/*

* (C) 2021 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include "fuzzers.h"

#include <botan/numthry.h>

namespace {

Botan::BigInt ref_gcd(Botan::BigInt a, Botan::BigInt b) {

   Botan::BigInt t;

   while(b != 0) {

      t = a % b;

      t.swap(b);

      t.swap(a);

   }

   return a;

}

}  // namespace

void fuzz(std::span<const uint8_t> in) {

   static const size_t max_bits = 4096;

   if(2 * in.size() * 8 > max_bits) {

      return;

   }

   const size_t half = in.size() / 2;

   const Botan::BigInt x = Botan::BigInt::from_bytes(in.subspan(0, half));

   const Botan::BigInt y = Botan::BigInt::from_bytes(in.subspan(half, in.size() - half));

   const Botan::BigInt ref = ref_gcd(x, y);

   const Botan::BigInt lib = Botan::gcd(x, y);

   if(ref != lib) {

      FUZZER_WRITE_AND_CRASH("X = " << x.to_hex_string() << "\n"

                                    << "Y = " << y.to_hex_string() << "\n"

                                    << "L = " << lib.to_hex_string() << "\n"

                                    << "R = " << ref.to_hex_string() << "\n");

   }

}