cbor_testing.h

// Copyright 2025 Google LLC.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#ifndef PRIVACY_PROOFS_ZK_LIB_CIRCUITS_CBOR_PARSER_CBOR_TESTING_H_
#define PRIVACY_PROOFS_ZK_LIB_CIRCUITS_CBOR_PARSER_CBOR_TESTING_H_
 
#include <stddef.h>
 
#include "circuits/cbor_parser/cbor.h"
#include "circuits/cbor_parser/cbor_constants.h"
#include "circuits/cbor_parser/cbor_witness.h"
#include "circuits/logic/counter.h"
#include "circuits/logic/evaluation_backend.h"
#include "circuits/logic/logic.h"
 
// The purpose of this class is to convert the witnesses from Elt to
// EltW.
//
// Why?
//
// We want EltW in the evaluation backend to be a distinct type from
// Elt.  They are really the same thing, but we want to be able to
// instantiate circuits in the compiler backend as well, and thus
// circuits ought not to rely on the fact that EvaluationBackend::EltW
// is really an Elt in disguise.
// Consequently, tests in the evaluation backend must accept EltW.
//
// The witness generator must produce Elt, otherwise this forces the
// inclusion of Logic in the app.  We don't like that because Logic
// is just a set of helpers to generate circuits, and the final app
// is not supposed to generate circuits (since circuits are part of the
// prover<->verifier API and so they must be set in stone in advance.)
//
// So this class is the price to be paid to maintain this typing
// hygiene.  Time will tell whether it was worth it.
 
namespace proofs {
 
template <class Field>
class CborTesting {
  using EvalBackend = EvaluationBackend<Field>;
  using LogicF = Logic<Field, EvalBackend>;
  using EltW = typename LogicF::EltW;
  using BitW = typename LogicF::BitW;
  using CborL = Cbor<LogicF>;
  using CborWitnessF = CborWitness<Field>;
 
 public:
  explicit CborTesting(const Field &F) : f_(F) {}
 
  void convert_witnesses(
      size_t n, typename CborL::v8 in[/*n*/],
      typename CborL::position_witness pw[/*n*/],
      typename CborL::global_witness &gw,
      const typename CborWitnessF::v8 inS[/*n*/],
      const typename CborWitnessF::position_witness pwS[/*n*/],
      const typename CborWitnessF::global_witness &gwS) const {
    const EvalBackend ebk(f_);
    const LogicF L(&ebk, f_);
    const Counter<LogicF> CTR(L);
 
    for (size_t i = 0; i < n; ++i) {
      for (size_t j = 0; j < 8; ++j) {
        in[i][j] = BitW(L.konst(inS[i][j]), f_);
      }
      pw[i].encoded_sel_header = L.konst(pwS[i].encoded_sel_header);
    }
 
    gw.invprod_decode = L.konst(gwS.invprod_decode);
    gw.cc0_counter = CTR.as_counter(gwS.cc0_counter);
    gw.invprod_parse = L.konst(gwS.invprod_parse);
  }
 
  // Return an index that can be fed to a circuit in the
  // evaluation backend (i.e., a bit vector).
  typename CborL::vindex index(size_t j) const {
    const EvalBackend ebk(f_);
    const LogicF L(&ebk, f_);
    return L.template vbit<CborConstants::kIndexBits>(j);
  }
 
 private:
  const Field &f_;
};
}  // namespace proofs
 
#endif  // PRIVACY_PROOFS_ZK_LIB_CIRCUITS_CBOR_PARSER_CBOR_TESTING_H_