prime_signature.h

// Copyright 2011-2024 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
//
//     https://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 PRIME_SIGNATURE_H_
#define PRIME_SIGNATURE_H_

#include <cstdint>
#include <string>

#include "third_party/zynamics/binexport/util/types.h"

namespace security::bindiff {

// Computes the result of raising a number to a non-negative integral power.
// baze^exp is computed in a way that is faster than std::pow (which supports
// arbitrary real exponents).
uint32_t IPow32(uint32_t base, uint32_t exp);

// Returns a numeric signature for the (short) string given in mnemonic. The
// number returned is not a prime number, but a modified Gödel encoding of the
// given mnemonic string. This is used in the instruction cache to uniquely
// identify mnemonics and in the basic block LCS algorithm.
// Note: This function is used instead of perfect hashing of the instruction
// mnemonics in the files participating in a BinDiff run. This is because
// historically, the values returned by this function were persisted to disk in
// the BinExport v1 format. Thus the mnemonic space was unbounded which made
// perfect hashing infeasible.
// TODO(cblichmann): Rename to GetMnemonicId().
uint32_t GetPrime(const std::string& mnemonic);

}  // namespace security::bindiff

#endif  // PRIME_SIGNATURE_H_