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       1                 :             : // Copyright (c) 2023-present The Bitcoin Core developers
       2                 :             : // Distributed under the MIT software license, see the accompanying
       3                 :             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4                 :             : 
       5                 :             : #include <test/util/random.h>
       6                 :             : 
       7                 :             : #include <logging.h>
       8                 :             : #include <random.h>
       9                 :             : #include <uint256.h>
      10                 :             : #include <util/check.h>
      11                 :             : 
      12                 :             : #include <cstdlib>
      13                 :             : #include <iostream>
      14                 :             : 
      15                 :             : std::atomic<bool> g_seeded_g_prng_zero{false};
      16                 :             : 
      17                 :             : extern void MakeRandDeterministicDANGEROUS(const uint256& seed) noexcept;
      18                 :             : 
      19                 :         628 : void SeedRandomStateForTest(SeedRand seedtype)
      20                 :             : {
      21                 :         628 :     constexpr auto RANDOM_CTX_SEED{"RANDOM_CTX_SEED"};
      22                 :             : 
      23                 :             :     // Do this once, on the first call, regardless of seedtype, because once
      24                 :             :     // MakeRandDeterministicDANGEROUS is called, the output of GetRandHash is
      25                 :             :     // no longer truly random. It should be enough to get the seed once for the
      26                 :             :     // process.
      27                 :         734 :     static const auto g_ctx_seed = []() -> std::optional<uint256> {
      28                 :         106 :         if constexpr (G_FUZZING) return {};
      29                 :             :         // If RANDOM_CTX_SEED is set, use that as seed.
      30         [ -  + ]:         106 :         if (const char* num{std::getenv(RANDOM_CTX_SEED)}) {
      31         [ #  # ]:           0 :             if (auto num_parsed{uint256::FromUserHex(num)}) {
      32                 :           0 :                 return *num_parsed;
      33                 :             :             } else {
      34                 :           0 :                 std::cerr << RANDOM_CTX_SEED << " must consist of up to " << uint256::size() * 2 << " hex digits (\"0x\" prefix allowed), it was set to: '" << num << "'.\n";
      35                 :           0 :                 std::abort();
      36                 :             :             }
      37                 :             :         }
      38                 :             :         // Otherwise use a (truly) random value.
      39                 :         106 :         return GetRandHash();
      40   [ +  +  +  -  :         628 :     }();
                   +  - ]
      41                 :             : 
      42         [ +  + ]:         628 :     g_seeded_g_prng_zero = seedtype == SeedRand::ZEROS;
      43                 :         628 :     if constexpr (G_FUZZING) {
      44                 :             :         Assert(g_seeded_g_prng_zero); // Only SeedRandomStateForTest(SeedRand::ZEROS) is allowed in fuzz tests
      45                 :             :         Assert(!g_used_g_prng);       // The global PRNG must not have been used before SeedRandomStateForTest(SeedRand::ZEROS)
      46                 :             :     }
      47         [ +  + ]:         628 :     const uint256& seed{seedtype == SeedRand::FIXED_SEED ? g_ctx_seed.value() : uint256::ZERO};
      48         [ +  - ]:         628 :     LogInfo("Setting random seed for current tests to %s=%s\n", RANDOM_CTX_SEED, seed.GetHex());
      49                 :         628 :     MakeRandDeterministicDANGEROUS(seed);
      50                 :         628 : }