)
 *****************************************************************************/
 
#ifndef BAR_GADGET_TCC_
#define BAR_GADGET_TCC_
 
namespace libsnark
{
 
template<typename FieldT>
bar_gadget<FieldT>::bar_gadget(
    protoboard<FieldT> &pb,
    const pb_linear_combination_array<FieldT> &X,
    const FieldT &a,
    const pb_linear_combination_array<FieldT> &Y,
    const FieldT &b,
    const pb_linear_combination<FieldT> &Z_packed,
    const std::string &annotation_prefix)
    : gadget<FieldT>(pb, annotation_prefix)
    , X(X)
    , a(a)
    , Y(Y)
    , b(b)
    , Z_packed(Z_packed)
{
    assert(X.size() == Y.size());
    width = X.size();
 
    result.allocate(pb, FMT(annotation_prefix, " result"));
    Z_bits.allocate(pb, width, FMT(annotation_prefix, " Z_bits"));
    overflow.allocate(pb, 2 * width, FMT(annotation_prefix, " overflow"));
 
    unpacked_result.insert(unpacked_result.end(), Z_bits.begin(), Z_bits.end());
    unpacked_result.insert(
        unpacked_result.end(), overflow.begin(), overflow.end());
 
    unpack_result.reset(new packing_gadget<FieldT>(
        pb, unpacked_result, result, FMT(annotation_prefix, " unpack_result")));
    pack_Z.reset(new packing_gadget<FieldT>(
        pb, Z_bits, Z_packed, FMT(annotation_prefix, " pack_Z")));
}
 
template<typename FieldT> void bar_gadget<FieldT>::generate_r1cs_constraints()
{
    unpack_result->generate_r1cs_constraints(true);
    pack_Z->generate_r1cs_constraints(false);
 
    this->pb.add_r1cs_constraint(
        r1cs_constraint<FieldT>(
            1,
            a * pb_packing_sum<FieldT>(X) + b * pb_packing_sum<FieldT>(Y),
            result),
        FMT(this->annotation_prefix, " compute_result"));
}
 
template<typename FieldT> void bar_gadget<FieldT>::generate_r1cs_witness()
{
    this->pb.val(result) = X.get_field_element_from_bits(this->pb) * a +
                           Y.get_field_element_from_bits(this->pb) * b;
    unpack_result->generate_r1cs_witness_from_packed();
 
    pack_Z->generate_r1cs_witness_from_bits();
}
 
} // namespace libsnark
 
#endif // BAR_GADGET_TCC_