fuzz coverage

// Copyright (c) 2021-2022 The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <node/caches.h>

#include <common/args.h>

#include <index/txindex.h>

#include <kernel/caches.h>

#include <logging.h>

#include <util/byte_units.h>

#include <algorithm>

#include <string>

// Unlike for the UTXO database, for the txindex scenario the leveldb cache make

// a meaningful difference: https://github.com/bitcoin/bitcoin/pull/8273#issuecomment-229601991

//! Max memory allocated to tx index DB specific cache in bytes.

static constexpr size_t MAX_TX_INDEX_CACHE{1024_MiB};

//! Max memory allocated to all block filter index caches combined in bytes.

static constexpr size_t MAX_FILTER_INDEX_CACHE{1024_MiB};

//! Maximum dbcache size on 32-bit systems.

static constexpr size_t MAX_32BIT_DBCACHE{1024_MiB};

namespace node {

CacheSizes CalculateCacheSizes(const ArgsManager& args, size_t n_indexes)

{

    // Convert -dbcache from MiB units to bytes. The total cache is floored by MIN_DB_CACHE and capped by max size_t value.

    size_t total_cache{DEFAULT_DB_CACHE};

    if (std::optional<int64_t> db_cache = args.GetIntArg("-dbcache")) {

        if (*db_cache < 0) db_cache = 0;

        uint64_t db_cache_bytes = SaturatingLeftShift<uint64_t>(*db_cache, 20);

        constexpr auto max_db_cache{sizeof(void*) == 4 ? MAX_32BIT_DBCACHE : std::numeric_limits<size_t>::max()};

        total_cache = std::max<size_t>(MIN_DB_CACHE, std::min<uint64_t>(db_cache_bytes, max_db_cache));

    }

    IndexCacheSizes index_sizes;

    index_sizes.tx_index = std::min(total_cache / 8, args.GetBoolArg("-txindex", DEFAULT_TXINDEX) ? 
MAX_TX_INDEX_CACHE0
 : 0);

    total_cache -= index_sizes.tx_index;

    if (n_indexes > 0) {

        size_t max_cache = std::min(total_cache / 8, MAX_FILTER_INDEX_CACHE);

        index_sizes.filter_index = max_cache / n_indexes;

        total_cache -= index_sizes.filter_index * n_indexes;

    }

    return {index_sizes, kernel::CacheSizes{total_cache}};

}

} // namespace node